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