The Monthly Digest – Aromas and Flavours July & August 2017

Aromas and flavours
R & D abstracts – July & August 2017
Fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of selected yeast (research)

Plum (Prunus domestica L.) is one of the most often grown fruit species, which is widespread all over the world. The processing potential of this fruit is not exploited enough. Fruit wines became very popular nowadays because of their nutritional and health-promoting values. Plums are fruit that can give wine with intensive red color and characteristic flavor, which can be compared with the best grape wines. Obtained results would contribute to global acceptance of wine as functional food. An important advantage of fruit wines (concretely plum wine) compared to traditional grape wine is lower alcohol content. Also, plum fruits losses in refrigeration industry could be avoided due to longer shelf life of this fermented beverage.
The aim of this study was to assess and compare fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of different selected yeast. Experiments were carried out with plum (Prunus domestica L.) varieties of different fruit ripening times (Čačanska rana, Čačanska lepotica, and Požegača). Wine fermentations were conducted by the activity of indigenous microbiota, commercially available Saccharomyces cerevisiae and Saccharomyces bayanus yeast strains and joint activity of Schizosaccharomyces pombe and S. cerevisiae (sequential inoculation). Statistically significant differences in fermentative characteristics and the content of certain volatile compounds were observed as a result of metabolic activity of various indigenous and/or selected yeasts during fermentation of plum pomace. Minimal duration of fermentation (4 to 5 d) and fastest ethanol production rate (from 12.3 to 15.5 g/L/d) were the characteristics of the studied S. cerevisiae strains. Isobutanol, 3-methyl-1-butanol, 1-heptanol, and 1-octanol were the most prevalent higher alcohols in the tested plum wine samples. The predominant ester in plum wines was ethyl acetate, ethyl lactate, amyl acetate, isoamyl acetate, and ethyl palmitate, esters responsible for the floral and fruity olfactory tones, were also present in large amounts. Also, the use of S. cerevisiae strains resulted in the production of plum wines with better sensory characteristics than ones produced with other investigated yeasts. Obtained results are significant since there is limited data on the compounds responsible for the unique flavor of plum wine, as well as on the impact of different yeast starter cultures application on the overall quality of fruit wines.

Miljic U et al (2017) Journal of Food Science 82:1443-1450

 

Agrowaste to vanillin conversion by a natural Pediococcus acidilactici strain BD16 (research)

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 (2017) Environmental Technology 38:1823-1834

 

Improvement of aroma and shelf-life of non-alcoholic beverages through cyclodextrins-limonene inclusion complexes (research)

Limonene is a monoterpene flavor compound found in several beverages. However, it easily degrades by oxidation reactions at acidic environment contributing to an undesirable off-flavor. Encapsulation technologies can protect compounds from degradation. This work focuses on the effect of using complexes of limonene with
α-, β-, and γ- and HP-β-cyclodextrins in non-alcoholic beverages to improve flavor and shelf-life stability due to the chemical structure of cyclodextrins. Spray-drying technology was applied to prepare different cyclodextrin/limonene forms, from which the most promising was selected and further applied in simulated lemon juice beverages. Different drying process conditions were tested, namely feed temperature (120, 160, and 180 °C) and setting of prior incubation (temperature, room and 50 °C; time, 0.17 and 24 h). An inlet temperature of 160 °C favored the encapsulation of limonene into resulting nano/microparticles. Moreover, incubation for 24 h enhanced limonene retention for all complexes, especially for β-cyclodextrin/limonene complexes, which achieved 66% of encapsulation efficiency and a 6.25 w/w of limonene load. The β-cyclodextrin/limonene particles which enabled higher load (160 °C, 24 h) presented particle size ranging between 1 and 3 μm and were chosen to undergo an accelerated aging process in a lemon juice
beverage model. This study revealed that the limonene content decreased over time for model and supplemented juice, but decreased less when β- cyclodextrin/limonene particles were added. After 10 days, which mimics 9 months of storage, 40% of complexed limonene remained in the model beverage.

Saldanha do Carmo C et al (2017) Food and Bioprocess Technology 10:1297-1309

 

Intracellular metabolite profiling of industrial yeast and the synthesis of flavour compounds in beer (research)

Beer quality is largely guaranteed by a rational ratio of different flavour compounds. In this study, we present intracellular metabolic profiles in the light of lager beer flavour compound synthesis on an industrial scale. A total of 62 intracellular metabolites were identified and quantitatively analysed. Among these, amino acid was identified as the most dominant category of metabolites. We also report gene expression profiling of relevant genes encoding six representing amino acids, including serine, alanine, lysine, valine, leucine and asparagine. Nine genes involved in the amino acid synthesis – ALT1, ALT2, ASN1, ASN2, BAT1, SER2, SHM1, SHM2 and LYA1 displayed significantly higher level of expression at various fermentation stages in an industrial lager fermentation. However, concentrations of the recovered amino acids decreased towards the end of fermentation. Our results suggested that the defined amino acids could be assimilated by the yeast to be utilized for synthesis of aroma-active metabolites at different stages in fermentation.

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

 

Great intraspecies diversity of Pichia kudriavzevii in cocoa fermentation highlights the importance of yeast strain selection for flavor modulation of cocoa beans (research)

The use of selected yeasts has recently been proposed as an interesting strategy to improve cocoa bean fermentation and chocolate quality. In this study, a total of 39 cocoa-derived yeast isolates were screened for their capacity to produce volatile aroma compounds in a cocoa pulp simulation medium. The seven highest aroma-producing yeasts were identified by ITS-rRNA gene sequencing as belonging to Pichia kudriavzevii, in spite of exhibiting different metabolic profiles. Repetitive extragenic palindromic (Rep)-PCR genomic fingerprinting approach confirmed this high intraspecies diversity of P. kudriavzevii in cocoa fermentation. Two strains with superior aroma production, namely P. kudriavzevii LPB06 and P. kudriavzevii LPB07, were used in cocoa beans fermentation at laboratory scale. They were able to establish an accelerated fermentation process with efficient yeast growth, sugars consumption and ethanol formation compared to the spontaneous process. The resulting cocoa beans were analyzed by diverse chemical analysis methods, including gas chromatography coupled to mass spectrophotometry (GC-MS), fermentation index and metal and colorimetric analysis. Altogether, the results indicated that inoculated fermentations generated cocoa beans with better color development and richer aroma composition, suggesting that cocoa-associated yeast diversity at strain level can be exploited for flavor modulation of cocoa beans.

Pereira GVM et al (2017) LWT – Food Science and Technology 84:290-297

 

Microbial diversity of traditional kefir grains and their role on kefir aroma (research)

Kefir grains consist of rich bacterial and fungal microflora responsible for the production of this traditional fermented milk beverage with unique flavour properties. Here, a pyrosequencing approach was applied for the identification of microbial flora of four kefir grains collected from different regions of Turkey and the volatile compounds in kefir samples produced with these grains were determined. Lactobacillus kefiranofacienspresented in all grains at important levels and Enterobacter, Acinetobacter, Enterococcus and Pseudomonas spp were observed in traditional kefir grains. The fungal microflora of kefir grains was dominated by yeast species and Dipodascaceaefamily was dominant and Saccharomyces cerevisiae presented in all grains. Other yeast species belonging to Kazachstania, Candida, Issatchenkia and Rhodotorula species were also detected in kefir grains. Volatile compounds of kefir samples were also diverse related to the microbial diversity of kefir grains. This study revealed the rich microflora of Turkish kefir grains and their interactions with the aromatic properties of kefir.

Dertli E and Çon AH (2017) LWT – Food Science and Technology 85A:151-157