Effect of raw material and starters on the metabolite constituents and microbial community diversity of fermented soy sauce

Correlation study on microbial communities and volatile flavor compounds in cigar tobacco leaves of diverse origins

To elucidate the significant influence of microorganisms on geographically dependent flavor formation by analyzing microbial communities and volatile flavor compounds (VFCs) in cigar tobacco leaves (CTLs) obtained from China, Dominica, and Indonesia. Microbiome analysis revealed that the predominant bacteria in CTLs were Staphylococcus, Aerococcus, Pseudomonas, and Lactobacillus, while the predominant fungi were Aspergillus, Wallemia, and Sampaiozyma. The microbial communities of CTLs from different origins differed to some extent, and the diversity and abundance of bacteria were greater than fungi. Metabolomic analysis revealed that 64 VFCs were identified, mainly ketones, of which 23 VFCs could be utilized to identify the geographical origins of CTLs. Sixteen VFCs with OAV greater than 1, including cedrol, phenylacetaldehyde, damascone, beta-damascone, and beta-ionone, play important roles in shaping the flavor profile of CTLs from different origins. Combined with the correlation analysis, bacterial microorganisms were more closely related to key VFCs and favored a positive correlation. Bacillus, Vibrio, and Sphingomonas were the main flavor-related bacteria. The study demonstrated that the predominant microorganisms were essential for the formation of key flavor qualities in CTLs, which provided a theoretical reference for flavor control of CTLs by microbial technology. KEY POINTS: • It is the high OAV VFCs that determine the flavor profile of CTLs. • The methylerythritol phosphate (MEP) pathway and the carotenoid synthesis pathway are key metabolic pathways for the formation of VFCs in CTLs. • Microbial interactions influence tobacco flavor, with bacterial microorganisms contributing more to the flavor formation of CTLs.

Evaluation of the differences between low-salt solid-state fermented soy sauce and high-salt diluted-state fermented soy sauce in China: from taste-active compounds and aroma-active compounds to sensory characteristics

BACKGROUND

The present study aimed to determine the components related to sensory properties in soy sauce and to characterize the differences between low-salt solid-state fermented soy sauce (LSFSS) and high-salt diluted-state fermented soy sauce (HDFSS). The taste and aroma active components of 18 commercially available soy sauces (eight types of LSFSS and 10 types of HDFSS) were characterized. The relationship between these compounds, soy sauce samples, and sensory properties was modeled by partial least squares regression.

RESULTS

The analysis showed that the 11 taste-active components, including glutamic acid, glycine, alanine, threonine, malic acid, citric acid, tartaric acid, acetic acid, lactic acid, reducing sugar and salt, contributed greatly to the taste of soy sauce. In addition, umami, saltiness and sweetness are the characteristic tastes of HDFSS, whereas sourness and bitterness were the characteristic tastes of LSFSS. At the same time, seven aroma-active compounds, namely 4-ethyl-2-methoxyphenol, ethanol, 3-methyl-1-butanol, ethyl acetate, 2-phenethyl alcohol, 3-methyl thiopropanol and 2-ethyl-4-hydroxy-5-methylfuran-3-one, played a decisive role in the flavor of soy sauce. In addition, HDFSS presented the aroma attributes of smoky, alcoholic, floral, fruity and caramel-like, whereas LSFSS mainly presented sour and malty aroma attributes.

CONCLUSION

The present study reveals new insight into the relationship between the chemical composition and sensory characteristics of soy sauce, which is of great significance for developing an objective measurement system and providing a theoretical basis to improve the sensory quality of soy sauce. © 2023 Society of Chemical Industry.

Flavor differences of soybean and defatted soybean fermented soy sauce and its correlation with the enzyme profiles of the kojis

BACKGROUND

Soybeans and defatted soybeans, commonly used as protein ingredients, have different flavors of their fermented soy sauce. Clarifying the differences between the two soy sauces, as well as the formation mechanism, is an important prerequisite for improving the flavor of defatted soybean soy sauce. To this goal, the aroma characteristics of two soy sauces and their volatile profiles were compared by sensory evaluation and gas chromatography-mass spectrometry, and eight enzyme activities and volatile profiles of matured koji were determined.

RESULTS

Sensory results showed that the acids, fruity and cooked potato-like attributes were higher in whole soybean fermented soy sauce, whereas defatted soybean soy sauce exhibited higher smoky and malty attributes, closely related to the contents of aroma-active compounds in soy sauce, such as isobutyl acetate, 2/3-methylbutanal, acetic acid and 2/3-methylbutanoic acid. The content of most volatiles in the matured kojis showed a consistent trend with that of soy sauce: alcohols, acids, furan(one)s and ketones. Interestingly, acid protease and cellulase activities were 3.3 and 1.6 times higher in the whole soybean koji than in defatted soybean koji, respectively, whereas neutral protease, aminopeptidase, glucoamylase and β-glucosidase were approximately 2.0 times higher in defatted soybean koji.

CONCLUSION

In summary, the flavor differences between soybean and defatted soybean fermented soy sauce were not only caused by the differences in the content of flavor precursors in the materials, but also closely related to the differences in the enzymatic profiles accumulated during the koji-making process. © 2022 Society of Chemical Industry.

Community structure of yeast in fermented soy sauce and screening of functional yeast with potential to enhance the soy sauce flavor

Yeast plays an important role in the formation of desirable aroma during soy sauce fermentation. In this study, the structure and diversity of yeast communities in seven different soy sauce residues were investigated by ITS sequencing analysis, and then the aroma characteristics of selected yeast species were examined by a combination of gas chromatography-mass spectrometry (GC-MS), headspace solid-phase microextraction (SPME) and liquid-liquid extraction (LLE). A total of 18 yeast genera were identified in seven soy sauce residues. Among them, Candid and Zygosaccharomyces were detected in all samples, followed by Millerozyma, Wickerhamiella, Meyerozyma, Trichosporon and Wickerhamomyces, which were found in more than two-thirds of the samples. Subsequently, eight representative species, isolated from soy sauce residues, were subjected to environmental stress tolerance tests and aroma production tests. Among them, three isolated species were regarded as potential aroma-enhancing microbes in soy sauce. Wickerhamiella versatilis could increase the contents of ethyl ester compounds and alcohols, thereby improving the fruity and alcoholic aroma of soy sauce. Candida sorbosivorans enhanced sweet and caramel-like aroma of soy sauce by producing 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 3-hydroxy-2-methyl-4h-pyran-4-one (maltol). Starmerella etchellsii could enhance the contents of 2,6-dimethylpyrazine, methyl pyrazine and benzeneacetaldehyde. This study is of great significance for the development and application of flavor functional yeasts in soy sauce fermentation.

Assessment of Lemon Juice Starter Addition on Secondary Fermented Soy Sauce

Soy sauce is one of the most popular ingredients for delicious cuisines across the world, and it is made via various fermentation processes using wheat and soybeans. The purpose of this study was to add a lemon juice starter into secondary fermentation soy sauce to produce a new flavor of soy sauce to meet current health awareness and innovation market trends. The results showed that the lactic acid bacteria of the A group (soy sauce/starter culture ratio of 3:1) gradually decreased from 9.89 to 8.32 log CFU/mL by the seventh day, and then to 5.39 log CFU/mL by the 30th day, while they were not detected by the 60th day. Meanwhile, those of the B group (soy sauce/starter culture ratio of 1:1) showed a decrease from 10.39 to 8.58 log CFU/mL by the seventh day, and then to 5.39 log CFU/mL by the 30th day and 4.43 log CFU/mL by the 60th day, while they were not detected by the 90th day. As for yeast, the A group showed a decrease from 10.83 to 9.29 log CFU/mL (or 10.25 to 9.27 log CFU/mL for the B group) by the seventh day. Yeasts were not detected after 30 days in either the A or B group. The acidity and salinity of the lemon-flavored sauce was maintained after secondary fermentation. Sensory evaluation showed that the soy sauce with a lemon juice starter was accepted by consumers and obtained a better result than commercial soy sauce. In conclusion, secondary fermentation with starters contributes to the flavor quality of sauce products. Fruit juice is adjustable in terms of the acidity and salinity of the soy sauce and produces good flavor after secondary fermentation whenever it acts as a starter. The fact that customers favored the innovative lemon-flavored soy sauce indicates that this study is on the right trend.

The effects of different coculture patterns with salt-tolerant yeast strains on the microbial community and metabolites of soy sauce moromi

In this study, the contributions of three strains and different coculture patterns to microbial community diversity and metabolites in the high-salt liquid-state fermentation (HLF) soy sauce moromi were investigated. A comparison of two strains of Zygosaccharomyces rouxii showed that strain QH-25 had a stronger ability to contribute metabolites, including both nonvolatile and volatile types, to the moromi than strain QH-1, except for volatile acids and ketones. Of the various fortification patterns tested, the content of metabolites was significantly increased by inoculating Z. rouxii QH-25 prior to C. versatilis, especially the content of volatiles, including ketones, esters, phenols, and alcohols, which increased 1.61-fold compared with those in the control sample; the contents of these components were increased 3.07-, 1.91-, 1.36-, and 1.22-fold, respectively. In particular, characteristic components such as ethyl octanoate, 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), 4-ethyl-2-methoxy-phenol (4-EG), and 3-methyl-1-butanol were increased 3.99-, 3.29-, 1.63-, and 0.70-fold, respectively. Redundancy analysis (RDA) showed that Staphylococcus, Zygosaccharomyces, and Candida were positively correlated with the unique components described above. In addition, the nodes of the interaction network between Zygosaccharomyces and Candida were increased, and the positive correlation of Zygosaccharomyces with Staphylococcus was enhanced by inoculating Z. rouxii prior to C. versatilis. These results suggested that the unique flavor of soy sauce was closely related to the metabolic characteristics of strains affiliated with Z. rouxii, whether cultured singly or cocultured with C. versatilis. This study also provided a reference method for determining the differences in community structure and metabolites between traditional techniques and modern processes for soy sauce fermentation.

Metagenomics assembled genome scale analysis revealed the microbial diversity and genetic polymorphism of Lactiplantibacillus plantarum in traditional fermented foods of Hainan, China

Exploring the microbiome in fermented foods and their effects on food quality and sustainability is beneficial to provide data support for understanding how they affects human physiology. Here, metagenomic sequencing and metagenomic assembled genomes (MAGs) were applied to appraise the microbial diversity of fermented Yucha (FYC) and fermented vegetables (FVE). The antibiotic resistance genes (ARGs) enrichment and genetic polymorphism of Lactiplantibacillus plantarum in fermented foods of different regions were compared. The results showed that Lactiplantibacillus plantarum was the dominant species in FYC, while Lactiplantibacillus fermentum in FVE occupied the dominant position. From 32 high-quality MAGs, the central differential Lactic acid bacteria were higher in FVE. By comparing the Lactiplantibacillus plantarum MAGs in Hainan and Other regions, we found that the total Single Nucleotide Polymorphisms of Lactiplantibacillus plantarum in Hainan were significantly higher than other areas. Six non-synonymous mutations were included in the primary differential mutation, especially TrkA family potassium uptake protein and MerR family transcriptional regulator, which may be related to the hypersaline environment and highest ARGs enrichment in Hainan. This research provides valuable insight into our understanding of the microbiome of fermented food. Meanwhile, the analysis of Lactiplantibacillus plantarum genetic polymorphism based on MAGs helps us understand this strain's evolutionary history.

Sugar profile regulates the microbial metabolic diversity in Chinese Baijiu fermentation

Cereals are widely used as raw material for food fermentation, and they can provide a variety of sugars in the fermentation via saccharification. However, the effect of sugar profile on microbial metabolism in spontaneous food fermentation is still unclear. Here, this work studied the regulation of sugar profile on the diversity of microbiota and their metabolism in Chinese Baijiu fermentation using sorghum as raw material. Six sugars were detected during Baijiu fermentation with 6 different cultivars of sorghum. The diversity of microbiota (ANOSIM: bacteria: P = 0.001, R = 0.77; fungi: P = 0.009, R = 0.33) and metabolites (ANOSIM: P = 0.001, R = 0.50) had different profiles during Baijiu fermentation. Among these sugars, glucose, fructose, and arabinose were identified as key sugars driving both the microbial and the metabolic diversity during Chinese Baijiu fermentation, and the metabolic diversity was positively correlated with the microbial diversity (P < 0.05). Hence, response surface methodology was used to establish a predictive model for regulating the metabolic diversity with the combination of three key sugars. The metabolic diversity significantly increased to 0.42 with the optimized levels of glucose (31.82 g/L), fructose (4.81 g/L), and arabinose (0.20 g/L), compared with unoptimized low-level average metabolic diversity (0.29). This work would provide a strategy to control microbial metabolism in spontaneous food fermentation, hence to improve the quality of fermented foods.

Metagenomic Analysis of Bacterial Diversity in Traditional Fermented Foods Reveals Food-Specific Dominance of Specific Bacterial Taxa

Traditional fermented foods have been recognized by various communities to be good for health since ancient times. There is a provincial legacy of traditional fermented foods among the ethnic population of North-East India. Fermented bamboo shoots (local name: Tuaither), soybeans (Bekang), and pork fat (Sa-um) are famous in the Mizoram state and represent a primary portion of the daily diet. These foods are prepared using methods based on cultural traditions inherited from previous generations, and prepared using a relatively uncontrolled fermentation process. Analysis of the bacterial diversity in these foods can provide important information regarding the flavor and texture of the final products of fermentation. Unfortunately, studies on the microbial composition and health benefits of such traditional fermented foods have rarely been documented. Therefore, the present study aims to highlight this bacterial diversity, along with the proximate composition of different traditional fermented foods (Tuaither, Bekang and Sa-um) primarily consumed in Mizoram state, India. Samples were collected on three different days of fermentation (3rd, 5th and 7th day), and bacterial diversity analysis was performed using the V3-V4 variable region of 16S rRNA gene with Illumina sequencing. Results revealed differences in the bacterial composition of dominant group members among all of the three food types. Firmicutes (82.72–94.00%), followed by Proteobacteria (4.67–15.01%), were found to dominate to varying degrees in all three of the fermented foods. However, at genus level high variation was observed in bacterial composition among these three different types of fermented foods. Lactobacillus (91.64–77.16%), Staphylococcus (52.00–17.90%), and Clostridium (72.48–55.40%) exhibited the highest relative abundances in the Tuaither, Bekang and Sa-um foods, respectively, in descending order from the 3rd to 7th day of fermentation. A few of the bacterial genera such as Lactobacilli were positively correlated with fermented bamboo shoot samples, and Staphylococcus was positively correlated with protein, carbohydrate and crude fiber content in soybean samples. In general, Tuaither, Bekang and Sa-um exhibited distinct differences in bacterial composition. This variation may be due to differences in the raw materials and/or methods used in the preparation of the different fermented food products. This is the first study to describe the bacterial composition of these traditional fermented foods using high-throughput sequencing techniques, and could help to drive research attention to comprehensive studies on improving understanding of the role of microbial communities in the preparation of traditional foods and their health benefits.

Rice varieties affect bacterial diversity, flavor, and metabolites of zha-chili

The structure and diversity of bacterial communities in spontaneously fermented zha-chili prepared using two different rice varieties (glutinous rice and indica rice) were investigated using high-throughput sequencing. Through metabolic pathway prediction, electronic senses and metabolite analysis, the relationships among the rice varieties used for preparation and the bacterial microbiota, flavor, and organic acid/amino acid metabolites in zha-chili were elucidated. We observed that the structure of bacterial communities in zha-chili samples differed significantly with the rice variety used during fermentation (p < 0.05), and that there was a greater abundance of bacterial species in zha-chili prepared using glutinous rice. Lactic acid bacteria were predominant in zha-chili, with an average relative abundance of 77.09%. The aroma of zha-chili was influenced by the raw material itself, while the characteristic tastes of zha-chili - including sourness, umami and richness - were significantly correlated with the bacterial microbiota. In addition, the abundance of lactic acid bacteria was positively correlated with the levels of organic acids and negatively correlated with the levels of amino acids. This also made the zha-chili prepared using glutinous rice sourer and imparted more umami taste to the zha-chili prepared using indica rice. Our observations provide a reference for the evaluation of zha-chili quality and could effectively guide the improvement of zha-chili products.

Synergistic Effects of the Jackfruit Seed Sourced Resistant Starch and Bifidobacterium pseudolongum subsp. globosum on Suppression of Hyperlipidemia in Mice

Approximately 17 million people suffer from cardiovascular diseases caused by hyperlipidemia, making it a serious global health concern. Among others, resistant starch (RS) has been widely used as a prebiotic in managing hyperlipidemia conditions. However, some studies have reported limited effects of RS on body weight and blood lipid profile of the host, suggesting further investigation on the synergistic effects of RS in combination with probiotics as gut microbes plays a role in lipid metabolism. This study evaluated the effects of jackfruit seed sourced resistant starch (JSRS) as a novel RS on mice gut microbes and hyperlipidemia by performing 16s rRNA and shotgun metagenomic sequencing. The results showed that 10% JSRS had a limited preventive effect on bodyweight and serum lipid levels. However, the JSRS promoted the growth of Bifidobacterium pseudolongum, which indicated the ability of B. pseudolongum for JSRS utilization. In the validation experiment, B. pseudolongum interacted with JSRS to significantly reduce bodyweight and serum lipid levels and had a therapeutic effect on hepatic steatosis in mice. Collectively, this study revealed the improvements of hyperlipidemia in mice by the synergistic effects of JSRS and B. pseudolongum, which will help in the development of “synbiotics” for the treatment of hyperlipidemia in the future.

Determination of microbial diversities and aroma characteristics of Beitang shrimp paste

Beitang shrimp paste (BSP) is fermented by different parts of shrimp, such as the head (H), meat (M), or the whole shrimp (S and W). Microbial communities of BSP were dominated by Firmicutes and Proteobacteria at the phyla level and Tetragenococcus at the genus level. However, the microbial diversity of M was the lowest than the others. Non-dominant bacterial communities were presented by a mutual symbiotic model in BSP fermentation. Tetragenococcus, Halanaerobium, Streptococcus, and Brevundimonas were positively correlated with the biosynthesis of amino acids, fatty acids, and metabolic cofactors; Marinilactibacillus and Pseudomonas might be the main contributors to inorganic sulfides, nitrogen oxides, and long-chain alkanes in BSP; Psychrobacter was closely related to the ester characteristics of methyl palmitoleate and methyl hexadecanoate in H. Halanaerobium and Streptococcus promoted the production of pyrazines in S. Tetragenococcus was positively correlated with acetic acid, decanoic acid, and palmitic acid that improved the sour aroma of M. The relationship between bacteria and aroma formation under different raw materials was expected to improve the quality of BSP.

Addition of Coriander during Fermentation of Korean Soy Sauce (Gangjang) Causes Significant Shift in Microbial Composition and Reduction in Biogenic Amine Levels

The microflora of Korean soy sauce (gangjang) play an important role in maintaining its quality and safety. Hence, it is important to study the microflora and the possible approaches to improve their composition. In this study, the effect of adding coriander during soy sauce fermentation on the microflora and biogenic amines was evaluated using metagenomics and ¹H NMR analyses, respectively. The β-diversity showed a clear distinction between the microbiota of the coriander and control groups. Microbial composition analysis revealed noticeable shifts, as Firmicutes abundance was significantly higher in the coriander group (91.77%) than that in the control (38.78%). The dominant bacterial family in the coriander group was the Bacillaceae (57.94%), while Halomonadaceae was dominant in the control group (49.77%). At the species level, Chromohalobacter beijerinckii dominated the microbial community in the control group (49.54%), but not (4.43%) in the coriander group. Moreover, there was a negative correlation between the Bacillaceae and several other bacterial families, including Halomonadaceae, which indicated a possible antagonism and partly explained the reduction in Chromohalobacter abundance in the coriander group. The levels of the biogenic amines histamine, putrescine, and tyramine, which are considered potential health risk factors, were significantly lower in the coriander soy sauce than those in the control sauce. The results of this study suggest that the addition of coriander during Korean soy sauce fermentation is beneficial, as coriander significantly reduces the levels of biogenic amines and the bacteria that produce them.

Characterizing the effect of packaging material and storage temperature on the flavor profiles and quality of soy sauce

The effect of packaging material and storage temperature on two types of soy sauce was investigated. Ethanol content decreased significantly in all tested samples after storage (P < 0.05). While the changes of physicochemical properties and CIELAB color space indexes varied with soy sauce types, packaging materials and storage temperatures. The changes of volatile profiles after storage indicated that storage temperature was a key factor resulting in flavor scalping. It also suggested that there was no significant difference of flavor compounds sorption between glass bottle and polyethylene terephthalate bottle. The abundances of acids and alcohols increased after stored at ambient temperature (AT) and low temperature (LT) for 90 days, but phenols decreased. The effect of the packaging material, raw soy sauce type and storage temperature resulted in changing the intensities of fruity, caramel-like, mushroom-like note as well as smoky note. For the inoculated soy sauces, 1-octen-3-ol, ethyl hexanoate and ethyl octanoate in the samples were dominant in samples stored at AT, while the samples stored at LT were characterized by multiple components according to the results of principal components analysis. These results were benefit for understanding the main factors affecting the flavor profiles and quality of soy sauce during storage, as well as optimizing the storage condition.

Fermentation for tailoring the technological and health related functionality of food products

Fermented foods are experiencing a resurgence due to the consumers' growing interest in foods that are natural and health promoting. Microbial fermentation is a biotechnological process which transforms food raw materials into palatable, nutritious and healthy food products. Fermentation imparts unique aroma, flavor and texture to food, improves digestibility, degrades anti-nutritional factors, toxins and allergens, converts phytochemicals such as polyphenols into more bioactive and bioavailable forms, and enriches the nutritional quality of food. Fermentation also modifies the physical functional properties of food materials, rendering them differentiated ingredients for use in formulated foods. The science of fermentation and the technological and health functionality of fermented foods is reviewed considering the growing interest worldwide in fermented foods and beverages and the huge potential of the technology for reducing food loss and improving nutritional food security.