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