The Monthly Digest – Food waste – May 2017

Food wastes and by-products
R & D abstracts – May 2017
Biofuels from food processing wastes (review)

Food processing industry generates substantial high organic wastes along with high energy uses. The recovery of food processing wastes as renewable energy sources represents a sustainable option for the substitution of fossil energy, contributing to the transition of food sector towards a low-carbon economy. This article reviews the latest research progress on biofuel production using food processing wastes. While extensive work on laboratory and pilot-scale biosystems for energy production has been reported, this work presents a review of advances in metabolic pathways, key technical issues and bioengineering outcomes in biofuel production from food processing wastes. Research challenges and further prospects associated with the knowledge advances and technology development of biofuel production are discussed.

Zhang Z et al (2016) Current Opinion in Biotechnology 38:97-105

 

Bioelectrochemical conversion of waste to energy using microbial fuel cell technology (review)

Numerous traditional methods are available for the conversion of waste to energy (WTE) such as incineration, anaerobic digestion, pyrolysis, gasification. Most of them suffer from low efficiency and high energy requirements. Microbial fuel cell (MFC) technology is an excellent alternative for the generation of renewable and sustainable energy and has the potential to help alleviate the current global energy crisis. The total wastewater generated in India is almost 250% of the total treatment capacity, and the Government is, therefore, looking for a sustainable solution for the treatment of waste. Indian population consumes around 700 billion cubic meters of water annually, and this figure will rise to 950 and 1422 billion m3 by 2025 and 2050 respectively. Although treatment of wastewater is a serious concern, the energy recovery potential of wastewater has not yet been fully developed. A survey has been conducted through this study, and it was estimated that MFC technology has the potential to generate around 23.3 and 40 Tera Watt (TW) power by 2025 and 2050 by treating wastewater generated throughout India (urban areas) if utilized properly. This review article presents a various aspect of MFC technology for a proper understanding by the readers. This will be a unique study wherein the energy recovery potential of the wastewater produced in the Indian subcontinent has been estimated through MFC technology. A number of factors affecting the performance of MFC such as electron losses, reactor configuration, and varying concentration must be taken into account to augment output energy. The article summarizes an extensive literature survey of some selected papers published in the last decade.

Khan MD et al (2017) Process Biochemistry (in press)

 

Fruit and vegetable waste management and the challenge of fresh-cut salad (review)

The fruit and vegetable sector generates large amounts of waste. In industrialized countries, fruit and vegetable waste (FVW) is mainly generated before reaching consumers, due to programmed overproduction and unfulfillment of retailer quality standards. FVW poses environmental problems due to its high biodegradability, represents a loss of valuable biomass and an economic cost for companies. Different reduction, reuse and recycle strategies to tackle FVW have been proposed.
This review paper summarizes these strategies, underlying their main advantages and pitfalls. In particular, fresh-cut salad waste was considered as a particularly challenging FVW, due to its low concentration of nutrients (e.g. polyphenols, pigments, fiber). Different management strategies can be successfully applied to FVW. Among them, the extraction of specific functional compounds was found to be one of the most studied in the last years. This suggests that FVW can be considered a source of valuable ingredients and products. To maximally exploit these FVW potentialities, a rational strategy is required. The latter should be developed using a step-procedure including waste characterization, output definition, process design and feasibility study. The application of this procedure to the case of fresh-cut salad waste was presented. Based on the review of currently applied and potential salad waste management strategies, an operational scheme for the development of alternative strategies was proposed. This scheme considers the exploitation of traditional and novel technologies, even applied in combination, for salad waste valorization.

Plazzotta S et al (2017) Trends in Food Science & Technology 63:51-59

 

An overview: Recycling of solid barley waste generated as a by-product in distillery and brewery (review)

This overview has focused on the options available for the utilisation of residual-biomass generated in distillery and brewery for the production of added-value products. Bio-processing approaches have been reviewed and discussed for the economical bioconversion and utilisation of this waste for the production of bioproducts, such as lactic acid, enzymes, xylitol and animal feed. Though this overview provides several options for the bioprocessing of this residual material, a more suitable one could be chosen according to the processing-facilities available and the amount of residue available in local area. The feasibility of any chosen process should be evaluated on the basis of cost of material available, its local utilisation for animal feed, and the overall economical advantages that could be gained by changing its current traditional landfill use to produce higher added value products.

Singh Nigam P (2017) Waste Management 62:255-261

 

Exploitation of grape marc as functional substrate for lactic acid bacteria and bifidobacteria growth and enhanced antioxidant activity (research)

This study aimed at using grape marc for the growth of lactic acid bacteria and bifidobacteria with the perspective of producing a functional ingredient having antioxidant activity. Lactobacillus plantarum 12A and PU1, Lactobacillus paracasei 14A, and Bifidobacterium breve 15A showed the ability to grow on grape marc (GM) based media. The highest bacterial cell density (>9.0 CFU/g) was found in GM added of 1% of glucose (GMG). Compared to un-inoculated and incubated control fermented GMG showed a decrease of carbohydrates and citric acid together with an increase of lactic acid. The content of several free amino acids and phenol compounds differed between samples. Based on the survival under simulated gastro-intestinal conditions, GMG was a suitable carrier of lactic acid bacteria and bifidobacteria strains. Compared to the control, cell-free supernatant (CFS) of fermented GMG exhibited a marked antioxidant activity in vitro. The increased antioxidant activity was confirmed using Caco-2 cell line after inducing oxidative stress, and determining cell viability and radical scavenging activity through MTT and DCFH-DA assays, respectively. Supporting these founding, the SOD-2 gene expression of Caco-2 cells also showed a lowest pro-oxidant effect induced by the four CFS of GMG fermented by lactic acid bacteria and bifidobacteria. This study aimed at using grape marc for the growth of lactic acid bacteria and bifidobacteria with the perspective of producing a functional ingredient having antioxidant activity. Lactobacillus plantarum 12A and PU1, Lactobacillus paracasei 14A, and Bifidobacterium breve 15A showed the ability to grow on grape marc (GM) based media. The highest bacterial cell density (>9.0 CFU/g) was found in GM added of 1% of glucose (GMG). Compared to un-inoculated and incubated control fermented GMG showed a decrease of carbohydrates and citric acid together with an increase of lactic acid. The content of several free amino acids and phenol compounds differed between samples. Based on the survival under simulated gastro-intestinal conditions, GMG was a suitable carrier of lactic acid bacteria and bifidobacteria strains. Compared to the control, cell-free supernatant (CFS) of fermented GMG exhibited a marked antioxidant activity in vitro. The increased antioxidant activity was confirmed using Caco-2 cell line after inducing oxidative stress, and determining cell viability and radical scavenging activity through MTT and DCFH-DA assays, respectively. Supporting these founding, the SOD-2 gene expression of Caco-2 cells also showed a lowest pro-oxidant effect induced by the four CFS of GMG fermented by lactic acid bacteria and bifidobacteria.

Campanella D et al (2017) Food Microbiology 65:25-35

 

Pie waste – A component of food waste and a renewable substrate for producing ethanol (research)

Sugar-rich food waste is a sustainable feedstock that can be converted into ethanol without an expensive thermochemical pretreatment that is commonly used in first and second generation processes. In this manuscript we have outlined the pie waste conversion to ethanol through a two-step process, namely, enzyme hydrolysis using commercial enzyme products mixtures and microbial fermentation using yeast. Optimized enzyme cocktail was found to be 45% alpha amylase, 45% gamma amylase, and 10% pectinase at 2.5 mg enzyme protein/g glucan produced a hydrolysate with high glucose concentration. All three solid loadings (20%, 30%, and 40%) produced sugar-rich hydrolysates and ethanol with little to no enzyme or yeast inhibition. Enzymatic hydrolysis and fermentation process mass balance was carried out using pie waste on a 1000 g dry weight basis that produced 329 g ethanol at 20% solids loading. This process clearly demonstrates how food waste could be efficiently converted to ethanol that could be used for making biodiesel by reacting with waste cooking oil.

Magyar M et al (2017) Waste Management 62:247-254

The Monthly Digest – Food waste – April 2017

Food wastes and by-products
R & D abstracts – April 2017
Wastes and by-products: Upcoming sources of carotenoids for biotechnological purposes and health-related applications

Bioresidues valorization has gained a pivotal relevance in the last years, directly moved by consumers’ demands for heathier and safer products (food, cosmetics, supplements, drugs, and so on) and by industrial companies that need to adapt their manufacturing procedures to increasingly strict regulatory guidelines. Most of the natural ingredients are considered more sought and safer than synthetic ones, but also more expensive and less abundant. Therefore, the recovery of valuable active ingredients from wastes and by-products may be an interesting and upcoming strategy. The present report aims to provide an extensive approach to bioresidues valorization, focusing its chemical composition in terms of carotenoids content and their upcoming uses for biotechnological purposes. Daily produced and discharged industrial bioresidues derived from vegetable (peel, seeds, pericarp) and animal (wastewater, crustacean’s cephalothorax and carapace, scales, tails) sources comprise the richest sources of carotenoids (carotenes and xanthophylls). Different techniques are commonly used for carotenoids recovery being the extraction with organic solvents the most frequently used. Supercritical fluid extraction, microwave- and enzyme-assisted extractions are applied, but mainly in combination. This area opens fascinating opportunities to discover and to design novel strategies for carotenoids production/accumulation, foodstuffs valorization and provide valuable ingredients to different industrial sectors.

Martins N and Ferreira CFR (2017) Trends in Food Science and Technology 62:33-48

Bioenergy potential from food waste in California

Food waste makes up approximately 15% of municipal solid waste generated in the United States, and 95% of food waste is ultimately landfilled. Its bioavailable carbon and nutrient content makes it a major contributor to landfill methane emissions, but also presents an important opportunity for energy recovery. This paper presents the first detailed analysis of monthly food waste generation in California at a county level, and its potential contribution to the state’s energy production. Scenarios that rely on excess capacity at existing anaerobic digester (AD) and solid biomass combustion facilities, and alternatives that allow for new facility construction, are developed and modeled. Potential monthly electricity generation from the conversion of gross food waste using a combination of AD and combustion varies from 420 to 700 MW, averaging 530 MW. At least 66% of gross high moisture solids and 23% of gross low moisture solids can be treated using existing county infrastructure, and this fraction increases to 99% of high moisture solids and 55% of low moisture solids if waste can be shipped anywhere within the state. Biogas flaring practices at AD facilities can reduce potential energy production by 10 to 40%.

Breunig HM et al (2017) Environmental Science and Technology 51:1120-1128

Utilization of inulin-containing waste in industrial fermentations to produce biofuels and bio-based chemicals

Inulins are polysaccharides that belong to an important class of carbohydrates known as fructans and are used by many plants as a means of storing energy. Inulins contain 20 to several thousand fructose units joined by β-2,1 glycosidic bonds, typically with a terminal glucose unit. Plants with high concentrations of inulin include: agave, asparagus, coffee, chicory, dahlia, dandelion, garlic, globe artichoke, Jerusalem artichoke, jicama, onion, wild yam, and yacón. To utilize inulin as its carbon and energy source directly, a microorganism requires an extracellular inulinase to hydrolyze the glycosidic bonds to release fermentable monosaccharides. Inulinase is produced by many microorganisms, including species of Aspergillus, Kluyveromyces, Penicillium, and Pseudomonas. We review various inulinase-producing microorganisms and inulin feedstocks with potential for industrial application as well as biotechnological efforts underway to develop sustainable practices for the disposal of residues from processing inulin-containing crops. A multi-stage biorefinery concept is proposed to convert cellulosic and inulin-containing waste produced at crop processing operations to valuable biofuels and bioproducts using Kluyveromyces marxianus, Yarrowia lipolytica, Rhodotorula glutinis, and Saccharomyces cerevisiae as well as thermochemical treatments.

Hughes SR et al (2017) World Journal of Microbiology and Biotechnology 33:78

Effect of seasonal variations of organic loading rate and acid phase on methane yield of food waste leachate in South Korea

The objective of this study was to determine the effect of seasonal variations of organic loading rate (OLR) and acidogenic phase on methane yield of food waste leachate (FWL) treated in biogas facility in South Korea. A biogas facility operating in G city was selected as the target for this study. Remarkable seasonal fluctuations in methane yield occurred in this facility repeatedly. Methane yield in the summer was significantly lower compared to that in other seasons. In order to determine the operation efficiency, precision investigation (methane yield, OLR, etc) was conducted from March 2014 to April 2015. Characteristic parameters and operating factors of a two-stage anaerobic digestion were analyzed to obtain volatile fatty acids (VFAs), chemical oxygen demand, nutrients, total nitrogen, and so on. Data comparison revealed that the monthly average values of OLR and VFAs tended to increase rapidly in the summer (up to 3.92 kgVS/m3 day and 9263 mg/L, respectively). In contrast, methane yield in the same season was at 0.28 Sm3CH4/kg VS, which was much lower than the average value (0.42 Sm3CH4/kg VS) of methane yield in other seasons. The decrease in methane yield ranged from 69.0 to 57.9% in the summer. These results suggested that methane yield might be influenced by the operating conditions with seasonal organic loading fluctuations. In other words, methane yield might be affected by a shock load of VFAs due to inapposite operation of acidogenic phase with easily degradable FWL, particularly in the summer. The results of this study will provide important information on how an ongoing biogas facility of FWL should be operated in the summer.

Lee DJ et al (2017) Applied Biological Chemistry 60:87-93

The Monthly Digest – Flavours – May 2017

Aromas and flavours
R & D abstracts – May 2017
Microbial cell factories for the production of terpenoid flavor and fragrance compounds (review)

Terpenoid flavor and fragrance compounds are of high interest to the aroma industry. Microbial production offers an alternative sustainable access to the desired terpenoids independent of natural sources. Genetically engineered microorganisms can be used to synthesize terpenoids from cheap and renewable resources. Due to its modular architecture, terpenoid biosynthesis is especially well suited for the microbial cell factory concept: a platform host engineered for a high flux toward the central C5 prenyl diphosphate precursors enables the production of a broad range of target terpenoids just by varying the pathway modules converting the C5 intermediates to the product of interest. In this review typical terpenoid flavor and fragrance compounds marketed or under development by biotech and aroma companies are given, and the specificities of the aroma market are discussed. The main part of this work focuses on key strategies and recent advances to engineer microbes to become efficient terpenoid producers.

Schempp FM et al (2017) Journal of Agricultural and Food Chemistry (in press)

A review on Lactococcus lactis: from food to factory

Lactococcus lactis has progressed a long way since its discovery and initial use in dairy product fermentation, to its present biotechnological applications in genetic engineering for the production of various recombinant proteins and metabolites that transcends the heterologous species barrier. Key desirable features of this gram-positive lactic acid non-colonizing gut bacteria include its generally recognized as safe (GRAS) status, probiotic properties, the absence of inclusion bodies and endotoxins, surface display and extracellular secretion technology, and a diverse selection of cloning and inducible expression vectors. This have made L. lactis a desirable and promising host on par with other well established model bacterial or yeast systems such as Escherichia coli, Sacharomyces cerevisiae and Bacillus subtilis. In this article, we review recent technological advancements, challenges, future prospects and current diversified examples on the use of L. lactis as a microbial cell factory. Additionally, we will also highlight latest medical-based applications involving whole-cell L. lactis as a live delivery vector for the administration of therapeutics against both communicable and non-communicable diseases.

Song AAL et al (2017) Microbial Cell Factories 16:55

Genetic, enzymatic and metabolite profiling of the Lactobacillus casei group reveals strain biodiversity and potential applications for flavour diversification (research)

The Lactobacillus casei group represents a widely explored group of lactic acid bacteria, characterized by a high level of biodiversity. In this study, the genetic and phenotypic diversity of a collection of more than 300 isolates of the L. casei group and their potential to produce volatile metabolites important for flavour development in dairy products was examined. Following confirmation of species by 16S rRNA PCR, the diversity of the isolates was determined by pulsed-field gel electrophoresis. The activities of enzymes involved in the proteolytic cascade were assessed and significant differences among the strains were observed. Ten strains were chosen based on the results of their enzymes activities and they were analysed for their ability to produce volatiles in media with increased concentrations of a representative aromatic, branched chain and sulphur amino acid. Volatiles were assessed using gas chromatography coupled with mass spectrometry. Strain-dependent differences in the range and type of volatiles produced were evident. Strains of the L. casei group are characterized by genetic and metabolic diversity which supports variability in volatile production. This study provides a screening approach for the knowledge-based selection of strains potentially enabling flavour diversification in fermented dairy products.

Stefanovic E et al (2017) Journal of Applied Microbiology 122:1245-1261

Flavour modulation by bio-processing using flavour forming bacteria strains (patent)

A fermentation of a milk source with Lactococcus lactis subsp. lactis biovar diacetylactis to form a fermented milk product. The fermented milk product has a flavour and aroma. The fermented milk product can be in the form of a powder or a concentrate. The fermented milk product has applications in the food industry.

WO2012085009 A1

Flavour modulation by bio-processing using cream-flavour forming bacteria strains (patent)

A fermentation of a milk source with Lactococcus lactis subsp. lactis diacetylactis strains to form a fermented milk product. The fermented milk product has at least a cream flavour and aroma. The fermented milk product can be in the form of a powder or a concentrate. The fermented milk product has applications in the food industry. A use of these bacterial strains for the manufacture of butter-cream flavouring milk ingredients containing at least one of diacetyl, acetoin and 3,4-dihydroxy-3,4-dimethyl-2,5-hexanedione.

WO2012085010 A1

Flavour modulation by fermenting a milk source for multi-flavour formation with a cocktail of bacteria strains (patent)

A fermentation of a milk source to manufacture a fermented milk product with malty-chocolate-honey-butter-cream flavor and aroma. Fermentation is achieved by addition of Lactococcus lactis subsp. lactis diacetylactis strains. A further bacterium Lactococcus lactis subsp. lactis biovar is also added to the milk source. The milk source comprises amino acids and citrate prior to fermentation.

WO2012085011 A1

Application of Plackett–Burman experimental design for investigating the effect of wort amino acids on flavour-active compounds production during lager yeast fermentation (research)

Aroma-active higher alcohols and esters are produced intracellularly in the cytosol by fermenting lager yeast cells, which are of major industrial interest because they determine aroma and taste characteristics of the fermented beer. Wort amino acid composition and their utilization by yeast during brewer’s wort fermentation influence both the yeast fermentation performance and the flavour profile of the finished product. To better understand the relationship between the yeast cell and wort amino acid composition, Plackett–Burman screening design was applied to measure the changes in nitrogen composition associated with yeast amino acids uptake and flavour formation during fermentation. Here, using an industrial lager brewing strain of Saccharomyces pastorianus, we investigated the effect of amino acid composition on the accumulation of higher alcohols and volatile esters. The objective of this study was to identify the significant amino acids involved in the flavour production during beer fermentation. Our results showed that even though different flavour substances were produced with different amino acid composition in the fermentation experiments, the discrepancies were not related to the total amount of amino acids in the synthetic medium. The most significant effect on higher alcohol production was exercised by the content of glutamic acid, aromatic amino acids and branch chain amino acids. Leucine, valine, glutamic acid, phenylalanine, serine and lysine were identified as important determinants for the formation of esters. The future applications of this information could drastically improve the current regime of selecting malt and adjunct or their formula with desired amino acids in wort.

Yin H et al (2017) Journal of the Institute of Brewing (in press)

Impact of pre-fermentative maceration and yeast strain along with glutathione and SO2 additions on the aroma of Vitis vinifera L. Pošip wine and its evaluation during bottle aging (research)

The aim of the research was characterization and improvement of aroma of white wine Vitis vinifera L. Pošip by application of several enological practices, either individually or in combinations. The effect of pre-fermentative maceration, indigenous yeast strain and antioxidant additions (higher sulfur dioxide and glutathione) was examined, and compared to conventional white wine production: reductive pressing, commercial yeast strain and typical doses of free sulfur dioxide (35 mg/L). The most significant aroma contributors were esters and higher alcohols (fermentation aroma), as well as varietal aroma compounds such as linalool, β-damascenone and thiols (3SH and 3SHA). Furthermore, results showed that pre-fermentative maceration affected the higher concentrations of several aroma compounds, primarily those important for varietal character of wines: terpenes, norisoprenoids and varietal thiols. Fermentation by indigenous yeasts resulted in higher concentrations of different compounds, especially of i-amyl acetate which contributes to desirable fruity, banana-like odors. Furthermore, during 12 months’ aging, most of the aroma compounds significantly decreased, but in wines bottled with antioxidant additions (higher free sulfur dioxide, glutathione and their combination) their slower decrease was observed. The most notable protective effect was observed using the combination of higher free sulfur dioxide (50 mg/L) with glutathione (20 mg/L).

Tomasevic M et al (2017) LWT – Food Science and Technology 81:67-76

Comparison between malolactic fermentation container and barrel toasting effects on phenolic, volatile, and sensory profiles of red wines (research)

Ellagitannin and anthocyanin profiles, woody volatile composition, and sensory properties of wines in which malolactic fermentation (MLF) took place in barrels or stainless steel tanks, have been compared after 12 months of barrel aging. Three different barrel toastings were evaluated. Barrel-fermented wines generally presented 1.2-fold higher total phenolics, whereas tank-fermented wines exhibited 1.1- and 1.2-fold greater total proanthocyanidin and anthocyanin contents, respectively. Concerning ellagitannin composition, the barrel toasting effect seemed to be more important than differences due to MLF container. Certain woody and fruity volatiles varied significantly (p < 0.05) depending on whether MLF occurred in barrels or tanks. Barrel-fermented wines were preferred in the mouth, whereas olfactory preference depended on barrel toasting. This is the first study that evaluates the impact of oak wood during MLF on ellagitannin wine composition, as well as the barrel toasting effect on wine attributes during aging when MLF occurred whether in barrels or in tanks.

Gonzalez-Centeno et al (2017) Journal of Agricultural and Food Chemistry (in press)

Immobilization of a cutinase from Fusarium oxysporum and application in pineapple flavor synthesis (research)

In the present study, the immobilization of a cutinase from Fusarium oxysporum was carried out as cross-linked enzyme aggregates. Under optimal immobilization conditions, acetonitrile was selected as precipitant, utilizing 9.4 mg protein/mL and 10 mM glutaraldehyde as cross-linker. The immobilized cutinase (imFocut5a) was tested in isooctane for the synthesis of short-chain butyrate esters, displaying enhanced thermostability compared to the free enzyme. Pineapple flavor (butyl butyrate) synthesis was optimized leading to a conversion yield of >99% after 6 h, with an initial reaction rate of 18.2 mmol/L/h. Optimal reaction conditions found to be 50 οC, vinyl butyrate:butanol molar ratio 3:1, vinyl butyrate concentration 100 mM and enzyme loading of 11U. Reusability studies of imFocut5a showed that after 4 consecutive runs, the reaction yield reaches the 54% of the maximum. The efficient bioconversion offers a sustainable and environmentally friendly process for the production of “natural” aroma compounds essential for the Food Industry.

Nikolaivits E et al (2017) Journal of Agricultural and Food Chemistry (in press)

High activity and selectivity immobilized lipase on Fe3O4 nanoparticles for banana flavour synthesis (research)

Lipase (E.C.3.1.1.3) from Thermomyces lanuginosus (TL) was directly bonded, through multiple physical interactions, on citric acid functionalized monodispersed Fe3O4nanoparticles (NPs) in presence of a small amount of hydrophobic functionalities. A very promising scalable synthetic approach ensuring high control and reproducibility of the results, and an easy and green immobilization procedure was chosen for NPs synthesis and lipase anchoring. The size and structure of magnetic nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The samples at different degree of functionalization were analysed through thermogravimetric measurements. Lipase immobilization was further confirmed by enzymatic assay and Fourier transform infrared (FT-IR) spectra. Immobilized lipase showed a very high activity recovery up to 144% at pH = 7 and 323% at pH = 7.5 (activity of the immobilized enzyme compared to that of its free form). The enzyme, anchored to the Fe3O4 nanoparticles, to be easy recovered and reused, resulted more stable than the native counterpart and useful to produce banana flavour. The immobilized lipase results less sensitive to the temperature and pH, with the optimum temperature higher of 5 °C and optimum pH up shifted to 7.5 (free lipase optimum pH = 7.0). After 120 days, free and immobilized lipases retained 64% and 51% of their initial activity, respectively. Ester yield at 40 °C for immobilized lipase reached 88% and 100% selectivity.

Sarno M et al (2017) Process Biochemistry 56:98-108

The Monthly Digest – Flavours – April 2017

Aromas and flavours
R & D abstracts – April 2017
Role of lactic acid bacteria on the yogurt flavour: a review

Considerable knowledge has been accumulated on the lactic acid bacteria (LAB) that affect the aroma and flavour of yogurt. This review focuses on the role of LAB in the production of flavour compounds during yogurt fermentation. The biochemical processes of flavour compound formation by LAB including glycolysis, proteolysis and lipolysis are summarized, with some key compounds described in detail. The flavour-related activities of LAB mostly depend on the species used for yogurt fermentation and some strategies have been developed to obtain more control of the flavour-forming process. Metabolic engineering can be a powerful tool to reroute the metabolic flux towards the efficient accumulation of the desired flavour compounds with the knowledge of the complex network of flavour-forming pathways and the availability of genetic tools. Further progress made in the omics-based techniques and the use of systems biology approaches are needed to fully understand, control, and steer flavour formation in yogurt fermentation processes.

Chen C et al (2017) International Journal of Food Properties (in press)

Milk-clotting properties of plant rennets and their enzymatic, rheological and sensory role in cheese making: a review

Plant rennets hold an important position amongst various coagulants used in cheese technology. The selection of a suitable plant coagulant is important due to the increasing global demands of cheese alongside reduced supply of calf rennet. Thus, a literature synthesis is presented to investigate recent achievements on their functional properties and enzymatic role in cheese making. Efforts have also been done to compare certain rheological and sensory properties of final products, arising from some plant and animal based rennets. In fact, some coagulants such as actinidin or dubiumin produce cheeses with sensory qualities similar to those produced by animal rennet. Others, like ginger, cucumisin or hieronymain proteases contribute to develop very different textures and flavors, due to excessive proteolytic activity and production of bitter peptides. For milk-clotting enzymes with high non-specific action, several improvement strategies have been developed to produce cheeses with sensory properties close to those of animal rennet. For example, the mixture of coagulants (cardosins/chymosin), the selection of appropriate milk or its ultrafiltration, as well as the increase of salting time of cheese during ripening could be efficient ways to improve texture and reduce bitterness. Concerning cheeses with high yield loss, the whey could be used for a traditional production of whey cheese. To conclude, the selection of appropriate plant rennet with high MCA/PA ratio and the optimization of all coagulation parameters play a central role in manufacturing cheese with superior rheological and sensory properties.

Ben Amira A et al (29017) International Journal of Food Properties (in press)

Flavour-active volatile compounds in beer: production, regulation and control

Many classes of compounds have been shown to play an important role in the development of flavour characteristics of beer. This significantly influences its taste and sensory properties, thus affecting its market performance. Despite the intensive research aimed at unravelling the precise mechanism and regulation of flavour formation in beer, current knowledge remains far from complete. Several reviews are available on the general composition of beer and yeast metabolic pathways involved in the production of volatile compounds in beer. However, a limited amount of work has been reported concerning the influence of some of the beer constituents and other important parameters on beer flavour. This paper reviews the current knowledge of the biochemistry behind flavour formation in beer and discusses the different factors that influence its formation and how it can be controlled during brewery fermentation.

Olaniran AO et al (2017) Journal of the Institute of Brewing (in press)

Aroma recovery of beer flavors by pervaporation through polydimethylsiloxane membranes

Five commercial beers and their corresponding no-alcohol presentations have been analyzed in terms of five aroma compounds: three alcohols and two esters (isobutyl alcohol, ethyl acetate, 2-methyl butanol, 3-methyl butanol, and isoamyl acetate). Substantial reductions of volatile aroma compounds have been encountered in these nonalcoholic beers. Pervaporation of these aromas in order to allow their recovery has been tested through two commercial membranes with polydimethylsiloxane active layers (Pervatech and Sulzer). Total fluxes are higher through the Pervatech membrane while individual aroma ones are similar for both the membranes. Mass recovery is higher for the Pervatech membrane for most of the aromas whereas their enrichment factors are better for the Sulzer membrane. The rest of the beer profile modulates to some extent the general trends referred. Mass recoveries and enrichment factors from 5 to 35% were obtained for the aromas tested. Mass recovery and enrichment factors could be improved by increasing membrane area or time of treatment. Pervaporation is a membrane technique which effectiveness has been proven to separate volatile organic compounds from aqueous mixtures. It could be useful in beer industry in a significant way, helping nonalcoholic beers to improve their organoleptic characteristics. In a near future, by controlling operating parameters involved in the full process, it will be possible to introduce this technique into the factories and produce a tastier and better quality beer by minimizing the lack of valuable aroma compounds.

Paz AI et al (2017) Journal of Food Process Engineering (in press)

Key volatile aroma compounds of lactic acid fermented malt based beverages – impact of lactic acid bacteria strains

This study aims to define the aroma composition and key aroma compounds of barley malt wort beverages produced from fermentation using six lactic acid bacteria (LAB) strains. Gas chromatography mass spectrometry–olfactometry and flame ionization detection was employed; key aroma compounds were determined by means of aroma extract dilution analysis. Fifty-six detected volatile compounds were similar among beverages. However, significant differences were observed in the concentration of individual compounds. Key aroma compounds (flavor dilution (FD) factors ≥16) were β-damascenone, furaneol, phenylacetic acid, 2-phenylethanol, 4-vinylguaiacol, sotolon, methional, vanillin, acetic acid, nor-furaneol, guaiacol and ethyl 2-methylbutanoate. Furthermore, acetaldehyde had the greatest odor activity value of up to 4266. Sensory analyses revealed large differences in the flavor profile. Beverage from L. plantarum Lp. 758 showed the highest FD factors in key aroma compounds and was correlated to fruity flavors. Therefore, we suggest that suitable LAB strain selection may improve the flavor of malt based beverages.

Dongmo NS et al (2017) Food Chemistry 229:565-573

Lactic acid fermentation drives the optimal volatile flavor-aroma profile of pomegranate juice

Pomegranate juice (PJ) fermented with Lactobacillus plantarum C2, POM1, and LP09, unstarted-PJ, and raw-PJ were characterized for the profile of the volatile components (VOC) by PT–GC–MS. Lactic acid fermentation through selected strains enhanced the flavor profile of PJ. Concentrations of desired compounds (e.g., alcohols, ketones, and terpenes) were positively affected, whereas those of non-desired aldehydes decreased. Unstarted-PJ mainly differentiated from fermented PJs for the highest levels of aldehydes and sulfur compounds, and in lesser extent of furans, whereas alcohols, ketones, and alkenes followed by terpenes and benzene derivatives mainly differentiated fermented PJs. As expected, the lowest level of VOC was found in raw-PJ. VOC profile reflected on the sensory features of fermented PJs, unstarted-PJ, and raw-PJ, which were evaluated using a consensus modified flavor profile based on 13 attributes. Fermented PJs were mainly discriminated by the higher intensity of floral, fruity and anise notes than the controls.

Di Cagno R et al (2017) International Journal of Food Microbiology 248:56-62

Biotransformation of α- and β-pinene into flavor compounds

Products that bear the label “natural” have gained more attention in the marketplace. In this approach, the production of aroma compounds through biotransformation or bioconversion has been receiving more incentives in economic and research fields. Among the substrates used in these processes, terpenes can be highlighted for their versatility and low cost; some examples are limonene, α-pinene, and β-pinene. This work focused on the biotransformation of the two bicyclic monoterpenes, α-pinene and β-pinene; the use of different biocatalysts; the products obtained; and the conditions employed in the process.

Vespermann KAC et al (2017) Applied Microbiology and Biotechnology 101:1805-1817

Optimizing bioconversion of ferulic acid to vanillin by Bacillus subtilis in the stirred packed reactor using Box-Behnken design and desirability function

A stirring bioreactor packed with a carbon fiber textiles (FT) biofilm formed by Bacillus subtiliswas used to produce vanillin from ferulic acid. Biofilm formation was characterized by scanning electron microscopy. The interactive effects of three variables on vanillin molar yield (M) and conversion efficiency of ferulic acid (E) were evaluated by response surface methodology (RSM) with a Box-Behnken design (BBD). The optimal conversion conditions with a maximum overall desirability D of 0.983 were obtained by a desirability function. Considering the actual operation, the confirmation tests were performed using the slightly modified optimal conditions (initial ferulic acid concentration 1.55 g/L, temperature 35°C, stirring speed 220 rpm). The results showed that M and E were 57.42 and 93.53%, respectively. This was only 1.03% and 1.87%, respectively, different from the predicted values, confirming the validity of the predicted models. These revealed that the stirred packed reactor could be successfully used in vanillin bioconversion from ferulic acid.

Chen P et al (2017) Food Science and Biotechnology 26 :143-152

Breeding of a sake yeast mutant with enhanced ethyl caproate productivity in sake brewing using rice milled at a high polishing ratio

Sake yeast produces a fruity flavor known as ginjo-ko—which is mainly attributable to ethyl caproate and isoamyl acetate—during fermentation in sake brewing. The production of these flavor components is inhibited by unsaturated fatty acids derived from the outer layer of rice as raw material. We isolated three mutants (hec2, hec3, and hec6) with enhanced ethyl caproate productivity in sake brewing using rice milled at a high polishing ratio from a cerulenin-resistant mutant derived from the hia1 strain, which shows enhanced isoamyl acetate productivity. The hec2 mutant had the homozygous FAS2 mutation Gly1250Ser, which is known to confer high ethyl caproate productivity. When the homozygous FAS2 mutation Gly1250Ser was introduced into strain hia1, ethyl caproate productivity was increased but neither this nor intracellular caproic acid content approached the levels observed in the hec2 mutant, indicating that a novel mutation was responsible for the high ethyl caproate productivity. We also found that the expression of EEB1 encoding acyl-coenzyme A: ethanol O-acyltransferase (AEATase) and enzymatic activity were increased in the hec2 mutant. These results suggest that the upregulation of EEB1 expression and AEATase activity may also have contributed to the enhancement of ethyl caproate synthesis from ethanol and caproyl-CoA. Our findings are useful for the brewing of sake with improved flavor due to high levels of isoamyl acetate and ethyl caproate.

Takahashi T et al (2017) Journal of Bioscience and Bioengineering (in press)

The Monthly Digest – March 2017

Solid-state fermentative production of aroma esters by Myroides sp. ZB35 and its complete genome sequence

Consumers prefer biotechnological food products with high nutritional values and good flavors. Solid-state fermentation is a commonly used technique with a long history. In the present study, Myroides sp. ZB35 was used in solid-state fermentative production of aroma volatiles on a rice medium. Using the headspace solid phase microextraction coupled with gas chromatography–mass spectrometry technique and authentic standards, 22 esters with molecular weight ranging from 102 to 172 were identified. At 192 h, the esters reached a total concentration of 1774 μg/kg. Subsequently, the complete genome of ZB35 was sequenced using the PacBio RS II platform. ZB35 has a single circular chromosome of 4,065,010 bp with a GC content of 34.1% and six putative novel esterase genes were found. ZB35 is the first bacterium here discovered being capable of producing so many kinds of aroma esters. The data revealed here would provide helpful information for further developing this strain as a promising source of aroma esters relevant in food and fragrance industries and the source of novel enzymes with potential usages.

Xiao Z et al (2017) Journal of Biotechnology (in press)

 

Brewing with 100 % unmalted grains: barley, wheat, oat and rye

Whilst beers have been produced using various levels of unmalted grains as adjuncts along with malt, brewing with 100 % unmalted grains in combination with added mashing enzymes remains mostly unknown. The aim of this study was to investigate the brewing potential of 100 % unmalted barley, wheat, oat and rye in comparison with 100 % malt. To address this, identical brewing methods were adopted at 10-L scale for each grain type by applying a commercial mashing enzyme blend (Ondea® Pro), and selected quality attributes were assessed for respective worts and beers. Different compositions of fermentable wort carbohydrates were observed in the worts (all at ca. 12°P), and in particular oat wort had lower concentration of maltose compared to the others, resulting in the lowest concentration of alcohol in final beer. Moreover, wort made from unmalted grains also showed lower free amino nitrogen and higher viscosity than malt wort. Furthermore, the use of 100 % unmalted grains resulted in a decrease in the levels of colour and brightness, as well as higher alcohols and esters in the final beers. Consequently, the study provides valuable information for exploring beer brewing with 100 % unmalted barley, oat, rye or wheat using exogenously added enzymes. It also helps to understand the process ability by revealing specific needs when manufacturing different type of beers from unmalted grains, potentially paving the way to process optimisation and development of future products.

Zhuang S et al (29017) European Food Research and Technology 243:447-454

 

Effect of non-Saccharomyces yeasts on the volatile chemical profile of Shiraz wine

This study evaluated the impact that the non-Saccharomyces yeasts, Torulaspora delbrueckii (TD), Lachanceathermotolerans (LT), Pichia kluyveri (PK), Metschnikowia pulcherrima (MP), Candida zemplinina(CZ) and Kazachstania aerobia (KA), in sequential inoculation with Saccharomyces cerevisiae (SC), had on the volatile chemical profile of Shiraz wine. Shiraz grape must was inoculated with monocultures of the non-Saccharomyces yeasts, which were allowed to ferment until 2% v/v ethanol concentration was reached at which point, SC was added to complete the alcoholic fermentation. The control was SC in monoculture. The final wines were subjected to solid phase microextraction-GC × GC-time of flight-MS to evaluate the untargeted volatile metabolite profile of each treatment. Each fermentation produced a unique chemical profile. The LT–SC sequential fermentation was the most significantly different from the control primarily in the ester, alcohol and terpene profile. The KA–SC sequential fermentation had the highest amount of volatile acidity, and the PK–SC sequential fermentation had a relatively high amount of acetaldehyde and a few esters. The MP–SC sequential fermentation also revealed a higher concentration of several esters. The TD–SC sequential fermentation was notable for its lack of a distinct pattern in comparison with that of the other fermentations.Given these characteristics, the LT–SC sequential fermentation showed the most potential for increased chemical complexity of the Shiraz volatile profile.The results demonstrate that there is no clear, singular trend for how different, non-Saccharomycesspecies of yeast – once thought to be wholly unfavourable in wine fermentations – will impact wine chemistry, flavour or quality. Each species presents unique metabolic characteristics, many of which could be beneficial, and their potential application in the wine industry should be considered.

Whitener MEB et al (2017) Australian Journal of Grape and Wine Research (in press) DOI: 10.1111/ajgw.12269

 

Impact of sequential co-culture fermentations on flavour characters of Solaris wines

Nowadays, the use of non-Saccharomyces yeasts in combination with Saccharomyces cerevisiae is being recognised to enhance the analytical composition of the wines. The aim of this work was to evaluate the influence of indigenous non-Saccharomyces yeasts on the flavour character of wines from the cool-climate grape cultivar Solaris in Denmark. The volatile and non-volatile compounds as well as the sensory properties of wines were evaluated. Solaris wines with Hanseniaspora uvarum sequentially inoculated with S. cerevisiae produced a larger amount of glycerol as well as heptyl acetate and 2-phenylethyl acetate. This co-culture fermentation also produced higher amounts of ethyl acetate and acetic acid, reducing the possibility of its use in winemaking. Three Metschnikowia strains, a M. chrysoperlae strain and two M. fructicola strains, gave a comparable production of volatile compounds. These wines were characterised by several floral and fruity attributes. The Metschnikowia strains turned out to be promising in winemaking from Solaris grapes.

Liu J et al (2017) European Food Research and Technology 243:437-445

 

Influence of different yeast/lactic acid bacteria combinations on the aromatic profile of red Bordeaux wine

The typical fruity aroma of red Bordeaux wines depends on the grape variety but also on microbiological processes, such as alcoholic and malolactic fermentations. These transformations involve respectively the yeast Saccharomyces cerevisiae and the lactic acid bacteria Oenococcus oeni. Both species play a central role in red winemaking but their quantitative and qualitative contribution to the revelation of the organoleptic qualities of wine has not yet been fully described. The aim of this study was to elucidate the influence of sequential inoculation of different yeast and bacteria strains on the aromatic profile of red Bordeaux wine. All microorganisms completed fermentations and no significant difference was observed between tanks regarding the main oenological parameters until 3 months’ aging. Regardless of the yeast strain, B28 bacteria required the shortest period to completely degrade the malic acid, compared to the other strain. . Quantification of 73 major components highlighted a specific volatile profile corresponding to each microorganism combination. However, the yeast strain appeared to have a predominant effect on aromatic compound levels, as well as on fruity aroma perception. Yeasts had a greater impact on wine quality and have more influence on the aromatic style of red wine than bacteria.

Gammacurta M et al (2017) Journal of the Science of Food and Agriculture (in press) DOI: 10.1002/jsfa.8272

 

Selected yeasts to enhance phenolic content and quality in red wine from low pigmented grapes

The aim of this work was to enhance—by yeast activity—the quality of red wine produced from black grapes of the Calabrian Gaglioppo variety, used as a model for grapes with reduced synthesis of anthocyanins. Six selected strains of Saccharomyces cerevisiae were used to control winemaking trials. Among the wines, there are significant differences, due to the wine starter used. The following technological parameters were significantly different from strain to strain: total acidity, alcoholic degree, tartaric, malic, lactic, and acetic acid, and free and total SO2; moreover, the following phenolic parameters were significantly different from strain to strain: A420, A520, A620, colour intensity, colour hue, Folin–Ciocalteu index, percentage of DPPH inactivation, total anthocyanins, total polyphenols (A280), total tannins, delphinidin-3-glucoside, cyanidin-3-glucoside, petunidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside. From a sensory standpoint, significant differences were observed among wine samples during a short bottle aging. Data validate the main role that wine yeast selection plays in enhancing the quality of red wine from low pigmented grape.

Caridi A et al (2017) European Food Research and Technology 243 :367-378

 

Aroma precursors in grapes and wine: Flavor release during wine production and consumption

Pioneering investigations into precursors to fruity and floral flavors established the importance of terpenoid and C13-norisoprenoid glycosides to the flavor of aromatic wines. Nowadays flavor precursors in grapes and wine are known to be structurally diverse, encompassing glycosides; amino acid conjugates; odorless volatiles; hydroxycinnamic acids and many others. Flavor precursors mainly originate in the grape berry, but also from oak or other materials involved in winemaking. Flavors are released from precursors during crushing and subsequent production steps by enzymatic and non-enzymatic transformations, via microbial glycosidases; esterases; C-S lyases and decarboxylases; and through acid catalysed hydrolysis and chemical rearrangements. Flavors can also be liberated from glycosides and amino acid conjugates by oral microbiota. Hence, it is increasingly likely that flavor precursors contribute to retronasal aroma formation through in-mouth release during consumption, prompting a shift in focus from identifying aroma precursors in grapes to understanding aroma precursors present in bottled wine.

Parker M et al (2017) Journal of Agricultural and Food Chemistry (in press) DOI: 10.1021/acs.jafc.6b05255

The Monthly Digest – February 2017

Biosynthesis of eight-carbon volatiles from tomato and pepper pomaces by fungi: Trichoderma atroviride and Aspergillus sojae

The aim of this study was to investigate the possibility of using tomato and red pepper pomaces for the production eight-carbon volatiles by Trichoderma atroviride and Aspergillus sojae. The fermentation of tomato and pepper pomace-based media by both moulds was conducted in shake flasks and bioreactors. Microbial growth behaviours and fermentation abilities of T. atroviride and A. sojae under both fermentation conditions were followed by microbial counting. The production of flavours from tomato and pepper pomaces by fungal metabolism was determined by gas chromatography–olfactometry, gas chromatography–mass spectrometry and sensory analysis. The results showed that T. atroviride grew faster than A. sojae, and the survival of T. atroviride in the tomato pomace was longer than that of A. sojae. However, T. atroviride grew slower than A. sojae in the pepper pomace. Eight-carbon flavour compounds, including (Z)-1,5-octadien-3-ol, 1-octen-3-ol, (E)-2-octenal and (E)-2-octenol, were produced by T. atroviride and A. sojae from the tomato and pepper pomaces. The highest production levels (265.55 ± 2.79 and 187.47 ± 0.92 μg kg−1) were observed for 1-octen-3-ol in the tomato fermentation by T. atroviride and A. sojae, respectively. The relationships between volatile compounds and their flavour characteristics in tomato and pepper pomaces were analysed using principal component analysis.

Güneser O and Yüceer YK (2017) Journal of Bioscience and Bioengineering (in press)

The role of immobilized rennet on carbon cloth in flavor development during ripening of Gouda cheese

Rennet-free Gouda (RFG) cheese was prepared to investigate the influence of rennet on the non-volatile and volatile profiles of cheese and was characterized by HPLC and GC/MS analyses. Chymosin, a major protease in rennet, was immobilized onto oxidized and chemically modified carbon cloth. The chymosin immobilization efficiency was 60.4%, and the milk-clotting activity used as an index of the stability of the immobilized chymosin decreased by around 20% in 2 weeks. However, the activity was maintained at 70–80% from 2 weeks to 32 weeks and was more stable than that of chymosin solution alone. Non-volatile (organic acids) and volatile profiles of the RFG cheese and rennet-containing normal Gouda cheese were not significantly different during ripening with a few exceptions. Therefore, it can be concluded that cheese flavor is developed by lactic acid fermentation, irrespective of the presence of rennet.

Jeong SH et al (2016) Food Science and Biotechnology 25:1561-1567

Flavor improvement of fermented soy sauce by extrusion as soybean meal pretreatment

Flavor, an important index of soy sauce quality, includes odor and taste which mainly depend on volatile compounds and amino acids. Soy sauce made from extruded mixture of soy meal and flour (EMSF) was employed in fermentation to improve the flavor of final product. Combination of Headspace solid phase microextraction (HS-SPME) and GC-MS was employed to identify the volatile compounds, 40 volatile compounds were identified in soy sauce made from EMSF and 24 volatile compounds in soy sauce made form cooked mixture of soy meal and flour (CMSF). Pyrazines and their derivatives occupied one-third of the total content of volatile compounds. Both samples had the same amino acid number, while total content of amino acids and contents of 15 kinds of amino acids in soy sauce made from EMSF were significantly higher than CMSF. Extrusion had the advantage in low cost and capability of continuous processing, extruded mixture of soy meal and flour were used in soy sauce fermentation. Content of amino acids was improved by extrusion, this pretreatment method also increased volatile compounds of soy sauce and produced more desirable flavor and taste soy sauce.

Zhang DJ et al (2017) Journal of Food Processing and Preservation (in press)

Aroma compounds and characteristics of noble-rot wines of chardonnay grapes artificially botrytized in the vineyard

Aroma characteristics and their impact volatile components of noble-rot wines elaborated from artificial botrytized Chardonnay grapes, obtained by spraying Botrytis cinerea suspension in Yuquan vineyard, Ningxia, China, were explored in this work. Dry white wine made from normal-harvested grapes and sweet wine produced from delay-harvested grapes were compared. Wine aromas were analysed by trained sensory panelists, and aroma compounds were determined by SPME-GC-MS. Results indicated that esters, fatty acids, thiols, lactones, volatile phenols and 2-nonanone increased markedly in noble-rot wines. In addition to typical aromas of noble-rot wines, artificial noble-rot wines were found to contain significant cream and dry apricot attributes. Partial Least-Squares Regression models of aroma characteristics against aroma components revealed that non-fermentative odorants were the primary contributor to dry apricot attribute, especially, thiols, C13-norisoprenoids, lactones, terpenols and phenolic acid derivatives, while cream attribute was dependent on both fermentative and non-fermentative volatile components. Chemical compounds studied in the article: 2-nonanone (PubChem: 13187); ethyl 4-hydroxybenzoate (PubChem: 8434); ethyl isovalerate (PubChem: 7945); α-terpineol (PubChem: 17100); isopentanoic acid (PubChem: 3085367); 3-methyl-3-sulfanyl butanol (PubChem: 520682); 3-sulfanylhexanol (PubChem: 521348); γ-nonalactone (PubChem: 7710); γ-decalactone (PubChem: 12813); phenyl acetic acid (PubChem: 999)

Wang XJ et al (2017) Food Chemistry (in press)

Genetic and phenotypic intraspecific variability of non-Saccharomyces yeasts populations from La Rioja winegrowing region (Spain)

To determine the intraspecific genetic diversity within five non-Saccharomyces yeast species and the diversity in phenotypic characteristic related to their technological properties. Seventy-one non-Saccharomyces yeasts isolated from different fermentations and facilities of the DOCa Rioja (Spain) belonging to five different wine species (Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, Zygosaccharomyces bailii and Williopsis pratensis) were subjected to clonal characterization by RAPD-PCR, which evidenced wide diversity between them. They were also submitted to a screening for some oenological traits related to the improvement of the aroma of the wine and yeast development in musts. Strains within the same species showed different enzyme activities, tolerated different levels of SO2 and possessed different killer phenotypes. These characteristics made them adjust better or worse to specific vinification processes or wine quality criteria.

A significant genetic and phenotypic variation within the non-Saccharomyces species studied was found, which makes necessary to carry out a selection process in each one. Williopsis pratensis, a species that has not been thoroughly explored, may deserve further consideration for oenological applications. Due to the wide range of variation within species, the strains adaptation to the SO2 levels in musts has to be taken into account in selection processes.

  1. González-Arenzana et al (2017) Journal of Applied Microbiology 122:378-388
Effect of sequential fermentations and grape cultivars on volatile compounds and sensory profiles of Danish wines

There has been increasing interest in the use of selected non-Saccharomyces yeasts in co-culture with Saccharomyces cerevisiae. In this work, three non-Saccharomyces yeast strains (Metschnikowia viticola, Metschnikowia fructicola and Hanseniaspora uvarum) indigenously isolated in Denmark, were used in sequential fermentations with S. cerevisiae on three cool-climate grape cultivars Bolero, Rondo and Regent. During the fermentations, the yeast growth was determined as well as key oenological parameters, volatile compounds and sensory properties of finished rosé wines. The different non-Saccharomyces strains and cool-climate grape cultivars produced wines with a distinctive aromatic profile. A total of 67 volatile compounds were identified, including 43 esters, 14 alcohols, 5 acids, 2 ketones, a C13-norisoprenoid, a lactone and a sulphur compound. The use of M. viticola in sequential fermentation with S. cerevisiae resulted in richer berry and fruity flavours in wines. However, the sensory plot showed a more clear separation among wine samples by grape cultivars compared with yeast strains. Knowledge on the influence of indigenous non-Saccharomyces strains and grape cultivars on the flavor generation contributed to producing diverse wines in the cool-climate wine regions.

Liu J et al (2017) Journal of the Science of Food and Agriculture (in press)

Linking wine lactic acid bacteria diversity with wine aroma and flavour

In the last two decades knowledge on lactic acid bacteria (LAB) associated with wine has increased considerably. Investigations on genetic and biochemistry of species involved in malolactic fermentation, such as Oenococcus oeni and of Lactobacillus have enabled a better understand of their role in aroma modification and microbial stability of wine. In particular, the use of molecular techniques has provided evidence on the high diversity at species and strain level, thus improving the knowledge on wine LAB taxonomy and ecology. These tools demonstrated to also be useful to detect strains with potential desirable or undesirable traits for winemaking purposes. At the same time, advances on the enzymatic properties of wine LAB responsible for the development of wine aroma molecules have been undertaken. Interestingly, it has highlighted the high intraspecific variability of enzymatic activities such as glucosidase, esterase, proteases and those related to citrate metabolism within the wine LAB species. This genetic and biochemistry diversity that characterizes wine LAB populations can generate a wide spectrum of wine sensory outcomes. This review examines some of these interesting aspects as a way to elucidate the link between LAB diversity with wine aroma and flavour. In particular, the correlation between inter- and intra-species diversity and bacterial metabolic traits that affect the organoleptic properties of wines is highlighted with emphasis on the importance of enzymatic potential of bacteria for the selection of starter cultures to control MLF and to enhance wine aroma.

Cappello MS et al (2017) International Journal of Food Microbiology 243 :16-27

Effect of mixed yeast starter on volatile flavor compounds in Chinese rice wine during different brewing stages

The volatile compounds of Chinese rice wine fermented by Saccharomyces cerevisiae FC 15 and S. cerevisiae BR 30 and their combination (MIX) were investigated. The results showed that the wines fermented with different starters differed mainly in the numbers of alcohols and esters. Furthermore, the amounts of volatile compounds among three starters were also obviously different. After clarification, the loss of esters was greater than that of alcohols and aldehydes, whereas after sterilization, the loss of aldehydes was the greatest. PCA showed diethyl succinate to be the key flavor component. Moreover, short-chain fatty acid ethyl esters were main flavor substances during fermentation, whereas long-chain fatty acid ethyl esters were typical compounds after clarification and sterilization. Analysis of the ratio of higher alcohols to esters showed that BR 30 wine presented a stronger ester aroma than MIX wine, whereas FC 15 wine exhibited an outstanding alcohol flavor. Sensory evaluation indicated that FC 15 wine was intense in alcohol-aroma, whereas BR 30 wine exhibited high levels of cereal-aroma. Furthermore, both MIX and BR 30 wine were highly assessed in continuation and full body mouth-feel. It means that flavor characteristic of Chinese rice wine could be adjust by combination of yeast starters.

Yang Y et al (2017) LWT – Food Science and Technology 78:373-381

A grapevine cytochrome P450 generates the precursor of wine lactone, a key odorant in wine

Monoterpenes are important constituents of the aromas of food and beverages, including wine. Among monoterpenes in wines, wine lactone has the most potent odor. It was proposed to form via acid-catalyzed cyclization of (E)-8-carboxylinalool during wine maturation. It only reaches very low concentrations in wine but its extremely low odor detection threshold makes it an important aroma compound.

Using LC-MS/MS, we show here that the (E)-8-carboxylinalool content in wines correlates with their wine lactone content and estimate the kinetic constant for the very slow formation of wine lactone from (E)-8-carboxylinalool. We show that (E)-8-carboxylinalool is accumulated as a glycoside in grape (Vitis vinifera) berries and that one of the cytochrome P450 enzymes most highly expressed in maturing berries, CYP76F14, efficiently oxidizes linalool to (E)-8-carboxylinalool.

Our analysis of (E)-8-carboxylinalool in Riesling × Gewurztraminer grapevine progeny established that the CYP76F14 gene co-locates with a quantitative trait locus for (E)-8-carboxylinalool content in grape berries.

Our data support the role of CYP76F14 as the major (E)-8-carboxylinalool synthase in grape berries and the role of (E)-8-carboxylinalool as a precursor to wine lactone in wine, providing new insights into wine and grape aroma metabolism, and new methods for food and aroma research and production.

Ilc et al (2017) New Phytologist

Optimization of the production of 1-phenylethanol using enzymes from flowers of tea (Camellia sinensis) plants

1-Phenylethanol (1PE) can be used as a fragrance in food flavoring and cosmetic industries and as an intermediate in the pharmaceutical industry. 1PE can be synthesized from acetophenone, and the cost of 1PE is higher than the cost of acetophenone. Therefore, it is important to establish an effective and low-cost approach for producing 1PE. Our previous studies found that tea (Camellia sinensis) flowers, which are an abundant and waste resource, contained enzymes that could transform acetophenone to 1PE. In the present study, we extracted crude enzymes from tea flowers and optimized the production conditions of 1PE using response surface methodology. The optimized conditions were an extraction pH of 7.0, a reaction pH of 5.3, a reaction temperature of 55 °C, a reaction time of 100 min, a coenzyme NADPH concentration of 3.75 μmol/mL in the reaction assay, and a substrate acetophenone concentration of 1.25 μmol/mL in the reaction assay. The results provide essential information for future industrial 1PE production using plant-derived enzymes.

Dong F et al (2017) Molecules 22(1):131; doi:10.3390/molecules22010131

Bioengineering of the plant culture of Capsicum frutescens with vanillin synthase gene for the production of vanillin

Production of vanillin by bioengineering has gained popularity due to consumer demand toward vanillin produced by biological systems. Natural vanillin from vanilla beans is very expensive to produce compared to its synthetic counterpart. Current bioengineering works mainly involve microbial biotechnology. Therefore, alternative means to the current approaches are constantly being explored. This work describes the use of vanillin synthase (VpVAN), to bioconvert ferulic acid to vanillin in a plant system. The VpVAN enzyme had been shown to directly convert ferulic acid and its glucoside into vanillin and its glucoside, respectively. As the ferulic acid precursor and vanillin were found to be the intermediates in the phenylpropanoid biosynthetic pathway of Capsicum species, this work serves as a proof-of-concept for vanillin production using Capsicum frutescens (C. frutescens or hot chili pepper). The cells of C. frutescens were genetically transformed with a codon optimized VpVAN gene via biolistics. Transformed explants were selected and regenerated into callus. Successful integration of the gene cassette into the plant genome was confirmed by polymerase chain reaction. High-performance liquid chromatography was used to quantify the phenolic compounds detected in the callus tissues. The vanillin content of transformed calli was 0.057% compared to 0.0003% in untransformed calli.

Yang Chee MJ et al (2017) Molecular Biotechnology 59:1-8

The Monthly Digest – January 2017

Novel umami ingredients: Umami peptides and their taste

Umami substances are very important for food seasoning and healthy eating. In addition to monosodium glutamate and some nucleotides, recent investigations have revealed that several peptides also exhibit umami taste. In recent years, 52 peptides have been reported to show umami taste, including 24 dipeptides, 16 tripeptides, 5 octapeptides, 2 pentapeptides, 2 hexapeptides, 1 tetrapeptide, 1 heptapeptide, and 1 undecapeptide. Twenty of these peptides have been examined for the present of umami taste. In this review, we have listed these umami peptides based on their category, source, taste, and threshold concentration. The evidence for peptides showing umami taste, the umami taste receptors on the human tongue, and the peptides whose umami taste is controversial are also discussed.
Zhang Y et al (2016) Journal of Food Science DOI: 10.1111/1750-3841.13576

 

Influence of yeast and lactic acid bacterium on the constituent profile of soy sauce during fermentation

Soy sauce is a Japanese traditional seasoning composed of various constituents that are produced by various microbes during a long-term fermentation process. Due to the complexity of the process, the investigation of the constituent profile during fermentation is difficult. Metabolomics, the comprehensive study of low molecular weight compounds in biological samples, is thought to be a promising strategy for deep understanding of the constituent contribution to food flavor characteristics. Therefore, metabolomics is suitable for the analysis of soy sauce fermentation. Unfortunately, only few and unrefined studies of soy sauce fermentation using metabolomics approach have been reported. Therefore, we investigated changes in low molecular weight hydrophilic and volatile compounds of soy sauce using gas chromatography/mass spectrometry (GC/MS)-based non-targeted metabolic profiling. The data were analyzed by statistical analysis to evaluate influences of yeast and lactic acid bacterium on the constituent profile. Consequently, our results suggested a novel finding that lactic acid bacterium affected the production of several constituents such as cyclotene, furfural, furfuryl alcohol and methional in the soy sauce fermentation process.
Harada R et al (2017) Journal of Bioscience and Bioengineering (in press)

 

Use of Torulaspora delbrueckii and Saccharomyces cerevisiae in semi-industrial sequential inoculation to improve quality of Palomino and Chardonnay wines in warm climates

We have evaluated for the first time the impact of two commercial yeast strains (Torulaspora delbrueckii TD291 and Saccharomyces cerevisiae QA23) inoculated sequentially in musts of Chardonnay and Palomino fino grape varieties grown under warm climate (South West of Spain). Semi-industrial scale alcoholic fermentations were performed during the 2011 and 2012 harvests. Implantation analyses demonstrated that T. delbrueckii became the predominant strain until the end of the alcoholic fermentation phase. Wines with sequential inoculation resulted in the production of low levels of acetic acid (which gives wine an undesirable ‘vinegary’ character), low acetaldehyde in Chardonnay and high in Palomino wines. The most salient attributes that contribute to the quality of the Chardonnay and Palomino wines produced were aroma intensity, fresh and tropical fruit character. This study demonstrated that sequential inoculation of T. delbrueckii and S. cerevisiae contribute significantly to the improvement of Chardonnay wine aromas and the creation of new styles of wine for Palomino. This study has generated new knowledge about the biotechnological potential of T. delbrueckii (TD219) and S. cerevisiae (QA23) for improving the organoleptic properties of Chardonnay and Palomino wines.
Puertas B et al (2017) Journal of Applied Microbiology (in press) DOI: 10.1111/jam.13375

 

Screening of Bacillus strains from Luzhou-flavor liquor making for high-yield ethyl hexanoate and low-yield propanol

This study aimed at isolating and culturing Bacilli from the omagari, pit mud, and fermented grains used in Luzhou-flavor liquor in an effort to produce better flavor and quality. After an enrichment culture of Bacillus in the omagari, pit mud, and fermented grains of Luzhou-flavor liquor, 52 total strains were obtained. Based on the standard of producing high-yield ethyl hexanoate and low-yield propanol, one strain named YB-1 was screened out. It was shown that YB-1 produced ethyl hexanoate at 214.7 mg/100 mL and propanol at 0 mg/100 mL. Based on strain morphology, and physiological and biochemical characteristics, YB-1 was identified as Bacillus. According to DNA sequencing and the constructed phylogenetic tree, YB-1 and Bacillus cereus strain CCM 2010 clustered into a branch and were each other’s closest relatives. Thus, YB-1 was identified as Bacillus cereus. Through this research, it is expected that the application of Bacillus cereus strain YB-1 to the traditional brewing process of Luzhou-flavor liquor could improve the flavor and quality, and enrich microbial resources for Luzhou-flavor liquor fermentation.
Zhao CQ et al (2017) LWT – Food Science and Technology 77:60-66

 

Modulation of the volatile and non-volatile profiles of coffee fermented with Yarrowia lipolytica: I. Green coffee

Yeast starter cultures have been used in the fermentation of different coffee substrates to modulate the volatile and aroma profiles of coffees with the exception of green coffee beans. This two-part study aimed to modulate the volatile profiles of roasted coffee via the fermentation of green coffee beans with a non-conventional aerobic yeast Yarrowia lipolytica. The objective of part I of this study was to evaluate the effects of Y. lipolytica fermentation on the volatile and non-volatile profiles of green coffee beans. After fermentation, sugars concentration decreased by 1.2-fold while the amino and phenolic acids concentrations decreased by 1.3-fold. The decrease in phenolic acid concentration could account for the 1.5-fold increase in the volatile phenols levels resulting from phenolic acid catabolism. The degradation of L-phenylalanine via the Ehrlich pathway by the yeast led to a 1.9-fold increase in 2-phenylethanol levels, whereas the decreases in alkanes, acids and aldehydes levels were attributed to the hydrophobic substrate metabolizing pathways that were unique to Y. lipolytica. Hence, this work showed that Y. lipolytica fermentation of green coffee beans resulted in the modification of the aroma precursors and volatile composition of green coffees.
Lee LW et al (2017) LWT – Food Science and Technology 77:225-232

 

Cocoa fermentation: Microbial identification by MALDI-TOF MS, and sensory evaluation of produced chocolate

Dynamic microbial over the cocoa fermentation using starter culture and the effect sensory characteristics of chocolate produced were investigated. The cocoa fermentation inoculated with Saccharomyces cerevisiae CCMA0681 and Lactobacillus fermentum UFLA CHBB 8.12 as starter cultures were assessed, and compared with spontaneous fermentation. The microbial succession was identified using polyphasic approach including classical morphological and biochemical assays, and Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF). Overall 873 colonies were isolated, 445 (51%) strains were isolated from the spontaneous fermentation, while 428 (49%) strains were isolated from the inoculated fermentation. The dominant yeast in both fermentation processes were S. cerevisiae and Candida magnolia. L. fermentum and Pediococcus acidilactici were detected in both fermentations, whereas L. coryniformis, L. curvatus, L. mali, L. plantarum, and L. sakei were isolated from the spontaneous fermentation only. Acinetobacter sp., Gluconobacter oxydans, and Acetobacter pasteurianus were isolated from both the fermentation processes. Chocolate produced from the spontaneous fermentative process presented dominance of the bitter flavour, while obtained through inoculated fermentation process presented bitter, astringent and acid as dominant flavours. Cocoa inoculation with S. cerevisiae and L. fermentum affected the sensory quality of the produced chocolate. The microbial inoculation influenced on fermentation and therefore the final product. Da Cruz Pedrozo Miguel MG et al (2017) LWT – Food Science and Technology 77:362-369

 

Biotechnological production of vanillin using immobilized enzymes

Vanillin is an important and popular plant flavor, but the amount of this compound available from plant sources is very limited. Biotechnological methods have high potential for vanillin production as an alternative to extraction from plant sources. Here, we report a new approach using immobilized enzymes for the production of vanillin. The recently discovered oxygenase Cso2 has coenzyme-independent catalytic activity for the conversion of isoeugenol and 4-vinylguaiacol to vanillin. Immobilization of Cso2 on Sepabeads EC-EA anion-exchange carrier conferred enhanced operational stability enabling repetitive use. This immobilized Cso2 catalyst allowed 6.8 mg yield of vanillin from isoeugenol through ten reaction cycles at a 1 ml scale. The coenzyme-independent decarboxylase Fdc, which has catalytic activity for the conversion of ferulic acid to 4-vinylguaiacol, was also immobilized on Sepabeads EC-EA. We demonstrated that the immobilized Fdc and Cso2 enabled the cascade synthesis of vanillin from ferulic acid via 4-vinylguaiacol with repetitive use of the catalysts. This study is the first example of biotechnological production of vanillin using immobilized enzymes, a process that provides new possibilities for vanillin production.
Furuya T et al (2017) Journal of Biotechnology (in press)

 

Novel brewing yeast hybrids: creation and application

The natural interspecies Saccharomyces cerevisiae × Saccharomyces eubayanus hybrid yeast is responsible for global lager beer production and is one of the most important industrial microorganisms. Its success in the lager brewing environment is due to a combination of traits not commonly found in pure yeast species, principally low-temperature tolerance, and maltotriose utilization. Parental transgression is typical of hybrid organisms and has been exploited previously for, e.g., the production of wine yeast with beneficial properties. The parental strain S. eubayanus has only been discovered recently and newly created lager yeast strains have not yet been applied industrially. A number of reports attest to the feasibility of this approach and artificially created hybrids are likely to have a significant impact on the future of lager brewing. De novo S. cerevisiae × S. eubayanus hybrids outperform their parent strains in a number of respects, including, but not restricted to, fermentation rate, sugar utilization, stress tolerance, and aroma formation. Hybrid genome function and stability, as well as different techniques for generating hybrids and their relative merits are discussed. Hybridization not only offers the possibility of generating novel non-GM brewing yeast strains with unique properties, but is expected to aid in unraveling the complex evolutionary history of industrial lager yeast.
Krogerus et al (2017) Applied Microbiology and Biotechnology 101:65-78

The Monthly Digest – December 2016

Formation of taste-active amino acids, amino acid derivatives and peptides in food fermentations – A review

Fermented foods are valued for their rich and complex odour and taste. The metabolic activity of food-fermenting microorganisms determines food quality and generates odour and taste compounds. This communication reviews the formation of taste-active amino acids, amino acid derivatives and peptides in food fermentations. Pathways of the generation of taste compounds are presented for soy sauce, cheese, fermented meats, and bread. Proteolysis or autolysis during food fermentations generates taste-active amino acids and peptides; peptides derived from proteolysis particularly impart umami taste (e.g. α-glutamyl peptides) or bitter taste (e.g. hydrophobic peptides containing proline). Taste active peptide derivatives include pyroglutamyl peptides, γ-glutamyl peptides, and succinyl- or lactoyl amino acids. The influence of fermentation microbiota on proteolysis, and peptide hydrolysis, and the metabolism of glutamate and arginine is well understood, however, the understanding of microbial metabolic activities related to the formation of taste-active peptide derivatives is incomplete. Improved knowledge of the interactions between taste-active compounds will enable the development of novel fermentation strategies to develop tastier, less bitter, and low-salt food products, and may provide novel and “clean label” ingredients to improve the taste of other food products.

Zhao CJ et al (2016) Food Research International 89:39–47

 

Contribution of 2-methyl-3-furanthiol to the cooked meat-like aroma of fermented soy sauce

The cooked meat-like aroma compound, 2-methyl-3-furanthiol (2M3F), was detected in fermented soy sauce (FSS) by GC-olfactometry and GC-MS. 2M3F was present in FSS at a concentration considerably greater than the perception threshold, and the 2M3F concentration increased with heating temperature. Sensory analysis indicated that with the addition of only 0.2 μg/L of 2M3F to the soy sauce sample, the cooked meat-like aroma is significantly stronger than that of sample without the addition of 2M3F. Hence, 2M3F contributes to the cooked meat-like aroma of FSS, which constitutes the key aroma component of FSS. In addition, 2M3F was generated from the addition of ribose and cysteine in FSS by heating at 120 °C, but it was not detected in a phosphate buffer under the same condition. Furthermore, 2M3F was not detected in acid-hydrolyzed vegetable-protein-mixed soy sauce (ASS) and heated ASS. These results indicated that fermentation by micro-organisms facilitates the generation of 2M3F in FSS. 2-methyl-3-furanthiol (2M3F) contributes to the cooked meat-like aroma of fermented soy sauce, and this compound is a very important aroma component of fermented soy sauce.

Meng Q et al (2017) Bioscience, Biotechnology and Biochemistry 81: 168-172

 

Microbial communities related to sensory attributes in Korean fermented soy bean paste (doenjang)

Various microbial communities play a role in generating the distinctive sensory characteristics of the traditional Korean soybean paste, doenjang. The objective of this study was to investigate the relationship between sensory characteristics and microbial communities in traditional doenjang. The results of the descriptive analysis revealed that some traditional doenjang (T1–T11) exhibited distinctive characteristics, such as fish sauce flavor, meju, bitterness, sourness, and saltiness, whereas the modified samples (M1–M3) demonstrated sweetness, umami, and an alcohol odor. According to the metagenomic analysis based on 16S rRNA gene sequencing, the phylum Firmicutes was the dominant bacterium in most doenjang. At the genus level, lactic acid bacteria (LAB) were frequently found in most doenjang. Among these LAB, the major genera of bacteria were Tetragenococcus in M2 (60.30%), T3 (91.20%), T8 (48.60%), and T9 (60.90%); Enterococcus in T1 (29.40%), T4 (34.10%), and T10 (50.50%); Leuconostoc in T7 (89.10%); and Lactobacillus in T9 (38.3%). The most frequently occurring non-LAB was Bacillus in M3 (50.10%), T5 (46.50%), and T6 (20.50%), and M1 and T2 contained Staphylococcus and Ochrobactrum as their major non-LAB, respectively. The results of a correlation analysis between the sensory attributes from the descriptive analysis and the microbial communities from 454 pyrosequencing provided an overview for the relationship between sensory characteristics and microbial communities. Ochrobactrum, Stenotrophomonas, Rhodobacteraceae, Proteus, and Luteimonas were found in samples that had a strong fish sauce characteristic. The presence of LAB Tetragenococcus, Enterococcus, Pediococcus, Carnobacterium, and Weissella—was related to sourness. Enterococcus and Enterobacter were found in samples with a matured flavor and a soft mouthfeel, respectively. The overall results of the study demonstrate that microbial communities found in doenjang were closely related to distinct sensory attributes.

Kim MJ et al (2016) Food Research International 89:724-732

 

Contribution of 2-methyl-3-furanthiol to the cooked meat-like aroma of fermented soy sauce

The cooked meat-like aroma compound, 2-methyl-3-furanthiol (2M3F), was detected in fermented soy sauce (FSS) by GC-olfactometry and GC-MS. 2M3F was present in FSS at a concentration considerably greater than the perception threshold, and the 2M3F concentration increased with heating temperature. Sensory analysis indicated that with the addition of only 0.2 μg/L of 2M3F to the soy sauce sample, the cooked meat-like aroma is significantly stronger than that of sample without the addition of 2M3F. Hence, 2M3F contributes to the cooked meat-like aroma of FSS, which constitutes the key aroma component of FSS. In addition, 2M3F was generated from the addition of ribose and cysteine in FSS by heating at 120 °C, but it was not detected in a phosphate buffer under the same condition. Furthermore, 2M3F was not detected in acid-hydrolyzed vegetable-protein-mixed soy sauce (ASS) and heated ASS. These results indicated that fermentation by micro-organisms facilitates the generation of 2M3F in FSS. 2-methyl-3-furanthiol (2M3F) contributes to the cooked meat-like aroma of fermented soy sauce, and this compound is a very important aroma component of fermented soy sauce.

Meng Q et al (2016) Bioscience, Biotechnology and Biochemistry In press

 

The effects of pre-fermentative addition of oenological tannins on wine components and sensorial qualities of red wine

Today in the wine industry, oenological tannins are widely used to improve wine quality and prevent oxidation in wine aging. With the development of tannin products, new oenological tannins are developed with many specific functions, such as modifying antioxidant effect, colour stabilization and aroma modifications. The aim of this work is to investigate effects of pre-fermentative addition of oenological tannins on wine colour, anthocyanins, volatile compounds and sensorial properties. In this case, Syrah juice was extracted with classic flash thermovinification from fresh must in order to release more colour and tannins. Three types of oenological tannins, which are, respectively, derived from grape skin, seed (Vitis vinifera) and French oak (Quercus robur and Querrus petraea), were selected to carry out the experiments with seven treatments. Results indicated that tannin treatments significantly improved wine aroma complexity and sensorial properties. However, the concentration of some stable pigments such as Vitisin A, Vitisin A-Ac and Vitisin B was negatively affected by tannin additions. Nevertheless, by means of cluster analysis and principal component analysis, it was observed that higher alcohols were significantly promoted by grape seed tannin while most anthocyanins can be improved by addition of grape tannins. In conclusion, low amount of oenological tannin derived from grape seed is a promising method to be applied especially for young red wine making.

Chen K et al (2016) Molecules 21(11), 1445; doi:10.3390/molecules21111445

 

3-Sulfanyl-4-methylpentan-1-ol in dry-hopped beers: First evidence of glutathione S-conjugates in hop (Humulus lupulus L.)

Monovarietal dry-hopped beers were produced with the dual-purpose hop cultivars Amarillo, Hallertau Blanc, and Mosaic. The grapefruit-like 3-sulfanyl-4-methylpentan-1-ol was found in all three beers at concentrations much higher than expected on the basis of the free thiol content in hop. Even cysteinylated precursors proved unable to explain our results. As observed in wine, the occurrence of S-glutathione precursors was therefore suspected in hop. The analytical standards of S-3-(4-methyl-1-hydroxypentyl)glutathione, never described before, and of S-3-(1-hydroxyhexyl)glutathione, previously evidenced in grapes, were chemically synthesized. An optimized extraction of glutathionylated precursors was then applied to Amarillo, Hallertau Blanc, and Mosaic hop samples. HPLC-ESI(+)MS/MS revealed, for the first time, the occurrence of S-3-(1-hydroxyhexyl)glutathione and S-3-(4-methyl-1-hydroxypentyl)glutathione in hop, at levels well above those reported for their cysteinylated counterparts. S-3-(1-Hydroxyhexyl)glutathione emerged in all cases as the major adduct in hop. Yet, although 3-sulfanylhexan-1-ol seems relatively ubiquitous in free, cysteinylated, and glutathionylated forms, the glutathione adduct of 3-sulfanyl-4-methylpentan-1-ol, never evidenced in other plants up to now, was found only in the Hallertau Blanc variety.

Kankolongo Cibaka ML et al (2016) Journal of Agricultural and Food Chemistry 64:8572-8582

 

Contribution of predominant yeasts to the occurrence of aroma compounds during cocoa bean fermentation

Cocoa flavor is the most important organoleptic property according to chocolate consumers. Raw cocoa beans sourced from Ivory Coast are not known for their fine aroma quality. In the global framework of raw cocoa quality improvement, this study dealt with the determination and control of the conditions of the aroma compound formation and aimed to determine the potential contribution of yeast associated with the fermentation to the formation of sensory profiling for cocoa beans. Using the method of SPME–GC–MS, the potential for flavor contribution of some predominant yeasts isolated from cocoa fermentation assays performed around Abidjan and then grown on Sabouraud-chloramphenicol medium was determined. Also, the flavor precursor compounds of final corresponding raw cocoa bean samples prepared according to specific post-harvest processing were analyzed. A total of around ten species of yeast involved in cocoa fermentation but among them, six strains were namely identified as Saccharomyces cerevisiae, Candida tropicalis, Pichia kudriavzevii, Pichia galeiforms, Galactomyces geotrichum and Wickerhamomyces anomalus. These identified yeasts produced a total of 33 aroma compounds grouped into four families such as esters, alcohols, acids and others. Among all yeasts involved in fermentation performed in Abidjan, P. kudriavzevii, S. cerevisiae, G. geotrichum and W. anomalus could be considered as the most important contributors to the formation of cocoa specific aroma compounds. These cocoa aroma producing capacities of yeast isolates could be used to improve the sensory profiling raw cocoa beans or other fermented food stuffs. Furthermore some specific yeast isolates could be used as biological markers to predict the determining of chocolate sensorial characteristics and to indicate the geographical origin or processing story of cocoa bean batches.

Koumba Koné M et al. (2016) Food Research International 89:910-917

 

Improving the functional and sensorial profile of cereal-based fermented foods by selecting Lactobacillus plantarum strains via a metabolomics approach

Metabolomics was recently applied in food science for monitoring the quality, processing, safety, and microbiology of both raw materials and final products to improve the consumer’s health and confidence. The present work aimed at using a metabolomics approach to detect the flavour and antioxidant profiles characteristic of different Lactobacillus plantarum strains in sourdoughs of durum wheat and KAMUT® khorasan wheat. The study was developed to improve sensorial and functional properties of cereal-fermented foods through the selection of optimal flour-microbial strain combinations. A large set of metabolites, including volatile compounds, polyphenols and flavonoids, was taken into consideration and the antioxidant activity was determined. The metabolic profiles were combined by using heat maps to visualise the result of a hierarchical clustering of profile data. In KAMUT® khorasan wheat-fermented dough, a high correlation was found between a group of volatiles (5 alcohols, 6 carbonils, dodecanoic acid and 1,3-hexadiene) and the polyphenolic compounds gallic acid (GA), epigallocatechin-gallate (EGCG), epigallocatechin (EGC), flavonoids (Flav), protocathecuic acid (Prot ac) and total polyphenols (Polyp). In durum wheat dough a different pattern of volatile molecules (10 alcohols, 5 carbonils, 3 acids and 3 hydrocarbons) resulted highly correlated with EGC, EGCG, Flav and Polyp. The results also evidenced a simultaneous increase of sensorial and health promoting compounds when using L. plantarum strains 98A and 6BHI in fermented durum wheat dough, while 94A and 206 strains had their highest performance with KAMUT® khorasan wheat dough. Our data show that metabolomics may represent an important tool for the rapid selection of strain/substrate combinations to simultaneously increase sensorial and health beneficial characteristics.

Ferri M et al (2016) Food Research International 89:1095-1105

 

Agrowaste to vanillin conversion by a natural Pediococcus acidilactici strain BD16

Owing to its flavoring, antimicrobial, antioxidant and anticarcinogenic nature, vanillin is widely used in foods, beverages, perfumes and pharmaceutical products. Ferulic acid (FA) is an important precursor of vanillin which is abundant in cereals like maize, rice and wheat and sugar beet. A major drawback of microbial vanillin production from FA is the degradation and biotransformation of toxic vanillin to other phenolic derivatives. The present study is undertaken to explore microbial vanillin production from FA precursor rice bran by employing vanillin-resistant Pediococcus acidilactici BD16, a natural lactic acid bacteria isolate. Extracellular, intracellular and cellular vanillin dehydrogenase activity was found least, which was minimized vanillin degradation, and the strain resists more than 5 g L−1 vanillin in the medium. A metabolomics approach was followed for the detection of FA, vanillin and other metabolites generated during fermentation of rice bran medium. A metabolic pathway was also predicted for vanillin biosynthesis. Approximately 1.06 g L−1 of crude vanillin was recovered from rice-bran-containing medium and this further offers scope for the industrial utilization of the organism and its genetic manipulation to enhance production of biovanillin. Owing to its flavoring, antimicrobial, antioxidant and anticarcinogenic nature, vanillin is widely used in foods, beverages, perfumes and pharmaceutical products. Ferulic acid (FA) is an important precursor of vanillin which is abundant in cereals like maize, rice and wheat and sugar beet. A major drawback of microbial vanillin production from FA is the degradation and biotransformation of toxic vanillin to other phenolic derivatives. The present study is undertaken to explore microbial vanillin production from FA precursor rice bran by employing vanillin-resistant Pediococcus acidilactici BD16, a natural lactic acid bacteria isolate. Extracellular, intracellular and cellular vanillin dehydrogenase activity was found least, which was minimized vanillin degradation, and the strain resists more than 5 g L−1 vanillin in the medium. A metabolomics approach was followed for the detection of FA, vanillin and other metabolites generated during fermentation of rice bran medium. A metabolic pathway was also predicted for vanillin biosynthesis. Approximately 1.06 g L−1 of crude vanillin was recovered from rice-bran-containing medium and this further offers scope for the industrial utilization of the organism and its genetic manipulation to enhance production of biovanillin.

Chakraborty D et al (2016) Environmental Technology In press

 

The Monthly Digest – November 2016

Synthesis of flavor esters and structured lipids by a new immobilized lipase, LipC12, obtained from metagenomics

Ibead-CELipC12 is a metagenomic lipase, LipC12, immobilized directly from a crude extract onto Immobead 150. We evaluated its solvent and thermal stability and its potential for producing flavor esters and structured lipids. Ibead-CELipC12 had residual activities above 88% after 24 h at 40 °C in toluene, iso-octane, n-hexane and n-heptane and 72% after 24 h at 60 °C in n-hexane. In esterification of palmitic acid, Ibead-CELipC12 gave higher activities with ethanol, propanol and butanol than with isopropanol. In esterification of caprylic acid with ethanol, propanol and butanol, Ibead-CELipC12 performed best with butanol, giving 62% conversion in 6 h. Ibead-CELipC12 was sn−1,3-specific during triolein hydrolysis and was therefore used to convert olive oil into an MLM structured lipid containing 23% of caprylic acid in the sn−1 and sn−3 positions. These results demonstrate that Ibead-CELipC12 has good potential to be used in the enzymatic synthesis of flavor esters and structured lipids. Ibead-CELipC12 is a metagenomic lipase, LipC12, immobilized directly from a crude extract onto Immobead 150. We evaluated its solvent and thermal stability and its potential for producing flavor esters and structured lipids. Ibead-CELipC12 had residual activities above 88% after 24 h at 40 °C in toluene, iso-octane, n-hexane and n-heptane and 72% after 24 h at 60 °C in n-hexane. In esterification of palmitic acid, Ibead-CELipC12 gave higher activities with ethanol, propanol and butanol than with isopropanol. In esterification of caprylic acid with ethanol, propanol and butanol, Ibead-CELipC12 performed best with butanol, giving 62% conversion in 6 h. Ibead-CELipC12 was sn−1,3-specific during triolein hydrolysis and was therefore used to convert olive oil into an MLM structured lipid containing 23% of caprylic acid in the sn−1 and sn−3 positions. These results demonstrate that Ibead-CELipC12 has good potential to be used in the enzymatic synthesis of flavor esters and structured lipids.

Dutra Madalozzo A et al (2017) Biocatalysis and Agricultural Biotechnology (in press)

 

Lipase-catalyzed modification of the flavor profiles in recombined skim milk products by enriching the volatile components

The purpose of this study was to modify the amount and composition of volatile components in bovine milk products, in an attempt to create a recombined skim milk product with full-fat milk flavor but with only 0.5% fat. The experimental plan included lipase-catalyzed hydrolysis and esterification reactions using Palatase 20000L (Novozymes, Bagsværd, Denmark). The results, measured by the methods of volatile compositional analysis and sensory evaluation, showed that the flavor profiles of the optimal recombined milk products were effectively modified in this way, possessing intensified characteristic volatile flavor components with rather low level of fat contents, and the sensory characters were quite realistic to natural whole milk flavor.

Zhang XM et al. (2016) Journal of Dairy Science 99:8665-8679

 

Formation of volatile compounds, peptidolysis and carbohydrate fermentation by mesophilic lactobacilli and streptoccocci cultures in a cheese extract

Many studies about the influence of Lactococcus lactis on cheese flavour have been reported, while the impact of mesophilic lactobacilli and Streptococcus thermophilus, either as single or mixed cultures, have been less studied. The ability of Lactobacillus paracasei 90, Lb. casei 72 (INLAIN collection) and S. thermophilus 2 (commercial strain) to produce flavour-related biochemical changes, as single or mixed (lactobacilli + streptococci) cultures, was assessed in a cheese model. These three strains, with different activities of glutamate dehydrogenase (GDH) and aminotransferases (AT), were incubated (14d/37 °C) alone or in mixed cultures in a cheese model consisting of a sterile extract of a fresh cheese. Mesophilic lactobacilli showed fermentation of carbohydrates, an increase of peptidolysis and production of volatile compounds that were correlated with their AT activities. In addition, these strains also produced completely different profiles of the amino acceptor compounds: pyruvate and α-ketoglutarate. S. thermophilus 2 increased the level of α-ketoglutarate due to its high GDH activity, but its contribution to flavour compound production was negligible; small additional changes existed when S. thermophilus 2 was mixed with the lactobacilli. Biochemical changes leading to flavour formation were mainly due to the activity of lactobacilli. Our results suggest that the AT profile and the peptidolytic activity of each strain influenced the volatilome of the extracts during incubation. So, both lactobacilli strains could be used as adjunct cultures in cheeses to increase/diversify the flavour, but more studies are needed to deepen the knowledge about the potential of S. thermophilus 2 for the production of flavour compounds.

Peralta GH et al (2016) Dairy Science & Technology 96:603-621

 

Yeast factories for the production of aromatic compounds: from building blocks to plant secondary metabolites

The aromatic amino acid biosynthesis pathway is a source to a plethora of commercially relevant chemicals with very diverse industrial applications. Tremendous efforts in microbial engineering have led to the production of compounds ranging from small aromatic molecular building blocks all the way to intricate plant secondary metabolites. Particularly, the yeastSaccharomyces cerevisiae has been a great model organism given its superior capability to heterologously express long metabolic pathways, especially the ones containing cytochrome P450 enzymes. This review contains a collection of state-of-the-art metabolic engineering work devoted towards unraveling the mechanisms for enhancing the flux of carbon into the aromatic pathway. Some of the molecules discussed include the polymer precursor muconic acid, as well as important nutraceuticals (flavonoids and stilbenoids), and opium-derived drugs (benzylisoquinoline alkaloids).

Suástegui M and Shao Z (2016) Journal of Industrial Microbiology & Biotechnology 43 :1611-1624

 

Meta-analysis of the core aroma components of grape and wine aroma

Wine aroma strongly influences wine quality, yet its composition and its evolution during the winemaking process are poorly understood. Volatile compounds that constitute wine aroma are traditionally divided into three classes according to their origin: grape, fermentation, and maturation aroma. We challenge this view with meta-analysis and review of grape and wine volatiles and their precursors from 82 profiling experiments. We compiled a list of 141 common grape and wine volatiles and quantitatively compared 43 of them. Our work offers insight into complex relationships between biosynthesis of aroma in grapes and the changes during the winemaking process. Monoterpenes are one of the largest and most researched wine aroma compounds. We show that their diversity in wines is mainly due to the oxidative metabolism of linalool in grapes. Furthermore, we demonstrate that most of the linalool produced in grapes is converted to these oxidized derivatives.

Ilc T et al (2016) Frontiers in Plant Science Vol 7 Article 1472 doi: 10.3389/fpls.2016.01472

 

Major phenolic and volatile compounds and their influence on sensorial aspects in stem-contact fermentation winemaking of Primitivo red wines

In red winemaking de-stemming is crucial since the stems contain polymeric phenolic compounds responsible for the astringency of wine. Wine such as Primitivo has low phenolic constituents and tannins and stems affect aroma, taste body and olfactory characteristics. The aim of the study was to evaluate the effects of presence of stems during fermentation on polyphenolic, volatile compounds and sensory characteristics of wine. Primitivo grapes vinified in presence of different percentage of stems: 100 % de-stemmed (D100), 75 % de-stemmed (D75) and 50 % de-stemmed (D50). Results confirmed that the wines vinified in presence of stems were higher in tannins, flavans, to vanillin and proanthocyanidins, colour intensity with lower anthocyanins. The presence of stems during fermentation conferred more structure and flavour to wines. They facilitated must aeration thus promoting synthesis of higher alcohols and ethyl esters by yeast. In particular, a higher content of hexan-1-ol, hex-3-en-1-ol and 2-phenyl ethanol in D50 and D75 gave the wines that suggest green grass, herb and floral. Wine from D75 seemed to be better than D50 in terms of volatile compounds as well as fruity, floral and balsamic components preserved, without any unpleasant taste of long chain fatty acids found in D50.

Suriano S et al. (2016) Journal of Food Science and Technology 53:3329-3339

 

Influence of the dominance of must fermentation by Torulaspora delbrueckii on the malolactic fermentation and organoleptic quality of red table wine

Torulaspora delbrueckii can improve wine aroma complexity, but its impact on wine quality is still far from being satisfactory at the winery level, mainly because it is easily replaced by S. cerevisiae yeasts during must fermentation. New T. delbrueckii killer strains were selected to overcome this problem. These strains killed S. cerevisiae yeasts and dominated fermentation better than T. delbrueckii non-killer strains when they were single-inoculated into crushed red grape must. All the T. delbrueckii wines, but none of the S. cerevisiae wines, underwent malolactic fermentation. Putative lactic acid bacteria were always found in the T. delbrueckii wines, but none or very few in the S. cerevisiaewines. Malic acid degradation was the greatest in the wines inoculated with the killer strains, and these strains reached the greatest dominance ratios and had the slowest fermentation kinetics. The T. delbrueckii wines had dried-fruit/pastry aromas, but low intensities of fresh-fruit aromas. The aroma differences between the T. delbrueckii and the S. cerevisiae wines can be explained by the differences that were found in the amounts of some fruity aroma compounds such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, and some lactones. This T. delbrueckii effect significantly raised the organoleptic quality scores of full-bodied Cabernet-Sauvignon red wines inoculated with the killer strains. In particular, these wines were judged as having excellent aroma complexity, mouth-feel, and sweetness.

Ramirez M et al. (2016) International Journal of Food Microbiology 238:311-319

 

Synthesis of taste-active γ-glutamyl dipeptides during sourdough fermentation by Lactobacillus reuteri

This study aimed to assess whether peptides influence the taste of sourdough bread. γ-Glutamyl dipeptides with known kokumi taste threshold, namely γ-Glu-Glu, γ-Glu-Leu, γ-Glu-Ile, γ-Glu-Phe, γ-Glu-Met, and γ-Glu-Val, were identified in sourdough by liquid chromatography–tandem mass spectrometry in MRM mode. γ-Glutamyl dipeptides were found in higher concentrations in sourdough fermented with Lactobacillus reuteri when compared to the chemically acidified controls. Proteolysis was an important factor for generation of γ-glutamyl dipeptides. Sourdoughs fermented with four strains of L. reuteri had different concentrations of γ-Glu-Glu, γ-Glu-Leu, and γ-Glu-Met, indicating strain-specific differences in enzyme activity. Buffer fermentations with L. reuteri confirmed the ability of the strains to convert amino acids to γ-glutamyl dipeptides as well as the strain-specific differences. Sensory evaluation of bread revealed that sourdough bread with higher concentrations of γ-glutamyl dipeptides ranked higher with respect to the taste intensity when compared to regular bread and type I sourdough bread. Sourdough breads fermented with L. reuteri LTH5448 and L. reuteri 100-23 differed with respect to the intensity of the salty taste; this difference corresponded to a different concentration of γ-glutamyl dipeptides. These results suggest a strain-specific contribution of γ-glutamyl dipeptides to the taste of bread. The use of sourdough fermented with glutamate and kokumi peptide accumulating lactobacilli improved the taste of bread without adverse effect on other taste or quality attributes.

Zhao CJ and Gänzle MG (2016) Journal of Agricultural and Food Chemistry 64:7561-7568

 

Implementing principles of traditional concentrated grape must fermentation to the production of new generation balsamic vinegars. Starter selection and effectiveness

In an effort to implement principles of traditional concentrated grape must fermentation to the production of new generation balsamic vinegars (BVs), the specific goals of the study were the isolation and molecular identification of the predominant yeasts in concentrated grape must (cv. Xinomavro), their technological characterization and the evaluation of the fermentative aptitude of the selected strains. Tolerance against 5-hydroxymethyl-furfural (HMF) and furfural, acetic acid and glucose concentration was examined by appropriate methods and tests. The enological characteristics studied were acetic acid and H2S production, foaming and flocculation ability and key enzymatic activity. PCR–RFLP analysis revealed only the presence of Saccharomyces cerevisiae and Hanseniaspora uvarum among the 14 predominant osmophilic yeast isolates. Tolerance to both HMF and furfural was found strain- and dose-dependent and was suggested as a critical factor in the pre-selection of yeast starters. The most tolerant yeasts to these stress factors, a S. cerevisiae and a non-Saccharomyces strain, showed satisfactory growth in the presence of high glucose and acetic acid content (up to 600 g/L and 2 % w/w, respectively) and desirable enological characteristics. Results from the comparative evaluation of the fermentative aptitude of these strains with a commercial wine strain highlighted that the isolates had glucophilic behaviour and ability to produce desirable amounts of ethanol (100–120 g/kg) in short time (~20 d). The key volatiles useful for varietal discrimination and differentiation between the BVs and the traditional ones were also evaluated.

Lalou S et al. (2016) Journal of Food Science and Technology 53:3424-3436

The Monthly Digest – October 2016

Synthetic genome engineering forging new frontiers for wine yeast

Over the past 15 years, the seismic shifts caused by the convergence of biomolecular, chemical, physical, mathematical, and computational sciences alongside cutting-edge developments in information technology and engineering have erupted into a new field of scientific endeavor dubbed Synthetic Biology. Recent rapid advances in high-throughput DNA sequencing and DNA synthesis techniques are enabling the design and construction of new biological parts (genes), devices (gene networks) and modules (biosynthetic pathways), and the redesign of biological systems (cells and organisms) for useful purposes. In 2014, the budding yeast Saccharomyces cerevisiaebecame the first eukaryotic cell to be equipped with a fully functional synthetic chromosome. This was achieved following the synthesis of the first viral (poliovirus in 2002 and bacteriophage Phi-X174 in 2003) and bacterial (Mycoplasma genitalium in 2008 and Mycoplasma mycoides in 2010) genomes, and less than two decades after revealing the full genome sequence of a laboratory (S288c in 1996) and wine (AWRI1631 in 2008) yeast strain. A large international project – the Synthetic Yeast Genome (Sc2.0) Project – is now underway to synthesize all 16 chromosomes (12 Mb carrying 6000 genes) of the sequenced S288c laboratory strain by 2018. If successful,S. cerevisiae will become the first eukaryote to cross the horizon of in silico design of complex cells through de novo synthesis, reshuffling, and editing of genomes. In the meantime, yeasts are being used as cell factories for the semi-synthetic production of high-value compounds, such as the potent antimalarial artemisinin, and food ingredients, such as resveratrol, vanillin, stevia, nootkatone, and saffron. As a continuum of previously genetically engineered industrially important yeast strains, precision genome engineering is bound to also impact the study and development of wine yeast strains supercharged with synthetic DNA. The first taste of what the future holds is the de novo production of the raspberry ketone aroma compound, 4-[4-hydroxyphenyl]butan-2-one, in a wine yeast strain (AWRI1631), which was recently achieved via metabolic pathway engineering and synthetic enzyme fusion. A peek over the horizon is revealing that the future of “Wine Yeast 2.0” is already here. Therefore, this article seeks to help prepare the wine industry – an industry rich in history and tradition on the one hand, and innovation on the other – for the inevitable intersection of the ancient art practiced by winemakers and the inventive science of pioneering “synthetic genomicists”. It would be prudent to proactively engage all stakeholders – researchers, industry practitioners, policymakers, regulators, commentators, and consumers – in a meaningful dialog about the potential challenges and opportunities emanating from Synthetic Biology. To capitalize on the new vistas of synthetic yeast genomics, this paper presents wine yeast research in a fresh context, raises important questions and proposes new directions.

Pretorius IS (2016) Critical Reviews in Biotechnology (in press) Published online 18 Aug 2016)

DOI: 10.1080/07388551.2016.1214945

 

Proteins differentially expressed during limonene biotransformation by Penicillium digitatum DSM 62840 were examined using iTRAQ labeling coupled with 2D-LC–MS/MS

This study focused on the differences in protein expression at various periods during limonene biotransformation by Penicillium digitatum DSM 62840. A total of 3644 protein-species were quantified by iTRAQ during limonene biotransformation (0 and 12 h). A total of 643 proteins were differentially expressed, 316 proteins were significantly up-regulated and 327 proteins were markedly down-regulated. GO, COG, and pathway enrichment analysis showed that the differentially expressed proteins possessed catalytic and binding functions and were involved in a variety of cellular and metabolic process. Furthermore, the enzymes involved in limonene transformation might be related to cytochrome P-450. This study provided a powerful platform for further exploration of biotransformation, and the identified proteins provided insight into the mechanism of limonene transformation. This study focused on the differences in protein expression at various periods during limonene biotransformation by Penicillium digitatum DSM 62840. A total of 3644 protein-species were quantified by iTRAQ during limonene biotransformation (0 and 12 h). A total of 643 proteins were differentially expressed, 316 proteins were significantly up-regulated and 327 proteins were markedly down-regulated. GO, COG, and pathway enrichment analysis showed that the differentially expressed proteins possessed catalytic and binding functions and were involved in a variety of cellular and metabolic process. Furthermore, the enzymes involved in limonene transformation might be related to cytochrome P-450. This study provided a powerful platform for further exploration of biotransformation, and the identified proteins provided insight into the mechanism of limonene transformation.

Zhang LL et al. (2016) Journal of Industrial Microbiology & Biotechnology 43:1481-1495

 

Impact of D-limonene synthase up- or down-regulation on sweet orange fruit and juice odor perception

Citrus fruits are characterized by a complex mixture of volatiles making up their characteristic aromas, being the D-limonene the most abundant one. However, its role on citrus fruit and juice odor is controversial. Transgenic oranges engineered for alterations in the presence or concentration of few related chemical groups enable asking precise questions about their contribution to overall odor, either positive or negative, as perceived by the human nose. Here, either down- or up-regulation of a D-limonene synthase allowed us to infer that a decrease of as much as 51 times in D-limonene and an increase of as much as 3.2 times in linalool in juice were neutral for odor perception while an increase of only 3 times in ethyl esters stimulated the preference of 66% of the judges. The ability to address these questions presents exciting opportunities to understand the basic principles of selection of food.

Rodriguez A et al. (2016) Food Chemistry 217:139-150

 

Use of vine-trimming wastes as carrier for Amycolatopsis sp. to produce vanillin, vanillyl Alcohol, and vanillic acid

Raw vine-trimming wastes or the solid residues obtained after different fractionation treatments were evaluated for their suitability as Amycolatopsis sp. immobilization carriers during the bioconversion of ferulic acid into valuable phenolic compounds such as vanillin, vanillyl alcohol, and vanillic acid, the main flavor components of vanilla pods. Previously, physical–chemical characteristics of the materials were determined by quantitative acid hydrolysis and water absorption index (WAI), and microbiological characteristics by calculating the cell retention in the carrier (λ). Additionally, micrographics of carrier surface were obtained by field emission-scanning electron microscopy to study the influence of morphological changes during pretreatments in the adhesion of cells immobilized. The results point out that in spite of showing the lowest WAI and intermediate λ, raw material was the most appropriated substrate to conduct the bioconversion, achieving up to 262.9 mg/L phenolic compounds after 24 h, corresponding to 42.9 mg/L vanillin, 115.6 mg/L vanillyl alcohol, and 104.4 mg/L vanillic acid. The results showed the potential of this process to be applied for biotechnological production of vanillin from ferulic acid solutions; however, further studies must be carried out to increase vanillin yield. Additionally, the liquors obtained after treatment of vine-trimming wastes could be assayed to replace synthetic ferulic acid.

Castañón-Rodríguez JF et al. (2016) Current Microbiology 73 :561-568

 

Okara (soybean residue) biotransformation by yeast Yarrowia lipolytica

Okara, or soybean residue, is a soy food processing by-product from the manufacture of soymilk and soybean curd (tofu). In this study, solid-state fermentation of okara was conducted over 5 days using yeast Yarrowia lipolytica, and the changes in proximate composition, antioxidant capacity, non-volatiles and volatiles were investigated. Yeast metabolism of okara significantly increased the amounts of lipid, succinate and free amino acids and enhanced the antioxidant capacity. In particular, there was a marked increase in important umami tastants after fermentation, with 3-fold increase in succinate and a 20-fold increase in glutamate. The final fermented okara contained 3.37 g succinate and 335 mg glutamate/100 g dry matter. Aldehydes and their derived acids in the fresh okara were catabolised by Y. lipolytica mainly to methyl ketones, leading to a reduced grassy off-odour and a slightly pungent, musty and cheese-like odour in the fermented okara. Amino acid-derived volatiles, such as 3-methylbutanal and 2-phenylethanol, were also produced. Overall, the okara fermented by Y. lipolytica had a greater amount of umami-tasting substances, a cheese-like odour, improved digestibility and enhanced antioxidant capacity. These changes highlight the potential of Yarrowia-fermented okara as a more nutritious, savoury food product or ingredient. Y. lipolyticawas thus demonstrated to be suitable for the biovalorisation of this soy food processing by-product.

Vong WC et al. (2016) International Journal of Food Microbiology 235:1-9

 

Impact of solid state fermentation on nutritional, physical and flavor properties of wheat bran

To improve the nutritional, physical and flavor properties of wheat bran, yeast and lactic acid bacteria (LAB) were used for fermenting wheat bran in solid state. Appearance properties, nutritional properties, microstructure, hydration properties and flavor of raw bran and fermented bran were evaluated. After treatments, water extractable arabinoxylans were 3–4 times higher than in raw bran. Total dietary fiber and soluble dietary fiber increased after solid state fermentation. Over 20% of phytic acid was degraded. Microstructure changes and protein degradation were observed in fermented brans. Water holding capacity and water retention capacity of fermented brans were improved. Results suggest that solid state fermentation is an effective way to improve the properties of wheat brans.

Zhao HM et al. (2017) Food Chemistry 217:28-36

 

Selected dehydrogenases in Yarrowia lipolytica JMY 861: their role in the synthesis of flavor compounds

The presence of selected dehydrogenases, including alcohol dehydrogenase (ADH-YL) and aldehyde dehydrogenase (ALDH-YL), in Yarrowia lipolytica JMY 861, and their potential role in flavor synthesis were investigated. The experimental findings showed that using reduced form of nicotinamide adenine dinucleotide (NADH) as cofactor, the ADH-YL activity in vitro was 6-fold higher than that with reduced form of nicotinamide adenine dinucleotide phosphate (NADPH); however, under the experimental conditions used in this study, an ALDH-YL activity was not detected. The in situ hexanal reduction reaction was found to be instantaneous; however, when the yeast cells suspension was diluted 150 times, the initial relative hexanal concentration was increased by 84.1%. The chromatographic analyses indicated the conversion, in situ, of linoleic acid hydroperoxides (HPODs) into volatile C6-compounds after 60 min of HPODs addition to the yeast cells suspension.

Aziz M et al (2016) Bioscience, Biotechnology, and Biochemistry 80: 2184-2191