Wine Fermentation Research Articles

Characterization and Identification of Yeast Peptides Released during Model Wine Fermentation and Lees Contact.

Aging wine on lees results in the release of different yeast components, including peptides, whose role in wine is unclear. In this study, peptides released in a synthetic must, fermented with an oenological yeast strain, and aged on lees for 180 days were quantified (RP-HPLC) and identified (LC-MS/MS) at different time points. A rapid increase in peptide concentration was observed in the first two months, with over 2600 sequences identified. During the following four months, the peptide concentration remained constant, while their variety decreased slightly, probably due to enzymatic hydrolysis to which longer and less charged sequences were more exposed. The majority of the most abundant peptides were present over the 6-month period. They mostly originated from proteins associated with glycolysis and with different stress-response mechanisms, and they showed different in silico bioactivities. These findings can contribute to understanding the role of yeast peptides in regulating the wine environment during aging.

Impact of fermented wine lees on gut microbiota and metabolic responses in Guanling crossbred cattle

BackgroundThe addition of wine lees to diets can make up for the deficiencies caused by traditional forages in beef cattle farming. However, the effects of different wine lees ratios on average daily weight, gastrointestinal microbial community structure and metabolites in Guanling crossbred cattle have been rarely studied. This study assessed the effects of feeds containing wine lees on weight gain, gastrointestinal microbial community structure, and metabolites in Guanling crossbred cattle and elucidated the metabolic responses induced by wine lees. Eighteen cows were randomly assigned to receive fed concentrate (C group), feed containing 15% wine lees (group A), or feed containing 30% wine lees (group B) for 60 days.ResultsThe average daily weight gain of group A and group B increased by 76.75% and 57.65%, respectively, compared with group C. Microbial community analysis showed that wine lees increased the abundance of Prevotella_1 in the rumen, decreased the abundance of Ruminococcaceae UCG 011 and Lachnospiraceae_FCS020_group in the rumen, and increased the abundance of Tyzzerella_4, Family_Xlll_AD3011_group, Granulicella, and Eisenbergiella in the cecum. Metabolomics analyses showed that wine lees decreased the concentrations of indole-3-ethanol in the rumen, and complexity cecal metabolism. Notably, linoleic acid metabolism was significantly enriched in both the rumen and cecum. Mantel test analyses indicated that the adverse effects of WL were reduced by stimulating the metabolism of linoleic acid, α-linolenic acid, and tryptophan, and these changes were mediated by intestinal microorganisms. The Guanling cattle cecum was enriched for several unfavorable metabolic pathways when wine lees concentrations reached 30%, which increased the likelihood of intestinal lesions.ConclusionThis study shows that WL supplementation alters gut microbiota and metabolic pathways, improving cattle growth and health. Moderate WL levels (15%) enhance gut health and beneficial pathways (e.g., linoleic and alpha-linolenic acid metabolism). However, higher WL inclusion (30%) may activate adverse pathways, raising the risk of intestinal damage. To maximize benefits and minimize risks, WL levels should be carefully managed.

Multi-omics framework to reveal the molecular determinants of fermentation performance in wine yeast populations

BackgroundConnecting the composition and function of industrial microbiomes is a major aspiration in microbial biotechnology. Here, we address this question in wine fermentation, a model system where the diversity and functioning of fermenting yeast species are determinant of the flavor and quality of the resulting wines.ResultsFirst, we surveyed yeast communities associated with grape musts collected across wine appellations, revealing the importance of environmental (i.e., biogeography) and anthropic factors (i.e., farming system) in shaping community composition and structure. Then, we assayed the fermenting yeast communities in synthetic grape must under common winemaking conditions. The dominating yeast species defines the fermentation performance and metabolite profile of the resulting wines, and it is determined by the initial fungal community composition rather than the imposed fermentation conditions. Yeast dominance also had a more pronounced impact on wine meta-transcriptome than fermentation conditions. We unveiled yeast-specific transcriptomic profiles, leveraging different molecular functioning strategies in wine fermentation environments. We further studied the orthologs responsible for metabolite production, revealing modules associated with the dominance of specific yeast species. This emphasizes the unique contributions of yeast species to wine flavor, here summarized in an array of orthologs that defines the individual contribution of yeast species to wine ecosystem functioning.ConclusionsOur study bridges the gap between yeast community composition and wine metabolite production, providing insights to harness diverse yeast functionalities with the final aim to producing tailored high-quality wines.74dL8hDE5Rym1TqBfqxSSDVideo

MANUFACTURING AND CHEMICAL CHARACTERIZATION OF ISABEL RED

Considering the potential consumption and economic importance that Isabel wine represents in the Brazilian consumer market, the aim of this research was to study the manufacturing and to determine the chemistry composition of red wine produced from Isabel grapes. The wine fermentation was achieved with 0.2 g/L of Saccharomyces cerevisiae yeast at 25ºC. After seven days of fermentation the correction of sugar was performed. After 40 days, the wine was separated from residues. The wine was clarified with commercial unflavored gelatin at the proportion of 0.2 g/L. The parameters total and volatile acidities, ethanol, dry extract, carotenoids, anthocyanins, total phenolic and reducing sugar were studied. Isabel grapes have the potential to be used to produce wine, hence its economic importance in Brazil. The chemical profile provided essential information about the Isabel red wine and the yeast used for inoculation result in good must fermentation, according to Brazilian legislation.

Evaluating of effects for the sequence fermentation with M. pulcherrima and I. terricola on mulberry wine fermentation: Physicochemical, flavonoids, and volatiles profiles

This study investigates the variation of physicochemical, flavonoids, and volatiles during sequential fermentation which Metschnikowia pulcherrima and Issatchenkia terricola as sequential co-fermenters and a single fermentation by Saccharomyces cerevisiae in mulberry wine. Sequential fermentation shown that β-glucosidase activity greater and fermentation time declined to 144 h. In addition, 11 flavonoids (apigenin-5-O-glucoside, aromadendrin-7-O-glucoside, kaempferol-3,7-O-diglucoside, and so on) were significantly increased. Significant differences were found between types of metabolic products enriched in flavone and flavonol biosynthesis and anthocyanins biosynthesis, with an enrichment ratio of 46.15 % and 23.08 %, respectively. 16 apple-scented compounds (2-Buten-1-one, (E)-1-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)-, Butanoic acid, (Z)-3-hexenyl ester, 3-methyl-1-methylethyl-Butanoic acid ester, and so on), 5 rose-scented (e.g. benzyl alcohol, ethyl geranate, hydrocinnamic acid), and 4 balsamic-scented compounds ((−)-myrtenol, benzoic acid 1-methylethyl ester, benzyl alcohol, p-cymen-7-ol) were distinctively present. Interestingly, tryptophan metabolism and indole alkaloid biosynthesis are only enriched in sequential fermentation.

Enhancing nutritional composition and aroma characteristics of kiwifruit wines through indigenous non-Saccharomyces yeast extracellular extract treatment

To unlock the potential of strains for further enhancing the aromatic complexity of kiwifruit wines while avoiding undesirable flavors, indigenous non-Saccharomyces yeast extracellular extract treatment for fermentation was established. The extracellular extract from Zygosaccharomyces rouxii, Pichia kudriavzevii, and Meyerozyma guilliermondii were prepared and supplemented individually or in pairs to the kiwifruit wine fermentation system. Subsequently, the changes in physicochemical properties, antioxidants, and volatile characteristics of kiwifruit wines produced by different protocols were comprehensively evaluated, and the major aroma descriptors affecting sensory acceptability were analyzed by sensory evaluation and partial least squares regression. The results showed that extracellular extract treatment significantly improved the organic acids and monomeric phenols content, antioxidant capacity, and volatiles of kiwifruit wines. Compared to Sc, the increase in esters and alcohols, along with the decrease in aldehydes and acids in Pk-Zr and Mg-Zr, enhanced the aromatic complexity while reduce grassy and fungal flavors, resulting in higher sensory acceptability.

Investigation of novel metabolites generated by Torulaspora delbrueckii to promote the aroma biosynthesis in Saccharomyces cerevisiae during wine fermentation

The co-fermentation of Saccharomyces cerevisiae and non-Saccharomyces has been recognized as an effective strategy for improving the quality of wine aroma. One of the most critical factors for the aroma enhancement is the yeast-produced metabolites, but the underlying mechanisms remain poorly understood. In this study, we used a cell/medium separation strategy to investigate the effects of metabolites generated by Torulaspora delbrueckii on the aroma biosynthesis in S. cerevisiae. The results demonstrated that T. delbrueckii metabolites enhanced the production of ethyl octanoate, ethyl decanoate, isoamyl acetate, and isopentanol within S. cerevisiae. Upregulation of aroma-related genes, including EEB1, SLI1, BAP3, BAT1, PDC1, and PDC5 in S. cerevisiae, was responsible for the aroma enhancement. The untargeted metabolomic analysis determined a total of 869 T. delbrueckii metabolites, in which three novel metabolites were identified to promote the aroma formation in S. cerevisiae. Specifically, 3-amino-4-methylpentanoic acid stimulated the levels of ethyl octanoate (up to 42.55%) and ethyl decanoate (up to 31.92%), while 4-methylaminobutyric acid and citraconic acid increased the production of ethyl hexanoate (up to 59.19%) and isoamyl acetate (up to 32.26%). A comprehensive understanding of the specific yeast metabolites provides a robust foundation for winemakers to purposefully modulate the aromatic characteristics of wines.

Dynamic changes in microbiota and volatile profiles of Marselan wine by single or pairwise inoculated three indigenous non-Saccharomyces yeasts

The object of this study was to compare the effects of three indigenous non-Saccharomyces cerevisiae strains (Hanseniaspora uvarum, Metschnikowia sinensis and Rhodotorula mucilaginosa) and their paired (co-inoculated) fermentation on the microbial communities and volatile profiles during the fermentation of Marselan wine. Results showed that both monoculture and mixed fermentation with non-Saccharomyces strain can complete alcohol fermentation wherein the alcohol content of indigenous yeast treatments were significantly higher than that of control NSD. A total of 44 aroma compounds were identified in all samples, among which the H + R mixed inoculation showed the highest aroma content (28581±1576.61 μg/L). In particular, the contents of ethyl butyrate (V5), ethyl octanoate (V9), and ethyl decanoate (V11) were significantly high, which could enhance the fresh fruit aroma in Marselan wine. Microbial diversity analysis showed that the diversity of fungi between groups was greater than that of bacteria, and H + R (Hanseniaspora and Rhodotorula) had higher microbial abundance (bacteria 79, fungi 78) than the other groups. Spearman correlation analysis revealed that Fructobacillus, Acinetobacter, and other indigenous microorganisms were positively correlated with volatile substances. In summary, the mixed fermentation of Hanseniaspora and Rhodotorula can be considered an effective strategy for improving the aroma quality of Marselan wine. This study provides new insight and useful references for the role and application of native non-Saccharomyces yeast in wine making.

Contribution of polyvinylpolypyrrolidone (PVPP) treatment to the distribution of polyphenols and the evolution of esters and higher alcohols in Rosa roxburghii Tratt wine

Polyvinylpolypyrrolidone (PVPP) is commonly employed for fining in fruit wine brewing. This study aimed to investigate the impact of PVPP pretreatment on the formation of fermentation aroma and polyphenol distribution in Rosa roxburghii Tratt (RRT) wine. A significant effect of PVPP on polyphenol adsorption was observed, and polyphenol families or subfamilies such as flavanols and flavonols showed specific affinity for PVPP, decreasing by over 19 % and 30 %, respectively. Furthermore, it was the first time to demonstrate a significant enhancement in the ester content of the corresponding RRT wine after PVPP treatment, particularly in imparting sweet and fruity esters (increased by over 40 %). In contrast, the RRT wine treated with PVPP exhibited a significant reduction of over 20 % in the concentration of higher alcohols, particularly reflected in the green and chemical aromas. This indicates that PVPP treatment could promote the transformation of RRT wine aroma from green and chemical to sweet and fruity. Correlation analysis revealed a positive relationship between the concentration of higher alcohols and most phenolic compounds in RRT wine, while quercetin 3-glucoside, rutin, and polydatin were negatively correlated with esters that can impart fruit flavor and floral aroma to fruit wine. As a practical insight into fruit wine fermentation, PVPP fining before fermentation is more likely to alter the phenolic compositions of RRT wine, thereby influencing its aroma characteristics. Specifically, polyphenols associated with energy metabolism of yeast could have stimulated the formed fluxes of esters. The association between the formation of esters and higher alcohols with phenolic compounds will provide new information on the impact of clarification treatments on yeast-derived volatile metabolites in RRT wine and hold promise in improving the aroma of RRT wine by modulating polyphenol composition through pre-clarification.

Dynamic changes in dissolved oxygen concentration, microbial communities, and volatile compounds during industrial oak-barrel fermentation of Sauvignon Blanc wine

Oak-barrel fermentation is used in white wine production to enhance aroma and flavor complexity. However, the dynamics of microbial communities and their impact on the formation of flavor compounds during barrel fermentation remain unclear. This study investigated the changes in dissolved oxygen concentrations, microbial communities, and volatile compounds during Sauvignon Blanc wine fermentation in various oak barrels (new and two-year-old Francois Freres and new Taransaud) and stainless-steel tanks. We found that oak barrels had higher dissolved oxygen levels than steel tanks, with new barrels exhibiting higher levels than the old ones during fermentation. The dominant bacterial genera across all the vessels during the fermentation included Ralstonia, Pantoea, Gluconobacter, and Mesorhizobium, whereas the dominant fungal genera were Saccharomyces, Aspergillus, Alternaria, and Aureobasidium. The fermentation environment altered the microbial composition as the fermentation progressed in various vessels. Compared with steel tanks, difference in microbial composition between oak barrels was less significant. The new oak barrels increased the levels of esters, alcohols, and acids in the wine, while only minor differences were observed between old barrels and steel tanks. Correlation analysis showed that Ralstonia, Gluconobacter, Mesorhizobium, and Saccharomyces were positively correlated with the production of wine volatiles. Structural equation modeling indicated the interactions between dissolved oxygen, microbial communities, and wine aromas. The impact of dissolved oxygen on fungal communities during fermentation differed significantly between new and old oak barrels, indirectly influencing aroma. Conversely, in stainless-steel tanks, dissolved oxygen weakly influenced the bacterial and fungal communities, with the influence on wine aroma primarily dependent on the fungal communities. These findings provide valuable insights for optimizing the Sauvignon Blanc wine fermentation in oak barrels

Metagenomic and Metabolomic Profiling Reveals the Differences of Flavor Quality between Hongqu Rice Wines Fermented with Gutian Qu and Wuyi Qu.

Jiuqu (starter) makes an important contribution to the formation of the flavor characteristics of Hongqu rice wine (HQW). Gutian Qu (GTQ) and Wuyi Qu (WYQ) are two kinds of Jiuqu commonly used in HQW brewing, but the comparison of the two kinds of HQW is still insufficient at present. The objective of this study was to compare the dynamic changes of amino acids (AAs), higher alcohols (HAs), bioamines (BAs), volatile flavor compounds (VFCs), and microbial communities in HQW fermentation, with GTQ and WYQ as starter. This study used an automatic amino acid analyzer, GC, HPLC, and GC-MS to detect AAs, HAs, Bas, and VFCs during fermentation; metagenomic sequencing technology was used to elucidate the microbial community and its functional characteristics. The results showed that the contents of AAs and HAs in HQW brewed with WYQ (WYW) were significantly higher than those in HQW brewed with GTQ (GTW). On the contrary, the majority of BAs in GTW were significantly higher than those in WYW. The composition of VFCs in WYW and GTW were obviously different, as most of the VFCs were notably enriched in WYW, while ethyl caproate, isoamyl acetate, ethyl heptanoate, ethyl nonanoate, 1-decanol, citronellol, phenethyl acetate, and hexanoic acid were more abundant in GTW. Burkholderia gladioli, Pantoea dispersa, Weissella cibaria, Monascus purpureus, and Saccharomyces cerevisiae were the predominant microbial populations in GTW brewing at the species level, while Sphingomonas sp., Kosakonia cowanii, Enterobacter asburiae, Leuconostoc lactis, Aspergillus niger, and Saccharomyces cerevisiae were the dominant microbial species in WYW brewing. The abundance of functional genes involved in BAs biosynthesis were much higher in GTW brewing, while the abundance of functional genes related to the metabolism of characteristic VFCs were much higher in WYW brewing. Collectively, these findings provided evidence for elucidating the effects of Jiuqu and microbial communities on HQW flavor quality, and laid a solid foundation for the improvement of HQW flavor quality.

Hydrophobic ZIF-8 nanoparticles loaded on chitosan for improved methanol adsorption from fermented wine.

Metal-organic frameworks (MOFs) have great potential for the adsorption of minor molecular alcohols in the vapor phase. However, the drawbacks of powdered MOFs, including low recyclability and problematic separation, limit their application in fermented wine. Chitosan (CS) is a low-cost, eco-friendly, moldable matrix used in the food industry. In this study, a novel CS@ZIF-8 adsorbent with excellent microporous surface area was successfully synthesized by incorporating hydrophobic ZIF-8 into CS. The results showed that CS@ZIF-8 beads had a high adsorption affinity for methanol at a Zn2+/2-methylimidazole molar ratio of 1:5. The adsorption mechanism of methanol on CS@ZIF-8 beads was systematically studied by X-ray photoelectron spectroscopy, isotherms, and kinetics. The Langmuir model calculated the maximum adsorption of methanol to 56.8mg/g. Adsorption kinetics are consistent with pseudo-second-order models. Furthermore, CS@ZIF-8 beads presented excellent recyclability for removing methanol for five consecutive cycles. It could treat 60 bed volumes of Chinese yellow wine in column filtration experiments to make the concentration below 50mg/L. In summary, the highly efficient CS@ZIF-8 adsorbent has great potential for methanol adsorption from fermented wines. PRACTICAL APPLICATION: Methanol will exhibit adverse symptoms such as weakness and headaches after it is ingested. Therefore, methanol control is an important safety factor in the production of fermented wine. The adsorption method is recognized as a widely used technique due to its high efficiency and selectivity. The CS@ZIF-8 adsorbent synthesized in this paper provides a new idea for methanol removal.

Contributions of Hanseniaspora species to Pinot Noir microbial terroir in Oregon's Willamette Valley wine region.

Hanseniaspora yeasts are frequently found in uninoculated wine fermentations, and depending upon the species present, their contributions to the wine may be positive or negative. We found that in Oregon's Willamette Valley, the most common species of Hanseniaspora in Pinot Noir vineyards was the known spoilage organism, H. uvarum. This species was one of the strongest contributors to differences in fungal communities between different vineyards and was enriched during typical Pinot Noir processing. These results support Hanseniaspora as an integral and functional component of vineyard "microbial terroir" within Oregon.

Use of commercial or indigenous yeast impacts the S. cerevisiae transcriptome during wine fermentation.

Understanding microbial functions during wine fermentation, particularly the role of Saccharomyces cerevisiae, is crucial for enhancing wine quality. While commercially available S. cerevisiae strains are commonly used, indigenous strains can offer unique flavors, potentially reflecting vineyard terroir. By leveraging high-throughput DNA sequencing and transcriptomic analysis, we explored the impact of vine age on the grape mycobiome and characterized microbial functions during grape fermentation. Our findings revealed that older vines harbor higher fungal loads, but fungal diversity remains similar across vine ages. Additionally, uninoculated fermentations exhibited diverse fungal dynamics, including the beneficial wine yeasts Metschnikowia and Pichia. Transcriptomic analysis uncovered significant differences in S. cerevisiae gene expression between inoculated and uninoculated fermentations, highlighting the potential of indigenous yeast to enhance wine diversity and inform winemaking practices.

Basi a Nakaisigudan: Axiological Relevance of Basi in the Present-day lives of Piddigeños

Basi is a fermented wine extracted from sugarcane that is prominent in the province of Ilocos Norte. The product is particularly known in Piddig, the town where Basi Revolt started during the Spanish Regime. This study focused into the axiological relevance of basi in the present-day lives of Piddigeños. This ethnographic research also aimed to explore the historical evolution of basi in Piddig; understand and identify the challenges or threats to the tradition of basi in Piddig, and obtain insights from the Piddigeños about the future of basi. The research instrument revolved around (1) the production and evolution basi; (2) life events where basi is being served; (3) the relevance of basi in the future; (4) threats and challenges to basi; (5) perception of the young generation to the traditional alcoholic beverage; (6) values that can be derived personal experiences with basi. Using the thematic method of analysing data, results revealed that the axiological relevance of basi for Piddigeños are manifested in different dimensions of the society that includes (1) intergenerational transmission; (2) production process continuation; (3) cultural identity; (4) social cohesion; and (5) economic livelihood. Basi, being a cultural symbol, should be given importance such that the government and local should initiate its continuation through collaboration.

Development of an alternative method to quantify H2S: application in wine fermentation.

A colorimetric method for the quantification of hydrogen sulfide (H₂S) produced in microbial fermentations was developed using lead gelled alginate microparticles packed in glass columns. The formation of a lead sulfide complex, between H₂S and lead ion (Pb2+) immobilized on the microparticles, allowed simple and accurate quantification by colorimetry. The microparticle-loaded columns were calibrated and showed significant analytical sensitivity. The calibration curve of the system showed a correlation coefficient (r2) of 0.995 and a detection limit of 1.29 ± 0.02 μg L-1. The application of the columns in laboratory wine fermentations was able to detect variations in H2S production from 10.6 to 23.5 μg L-1 by increasing the sugar content in the medium, and from 10.6 to 3.2 μg L-1 with decreasing nitrogen content in the medium. Validation of the proposed method was carried out by determining H₂S in a vinic fermentation model, the results of which were compared with those obtained using a reference chemical method. The data obtained showed no statistically significant differences between the two methods, confirming the reliability and accuracy of the developed system. © 2024 Society of Chemical Industry.

Effects of Cultivar Factors on Fermentation Characteristics and Volatile Organic Components of Strawberry Wine.

Strawberry wine production is a considerable approach to solve the problem of the Chinese concentrated harvesting period and the short shelf life of strawberries, but the appropriative strawberry cultivars for fermentation are still undecided. In this study, the strawberry juice and wines of four typical strawberry cultivars named Akihime (ZJ), Sweet Charlie (TCL), Snow White (BX), and Tongzhougongzhu (TZ) were thoroughly characterized for their physicochemical indicators, bioactive compounds, and volatile organic components (VOCs) to determine the optimal strawberry cultivars for winemaking. The results showed that there were significant differences in the total sugar content, pH, total acid, and other physicochemical indexes in the strawberry juice of different cultivars, which further affected the physicochemical indexes of fermented strawberry wine. Moreover, the content of polyphenols, total flavonoids, vitamin C, and color varied among the four strawberry cultivars. A total of 42 VOCs were detected in the strawberry juice and wines using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and 3-methyl-1-butanol, linalool, trans-2-pinanol, hexanoic acid, and hexanoic acid ethyl ester were the differential VOCs to identify the strawberry wine samples of different cultivars. Overall, strawberry cultivar ZJ had a relatively high VOC and bioactive compound content, indicating that it is the most suitable cultivar for strawberry wine fermentation. In addition to determining the relatively superior fermentation characteristics of cultivar ZJ, the results may provide a theoretical basis for the raw material quality control and quality improvement of strawberry wine.

Unveiling the relationship of volatile compounds and microbial communities in light-struck taste rice wine: A comprehensive analysis

Light-struck taste rice wine (LST-RW) is the most popular new rice wine at present, which is brewed by a variety of microorganisms. However, the relationship between microorganisms and flavor substances in light-struck taste rice wine is still unexplored. In this study, high-throughput sequencing, high-performance liquid chromatography (HPLC), headspace solid-phase microextraction (HS-SPME), and gas chromatography–mass spectrometry (GC–MS) were used to prove that microbial community had significant influence on flavor substances during light-struck taste rice wine fermentation. The results indicated a consistent increase in the majority of amino acids and organic acids within LST-RW with extended fermentation duration. A total of 49 volatile flavor compounds, including alcohols, esters, and aldehydes, were identified. In the brewing process of LST-RW, Bacillus (17.13 %) and Saccharopolyspora (15.55 %) emerge as the predominant bacterial genera; Aspergillus (83.34 %) and Saccharomyces (15.21 %) emerged as the dominant fungal genera. A notable correlation was observed between fermentation microorganisms and flavor substances. Microorganism species exhibiting strong co-exclusion or symbiotic relationships were also identified. The research findings offer a theoretical reference for optimizing and innovating the fermentation process of LST-RW.

Quality of jujube wines fermented by different jujube varieties: Physicochemical parameters, antioxidant activity, non-volatile and volatile substances

The varieties of raw materials are significant to the quality of jujube wine. In this study, the physicochemical quality, antioxidant activity, non-volatile and volatile substances of different jujube wines were analyzed. The alcohol content of the different wines ranged from 12.70% (v/v) to 14.19% (v/v). Wine fermented by J60Z showed the highest alcohol content. ZHDZ-fermented wine was the yellowest and its color quality was the best. The main monomeric phenols in date wine are chlorogenic acid, epicatechin and catechin. DZ-fermented wine had the strongest DPPH, ABTS radical scavenging activity and FRAP. The organic acids in date wine were mainly succinic acid, malic acid and lactic acid. JUZ-fermented wine had the highest content of total free amino acids, essential amino acids, and sweet amino acids, which were 817.42, 53.23, and 751.01 mg/L, respectively. Seventy-nine volatile compounds were found in the nineteen jujube wines. Wine fermented by JUZ had the highest total volatiles content (8329.52 mg/L). Principal component analysis and sensory evaluation revealed that DZ-fermented date wine had the highest composite and sensory scores. Therefore, this study showed that DZ was more suitable for making jujube wine. This study provides theoretical guidance for screening suitable varieties for jujube wine fermentation.

Improving wine fermentation efficiency of Torulaspora delbrueckii by increasing the ploidy of yeast inocula

The life cycle of most non-conventional yeasts, such as Torulaspora delbrueckii (Td), is not as well-understood as that of Saccharomyces cerevisiae (Sc). Td is generally assumed to be haploid, which detracts from some biotechnological properties compared to diploid Sc strains. We analyzed the life cycle of several Td wine strains and found that they were mainly diploid during exponential growth in rich medium. However, most cells became haploid in stationary phase, as observed for Sc haploid heterothallic strains. When transferred and incubated in nutrient-deficient media, these haploid cells became polymorphic, enlarged, and transitioned to diploid or polyploid states. The increased ploidy, that mainly results from supernumerary mitosis without cytokinesis, was followed by sporulation. A similar response was observed in yeasts that remained alive during the second fermentation of base wine for sparkling wine making, or during growth in ethanol-supplemented medium. This response was not observed in the Sc yeast populations under any of the experimental conditions assayed, which suggests that it is a specific adaptation of Td to the stressful fermentation conditions. This response allows Td yeasts to remain alive and metabolically active longer during wine fermentation. Consequently, we designed procedures to increase the cell size and ploidy of haploid Td strains. Td inocula with increased ploidy showed enhanced fermentation efficiency compared to haploid inocula of the same strains.