Non-Saccharomyces Yeasts Highly Contribute to Characterisation of Flavour Profiles in Greengage Fermentation

Exogenous Mogroside V Drove Microbial Carbohydrate Metabolism and Consequently Enhanced Fruity Aroma in Greengage Wine

The microbial community is essential for the formation of aroma development in high-acidity greengage wine fermentation. Recent observations also highlight positive effects of mogroside V (MG V) on microorganisms in fermented foods, but the underlying chemical and biological mechanisms remain inadequate. The results indicated differences in the physicochemical properties among greengage wines, particularly a 50% increase in the ethanol conversion rate. Concurrently, GC-MS and sensory analyses demonstrated that MG V augmented carbohydrate conversion into ethyl esters (twice as much as in the control group), exhibiting tropical fruit and floral aroma profiles. The perceived intensity of these aromatic compounds increased by over 30%, thereby enriching the overall aromatic harmony of the wine. Integrated analysis of KEGG pathways and CAZymes annotations demonstrated that the enhancement of ethyl ester formation by MG V depends on improvement of the transport of carbohydrates and MG V, as well as accelerating the flux of pyruvate to acetyl-CoA in yeast. In conclusion, our study presents a targeted strategy for the high-acidity fruit wine industry of modulating this metabolic node in yeast, thereby achieving a focused enhancement of tropical fruit aroma characteristics in fruit wines.

The Antioxidant Capacity and Flavor Diversity of Strawberry Wine Are Improved Through Fermentation with the Indigenous Non-Saccharomyces Yeasts Hanseniaspora uvarum and Kurtzmaniella quercitrusa

The production of strawberry wine is an effective strategy for addressing the significant economic losses caused by strawberry spoilage. In recent years, there has been an increase in consumer demand for quality and flavor diversity in fruit wines. Therefore, it is necessary to develop novel strawberry wine products. In this research, we assessed and analyzed the influences of fermentation with Hanseniaspora uvarum, Kurtzmaniella quercitrusa, and Saccharomyces cerevisiae under four fermentation conditions on the fermentation kinetics, organoleptic characteristics, chemical compositions, antioxidant capacities, and flavor profiles of strawberry wines. Strawberry wines fermented with the indigenous non-Saccharomyces yeasts H. uvarum and K. quercitrusa showed higher 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) free-radical-scavenging capacities and significantly different flavor profiles compared to strawberry wines fermented with S. cerevisiae. In addition, adjusting the initial soluble solids contents of strawberry juices and fermentation temperatures positively affected the quality and flavor profiles of strawberry wines fermented with the H. uvarum and K. quercitrusa strains. Under the condition of 18 °C-20 °Brix, strawberry wine fermented with K. quercitrusa presented the highest antioxidant capacity, with enhanced flavor diversity and color intensity. It is worth noting that K. quercitrusa can be an alternative yeast for producing high-quality strawberry wine with a distinct floral aroma.

Exploring the Impact of Different Saccharomyces cerevisiae Strains on the Flavor Profile of Greengage Alcoholic Beverage Using GC-E-Nose, HS-GC-IMS, and HS-SPME-GC-MS

Greengage alcoholic beverage (GAB) is gaining popularity for its distinctive fruity aroma and nutritional benefits. The Saccharomyces cerevisiae strain applied for fermentation significantly influences the metabolic production of aroma compounds, making the selection of S. cerevisiae strains to be critical for enhancing the unique flavor profile of the GAB in commercial production. In this study, the effects of two common commercial S. cerevisiae strains (SY, EC-1118) and two laboratory-derived strains (ET008-c54, NM-8) on the flavor profile of the GAB were investigated. Volatile organic compounds (VOCs) of the GAB samples were analyzed using GC-E-Nose, HS-SPME-GC-MS, and HS-GC-IMS. Results showed significant differences in the flavor compound content of the GAB fermented by different strains. Nine VOCs were identified as potential markers by partial least squares-discriminant analysis (PLS-DA) combined with variable importance in projection (VIP), with ethyl esters playing a key role in distinguishing the aroma characteristics of different groups. Consequently, 13 aromatic compounds were selected and considered to be the typical VOCs of the GAB. Notably, β-ionone and ethyl octanoate emerged as representative aroma compounds, both showing the highest concentrations in the SY sample. These findings will provide valuable insights into the aroma differences of the GAB fermented by different strains and offer theoretical guidance for selecting suitable strains in the industrial production of the GAB.

Multi-omics analyses of the mechanism for formation of key aroma-active compounds in blood orange wine fermented by Pichia kudriavzevii

Pichia kudriavzevii is an emerging non-Saccharomyces yeast recognized for its ability to enhance aroma quality in fermented foods, though the precise mechanisms underlying its effects remain poorly understood. This study delves into the influence of P. kudriavzevii BP15 on the formation of key aroma-active compounds (KAACs) and metabolic pathways during the fermentation of blood orange wine. By integrating multi-omics approaches, including volatilomics, genomics, and transcriptomics, this work systematically evaluated the profile of volatile organic compounds (VOCs), pinpointed the genes implicated in KAACs metabolism, and elucidated the biotransformation pathways of KAACs. The volatilomics results demonstrated that inoculation with P. kudriavzevii BP15 significantly improved the complexity and desirability of aroma by promoting the accumulation of diverse VOCs, particularly esters. The genomics analysis further revealed that a substantial portion of P. kudriavzevii BP15 genome was dedicated to carbohydrate, amino acid, and energy metabolisms. The transcriptomics data identified the high expression of multiple genes (e.g., ARO8, ACC1, ALD4, ILV5) during the early stages of fermentation by P. kudriavzevii BP15 that are integral to the biosynthesis of KAACs. These insights provide a deeper understanding of P. kudriavzevii BP15's potential application in the production of high-quality blood orange wine, underscoring its role in enhancing the aroma profile through sophisticated metabolic interventions.

Widely targeted metabolomics and flavoromics reveal the effect of Wickerhamomyces anomalus fermentation on the volatile and nonvolatile metabolites of black garlic juice

Black garlic has a variety of biological activities, but many consumers cannot accept it because of the garlic odor and the bitter taste. In this study, fermentation with yeast Wickerhamomyces anomalus was adopted to improve the flavor of black garlic juice. Although fermentation reduced antioxidant activities, the garlicky odor and bitter taste were weakened. Metabolomic analysis revealed 141 metabolites were significantly differentially regulated. The upregulated metabolites were mainly related to nucleotides, organic acids and their derivatives, while the downregulated metabolites were mainly related to amino acids, lipids and their derivatives. Flavoromics analysis revealed that 137 metabolites were significantly differentially regulated, particularly garlicky and pungent volatiles were significantly downregulated. Correlation analysis indicated that esters are most closely related to nonvolatile metabolites, and lipids degradation was significantly correlated with volatiles. The results indicated that W. anomalus fermentation is an effective strategy to improve the flavor of black garlic juice.

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.

Recent advances of fermented fruits: A review on strains, fermentation strategies, and functional activities

Fruits are recognized as healthy foods with abundant nutritional content. However, due to their high content of sugar and water, they are easily contaminated by microorganisms leading to spoilage. Probiotic fermentation is an effective method to prevent fruit spoilage. In addition, during fermentation, the probiotics can react with the nutrients in fruits to produce new derived compounds, giving the fruit specific flavor, enhanced color, active ingredients, and nutritional values. Noteworthy, the choice of fermentation strains and strategies has a significant impact on the quality of fermented fruits. Thus, this review provides comprehensive information on the fermentation strains (especially yeast, lactic acid bacteria, and acetic acid bacteria), fermentation strategies (natural or inoculation fermentation, mono- or mixed-strain inoculation fermentation, and liquid- or solid-state fermentation), and the effect of fermentation on the shelf life, flavor, color, functional components, and physiological activities of fruits. This review will provide a theoretical guidance for the production of fermented fruits.

The improvement of Hovenia acerba-sorghum co-fermentation in terms of microbial diversity, functional ingredients, and volatile flavor components during Baijiu fermentation

The quality of Baijiu was largely affected by raw materials, which determine the flavor and taste. In the present study, organic acids, polyphenols, volatile flavor components and microbial community in Hovenia acerba-sorghum co-fermented Baijiu (JP1) and pure sorghum-fermented Baijiu (JP2) were comprehensively analyzed. Organic acids, polyphenols and volatile flavor components in JP1 were more abundant than JP2. The abundance and diversity of bacteria and fungi in JP1 was higher than that in JP2 in the early stage of fermentation, but presented opposite trend in the middle and late stages. Leuconostoc, Lentilactobacillus and Issatchenkia were dominant genera in JP1. Whereas, Cronobacter, Pediococcus and Saccharomyces occupied the main position in JP2. Lentilactobacillus and Issatchenkia were positively related to most of organic acids and polyphenols. Pseudomonas, Rhodococcus, Cronobacter, Pediococcus, Brucella, Lentilactobacillus, Lactobacillus, Saccharomycopsis, Wickerhamomyces, Aspergillus, Thermomyces and unclassified_f-Dipodascaccae were associated with the main volatile flavor components. The main metabolic pathways in two JPs exhibited the variation trend of first decreasing and then increasing, and the metabolism activity in JP1 were higher than that in JP2. The results demonstrated the introduction of Hovenia acerba improved the functional ingredients and volatile flavor components, which is helpful for the quality promotion of Baijiu. This study identified the key microorganisms and discussed their effect on organic acids, polyphenols and volatile flavor components during the fermentation of Baijiu with different raw materials, providing a scientific basis for the development and production of high-quality Baijiu.

Addition of Saccharomyces eubayanus to SCOBY fermentations modulates the chemical and volatile compound profiles in kombucha

Kombucha is a fermented beverage derived from a sweetened tea fermentation inoculated with a bacteria-yeast consortium referred to as Symbiotic Culture of Bacteria and Yeast (SCOBY). Different SCOBY cultures can impact the beverage's quality and make the whole process highly variable. Adding Saccharomyces yeast cultures to the fermentation process can avoid stalled fermentations, providing a reproducible beverage. Here, we explored using different Saccharomyces eubayanus strains together with SCOBY in the context of kombucha fermentation. Our results show that yeast x SCOBY co-cultures exhibited a robust fermentation profile, providing ethanol and acetic acid levels ranging from 0,18-1,81 %v/v and 0,35-1,15 g/L, respectively. The kombucha volatile compound profile of co-cultures was unique, where compounds such as Isopentyl acetate where only found in yeast x SCOBY fermentations. Metabarcoding revealed that the SCOBY composition was also dependent on the S. eubayanus genotype, where besides Saccharomyces, amplicon sequence variants belonging to Brettanomyces and Starmerella were detected. These differences concomitated global changes in transcript levels in S. eubayanus related to the metabolism of organic molecules used in kombucha fermentation. This study highlights the potential for exploring different S. eubayanus strains for kombucha fermentation, and the significant yeast genotype effect in the profile differentiation in this process.

Reviewing the Source, Physiological Characteristics, and Aroma Production Mechanisms of Aroma-Producing Yeasts

Flavor is an essential element of food quality. Flavor can be improved by adding flavoring substances or via microbial fermentation to impart aroma. Aroma-producing yeasts are a group of microorganisms that can produce aroma compounds, providing a strong aroma to foods and thus playing a great role in the modern fermentation industry. The physiological characteristics of aroma-producing yeast, including alcohol tolerance, acid tolerance, and salt tolerance, are introduced in this article, beginning with their origins and biological properties. The main mechanism of aroma-producing yeast is then analyzed based on its physiological roles in the fermentation process. Functional enzymes such as proteases, lipases, and glycosidase are released by yeast during the fermentation process. Sugars, fats, and proteins in the environment can be degraded by these enzymes via pathways such as glycolysis, methoxylation, the Ehrlich pathway, and esterification, resulting in the production of various aromatic esters (such as ethyl acetate and ethyl caproate), alcohols (such as phenethyl alcohol), and terpenes (such as monoterpenes, sesquiterpenes, and squalene). Furthermore, yeast cells can serve as cell synthesis factories, wherein specific synthesis pathways can be introduced into cells using synthetic biology techniques to achieve high-throughput production. In addition, the applications of aroma yeast in the food, pharmaceutical, and cosmetic industries are summarized, and the future development trends of aroma yeasts are discussed to provide a theoretical basis for their application in the food fermentation industry.

Exploring the Health Benefits of Yeast Isolated from Traditional Fermented Foods in Korea: Anti-Inflammatory and Functional Properties of Saccharomyces and Non-Saccharomyces Strains

Traditional yeast (Saccharomyces cerevisiae) has been used for its benefits in various fermentation processes; the benefits of non-Saccharomyces yeast as a material for food, feed, and pharmaceuticals have been studied recently. This study evaluated the anti-inflammatory activity and extracellular functional characteristics of wild-type yeasts isolated from traditional fermented foods (doenjang (common name: soybean paste) and nuruk) in Korea. The viability of the yeast and lipopolysaccharide (LPS)-stimulated RAWBlue™ cells was improved, similar to unstimulated RAWBlue™ cells, and the isolates demonstrated NF-κB inhibitory activity. Yeast suppressed the nitric oxide production in LPS-stimulated RAWBlue™ cells, which was attributed to the inhibition of iNOS or COX-2 mRNA expression depending on the strain. Although there were differences depending on the strain, the production of anti-inflammatory cytokines was reduced in the yeast and LPS-stimulated RAWBlue™ cells, some of which were demonstrated at the mRNA level. In addition, the isolates exhibited high antioxidant and antihypertensive activities (similar to the positive control), which varied depending on the strain. This suggests that yeast can be used for fermentation with enhanced antioxidant and antihypertensive activities. Furthermore, the isolates inhibited the growth of pathogenic Gram-negative bacteria, indicating that yeast can inhibit food spoilage and the growth of pathogenic bacteria during fermentation. Consequently, utilizing raw materials to cultivate yeast strains could be a promising avenue for developing functional foods to prevent and treat inflammatory reactions; such foods may exhibit antioxidant, antihypertensive, and antibacterial properties.

Effects of Torulaspora delbrueckii co-fermented with Saccharomyces cerevisiae on physicochemical and aromatic profiles of blueberry fermented beverage

To investigate the effects of mixed fermentation with T. delbrueckii on aroma profiles of blueberry fermented beverage, five fermentations were conducted: monoculture of T. delbrueckii and S. cerevisiae, respectively; co-inoculation of two strains; sequential inoculation of two strains at time intervals of 24 h and 48 h, respectively. Compared with pure S. cerevisiae fermentation, ethanol level was decreased by up to 1.1% vol., while total anthocyanins were increased by 27.7%-85.0% in mixed fermentations. Marker aroma compounds in different fermentations with relative odor activity values higher than 1were identified. T. delbrueckii significantly decreased volatile acid content (especially acetic acid) by 22.2%-83.3%. Ethyl 3-methylbutanoate, ethyl hexanoate and ethyl octanoate, in pure T. delbrueckii fermentation were significantly decreased, while their concentrations were increased by 1.6-4.4 folds in sequential fermentations. Besides, linalool, rose oxide, benzeneacetaldehyde were significantly increased by sequential fermentation, which was associated with the enhancement of fruity and sweet notes.

Flavor Profile Evaluation of Soaked Greengage Wine with Different Base Liquor Treatments Using Principal Component Analysis and Heatmap Analysis

The selection of base liquor plays a crucial role in the flavor of soaked greengage wine. This study aimed to investigate the effects of different base liquor treatments on the physicochemical characteristics and aroma composition of greengage wine. We carried out a comprehensive analysis using HPLC for the determination of organic acids and GC-MS for the determination of volatile aroma compounds, combined with sensory evaluation. The results showed that the red and yellow colors were the darkest in the high-alcohol group, while the citric acid content was the highest in the sake group (21.95 ± 2.19 g/L). In addition, the greengage wine steeped in 50% edible alcohol had more terpenes, a significantly higher concentration of acid-lipid compounds, and a more intense aroma compared to that of the low-alcohol group, whose typical aroma compounds were greatly reduced. The sensory results showed that the greengage wine treated with baijiu had a distinct alcoholic flavor, while almond flavors were more intense in the greengage wine treated with 15% edible alcohol. In this study, base liquor was used as the main influencing factor to provide new research ideas for the flavor optimization of soaked greengage wine.

Free amino acids identification and process optimization in greengage wine fermentation and flavor formation

Greengage wine with low alcohol content is increasing in popularity owing to its fruity taste and rich nutrition. The key to wine aroma and taste is flavor substances like free amino acids (FAAs), volatile fatty acids, higher alcohols, and esters. Amino acid (AA) metabolisms in yeast are an important source of these secondary compounds, which vary with the fermentation conditions. This study explored and optimized the impact of different parameters (carbon source, inoculum, pH, temperature) on FAA contents and dynamics in greengage wine. The results demonstrated that total and essential amino acid (EAA) content rose with a higher proportion of glucose, less yeast inoculation, higher temperature, and higher initial pH. With the results obtained it was concluded that the condition of 22.4°C, pH 4.5, and 3% inoculation was optimum for a 14.9-fold increase of EAAs in fermented greengage wine. In the long run, the research will aid in the development of the greengage brewing industry.

Characterization of Key Odorants in Lingtou Dancong Oolong Tea and Their Differences Induced by Environmental Conditions from Different Altitudes

Lingtou Dancong oolong tea is a famous Chinese oolong tea due to its special honey-like aroma. However, little is known about its specific aroma profile and key contributors. Furthermore, whether the aroma characteristics of Lingtou Dancong oolong tea are affected by the environmental conditions at different altitudes is unknown. In this study, the aromas in Lingtou Dancong oolong tea were extracted and analyzed by stir-bar sorptive extraction (SBSE) combined with gas chromatography-olfactometry (GC-O) and GC-mass spectrometry (GC-MS), and the aroma profiles of tea plants grown at different altitudes were compared. We detected 59 odor compounds in Lingtou Dancong oolong tea. Eight compounds with honey and floral odors were identified as key components on the basis of GC-O, GC-MS, odor activity value, and flavor dilution analyses. Differences in the contents of precursor geranyl diphosphate and transcript levels of structural genes were found to be responsible for the differential accumulation of linalool and hotrienol among plants grown at different altitudes. This is the first report on the aroma characteristics and key contributors of Lingtou Dancong oolong tea and their differences, as affected by altitude. These results provide details of the chemical basis of the aroma quality of Lingtou Dancong oolong tea.