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BACKGROUND: Ginseng-Douchi (GD) is a complex fermented product of ginseng and soybean, similar to natto, and is effective in the treatment of hyperlipidemia, but the mechanism of action involved needs to be further explored. RESULTS: The present study combines a comprehensive strategy of network pharmacology and metabolomics to explore the lipid-lowering mechanism of GD. First, a hyperlipidemia rats model induced by a high-fat diet was established to evaluate the therapeutic effects of GD. Second, potential biomarkers were identified using serum metabolomics and metabolic pathway analysis was performed with MetaboAnalyst. Third, network pharmacology is used to find potential therapeutic targets based on the blood-influencing components of GD. Finally, core targets were obtained through a target-metabolite and the enrichment analysis of biomarkers-genes. Biochemistry analysis showed that GD exerted hypolipidemic effects on hyperlipidemic rats. Nineteen potential biomarkers for the GD treatment of hyperlipidemia were identified by metabolomics, which was mainly involved in linoleic acid metabolism, glycerophospholipid metabolism, ether lipid metabolism, alpha-linolenic acid metabolism and glycosylphosphatidylinositol-anchor biosynthesis. GD had a callback function for ether lipid metabolism and glycerophospholipid metabolism pathways. Eighteen blood components were identified in serum, associated with 85 potential therapeutic targets. The joint analysis showed that three core therapeutic targets were regulated by GD, including PIK3CA, AKT1 and EGFR. CONCLUSION: This study combines serum medicinal chemistry of traditional Chinese medicine, network pharmacology and metabolomics to reveal the regulatory mechanism of GD on hyperlipidemia. © 2024 Society of Chemical Industry.
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The present study comprehensively characterized the flavor differences between different varieties of douchis from different origins using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) coupled with gas chromatography-olfactometry-quadrupole time-of-flight mass spectrometry (GC-O-QTOF/MS). A total of 91 volatile organic compounds (VOCs) were identified using HS-GC-IMS and 70 VOCs were identified using GC-O-QTOF/MS, mainly including acids, aldehydes, esters and alcohols. Additionally, 23 key aroma-presenting compounds were screened in five douchi species using relative odor activity value (ROAV) and the aroma compounds that contributed the most to the aroma varied among the five douchi species. Comparative analysis of the GC-IMS and GC-O-QTOF/ MS results yielded 13 VOCs that were detected by both techniques. Nonanal, hexanal, eucalyptol, 1-octen-3-ol, isoamyl acetate, and 2-pentylfuran were identified as key VOCs in the douchi species using both methods. These findings will provide deeper insights for exploring flavor differences in douchi from different geographic sources.
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Aromatizantes , Cromatografía de Gases y Espectrometría de Masas , Odorantes , Gusto , Compuestos Orgánicos Volátiles , Compuestos Orgánicos Volátiles/química , Compuestos Orgánicos Volátiles/análisis , Aromatizantes/química , Aromatizantes/análisis , Odorantes/análisis , Espectrometría de Movilidad Iónica/métodosRESUMEN
Douchi is a Chinese traditional fermented food with a unique flavor. Methyl anthranilate (MA) plays an important role in formation of this flavor. However, the complicated relationship between the MA formation and the metabolic mechanism of the key functional microorganisms remains unclear. Here, we elucidated the response mechanism of aroma production driven by high salt stress in Trichomonascus ciferrii WLW (T. ciferrii WLW), which originates from the douchi fermentation process. The highest production of MA was obtained in a 10% NaCl environment. The enhanced expression of the key enzyme genes of the pentose phosphate pathway and shikimic acid pathway directed carbon flow toward aromatic amino acid synthesis and helped sustain an increased expression of metK to synthesize a large amount of the methyl donor S-adenosylmethionine, which promoted methyl anthranilate yield. This provides a theoretical basis for in-depth research on the applications of the flavor formation mechanisms of fermented foods.
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BACKGROUND: Yangjiang douchi (YD) is a traditional fermented soybean product, which is popular in Chinese cuisine for its unique flavor. However, due to its high salt content and unstable flavor, its competitiveness in the international market is gradually weakening. Microorganisms have a key role in the production process of YD because it is a fermented food but the effect of microorganisms on the volatile compounds of YD is also not currently clear. RESULTS: In this paper, aroma compounds and microbial diversity in different fermentation stages of YD were analyzed using gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and IlluminaMiseq system sequencing. A total of 78 aroma-active compounds were detected throughout the fermentation process and they influenced the formation of flavor in YD. Fungi flora were relatively single in YD, and bacteria were rich and varied. A total of 418 species of bacteria were present during fermentation, with unclassified_Staphylococcus, Staphylococcus_kloosii, and Bacillus_velezensis_Bacillus predominating. There were 25 species of fungi at the species level, and Aspergillus minisclerotigenes (OTU 4) played a dominant role in the whole fermentation process. CONCLUSION: Staphylococcus and Bacillus in the bacterial genus were strongly correlated with most flavor compounds detected, and A. minisclerotigenes in the fungi were more relevant to flavor compounds. This research provides a theoretical basis for the enhancement of the flavor of traditional fermented douchi in China. © 2024 Society of Chemical Industry.
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Bacterias , Fermentación , Aromatizantes , Hongos , Cromatografía de Gases y Espectrometría de Masas , Alimentos de Soja , Gusto , Compuestos Orgánicos Volátiles , Compuestos Orgánicos Volátiles/metabolismo , Compuestos Orgánicos Volátiles/química , Compuestos Orgánicos Volátiles/análisis , Bacterias/clasificación , Bacterias/metabolismo , Bacterias/genética , Bacterias/aislamiento & purificación , Hongos/metabolismo , Hongos/clasificación , Hongos/genética , Hongos/aislamiento & purificación , Aromatizantes/metabolismo , Aromatizantes/química , Alimentos de Soja/análisis , Alimentos de Soja/microbiología , Glycine max/química , Glycine max/microbiología , Glycine max/metabolismo , Alimentos Fermentados/microbiología , Alimentos Fermentados/análisis , Odorantes/análisis , ChinaRESUMEN
BACKGROUND: The excessive salt intake associated with Douchi has become a topic of controversy. Addressing this concern and enhancing its market competitiveness necessitates the application of salt reduction fermentation in Douchi. Therefore, to promote the application of salt reduction fermentation in Douchi, a comprehensive study was undertaken aiming to investigate the differences in biogenic amines, volatile compounds and non-volatile compounds in Douchi with varying salt content. RESULTS: The findings unequivocally demonstrate that salt hampers the formation of metabolites in Douchi. As the salt content increased, there was a significant decrease (P < 0.05) in the levels of total acid, amino-type nitrogen and free amino acids in Douchi. Notably, when the salt content exceeded 80 g kg-1, there was a substantial reduction (P < 0.05) in putrescine, lactic acid and malic acid levels. Similarly, when the salt content surpassed 40 g kg-1, ß-phenethylamine and oxalic acid levels exhibited a significant decline (P < 0.05). Furthermore, the results of E-nose and principal component analysis based on headspace solid phase microextraction gas chromatography-mass spectrometry revealed notable discrepancies in the volatile compound content between Douchi samples with relatively low salt content (40 and 80 g kg-1) and those with relatively high salt content (120, 160 and 200 g kg-1) (P < 0.05). By employing partial least squares discriminant analysis, eight distinct volatile compounds, including o-xylene, benzaldehyde and 1-octen-one, were identified. These compounds exhibited higher concentrations in Douchi samples with relatively low salt content (40 and 80 g kg-1). The sensory results showed that Douchi samples with lower salt content exhibited higher scores in the soy sauce-like and Douchi aroma attributes. CONCLUSION: In conclusion, this study significantly enhances our understanding of the impact of salt on metabolites in Douchi and provides invaluable insights for the development of salt reduction fermentation in this context. © 2024 Society of Chemical Industry.
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Aminas Biogénicas , Fermentación , Cromatografía de Gases y Espectrometría de Masas , Compuestos Orgánicos Volátiles , Aminas Biogénicas/análisis , Aminas Biogénicas/metabolismo , Compuestos Orgánicos Volátiles/metabolismo , Compuestos Orgánicos Volátiles/química , Compuestos Orgánicos Volátiles/análisis , Cloruro de Sodio/análisis , Cloruro de Sodio/metabolismoRESUMEN
In this study, we conducted an analysis of the differences in nutrient composition and protein structure among various fermented soybean products and their impacts on the gut microbiota of rats. Conventional physicochemical analysis was employed to analyze the fundamental physicochemical composition of the samples. Additionally, we utilized high-performance liquid chromatography and ELISA techniques to quantify the presence of antinutritional compounds. Fourier infrared spectroscopy was applied to delineate the protein structure, while 16 s rRNA gene sequencing was conducted to evaluate alterations in gut microbiota abundance. Subsequently, KEGG was utilized for metabolic pathway analysis. Our findings revealed that fermented soybean products improved the nutritional profile of soybeans. Notably, Douchi exhibited the highest protein content at 52.18 g/100 g, denoting a 26.58 % increase, whereas natto showed a 24.98 % increase. Douchi and natto demonstrated the most substantial relative amino acid content, comprising 50.86 % and 49.04 % of the total samples, respectively. Moreover, the levels of antinutritional factors markedly decreased post-fermentation. Specifically, the α-helix content in doujiang decreased by 13.87 %, while the random coil content in soybean yogurt surged by 132.39 %. Rats that were fed FSP showcased notable enhancements in gut microbiota and associated metabolic pathways. A strong correlation was observed between nutrient composition, protein structure, and gut microbiota abundance. This study furnishes empirical evidence supporting the heightened nutritional attributes of FSPs.
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Fermentación , Microbioma Gastrointestinal , Glycine max , Valor Nutritivo , Animales , Glycine max/química , Ratas , Masculino , Ratas Sprague-Dawley , Alimentos Fermentados/microbiología , Proteínas de Soja , Alimentos de Soja/análisis , Alimentos de Soja/microbiología , Aminoácidos/análisisRESUMEN
In order to enhance the aromatic profile of industrial Douchi, a comprehensive investigation was undertaken to assess the impact of aroma-enhancing microorganisms on the sensory attributes of Douchi. This evaluation utilized a combination of analytical techniques, including electronic nose analysis, gas chromatography-ion mobility spectrometry (GC-IMS), gas chromatography-mass spectrometry (GC-MS), and descriptive sensory analysis (DA). Both GC-IMS and GC-MS revealed significant changes in the volatile composition of Douchi following the addition of aroma-enhancing microorganisms (p < 0.05). Partial least squares-discriminant analysis (PLS-DA) identified benzaldehyde, benzene acetaldehyde, 3-octanone, and ethyl 2-methylbutyrate as significant differentiating volatile compounds. Additionally, compared to the control group, the sensory attributes of sourness in Douchi were significantly reduced (p < 0.001), while the attributes of wine-like and sweetness were notably enhanced (p < 0.05) when the ratio of G. candidum to C. versatilis was 1:1 (GCC group). By calculating the odor-activity values (OAVs) of key volatiles, it can be hypothesized that this aroma improvement of Douchi may be attributed to an increase in the typical volatiles (3-methyl-1-butanol, 1-octen-3-ol, 3-octanol, and 3-octanone) and ethyl 2-methylbutanoate with high OAVs (2340849.64 â¼ 16695327.86), as well as to decreases in the musty acetophenone. In conclusion, the aroma profile of Douchi was significantly enhanced when G. candidum and C. versatilis were added at a ratio of 1:1. This study provides valuable insights into the development of aroma enhancers for improving the sensory profile of Douchi.
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Cetonas , Odorantes , Compuestos Orgánicos Volátiles , Odorantes/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Nariz Electrónica , Espectrometría de Movilidad Iónica , Compuestos Orgánicos Volátiles/análisisRESUMEN
Douchi is a kind of traditional Chinese fermented soybean product with outstanding umami taste. Besides the umami amino acids in Douchi, peptides were also considered as an important contributor for the umami taste of Douchi. Peptides with molecular weight below 0.66 kDa accounted for more than 50 % in all samples except for TongChuan Douchi, and a total of 421 peptides were identified from the ten kinds of Douchi samples by using LC-MS/MS. Combined with sensory evaluation results, 19 peptides containing Glu, Asp or known umami peptide sequences were chosen as potential umami peptides via PLS-DA and RDA analysis. Among them, 17 soluble peptides exhibited obvious umami taste and the threshold of 7 peptides were lower than MSG solution. Especially, the VD was detected with a minimum umami taste threshold at 0.16 mg/mL. The results indicated that the umami peptides might be the important components affecting the umami taste of Douchi.
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Péptidos , Espectrometría de Masas en Tándem , Cromatografía Liquida , Péptidos/química , Gusto , China , Proteómica , Receptores Acoplados a Proteínas G/metabolismo , Simulación del Acoplamiento MolecularRESUMEN
To attain the differences in the flavor profile of Douchi, the key aroma-active compounds of three types of Douchi were investigated. The "Sauce-like", "Smoky", "Nutty", "Roast", "Caramel", and "Flower" of Douchi were favored by customers. Further, a total of 179 volatile compounds were identified using HS-SPME-GC-MS, and 29 aroma compounds were detected using GC-O-MS. Based on the quantification, 9, 13, and 10 compounds were regarded as aroma-active compounds in Yangjiang Douchi (YJ), Pingjiang Douchi (PJ), and Liuyang Douchi (LY), respectively. Moreover, the mixture of these aroma-active compounds successfully simulated the main aromas of PJ, LY, and YJ. And omission experiments confirmed that guaiacol was the key aroma compound for LY, benzene acetaldehyde, dimethyl trisulfide, and 2-acetyl pyrrole were important for YJ, benzene acetaldehyde and 3,5-diethyl-2-methyl pyrazine notably contributed to key aroma of PJ.
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Yongchuan douchi is a well-loved condiment. However, the aroma of rapid Yongchuan douchi is inferior to that of traditional Yongchuan douchi. The objective of this study was to improve the aroma quality of rapid Yongchuan douchi and evaluate the effect of aroma enhancement from the perspective of consumers. The aroma characteristics of samples were analyzed by consumers through flash profile (FP) (n = 15) and rate-all-that-apply (RATA) (n = 75). The results showed improvement in the aroma quality of rapid Yongchuan douchi with the two yeast strains, and consumers could perceive the modification of the aroma characteristics. It shows that the douchi aroma and sour aroma of rapid Yongchuan douchi increased significantly after aroma-enhancing fermentation, while the soy sauce aroma, soybean aroma, and musty aroma decreased. Similar results were obtained from FP and RATA. RATA showed that rapid Yongchuan douchi with aroma-enhancing fermentation aroused higher levels of positive emotions, which may increase the acceptance of consumers to rapid Yongchuan douchi. In summary, the aroma quality and consumer preference of rapid Yongchuan douchi were enhanced. The work provides insights into the quality improvement of rapid Yongchuan douchi from the perspective of consumers.
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In this study, the effect of Douchi extract (DWE) on α-glucosidase and angiotensin-converting enzymes (ACE) were investigated, and several novel peptides with inhibitory activity against α-glucosidase and ACE were identified using peptidomics approach based on UPLC-MS/MS. The average inhibition rates of DWE on α-glucosidase and ACE were 73.75-78.10% and 4.56-27.07%, respectively. In the DWE, a total of 710 peptides were detected. Two novel peptides with potential inhibitory activity against α-glucosidase were identified using the correlation analysis, database alignment and molecular docking methods. They were DVFRAIPSEVL and DRPSINGLAGAN, with the IC50 values of 0.121 and 0.128 mg/mL, respectively. Also, four novel peptides with potential inhibitory activity against ACE were identified: PSSPFTDLWD, EEQDERQFPF, PVPVPVQQAFPF and PSSPFTDL, with IC50 values of 1.388, 0.041, 0.761 and 0.097 mg/mL, respectively. These results indicated that combining peptidomics and molecular docking is an effective alternative strategy for rapidly screening numbers of novel bioactive peptides from foods.
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The food industry is facing the challenge of creating innovative, nutritious, and flavored plant-based products, due to consumer's increasing demand for the health and environmental sustainability. Fermentation as a unique and effective tool plays an important role in the innovation of food products. Traditional fermented soy foods are popular in many Asian and African countries as nutritious, digestible and flavorful daily staples or condiments. They are produced by specific microorganisms with the unique fermentation process in which microorganisms convert the ingredients of whole soybean or soybean curd to flavorful and functional molecules. This review provides an overview on traditional fermented food produced from soy, including douchi, natto, tempeh, and sufu as well as stinky tofu, including the background of these products, the manufacturing process, and the microbial diversity involved in fermentation procedures as well as flavor volatiles that were identified in the final products. The contribution of microbes to the quality of these five fermented soy foods is discussed, with the comparison to the role of cheese ripening microorganisms in cheese flavor formation. This communication aims to summarize the microbiology of fermented soy foods in Asia, evoking innovative ideas for the development of new plant-based fermented foods especially plant-based cheese analogues.
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Queso , Alimentos Fermentados , Alimentos de Soja , Alimentos de Soja/microbiología , Alimentos Fermentados/microbiología , Asia , Glycine max , FermentaciónRESUMEN
SCOPE: Two peptides VY (Val-Tyr) and SFLLR (Ser-Phe-Leu-Leu-Arg) are recently identified from soy-fermented douchi with hypoglycemic activity in cells. The study aims to understand their potential effects on glucose metabolism and insulin sensitivity as well as their mechanisms of action in a high-fat diet (HFD) induced insulin resistant model. METHODS AND RESULTS: C57BL/6 mice are fed HFD for 8 weeks, followed by peptide supplementation (doses: 10 and 50 mg kg-1 body weight) for 8 weeks. Peptides supplementation, especially SFLLR, reduces body weight gain, insulin resistance, hyperglycemia, inflammation, liver injury, and lipid accumulation. In both muscle and liver, both peptides activate glycogen synthase (GS), the key enzyme for glycogen synthesis, and also inhibit phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6PC), two rate-limiting enzymes for gluconeogenesis, via insulin and AMPK (5'-adenosine monophosphate-activated protein kinase) signaling pathways. Furthermore, VY and SFLLR supplementation reverse HFD-induced gut dysbacteriosis by decreasing the abundance of Enterococcus, Oscillibacter, and Deferribacter, and also increase the abundances of Alistipes, Lactobacillus, Faecalibaculum, Akkermansia, and Bifidobacterium (usually beneficial in the intestine). CONCLUSION: The study reveals the potential applications of peptides VY and SFLLR as a diet-based strategy for the prevention of type 2 diabetes.
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Diabetes Mellitus Tipo 2 , Resistencia a la Insulina , Animales , Ratones , Insulina/metabolismo , Dieta Alta en Grasa/efectos adversos , Diabetes Mellitus Tipo 2/metabolismo , Disbiosis/metabolismo , Ratones Endogámicos C57BL , Hígado/metabolismo , Peso Corporal , Glucosa/metabolismo , HomeostasisRESUMEN
Two novel hypoglycemic peptides VY and SFLLR were identified from douchi as the major peptides responsible for the glucose uptake activity. The present work aimed to elucidate their digestion, absorption and transport properties using simulated digestion and Caco-2 cell monolayers transport models. Besides, the effects of digestion and absorption on the structure and activity were also studied. The results showed that VY was resistant to gastrointestinal tract digestion and could cross Caco-2 cell monolayers intactly via both TJs-mediated passive paracellular pathway and PepT1-mediated active route. In comparison, SFLLR was partially degraded into small fragments of SFLL, SFL, and SF by the digestive system, leading to increased glucose uptake activity. Notably, SFLLR, SFLL, and SFL were partly hydrolyzed by aminopeptidase N or dipeptidyl peptidase IV during transport, but they were transported intact. SFL was transported via both paracellular diffusion and PepT1-mediated routes, while SFLLR and SFLL were via paracellular route only.
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Digestión , Péptidos , Humanos , Células CACO-2 , Péptidos/química , Transporte Biológico , GlucosaRESUMEN
Mucor racemosus is the predominant fungal in the zhiqu stage of the fermentation of Yongchuan Douchi (Mucor-type), which plays an important role in the fermentation process of Yongchuan Douchi. However, there is a lack of information on the genetic analysis of M. racemosus. In this study, we isolated and identified M. racemosus C (accession no JAPEHQ000000000) from Yongchuan Douchi and analyzed the physiological indicators, then genomic information of the strain to perform a comprehensive analysis of its fermentation capacity and safety. M. racemosus C had neutral protease activity up to 68.051 U/mL at 30 °C and alkaline protease activity up to 57.367 U/mL at 25 °C. In addition, comparing the genomic data with the COGs database (NCBI), it was predicted that M. racemosus C undergoes extensive amino acid metabolism, making C suitable for the production of fermented foods (e.g., Douchi, Syoyu, and sufu). Finally, we performed virulence genes and resistance genes analysis, hemolysis experiment, aflatoxins assay, antibiotic resistance assay to evaluate the safety of M. racemosus C, and the results showed that M. racemosus C was safe, non-toxin-producing and non-hemolytic.
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Alimentos Fermentados , Mucor , Mucor/genética , Mucor/química , FermentaciónRESUMEN
This study aims to understand the development and succession of the microbial community during the production of traditional Aspergillus-type Douchi as well as their effects on the formation and variation of characteristic aroma compounds. High-throughput sequencing technology, solid-phase microextraction, gas chromatography-mass spectrometry, and Spearman correlation analysis were conducted to study the changes in the microbial community and characteristic flavor during the fermentation process. Aspergillus spp. was dominant in the early stage of fermentation, whereas Staphylococcus spp., Bacillus spp., and Millerozyma spp. became dominant later. At the early stage, the main flavor compounds were characteristic soy-derived alcohols and aldehydes, mainly 1-hexanol, 1-octen-3-ol, and nonanal. In the later stage, phenol, 2-methoxy-, and 3-octanone were formed. Correlation analysis showed that six bacterial genera and nine fungal genera were significantly correlated with the main volatile components, with higher correlation coefficients, occurring on fungi rather than bacteria. Alcohols and aldehydes were highly correlated with the relative abundance of bacteria, while that of yeast species such as Millerozyma spp., Kodamaea spp., and Candida spp. was positively correlated with decanal, 3-octanol, 2-methoxy-phenol, 4-ethyl-phenol, 3-octanone, and phenol. The novelty of this work lies in the molds that were dominant in the pre-fermentation stage, whereas the yeasts increased rapidly in the post-fermentation stage. This change was also an important reason for the formation of the special flavor of Douchi. Correlation analysis of fungi and flavor substances was more relevant than that of bacteria. As a foundation of our future focus, this work will potentially lead to improved quality of Douchi and shortening the production cycle by enriching the abundance of key microbes.
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Douchi is a traditional famous seasoning in China. This study adopted electronic tongue and metabolomics to analyze the taste characteristics and taste active compounds of 12 samples from three most famous types of Douchi (Liuyang Douchi, Yangjiang Douchi, Yongchuan Douchi). Thirty-six differential metabolites mainly enriched from the arginine biosynthesis were identified among these Douchis. Umami and bitterness are considered as two taste that bring positive and negative perceptions for Douchi. The succinic acid was found to be responsible for the umami in LY, YJ and YC Douchi, with the TAVs of 2054, 643, 174, respectively, rather than the glutamic acid and aspartic acid. The leucine was identified as the main metabolite for bitterness, with the TAVs of 9, 9, 7 respectively. KEGG enrichment analysis found that the umami, sourness and saltiness might be related to alanine, aspartate and glutamate metabolism and the bitterness might be related to aminoacyl-tRNA biosynthesis pathway.
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Metabolómica , Gusto , Ácido Glutámico , ChinaRESUMEN
BACKGROUND: As a traditional Chinese condiment, douchi has attracted attention in Asian and European countries because of its high nutrient content and unique flavors. Douchi is currently produced mostly by natural fermentation. The quality of douchi produced in this way is affected by microbial species, temperature, humidity, and season, so the physical and chemical properties of the product, the content of flavor substances, and its safety vary. In this study, four safe strains with high protease activity, screened previously, namely Bacillus velezensis, Bacillus amyloliquefaciens, Lichtheimia ramosa, and Lichtheimia corymbifera, were used as starter cultures for douchi fermentation. RESULTS: After 35 days, the results showed that the pH, titratable acids, free amino-type nitrogen, amino acids, the total number of colonies, and neutral protease activity of all samples had reached an average level. Through gas chromatography-mass spectrometry (GC-MS), the content of key aroma substances aldehydes and esters was higher than in commercial douchi and the free amino acid content of douchi fermented by the four strains was three to five times that of commercial douchi. Douchi fermented by Bacillus amyloliquefaciens had more flavor substances and the highest 2, 2-diphenyl-1-(2, 4, 6-trinitrophenyl) hydrazyl (DPPH) free radical scavenging rates of 92.4%. Four samples yielded total phenolic content and soy isoflavones in the range of 0.98-1.93 g kg-1 and 0.58-0.89 g kg-1 , respectively. CONCLUSION: These findings indicate that the use of a high-protease activity starter to produce douchi can improve the quality of douchi to a certain extent. The douchi obtained using Bacillus amyloliquefaciens not only has a good flavor but also has a high level of antioxidant activity. © 2023 Society of Chemical Industry.
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Antioxidantes , Péptido Hidrolasas , Antioxidantes/metabolismo , Fermentación , Péptido Hidrolasas/metabolismo , Aminoácidos/metabolismo , Endopeptidasas/metabolismoRESUMEN
Douchi is a traditional salt-fermented soybean food with various bioactivities, such as anti-oxidation, anti-diabetes, and anti-hypertension, which are greatly affected by the activities of protease and ß-glucosidase during koji production. Edible mushroom by-products are ideal ingredients for enhancing food flavor and nutritional quality due to their unique nutritional characteristics of high protein, rich amino acids, and low calories. However, there is no research on the preparation of Douchi by the mixed fermentation of edible mushroom by-products and soybeans. In this study, response surface methodology (RSM) was used to optimize the fermentation conditions of edible mushroom by-product Douchi koji (EMDK) with protease and ß-glucosidase activities as indicators, and the changes in the main bioactive compounds and antioxidant activities of unfermented raw samples (URS), Douchi koji without edible mushroom by-product (DKWE), and EMDK were compared. The results of single-factor tests and RSM showed that the optimal fermentation conditions of EMDK were the Aspergillus oryzae to Mucor racemosus ratio of 1:1, inoculation amount of 6%, edible mushroom amount of 21%, and fermentation time of 63 h, and the activities of protease and ß-glucosidase under these conditions were 796.03 ± 15.01 U/g and 1175.40 ± 36.98 U/g, respectively. Additionally, compared with URS and DKWE, the contents of total isoflavones and ß-glucoside isoflavones in EMDK were notably decreased, while the contents of amino nitrogen, total phenolics, total flavonoids, and aglycone isoflavone, as well as the antioxidant capacity were significantly increased. Furthermore, significant correlations were found between the above components and antioxidant capacity. These results showed that edible mushroom by-product could be incorporated into soybeans for co-fermentation, conferring higher nutritional value to and antioxidant capacity of Douchi koji.
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Ba-bao Douchi, traditionally produced and spontaneously fermented for 1-2 years, has a unique flavor. However, little information is known about microorganisms and volatile flavors, particularly their relationship. In this study, the aroma profiles including the key aroma compounds, and bacterial communities were characterized and the correlations between dominant bacterial genera with key aroma compounds were studied during the post-fermentation of Ba-bao Douchi. The research showed that 12 bacterial genera were identified as the dominant genus by high-throughput sequencing. A total of 84 volatile compounds were detected by HS-GC-IMS and HS-SPME-GC-MS. Odor activity value (OAV) and gas chromatography-Mass spectrometry-olfactometry (GC-MS-O) were combined to determine the key volatile compounds, and the main volatile compounds including ethyl hexanoate, ethyl heptanoate, isovaleraldehyde, (+)-α-pinene, beta-phellandrene, were found to be responsible for the strong fruitiness, chocolate fragrance, fresh scent flavor, and ginger flavor of Ba-bao Douchi. Pearson correlation analysis showed that 5 dominant bacterial genera were positively associated with > 6 key volatile compounds (p < 0.01, |r| > 0.7). Thus, these bacterial genera might have an effect on the biosynthesis of volatile components. This study provides a theoretical reference for revealing the functional microorganisms and improving the flavor quality of Ba-bao Douchi.