Later Stages Of Fermentation Research Articles

Acidity, sugar, and alcohol contents during the fermentation of Osmanthus-flavored sweet rice wine and microbial community dynamics.

Sweet rice wine is a popular traditional Chinese rice wine widely loved by Chinese people for its high nutritional value. Osmanthus flower petals contain various nutrients and have good medicinal value. However, the dynamics of the sugar level, acidity, alcohol content, and microbial community during the fermentation of Osmanthus-flavored sweet rice wine have not been evaluated, which can lead to the unstable quality of Osmanthus flower sweet rice wine (OFSRW). In this study, the dynamic changes in sugar level, acidity, alcohol content, microbial community composition, and microbial metabolic pathways during traditional fermentation of OFSRW at four-time points-0 h (AG0), 24 h (AG24), 36 h (AG36), and 43 h (AG43)-were analyzed via direct titration, total acid assays, alcoholometry, and high-throughput macrogenomic techniques. First, we found that bacteria were the dominant microorganisms in the early stage of OFSRW fermentation (AG0), fungi were the dominant microorganisms in the middle and late stages of fermentation (AG24 and AG36), and Rhizopus was the main fungal genus throughout fermentation. Acidity and total sugars increased with fermentation time, and alcohol was not detected until the end of fermentation. Diversity analysis revealed that the dominant species at the beginning of natural fermentation was A. johnsonii, and R. delemar became the dominant species as natural fermentation progressed. Metabolic pathway analysis revealed that energy production and conversion, carbohydrate transport, amino acid transport, and metabolic pathways were the most active metabolic pathways in the fermenter. These results provide a reference basis for changes in the microbial community during the fermentation of cinnamon-flavored sweet rice wine.

Effects of Lactiplantibacillus plantarum on Metabolites and Flavors in Synthetic Microbiota During Baijiu Fermentation.

The distinctive flavor and aroma of Chinese baijiu are closely linked to the microorganisms involved in the fermentation process. Lactiplantibacillus plantarum, a dominant species in the fermentation of Chinese baijiu, has become a prominent research focus. In this study, we selected well-characterized pure cultures of microorganisms to construct diverse chassis microflora. The primary objective was to investigate the effects of L. plantarum on the fermentation process of Chinese baijiu and its association with metabolites produced by different chassis microflora. Our results demonstrated that the concentrations of ethyl lactate and other volatile aromatic compounds increased in all fermentation protocols where L. plantarum was added. The addition of L. plantarum also significantly increased the concentration of total organic acids, particularly lactic acid, which rose by 17 to 123 times. Furthermore, L. plantarum helped maintain the stability of ethanol concentration during the middle and late stages of fermentation. Notably, among the three different chassis microbial fermentation protocols involving L. plantarum, the protocol with the highest microbial diversity exhibited a greater capacity to produce lactic acid (1.56 ± 0.19 mg/g), ethanol (5.74 ± 0.47 mg/g), and reducing sugars (6.39 ± 0.31 mg/g). These findings provide valuable insights into the potential of L. plantarum for modulating the flavor of Chinese baijiu.

Analysis of Microbial Diversity Dominating Nitrite Enzymatic Degradation and Acidic Degradation in the Fermentation Broth of Northeast Sauerkraut.

Nitrite hazard is an important food safety issue in the production process of Chinese Northeastern sauerkraut, but this nitrite can be eliminated through microbial enzymatic degradation and acidic degradation as fermentation progresses. Therefore, analyzing the microbial diversity that dominates nitrite degradation in Chinese Northeastern sauerkraut can provide a reference for its safe production. In this study, based on the dynamic monitoring of nitrite concentration, pH, and the abundance of nitrite reductase genes (nirK and nirS) and the application of high-throughput sequencing technology and various statistical analysis methods, the microbial groups associated with nitrite enzymatic degradation and acidic degradation in Northeast sauerkraut fermentation broth were analyzed. During the nitrite peak period of Northeast sauerkraut fermentation broth, the nitrite concentration reached 32.15 mg/kg, the pH was 4.7, and the abundances of the nitrite reductase genes nirK and nirS were 3.0 × 104 and 4.9 × 104 copies/μL, respectively. At this stage, nitrite degradation was likely dominated by enzymatic activities. Microbial phyla such as Bacteroidetes (38.8%), Proteobacteria (19.2%), and the archaeal phylum Euryarchaeota (1.1%) showed strong correlations with nitrite. Among the genera within these three phyla, Chryseobacterium, Elizabethkingia, and Aeromonas exhibited significant differences in abundance compared to the late fermentation stage and were identified as the primary microbial groups likely driving the enzymatic degradation. During the nitrite degradation period, the nitrite concentration decreased to 0.04 mg/kg, the pH dropped to 3.6, and the abundances of nirK and nirS genes were reduced to 1.0 × 103 copies/μL. At this stage, the nitrite degradation was primarily driven by acid activity. The bacterial phylum Firmicutes (99%) exhibited a strong correlation with pH. Within this phylum, the genus Lactobacillus, which showed significant differences in abundance compared to the early fermentation stage, was identified as the primary microbial group indirectly contributing to acidic degradation. This study provides guidance for the isolation of food-grade prokaryotic microbial strains capable of nitrite degradation. Additionally, the findings offer a methodological reference for conducting future research on nitrite-degrading microorganisms in fermented vegetable broths.

Influence of indigenous non-Saccharomyces yeast strains on the physicochemical and sensory properties of wine fermentation: a promising approach to enhancing wine quality.

This study explores the potential of indigenous non-Saccharomyces yeasts isolated from Vitis vinifera L. grape skins to improve the quality of regional wines by enhancing their physicochemical and sensory characteristics. Five promising yeast strains were identified at different stages of fermentation: Hanseniaspora opuntiae (J1Y-T1), H. guilliermondii (Y5P-T5), H. uvarum (JF3-T1N), Pichia kudriavzevii (Y8P-T8), and Starmerella bacillaris (WMP4-T4). Among these, H. uvarum and S. bacillaris were particularly noteworthy due to their superior alcohol production, achieving levels of 8.16 ± 0.05% and 8.04 ± 0.04% (v/v), respectively, and demonstrating higher alcohol tolerance even in later fermentation stages. Hanseniaspora uvarum also showed exceptional resilience, with a half-life of 3.34 ± 0.03 days and a Km value of 1.0200 ± 0.0100 mol L⁻¹, achieving the highest biomass even in the later stages of fermentation. High-Performance Liquid Chromatography analysis revealed that while tartaric acid levels remained constant, malic acid content decreased, and acetic acid was produced by all strains. Solid-Phase Microextraction-Gas Chromatography Mass Spectrometry identified ethyl acetate as the dominant volatile compound, with H. uvarum producing the highest concentration (43.411 ± 1.602%), contributing to a fruitier aroma and flavor. The combined attributes of H. uvarum higher alcohol content, enhanced fruity notes, improved clarity, lower acetic acid (0.52 ± 0.03 g L⁻¹), and significant residual sugar (162.37 ± 2.48 g L⁻¹) make it a promising candidate for improving the overall quality of regional wines. Incorporating H. uvarum into mixed starter cultures with specific Saccharomyces strains could further optimize the wine fermentation process.

Engineering the Methylerythritol Phosphate Pathway and Using a Temporal Promoter for Enhanced Lycopene Production in Rhodobacter sphaeroides HY01.

Rhodobacter sphaeroides HY01 is a high-yield strain for industrial production of coenzyme Q10 (Q10), indicating its potential for producing other terpenoids. However, the production of Q10 substantially depletes isoprene precursors, nearly eliminating other terpenoids like spheroidene and spheroidenone commonly found in wild-type R. sphaeroides. Lycopene was used as an example to demonstrate its potential for terpenoid biosynthesis. By refactoring the methylerythritol phosphate (MEP) pathway, such as overexpressing crtE and introducing crtI4, lycopene production reached 126.1 mg/L in HY01. However, further overexpression of the deoxy-d-xylulose-5-phosphate synthase, 1-deoxy-d-xylulose 5-phosphate reductoisomerase, and isopentenyl-diphosphate isomerase genes led to strain degradation, significantly reducing lycopene production. Fine-tuning the engineered PrrAB two-component system, which upregulated the MEP pathway, increased lycopene production to 154.9 mg/L. Inspired by this result, a series of native promoters with varying strengths were identified and characterized through transcriptomic analysis during the late fermentation stage. Using these temporal promoters to control genes in the MEP pathway ultimately increased lycopene production to 283.1 mg/L, the highest reported in R. sphaeroides. These results underscore the potential of HY01 as a chassis for terpenoid biosynthesis.

Study on the relationship between microbial community succession and physicochemical factors in the fermentation of rice-flavor Baijiu based on high-throughput and redundancy analysis techniques

Fermented grains are the main carrier of microbial fermentation and the direct source of Baijiu flavor substances, but so far, there are few studies on the changes in the fermented grains of rice-flavor Baijiu. This experiment systematically analyzed the correlation between microbial community succession and physicochemical factors in the fermentation process of two different types of rice (japonica: M and indica: H) fermented grains. The results showed that during the fermentation process, the changes in total acid, pH, starch, and total phenols of H and M were consistent. However, M and H showed different trends in terms of reducing sugar content and alcohol content. At the phylum level, both types of fermented grains had Firmicutes and Proteobacteria as the absolute dominant phyla. At the genus level, there was a slight difference in the dominant genera of M and H in the early stages, but the main genera in the later stages of fermentation were different. RDA analyses showed different correlations between dominant genera and physicochemical factors with some interesting results. The results of this study will provide a theoretical basis for the regulation of rice-flavor Baijiu fermentation.

Osteopontin associated Bifidobacterium bifidum microencapsulation modulates infant fecal fermentation and gut microbiota development

Probiotic supplementation is an effective method for improving infant gut health, and probiotic encapsulation can enhance probiotic viability under adverse environmental conditions while ensuring an adequate amount of probiotic is delivered to the target site to confer a health benefit for the host. In this study, Bifidobacterium bifidum R0071 was microencapsulated using pectin or alginate, combined bovine milk osteopontin (OPN) as an excipient during the microencapsulation process. The microencapsulated probiotics were subjected to in vitro simulated infant gastrointestinal digestion and a fecal fermentation model to assess survival capacity and their impact on gas and organic acid production, as well as the development of gut microbiota. The results demonstrated that microencapsulation in the presence of osteopontin increased simulated gastrointestinal survival. During infant fecal fermentation, a significant increase in total gas production (5.5–9.1 mL) was observed for the microencapsulated probiotic with even higher level of gas production observed for osteopontin associated microencapsulated probiotic during the late stage of fermentation (8–24 h). Infant fecal fermentation of the microencapsulated probiotic also produced substantial amounts of acetate (8–17 mM) and lactate (12–35 mM), along with minor amounts of succinate (1–2 mM) and propionate (0.5–2 mM). A positive correlation was observed between metabolite production and the number of viable B. bifidum R0071 entering colon fermentation, which significantly increased with the use of OPN in the microencapsulation process. The osteopontin associated microencapsulated probiotic also significantly elevated the relative abundance of Veillonella, which, along with Bifidobacterium, influenced gas and metabolite production. Overall, our findings demonstrate that incorporating OPN as an excipient in the microencapsulation of Bifidobacterium bifidum R0071 enhances probiotic viability and positively influences the development of infant gut microbiota, highlighting its potential application in promoting infant health.

Dynamic Analysis of Fermentation Quality, Microbial Community, and Metabolome in the Whole Plant Soybean Silage

Soybean (Glycine max (L.) Merr.) is an important oilseed crop, known for its rich nutritional content and high-quality protein. To address the shortage of feed protein resources and better utilize soybeans as a raw material, this study investigated the feasibility of using whole-plant soybean (WPS) as silage. As the ensiling period is a critical fermentation parameter, identifying the optimal fermentation duration was a key objective. The research involves fermenting WPS for silage production, conducted over five fermentation durations: 7, 15, 30, 60, and 90 days. The fermentation quality, microbial community, and metabolome of WPS silage were analyzed across these different time points. WPS silage fermented for 30 days exhibited optimal fermentation characteristics, with the highest lactic acid (LA) content observed at 30 days (p < 0.05), while butyric acid (BA) was detected only at 60 and 90 days. At 30 days, Enterococcus genera reached its peak relative abundance and was identified as the dominant genus. Random forest analysis highlighted Pantoea genera as the most influential biomarker. Metabolomic analysis revealed that the metabolic pathways involved in the biosynthesis of essential amino acids valine, leucine, and isoleucine were significantly enhanced during the later stages of fermentation compared to the earlier stages. Under natural fermentation conditions, the optimal fermentation period for WPS silage is approximately 30 days. These findings provide a theoretical basis for the utilization of WPS and the subsequent optimization of fermentation quality.

Effect of Lentilactobacillus buchneri on Chemical and Microbial Compositions of Herba Leonuri (Leonurus japonicus Houtt.)-Contained Alfalfa Silage

Lactic acid bacteria (LAB) inoculants are commonly used in silage production, yet their effects on silage containing antimicrobial components, such as those found in Leonurus japonicus, remain less explored. Herein, the harvested alfalfa were thoroughly mixed with dried Leonurus japonicus Houtt. (LJH) at a ratio of 9:1 on a fresh weight basis and treated without (CK) or with a lactic acid bacterial inoculant (L; Lentilactobacillus buchneri). The mixtures were stored under anaerobic conditions in vacuum-sealed polyethylene bags for 30 days at ambient temperature. The L-treated silage exhibited high levels of water-soluble carbohydrates (4.98% dry matter (DM)) and acid detergent fiber (27.88% DM). Compared to that of treatment CK, treatment with L increased the acetic acid content of the silage, as a result of increased (p < 0.05) bacterial dominance and decreased (p < 0.05) bacterial richness indices (e.g., Pielou’s E, Shannon, and Simpson) in the pre-storage period. However, these changes gradually reduced as the storage length increased. Treatment L reshaped the bacterial community structure of silage, by increasing the prevalence of Lactobacillus and reducing relative abundances of Enterococcus and Weissella. However, the principal coordinate and Bray–Curtis index analyses illustrated that samples from the L-treated silages exhibited similarities to the CK samples post-fermentation. Overall, the effect of LJH on LAB was only observed in the later stages of fermentation, which did not sufficiently change the silage quality. Hence, using LJH in silage is vital for clean livestock production without compromising the function of LAB when mixed with alfalfa silage.

Dynamic Changes in Yeast Populations and Aroma Composition of ‘Beimei’ (Vitis vinifera × Vitis amurensis) during Spontaneous Fermentation

‘Beimei’ is a hybrid cultivar of Vitis vinifera and wild Vitis amurensis with fungus- and cold-resistant characteristics that is widely grown in many regions of China. However, studies on the yeast diversity and aroma compound composition of this cultivar remain scarce. Here, indigenous yeast diversity, aroma compound composition, and their dynamic changes during the spontaneous fermentation of ‘Beimei’ were investigated and monitored using high-throughput sequencing and gas chromatography-mass spectrometry. The result indicated that non-Saccharomyces yeasts were predominant at the initial stages of ‘Beimei’ spontaneous fermentation and then sharply decreased. Cladosporium herbarum and Hanseniaspora uvarum were identified as the dominant species of filamentous fungi and yeast, respectively, at the beginning and on the first day of fermentation, whereas unclassified_f_Saccharomycetacease was dominant throughout fermentation, starting from the third day until the end of fermentation. The main volatile aroma chemicals were esters and alcohols, which accumulated abundantly at the late stage of fermentation. Taken together, this study represents the first step in exploring untapped yeast species and aroma compounds, which is helpful for the screening of native yeasts from ‘Beimei’ and producing distinctive aroma wines.

Enhancement of microbial safety and shelf life of salmon fillets by Lactiplantibacillus plantarum 299 V fermented in pomelo (Citrus maxima) peel extract

This study demonstrated the selective support of pomelo (Citrus maxima) peel extract (PPE) on Lactiplantibacillus plantarum 299 V growth, of which the resultant enhanced microbial safety and shelf life of salmon fillets. Incorporating PPE fermented with L. plantarum 299 V for 48 h (FPPE-48h) into alginate coating inhibited both the spiked Listeria monocytogenes and the spoilage - causing bacteria (psychotrophic bacteria, Enterobacteriaceae, Pseudomonas spp.) on salmon fillets during the 4-day chilled storage, resulting in 1–1.5 log CFU/g lower bacterial counts (P < 0.05). FPPE-48h effectively suppressed biogenic amine-producing bacteria, and remarkably retarded the accumulation of putrescine, cadaverine, histamine, and tyramine (P < 0.05). Last, the key antimicrobial substances generated during the late stage of PPE fermentation were profiled using non-target ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) analysis. This study exemplifies a successful approach of fermenting probiotic utilizing food by-products/food waste to enhance the safety and shelf life of ready-to-eat foods.

Analysis of the microbial community structure and characteristic flavor of traditional fermented bean paste.

Bean paste is a traditional Chinese fermented condiment, which is loved by consumers for its pleasant flavor and nutritional properties. However, the microbial communities and related flavor compounds in bean paste remain unclear. We studied the correlation between the core functional microorganisms and flavor compounds in bean paste samples at different fermentation stages. Bacterial and fungal communities changed significantly during fermentation. The results indicated that the dominant bacterial genera were Staphylococcus, Lactococcus, and Bacillus. The dominant fungi were Aspergillus and Lichtheimia. During the early and late stages of bean paste fermentation, alcohols, hydrocarbons, esters, and phenols were the main flavor compounds detected. The types and proportions of alcohols and esters in the bean pastes fermented for different durations were similar, whereas the relative contents of phenols and hydrocarbons were higher in the later stages of fermentation. Correlation analysis revealed that core functional microorganisms played a key role in the fermentation process, and the potential correlation between bacterial genera and flavors was stronger than that of fungal genera. Staphylococcus abundance was significantly correlated with the flavor levels of ethyl oleate, ç-pinene, diallyl disulfide, á-myrcene, D-limonene, and tetradecanoic acid, ethyl ester. The abundance of Aspergillus and Lichtheimia was significantly correlated with the flavor levels of á-myrcene, ç-pinene, and DL-3-phenyllactic acid. This study explored the relationship between microorganisms and flavor compounds in bean paste to deepen our understanding of the mechanism of flavor formation for bean paste.

Insight into the autochthonous lactic acid bacteria as starter culture for improving the quality of Sichuan radish paocai: Changes in microbial diversity and metabolic profiles

Paocai is a traditional Chinese fermented vegetable product popular in Asian countries. Recently, functional starters were used to control the fermentation process and improve the quality of paocai. In this study, three autochthonous lactic acid bacteria including Lactiplantibacillus plantarum LB6, Lactiplantibacillus pentosus LB3, and Weissella cibaria W51 were selected as starters and the effect of the starters on the fermentation of paocai was investigated. The results suggested that the inoculated fermentation led to a lower nitrite peak and more pronounced changes in pH and total titratable acid in the early stage of fermentation, compared with natural fermentation. Analysis of the flavor compounds indicated that the total content of volatile organic compounds of paocai through natural fermentation was significantly lower than that in inoculated fermentation. As for free amino acids, in the early stage of fermentation, the types and contents of free amino acids in the inoculated fermentation paocai were higher than those in the blank group. In the later stage of fermentation, the contents of amino acids representing umami and sweet tastes were also higher than those in the blank group. The bacterial community analysis showed that Lactobacillus and Lactococcus were the dominant bacteria in both inoculated fermentation and natural fermentation. Then, the correlations among physicochemical properties, microbial community and flavor compounds were revealed, and it was found that the dominant bacteria such as Lactococcus, Leuconostoc, Lactobacillus and Weissella displayed a considerable impact on the physical and chemical properties and flavor of paocai. In addition, the metabolic pathways involved in flavor formation and the abundance of related enzymes were elucidated. The abundance of enzymes involved in generating prephenic acid, 2-methylbutanoic acid, L-lactic acid, D-lactic acid, butanoic acid, etc., and in the pathway of producing flavor substances (His, Met, ethyl hexanoate, etc.) was up-regulated in the inoculated fermentation. Results presented in this study may provide a reference for the development of paocai starters and further guidance for the flavor improvement of Sichuan paocai.

Deciphering the microbial succession and color formation mechanism of "green-covering and red-heart" Guanyin Tuqu.

"Green-covering and red-heart" Guanyin Tuqu (GRTQ), as a type of special fermentation starter, is characterized by the "green-covering" formed on the surface of Guanyin Tuqu (SQ) and the "red-heart" in the center of Guanyin Tuqu (CQ). However, the mechanisms that promote temporal succession in the GRTQ microbial ecology and the formation of "green-covering and red-heart" characteristics remain unclear. Herein, we correlated the temporal profiles of microbial community succession with the main environmental variables (temperature, moisture, and acidity) and spatial position (center and surface) in GRTQ throughout fermentation. According to the results of high-throughput sequencing and culture-dependent methods, the microbial communities in the CQ and SQ demonstrated functional complementarity. For instance, the bacterial richness index of the CQ was greater than that of SQ, and the fungal richness index of the SQ was greater than that of CQ at the later stage of fermentation. Furthermore, Saccharomycopsis, Saccharomyces, Aspergillus, Monascus, Lactobacillus, Bacillus, Rhodanobacter, and Chitinophaga were identified as the dominant microorganisms in the center, while the surface was represented by Saccharomycopsis, Aspergillus, Monascus, Lactobacillus, Acetobacter, and Weissella. By revealing the physiological characteristics of core microorganisms at different spatial positions of GRTQ, such as Aspergillus clavatus and Monascus purpureus, as well as their interactions with environmental factors, we elucidated the color formation mechanism behind the phenomenon of "green" outside and "red" inside. This study provides fundamental information support for optimizing the production process of GRTQ.

The quality characteristics and microbial communities of three components in traditional split-fermented red sour soup.

Red sour soup is a Guizhou specialty condiment made by the natural fermentation of tomatoes and chili. In this study, three components (tomato acid, chili acid, and tomato and chili mixed acid) of split-fermented red sour soup were explored to compare the quality characteristics and microbial communities in the middle and late fermentation stages. The titratable acidity of mixed acids was lower than that of tomato acid and chili acid in the middle stage, but it was significantly increased in the late stage. The cell viability of lactic acid bacteria was mostly higher than that of yeasts during the whole fermentation. Also significantly increased in the late stage of fermentation were sensory scores and the signal intensity of sour substances. However, the signal intensity of both bitter and salty substances decreased, and the total amount of free amino acids was reduced. In addition, the antioxidant capacity of the samples and the dominant microorganisms were different between the two fermentation stages, Lactobacillus and Kazachstania were the key common genus of the different components of split-fermented red sour soup. It is anticipated that this study would provide us an insight into the quality characteristics and microbial communities of split-fermented red sour soup.

Microbial Population and Physicochemical Properties of Miang Fermented in Bamboo Tubes by the Luar Ethnic Group in Lao PDR.

Miang is a traditional fermented food made from Assam tea leaves and consumed as a snack. This study investigated the underground Miang fermentation process practiced by the Luar ethnic group in Laos, specifically examining the nutritional composition and microbial dynamics. Lactic acid bacteria and yeast were dominant in the fermentation process, reaching 8.43 and 8.50 log CFU/g after one week before gradually declining, while the coliform bacterial count was at 5.31 log CFU/g in the initial week but became undetectable in the later stages of fermentation. Next-generation sequencing identified Firmicutes (75.02%) and Proteobacteria (23.51%) as the primary phyla. Bacterial genera included Lactobacillus (73.36%) and Acetobacter (21.06%), with fungi mainly represented by Pichia (85.52%) and Candida (13.45%). Fundamental microbes such as Lactobacillus and Acetobacter were predominantly present, alongside Pichia and Candida, in the fungal communities. Microbial activities played a crucial role in generating essential enzymes for Miang's transformation. The nutritional transformation appears to be complete at 5 weeks of fermentation. The moisture content in the final products was approximately 74% and correlated with a change in nitrogen-free extract (NFE) and crude fiber. The fat content showed a slight increase from 1.3% to 2.52%, but protein content slightly declined from 17.21% to 16.05%, whereas ash content did not change significantly. Key polysaccharide-degrading enzymes, particularly pectinase and β-mannanase, were revealed and peaked at 48.32 and 25.32 U/g Miang, respectively. The total polyphenols increased from 103.54 mg/g dry Miang to 144.19-155.52 mg/g during fermentation. The lowered IC50 value indicated an increase in antioxidant activity. A fermentation period of at least 3 weeks proved to be optimal for enhancing antioxidant properties and bioactive compounds, and mitigating the risk of coliform bacteria.

Effects of Various Flavors of Baijiu on the Microbial Communities, Metabolic Pathways, and Flavor Structures of Dongbei Suancai.

This study aimed to assess the effects of Chinese Baijiu with different flavors as supplementary material on microbial communities and flavor formation during inoculated fermentation of Chinese Dongbei Suancai. The results showed that the addition of Fen flavor Baijiu significantly increased the relative abundance of Candida, Luzhou flavor Baijiu increased the relative abundance of Pedobacter and Hannaella, while Maotai flavor Baijiu increased the Chryseobacterium and Kazachstania. A total of 226 volatile metabolites were detected in Suancai fermented when adding different flavors of Baijiu. Furthermore, the significantly upregulated metabolites (p < 0.01) of Suancai after adding Baijiu increased by 328.57%, whereas the significantly downregulated metabolites decreased by 74.60%. Simultaneously, the addition of Baijiu promoted the synthesis and decomposition of amino acids and short-chain fatty acids in the early and middle stages of fermentation. Further, Maotai flavor Baijiu improved the diversification of metabolic pathways in the late stage of Suancai fermentation. The E-nose response showed that sulfur-organic, broad-alcohol, sulfur-chlor was the principal differential flavor in Suancai caused by adding Baijiu with different flavors. Simultaneously, Fen flavor Baijiu and Luzhou flavor Baijiu accelerated the formation of the Suancai flavor. These results indicated that Baijiu with different flavors had significant effects on the flavor formation of inoculated fermented Suancai.

Dynamic changes in aromas and precursors of edible fungi juice: mixed lactic acid bacteria fermentation enhances flavor characteristics.

Lactic acid bacteria (LAB) fermentation technology has been increasingly used in the deep processing of edible fungi. However, the flavor profiles of edible fungi products after mixed LAB fermentation have received less attention and how aromas changes during the mixed LAB fermentation are still open questions. In the present study, fermented Hericium erinaceus and Tremella fuciformis compound juice (FHTJ) was prepared by mixed LAB strains. We aimed to systematically monitor the dynamic changes of aromas and precursors throughout the fermentation process and a data-driven association network analysis was used to tentatively illustrate the mechanisms of formation between aromas and their precursors. Mixed LAB fermentation could enrich the aroma profile of FHTJ, reducing the unpleasant flavors such as nonanal and 1-octen-3-ol, as well as increasing the floral flavors such as ethyl acetate and α-pinene. Partial least squares-discriminant analysis and relative odor activity values revealed that 11 volatile chemicals were recognized as aroma-active markers. Volcano plot analysis showed that 3-octen-2-one (green flavor) was the key aroma-active marker in each stage, which was down-regulated in fermentation stages I, II and IV, whereas it was up-regulated in stage III. 3-Octen-2-one was significantly negatively correlated with organic acids, particularly pyruvate (r2 = -0.89). Ethyl caprylate (floral flavor) was up-regulated in the late fermentation stage, and showed a negative correlation with sugar alcohols and a positive correlation with organic acids, especially tartaric acid (r2 = 0.96). The present study demonstrates the beneficial effect of mixed LAB fermentation on flavor characteristics, providing guidance for fermented edible fungi juice flavor quality monitoring and control. © 2024 Society of Chemical Industry.

Engineering Implementation of the Acosta Fermentation Method to Obtain Cuban Schnapps with Reduced Concentrations of Higher Alcohols

The Acosta method involves rewiring the yeast metabolic pathway to enhance biomass production and prevent a significant increase in higher alcohols during the late stages of fermentation. This study aimed to assess fermentation conditions to achieve Cuban schnapps with reduced concentrations of higher alcohols and replicate the process on an industrial scale. To achieve this, the quality of final sugarcane molasses for fermentation by Saccharomyces cerevisiae (S. cerevisiae) yeast was evaluated. Industrial pre-fermentation and fermentation processes were successfully conducted, followed by laboratory-scale fermentation using the Acosta fermentation method to determine crucial parameters for industrial implementation. Operational parameters for fermentation were identified from the following results: 13.5 °Brix seeding, metabolic pathway inversion of S. cerevisiae at 16 h, and an air concentration of 0.1 m3/min. The resulting Cuban schnapps obtained using this method exhibited a concentration of higher alcohols of 132.5 mg/L, a value that is within the standard parameters, showing a positive impact of this fermentation method on the quality of the schnapps. Scaling up this method to an industrial level, in addition to offering higher quality products and being an economically viable alternative, also stands out for its sustainable and environmentally friendly aspect, and results in higher production of yeast biomass as a byproduct, which can be used for various purposes, such as animal feed. This method constitutes an important update to the schnapps production process as a technological improvement that respects sustainable production trends and the characteristics of the final product.

Pectin forms polymeric pigments by complexing anthocyanins during red winemaking and ageing

The long-term stability of red wine color depends on the formation of polymeric pigments from anthocyanins. Although there is still a lot of uncertainty about the specific structure of this diverse group of pigments, there is consensus that they are reaction products of anthocyanins and other polyphenols. Interactions between anthocyanins and pectic polysaccharides have been suggested to stabilize anthocyanins. This study explores the impact of such interactions by adding pectin during red winemaking.The results demonstrate that these interactions induce the formation of additional polymeric pigments which enhance the pigment stability during fermentation and aging. While initial pigment formation is higher in wines with added pectin, a notable proportion of the complexes degrades in the later stages of fermentation. Presumably, tannins form insoluble complexes with pectin, reducing tannin concentration by more than 300 mg/L. Anthocyanin concentrations decrease by over 400 mg/L, and polymeric pigments double.Anthocyanins that form polymeric pigments with pectic polysaccharides expand the range of pigments in red wines with possible consequences for the sensory properties of the wine. These findings highlight the complex interactions between pectin, anthocyanins, and tannins, and their influence on pigment formation and wine composition during fermentation and aging.