End Of Fermentation Research Articles

Impact of Condensed Tannin and Sulfur Dioxide Addition on Acetaldehyde Accumulation and Anthocyanin Profile of Vitis vinifera L. Cv. Cabernet Sauvignon Wines During Alcoholic Fermentation

Acetaldehyde is a key carbonyl by-product during red wine alcoholic fermentation; it is reactive and takes part in certain reactions involving anthocyanin. The aim of this study was to investigate the influence of SO2 and condensed tannin on the acetaldehyde accumulation of Saccharomyces cerevisiae (S. cerevisiae) during alcoholic fermentation and the ripple effect on wine anthocyanin. In this study, six sets of Cabernet Sauvignon alcoholic fermentation with two different sulfur levels (HS and LS) were carried out by adding exogenous condensed tannins before fermentation (T0) in the acetaldehyde rise period (TA) of S. cerevisiae and at the end of fermentation (TE), separately. The acetaldehyde evolution was identified during fermentation and anthocyanin was analyzed comparatively. The results showed that HS treatment slowed down the degradation of acetaldehyde, while tannins accelerated the degradation of acetaldehyde during alcoholic fermentation, especially TA wines. Furthermore, TA wines possessed a unique anthocyanin profile after fermentation regardless of SO2 level compared with other wines. These results suggest that acetaldehyde-mediated anthocyanin polymerization most likely occurs timely at the acetaldehyde production phase of S. cerevisiae during alcoholic fermentation, and managing tannin addition time during production could be used to regulate the anthocyanin profile.

Oat Okara Fermentation: New Insights into the Microbiological and Metabolomic Characterization

The importance of the valorization of industrial by-products has led to increasing research into their reuse. In this research, the innovative by-product okara oat flour, derived from the vegetable beverage industry, was studied. Oat okara sourdough was also produced and evaluated. The microbiological identification and typing involved bacterial and yeast isolates from both flour and sourdough. Untargeted metabolomics allowed the identification of biomarkers of fermented flour, such as phenolic classes, post-fermentation metabolites, fatty acids, and amino acids. The microorganisms most found were Weissella confusa, Enterococcus faecium, Pediococcus pentosaceus, and Pichia kudriavzevii, while Saccharomyces cerevisiae appeared only at the end of the sourdough’s back-slopping. Untargeted metabolomics identified a total of 539 metabolites, including phenolic compounds, lipids, amino acids, and organic acids. An increase in polyphenols released from the food matrix was detected, likely because of the higher bio-accessibility of phenolic metabolites promoted by microbial fermentation. Fermentation led to an increase in isoferulic acid, p-coumaric acid, sinapic acid, and a decrease in amino acids, which can be attributed to the metabolism of lactic acid bacteria. Some key markers of the fermentation process of both lactic acid bacteria and yeast were also measured, including organic acids (lactate, succinate, and propionate derivatives) and flavor compounds (e.g., diacetyl). Two bioactive compounds, such as gamma-aminobutyric acid and 3-phenyl-lactic acid had accumulated at the end of fermentation. Taken together, our findings showed that oat okara flour can be considered an excellent raw material for formulating more sustainable and functional foods due to fermentation promoted by autochthonous microbiota.

Differences in microbial communities among different types of zaopei and their effects on quality and flavor of baijiu

Three types of zaopei (fermented grain) of xiaoqu light-flavor baijiu (XQZP), daqu light-flavor baijiu (DQZP), and strong-flavor baijiu (SFZP) at the end of fermentation and their dominant lactic acid bacteria were systematically compared and analyzed in this study. The results showed that these three types of zaopei differed significantly in acidity, reducing sugar content, and ethanol content, and that the main factors influencing their microbial community were acidity and lactic acid. The diversity and contents of flavor substances were significantly higher in SFZP than in DQZP and XQZP. Additionally, there was a strong correlation between dominant lactic acid bacteria and flavor substances in all three zaopei, but the correlation between fungi and flavor substances was higher than that between bacteria and flavor substances. Differential gene analysis revealed that the microbial activities followed the order of SFZP > DQZP > XQZP. The KEGG enrichment analysis indicated that the differential genes from different zaopei were enriched in different metabolic pathways. Furthermore, various microorganisms in 3 types of zaopei contained different functional genes, of which fungi mainly contained genes responsible for the synthesis of ethanol and acetic acid, while lactic acid bacteria mainly contained genes responsible for the synthesis of lactic acid. In XQZP, L. helveticus was dominant lactic acid bacteria prominent in acetic acid tolerance and lactic acid production; in DQZP, L. acetotolerans was remarkable in its tolerance to lactic acid, acetic acid, ethanol and lactic acid production; and in SFZP, A. jinshanensis was superior in acetic acid tolerance and production. Taken together, this study reveals the mechanism underlying flavor differences among three types of baijiu and provides valuable references for the development and utilization of baijiu microbial resources.

Bacterial community succession and its correlation with the dynamics of flavor compound during processing of Enshi bacon

Enshi bacon, a famous specialty in Enshi Prefecture, Hu Bei, China, is renowned among customers for the nutritious content and distinct smoky flavor. This study explored the flavor and bacterial flora changes of Enshi bacon during processing and investigated the effect of bacteria on flavor formation. The results showed that the main genera in the pre-processing stage were Brochothrix, Lactococcus and Psychrobacter, which originated from raw meat. Salt-tolerant Staphylococcus and Cobetia were the dominant genera in the late stage of processing. Five free amino acids (aspartic acid, glutamic, alanine, valine, and lysine) were recognized as the flavor substances promoting taste, while aldehydes and phenols were the volatiles that contributed the most to odor. Particularly, compared to the smoking phase, phenolic content increased 2.25-fold at the end of fermentation through microbial action and tyrosine catabolism. The correlation study showed Staphylococcus and Lactococcus as fundamental functional genera that are essential for the formation of bacon flavor. This study provided reference data for the changes in flavor indicators and flora during the processing of Enshi Bacon, revealed the potential mechanism of core functional flora and characteristic flavor formation, and provided a theoretical basis for quality control of the manufacturing process.

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.

Potential Fermentation of Sweet Potato Pickle (Ipomoea batatas L.) with Lactobacillus plantarum B1765 in the Production of Short Chain Fatty Acids

Short-chain fatty acid (SCFA) is the final metabolic product of inulin that can provide various health benefits. In this study, the effect of fermentation duration of sweet potato pickle using Lactobacillus plantarum B1765 starter culture in the production of SCFA was studied, as well as its relationship with total Lactic Acid Bacteria (LAB), pH, and Total Titratable Acid (TTA). Fermentation was carried out with the addition of starter culture as much as 10% (v/v) at 37ºC for 4, 8, 12, 24, and 0 hours which was used as a control. The number of LAB was measured using the Total Plate Count (TPC) method, pH value was measured with a pH meter, TTA was measured using the acid-alkalimetric titration method, and SCFA was measured using an HPLC instrument with 0.1% H3PO4 eluent and 25% acetonitrile. Fermentation duration affects LAB growth, TTA, SCFA, and pH. The results showed that total LAB growth was optimal at 8 hours fermentation time at 2.81×108 CFU/mL, which increased by 2 log cycles from the initial fermentation time of 0 hours. Still, the pH decreased until it reached 3.23 ± 0.20, and TTA increased to 0,56 ± 0.02% until the end of fermentation at 24 hours. SCFA also increased until the end of fermentation at 24 hours, where acetic acid levels showed the highest levels (6.85 ± 0.30 mg/mL), followed by propionic acid (5.04 ± 0.20 mg/mL) and butyric acid (2.14 ± 0.10 mg/mL). Sweet potato pickles fermented with L. plantarum B1765 starter culture have met the SNI 01-3784-1995 standard and have the potential to be developed as a functional food source of SCFA, which has many health benefits.

Effect of Blending Cashew Apple (Anacardium occidentale L.) and Aonla (Emblica officinalis Gaertn.) Juice on Fermentation of Wine

A Completely Randomized Design (CRD) was employed to assess nine different treatment combinations, varying in juice ratios and fermentation conditions. The study aimed to evaluate the effects of blending cashew apple and aonla juices on the quality and fermentation characteristics of the resulting wine. While studying the chemical composition of cashew apple and aonla juice, cashew apple juice had a maximum value for T.S.S., reducing sugars, total sugars and pH. Aonla aonla juice had a maximum value for titratable acidity, ascorbic acid and tannin content. The T.S.S. of must was adjusted to 24 ºBrix and pH kept natural. The T.S.S. and pH was found to be decreased during fermentation of must. The treatment T5 i.e. 60 % cashew apple: 40 % aonla juice (6.13 ºBrix) recorded lowest T.S.S. and T9 i.e. 20 % cashew apple: 80 % aonla juice (10.53 ºBrix) recorded highest T.S.S. at 12th day of fermentation. The lowest pH recorded in treatment T9 i.e. 20 % cashew apple: 80 % aonla juice (2.10) and highest recorded in T1 i.e. 100 % cashew apple juice (3.38) at 12th day of fermentation. On the other hand, titratable acidity of must was found to be increased during fermentation of must. The minimum titratable acidity was found in treatment T1 i.e. 100 % cashew apple juice (0.62 %) and maximum was recorded in T9 i.e. 20 % cashew apple: 80 % aonla juice (1.74 %) at 12th day of fermentation. The yeast count increases rapidly until the 3rd day (1524 x 103) and after that yeast count subsequently declined until the fermentation reaches the 12th day (36.07 x 103), irrespective of treatments. At the end of fermentation (12th day) highest yeast count was recorded by treatment T5 i.e. 60 % cashew apple: 40 % aonla juice (60 x 103) and lowest yeast count was recorded by treatment T9 i.e. 20 % cashew apple: 80 % aonla juice (21 x103). Wine recovery from must ranged between 73.86 and 83.20 per cent. As a result, treatment T5 (60 % cashew apple juice: 40 % aonla juice) showed better fermentation among all other treatments.

Metagenomic and metatranscriptomic analyses of microbial genera and volatiles produced during the fermentation of doubanjiang meju

Fermented broad beans (Vicia faba L.), commonly known as meju, serve as a crucial raw material for producing Pixian Doubanjiang (DBJ), a traditional condiment in Chinese cuisine. However, there is limited information on the dynamics of fungal populations and the activity shifts of key enzymes during DBJ meju fermentation. This study aimed to elucidate the microbial composition, active genera, expressed genes and pathways during the DBJ meju fermentation. The general chemical components, free amino acids, enzymes and volatile compounds were also investigated; the correlations between active genera and physicochemical factors were analyzed, at different fermentation stages. The results demonstrated that protease was the predominant enzyme during meju fermentation. A total of 32 major volatile compounds were identified, with most alcohols and aldehydes showing a sharp increase from the early to the middle stages, followed by stabilization until the end of fermentation. Significant shifts in metatranscriptomic composition at the genus level were observed, with Aspergillus, Staphylococcus, and Tulasnella emerging as the core active genera in the process. Notably, cellulase activity was positively correlated with the presence of Tulasnella. Additionally, Aspergillus and Tulasnella were found to play a crucial role in developing the unique aroma of DBJ meju. Our findings on the succession of active genera and their correlation with physicochemical factors are expected to provide substantial evidence for potential quality control and enhancement of this renowned Chinese condiment.

The interaction between Lactobacillus delbrueckii ssp. bulgaricus M58 and Streptococcus thermophilus S10 can enhanced texture and flavor profile of fermented milk: Insights from metabolomics analysis

Lactobacillus delbrueckii ssp. bulgaricus M58 (M58) and Streptococcus thermophilus S10 (S10) are 2 dairy starter strains known for their favorable fermentation characteristics. Therefore, this research aimed to study the effects of 1-d low-temperature ripening on the physicochemical properties and metabolomics of fermented milk. Initially, the performance of single (M58 or S10) and dual (M58+S10) strain fermentation was assessed, revealing that the M58+S10 combination resulted in a shortened fermentation time, a stable gel structure, and desirable viscosity, suggesting positive strain interactions. Subsequently, non-targeted metabolomics analyses using LC-MS and GC-MS were performed to comparatively analyze M58+S10 fermented milk samples collected at the end of fermentation and after 1-d low-temperature ripening. The results showed a significant increase in almost all small peptides and dodecanedioic acid in the samples after one day of ripening, while there was a substantial decrease in indole and amino acid metabolites. Moreover, notable increases were observed in high-quality flavor compounds, such as geraniol, delta-nonalactone, 1-hexanol,2-ethyl-, methyl jasmonate, and undecanal. This study provides valuable insights into the fermentation characteristics of the dual bacterial starter consisting of M58 and S10 strains and highlights the specific contribution of the low-temperature ripening step to the overall quality of fermented milk.

Effects of sorghum varieties on microbial communities and volatile compounds in the fermentation of light-flavor Baijiu.

Light-flavor Baijiu (LFB) fermentation is a representative spontaneous mixed-culture solid-state fermentation process in which sorghum is used as the raw material. Raw materials and microorganisms are crucial to the flavor formation and quality of LFB. However, the microbial and physicochemical dynamics of different sorghum varieties during LFB fermentation, as well as their impact on flavor compounds are still largely unknown. Herein, PacBio single-molecule real-time (SMRT) sequencing and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were applied to investigate microbial community succession and volatile flavor formation in glutinous/non-glutinous sorghum-based fermented grains during LFB fermentation. Fermented grains made of glutinous sorghum Liangnuo No. 1 (GLN) had higher bacterial α-diversity and lower fungal α-diversity than those with fermented grains prepared with non-glutinous red sorghum (NRS) (p < 0.05). The dominant microbial species were Saccharomyces cerevisiae, Acetobacter pasteurinus, and Lactobacillus helveticus, the latter two of which were the predominant bacteria observed at the end of fermentation in GLN and NRS, respectively. Moisture content and reducing sugar had a more significant impact on the microorganisms in GLN, while amino acid nitrogen, total free amino acids, and residual starch were the main driving factors driving the microbial community in NRS. The correlation network and discriminant analysis indicated that a relatively high content of 4-vinylguaiacol showed a significant positive association with significant differential microbial species in GLN. These results provided valuable insights for improving the quality of LFB.

Fishmeal-Based Media Supports Growth and Endospore Production of Locally-Isolated Lysinnibacillus sphaericus and Induces its Toxicity to 3rd Instar Aedes aegypti Larvae in Laboratory Conditions

The aim of this study was to determine whether fishmeal-based media could be used to grow L. sphaericus and induce its toxicity against Aedes aegypti larvae. Three concentrations (10, 20 and 30%) of fishmeal-based media were used to grow L. sphaericus isolate Bs2-1-2. Cell growth and endospore production were observed every 12 hours for 72 hours. The lethal concentration was measured every 24 hours for 72 hours of fermentation. The highest cell concentration was found in L. sphaericus grown on the media with 30% fishmeal concentration (3.03x1008 cells/mL), followed by 20% concentration (2.43x1008 cells/mL) and the lowest at 10% concentration (2.20x1008 cells/mL). At the end of fermentation, the highest concentration was found in L. sphaericus grown on 30% fishmeal-based media (1.51x1008 cells/mL), followed by 20% media (6.95x1007 cells/mL) and 10% media (3.21x1007 cells/mL). After 72-hour incubation, the highest endospore concentration was achieved by L. sphaericus grown on 20% (2.51x1008 cells/mL) and 10% (2.19x1008 cells/mL) fishmeal-based media. Initial larval toxicity of L. sphaericus showed the highest mortality on 20 and 30% fishmeal-based media (both reaching 53.33%), while 10% fishmeal-based media gave only 26.67% larval mortality. The LC50 value at 72 hours was achieved by L. sphaericus cultured on 30% fishmeal-based media (2.47 x 1008 cells/mL), followed by 20% concentration (4.82 x 1008 cells/mL) and 10% concentration (9.01 x 1009 cells/mL). The conclusion of this study was all concentrations of fishmeal-based media could support cell growth, endospore production and larval toxicity induction of L. sphaericus.

Probiotic Growth Pattern and Physicochemical Evaluation of Water Kefir Fermentation

Probiotics are live-friendly microorganisms that can confer a health benefit on the host if it is consumed in sufficient amounts. Water kefir is a probiotic-rich fermented beverage that contains multi-species of live cultures. Brown sugar and palm sugar were used for water kefir fermentation due to their high sucrose and mineral contents. The objective of this study was to determine the probiotic growth pattern of water kefir and to evaluate the physicochemical parameters, including the pH changes, lactic acid content, reducing sugar content, and total soluble solids. The fermented water kefir was collected at every 6-hour interval, until the end of 72 hours of fermentation. The growth curve was determined by enumerated probiotics on De Man, Rogosa, and Sharpe (MRS) agar, Yeast Extract-Peptone-Dextrose (YPD) agar, and Gluconobacter (GM) agar plates, respectively. MRS, YPD, and GM agar plates were used to enumerate lactic acid bacteria, yeast, and acetic acid bacteria, respectively. The result showed increased probiotic growth as fermentation time increased with different phases observed from the growth curve. The stationary phase of probiotics was recorded at 30-42 h and was recommended as the optimal harvesting point. Besides, longer fermentation time produced lower pH values and lower total soluble solids while higher lactic acid and higher reducing sugars. At the end of fermentation, the concentration of lactic acid and reducing sugars were 2.16 ± 0.09 g/L and 13.66 ± 0.14 mg/mL, respectively. In conclusion, probiotics from water kefir fermentation are suggested to be best harvested between 30-42 hours and can be used for self-consume or downstream processing.

Determining the possibility of making mulberry wine by using the osmotic dehydration process

This study aimed to determine the possibility of using osmotic dehydration in the production of mulberry wine. Mulberry fruits (Mórus nígra L.) were mixed with 70 % sucrose solution and osmotic dehydration was carried out (τ=1 h, t=50±5 °C). At the stage of active fermentation, the osmotic solution separated from the fruits was added to the must (10 % by mass). Partially dehydrated mulberry fruits were infused for 12 hours in water at a temperature of 10–15 °C. The formed must was separated from the fruits, mixed with an osmotic solution, and a solution formed during pressing of dehydrated fruits. The mixture was fermented at 20±2 °C for 20 days under static conditions. At the end of fermentation, the young wine was kept at a temperature of 3–5 °C for 1 month. A second transfusion was performed, and its quality indicators were analyzed. It was established that the osmotic solutions formed during the osmotic dehydration of black mulberry fruits contain 42.60±0.25 mg/100 g of anthocyanins, which makes them an effective basis and additive for giving wine the desired sensory characteristics. The high content of anthocyanins in wine (35.8±0.5 mg/100 g) provides for its stable red-ruby color. As a result of hydrolysis, sucrose, which was the main component of the osmotic solution before mulberry dehydration, is transformed into glucose (27.74±0.05 g/100 g) and fructose (28.60±0.05 g/100 g). This significantly increases its biological value and gives the wine a harmonious taste characteristic of fruit wines. The wine made on the basis of mulberry fruit processing products is rated at 7.5 points. It had a pleasant taste and color, but a poorly developed aroma. Mulberry wine was classified as semi-dry because it had a low alcohol content (6±0.5 %), a low concentration of sugars (13.0±0.5 g/dm3), and a high concentration of volatile acids (1.4±0.5 g/dm3)

Correlation between Microorganisms and Volatile Compounds during Spontaneous Fermentation of Sour Bamboo Shoots

Chinese sour bamboo shoot is a traditionally, spontaneous fermented food that is particularly popular due to its complex and distinctive flavor. The volatile compounds of sour bamboo shoot originate mainly from the raw materials and the microbial fermentation. To reveal the correlation between microorganisms and flavor, third-generation sequencing and Gas Chromatography-Ion Mobility Spectrometry were applied to analyze the dynamics of microbial communities at the species level and volatile compounds during sour bamboo shoot fermentation. The abundance of Lactobacillus acetotolerans and Lactobacillus fermentum increased during the fermentation, while Lactobacillus amyloliquefaciens decreased at first but then began to rise. At the end of fermentation, Lactobacillus amyloliquefaciens and Lactobacillus acetotolerans became the predominant species. A total of sixty-seven volatile compounds, which included twenty-three esters, nineteen alcohols, eight ketones, six aldehydes, six aromatic hydrocarbons, four acids and one ether, were identified. These compounds constituted the primary flavor of sour bamboo, which created a complex flavor of sour bamboo shoot. Among them, the contents of acetic acid, propionic acid, and isoamyl alcohol gradually increased during the fermentation process, and they became the main volatile compounds. Furthermore, the correlation between microorganisms and volatile compounds was investigated through two-way Orthogonal Partial Least Squares (O2PLS), which revealed a positive correlation between Lactobacillus amylolyticus and ethyl propanoate. Additionally, the abundance of Lactobacillus acetotolerans and Lactobacillus fermentum was found to be positively correlated with 2-heptenal. These findings provide a theoretical basis for understanding the formation mechanism of sour bamboo shoot flavor and the standardized production of high-quality sour bamboo shoots.

The effects of Lactiplantibacillus plantarum 3-19 and Pediococcus pentosaceus 18-1 on preventing the accumulation of biogenic amines and promoting the production of volatile organic compounds during sour meat fermentation

Lactic acid bacteria (LAB) are frequently used in meat fermentation, and mixed stater cultures are reported to perform better than single ones. Lactiplantibacillus plantarum 3-19 and Pediococcus pentosaceus 18-1 were chosen from 28 sour-meat-origin strains to examine the effects of single and combined inoculation on sour meat quality. Natural fermentation was used as a control to investigate changes in pH, water activity (aw), amino acid nitrogen (AN), texture, microbial diversity, and volatile organic compounds (VOCs) during fermentation. The pH and aw of each inoculation group were significantly decreased, and AN content was significantly increased. The inoculation of P. pentosaceus 18-1 significantly reduced putrescine, cadaverine, and tryptamine content (p < 0.05), while the inoculation of Lpb. plantarum 3-19 significantly reduced cadaverine amounts (p < 0.05). At the fermentation endpoint, the total biogenic amines content in the C group was 992.96 ± 14.07, which was 1.65, 2.57, and 3.07 times higher than that in the Lp, Pe, and M groups, respectively. The mixed inoculation group combined the advantages of both strains and decreased total biogenic amines most significantly. At the end of fermentation, the VOCs in C, Lp, Pe, and M groups were 10.11, 11.56, 12.45, and 13.39 times higher than those at the beginning of fermentation. Inoculation promoted the production of key VOCs (OAV > 2000) such as heptanal, octanal, and (E)-2-nonanal. The mixed inoculation group had the highest variety and content of VOCs and the highest content of the above key VOCs, significantly enhancing its fruity, floral, ester, and other aromas. Sensory evaluation indicated that the M group had the best overall acceptability. Finally, it was suggested that a combination of Lpb. plantarum 3-19 and P. pentosaceus 18-1 is a novel and efficient starter culture for processing sour meat since they lower the amounts of biogenic amines in the meat and promote the production of VOCs.

Copper (II) Level in Musts Affects Acetaldehyde Concentration, Phenolic Composition, and Chromatic Characteristics of Red and White Wines.

Copper (II), a vital fungicide in organic viticulture, also acts as a wine oxidation catalyst. However, limited data are currently available on the impact that maximum allowed copper (II) ion doses in wine grapes at harvest can have on aged wine quality. This was the focus of the present study. We investigated the copper (II) effects by producing both white and red wines from musts containing three initial metal concentrations according to the limits set for organic farming. In detail, the influence of copper (II) on fermentation evolution, chromatic characteristics, and phenolic compounds was evaluated. Interestingly, the white wine obtained with the highest permitted copper (II) dose initially exceeded the concentration of 1.0 mg/L at fermentation completion. However, after one year of storage, the copper (II) content fell below 0.2 ± 0.01 mg/L. Conversely, red wines showed copper (II) levels below 1.0 mg/L at the end of fermentation, but the initial copper (II) level in musts significantly affected total native anthocyanins, color intensity, hue, and acetaldehyde concentration. After 12-month aging, significant differences were observed in polymeric pigments, thus suggesting a potential long-term effect of copper (II) on red wine color stability.

Targeted microbial collaboration to enhance key flavor metabolites by inoculating Clostridium tyrobutyricum and Saccharomyces cerevisiae in the strong-flavor Baijiu simulated fermentation system

Ethyl hexanoate and ethyl butyrate are indispensable flavor metabolites in strong-flavor Baijiu (SFB), but batch production instability in fermenting grains can reduce the quality of distilled Baijiu. Biofortification of the fermentation process by designing a targeted microbial collaboration pattern is an effective method to stabilize the quality of Baijiu. In this study, we explored the metabolism under co-culture liquid fermentation with Clostridium tyrobutyricum DB041 and Saccharomyces cerevisiae YS219 and investigated the effects of inoculation with two functional microorganisms on physicochemical factors, flavor metabolites, and microbial communities in solid-state simulated fermentation of SFB for the first time. The headspace solid-phase microextraction-gas chromatography-mass spectrometry results showed that ethyl butyrate and ethyl hexanoate significantly increased in fermented grain. High-throughput sequencing analysis showed that Pediococcus, Lactobacillus, Weissella, Clostridium_sensu_stricto_12, and Saccharomyces emerged as the dominant microorganisms at the end of fermentation. Co-occurrence analysis showed that ethyl hexanoate and ethyl butyrate were significantly correlated (|r| > 0.5, P < 0.05) with a cluster of interactions dominated by lactic acid bacteria (Pediococcus, Lactobacillus, Weissella, and Lactococcus), which was driven by the functional C. tyrobutyricum and S. cerevisiae. Mantel test showed that moisture and reducing sugars were the main physicochemical factor affecting microbial collaboration (|r| > 0.7, P < 0.05). Taken together, the collaborative microbial pattern of inoculation with C. tyrobutyricum and S. cerevisiae showed positive results in enhancing typical flavor metabolites and the synergistic effects of microorganisms in SFB.

Comparison of the physicochemical property and volatile flavour compounds of yoghurt made from ultra-pasteurised and membrane-filtered milk

In this study, we aimed to compare and contrast the physicochemical and flavour attributes of yoghurt crafted from ultra-pasteurised (UPM-yoghurt) and membrane-filtered milk (MFM-yoghurt). The results indicated that MFM-yoghurt required 1.5 h longer than UPM-yoghurt to reach a pH of 4.5 at the end of fermentation, primarily owing to differences in Streptococcus thermophilus growth and lactoferrin (LF) content. UPM-yoghurt exhibited greater hardness, consistency, and water-holding capacity, resulting in a firmer gel texture. Conversely, MFM-yoghurt demonstrated lower viscosity but a smoother texture, possibly due to biologically active components. LF and lactoperoxidase (LPO) were absent in UPM-yoghurt, whereas MFM-yoghurt contained 106.00 mg/L of LF and 2986.25 U/L of LPO. Free amino acid analysis revealed lower levels of umami and bitter amino acids in MFM-yoghurt than those in UPM-yoghurt, while sweet amino acid levels were similar in both. The predominant volatile flavour compounds included aldehydes and ketones, with no significant differences observed in key compounds, such as 2-acetone, ethyl acetate, 3-hydroxy-2-butanone, and 2,3-butanedione, between the two yoghurts. However, notable variations were observed in 41 volatile flavour compounds between the samples, suggesting distinct flavour profiles. This study offers insights and directions for enhancing the nutritional quality of yoghurt.

The role of debittering process with normal water, NaOH and lye on chemical properties of brine, antioxidant activity, phenolic compounds and sensory characteristics of fermented caper (Capparis ovata Desf. var. Ovata) buds

In this study, the effect of the application of salt water (brine), lye and caustic (NaOH) on salt content, acidity, pH in caper brine during fermentation was investigated. The total carotenoid quantity of the caper buds were assessed to be between 0.46 (lye) and 1.57 µg/g (hot water) on the 5th day, while the total carotenoid quantities of the buds on the 30th are found between 0.22 (normal water) and 0.94 µg/g (brine). The total carotenoid values of the caper buds on the 45th day were changed to be between 0.05 (hot water) and 0.75 µg/g (brine). The total phenol quantities of the buds on the 30th day were detected between 111.23 (caustic) and 194.48 mg GAE/100 g (hot water), while the total phenol quantities of the caper buds on the 45th day were assigned between 66.87 (lye) and 159.33 mgGAE/100 g (brine). The total flavonoid quantities of thecaper buds were assigned between 289.29 (lye) and 458.81 mg catechin equivalent (CE)/100 g (normal water) on the 45th day. The highest decrease in phenolic components during fermentation was detected in catechin, rutin and resveratrol. Fermented caper buds, whose bitterness was removed with normal water on the 45th day, received the most appreciation. At the end of fermentation, the buds whose bitterness was removed with soda water, normal and hot water, normal water and caustic were most appreciated in terms of color, smell, taste and hardness.Graphical abstractIn this study, the effect of the application of salt water (brine), oak wood ash and caustic (NaOH) on salt content, acidity, pH in caper brine during fermentation and to determine the moisture, bioactive properties (antioxidant). activity, total phenol carotenoid, flavonoid), phenolic constituents and sensory characteristics of caper buds using hot water as an alternative to the bittering process with normal water in the production of fermented caper budswas investigated

Isolation and identification of blueberry-derived lactic acid bacteria and their probiotic, antioxidant, and fermentation properties

In this study, high-throughput sequencing was used to analyze the microbial diversity and relative abundance of the blueberry epidermis and found that lactic acid bacteria (LAB) represent a relatively abundant group. Putative LAB strains were isolated and purified from the blueberry epidermis by traditional biological methods. Thirty LAB strains were identified by genotype identification, physiological and biochemical test, and 16 S rDNA sequence analysis revealed 100% sequence identity between 8 isolated strains and the representative LAB in the blueberry epidermis. Of the 8 strains, ZYN-0417 (Lactobacillus rhamnosus) and ZYN-0221 (Lactobacillus plantarum) showed strong tolerance in the probiotic test. Under gastric acid conditions with a pH of 2.0, the respective survival rate reached 65.71% and 68.85%. The respective survival rate reached 96.45% and 98.37% in 1.8% bile salt. After incubation in vitro gastrointestinal fluid for 240 min, the respective survival rate reached 91.00% and 86.26%. The antioxidant capacity test showed that the DPPH scavenging rate of ZYN-0417 and ZYN-0221 reached 85.45% and 87.45%, with ABTS free radical scavenging rate of 76.03% and 66.17%, OH scavenging rate of 57.30% and 46.93%, and Fe2+ chelating ability of 46.34% and 43.70%, respectively. Fermentation study showed that ZYN-0417 and ZYN-0221 were capable of strong acid production with respective pH values and total acid content of 3.64 and 3.63, 14.88 mg⋅L−1 and 14.85 mg⋅L−1 after 36 h of fermentation. Moreover, ZYN-0417 and ZYN-0221 showed strong extracellular protease activity (82.99 U⋅mL−1 and 95.17 U⋅mL−1, respectively). Blueberry juice fermentation showed robust growth of ZYN-0417 and ZYN-0221 and the viable bacterial number of LAB reached 13–14 log CUF⋅mL−1 at the end of fermentation. In summary, blueberry-derived LAB have good probiotic and antioxidant properties, and strong fermentation properties in low acid environments, thus showing the potential of their use for the lactobacillus fermentation of fruit and vegetables.