Isolation and Investigation of Potential Non-Saccharomyces Yeasts to Improve the Volatile Terpene Compounds in Korean Muscat Bailey A Wine

Improvement of volatile aromatic compound levels and sensory quality of distilled soju derived from Saccharomyces cerevisiae and Wickerhamomyces anomalus co-fermentation

Distilled soju, a Korean traditional alcoholic beverage, is produced by fermenting rice with a variety of microorganisms including molds, yeasts, and lactic acid-producing bacteria, followed by distillation. Our study sought to improve the quality of distilled soju through co-fermentation with Saccharomyces cerevisiae and Wickerhamomyces anomalus, known for producing volatile aromatic compounds during the early stages of fermentation. Analysis of volatile aromatic compounds in co-fermented distilled soju revealed a substantial increase in compounds with boiling points below 200 °C. Among them, ethyl hexanoate, isobutanol, and isoamyl alcohol were identified as the major volatile aromatic compounds based on Log2 fold change analyses of the volatile aromatic compound pattern. In sensory evaluation, co-fermented distilled soju received higher scores in terms of odor and overall preference. Therefore, incorporating W. anomalus may improve the quality of distilled soju.

Valorization of Cashew Apple Waste into a Low-Alcohol, Healthy Drink Using a Co-Culture of Cyberlindnera rhodanensis DK and Lactobacillus pentosus A14-6

This study investigated the potential of microbial fermentative transforming processes in valorizing the cashew apple by-product into a low-alcohol, health-benefiting beverage. We particularly investigated the use of a non-Saccharomyces yeast, Cyberlindnera rhodanensis DK, as the main targeted microbe. At 30 °C without agitation, C. rhodanensis DK caused changes in key parameters during the fermentation of cashew apple juice (CAJ) in terms of varied pH values and initial sugar concentrations. This result indicated that pure CAJ, with pH adjusted to 6 and with the original 6.85% (w/v) total sugar content, was the most feasible condition, as glucose and fructose were mostly consumed at 12 days of fermentation. A co-culture approach with either Saccharomyces cerevisiae TISTR 5088 or Lactobacillus pentosus A14-6 was investigated to improve both physicochemical and fermentation characteristics. Co-fermentation with S. cerevisiae TISTR 5088 resulted in significantly increased ethanol accumulation to 33.61 ± 0.11 g/L, but diminished bioactive compounds, antioxidant activity, and antidiabetic potential. In contrast, co-fermentation with L. pentosus A14-6 demonstrated excellent outcomes, as it significantly increased sugar consumption and finally remained at only 4.95 g/L compared to C. rhodanensis DK alone, produced lower levels of ethanol at only 19.47 ± 0.06 g/L, and higher total titratable acid (TTA), resulting in a final pH of 3.6. In addition, co-fermentation with this lactic acid bacterium significantly enhanced bioactive compounds and antioxidant activity and also retained potential antidiabetic properties. These findings highlight the feasibility of using tailored microbial fermentation strategies to produce low-alcohol beverages with enhanced health-promoting properties from CAJ; however, product-development processes following health food regulations and sensory evaluation are necessary.

New Insights into the Production of Assyrtiko Wines from the Volcanic Terroir of Santorini Island Using Lachancea thermotolerans

Assyrtiko is a rare ancient grape variety of Greece, which is known to produce Protected Designation of Origin (PDO) Santorini white wines. Besides the famous character of the volcanic terroir, Assyrtiko of Santorini is also marked by a low pH value and sharp acidity. The aim of the present study was to apply a new inoculation procedure that modulates the fermentation process by maintaining the unique sensorial characteristics of Assyrtiko wines based on acidity. For this purpose, the Lachancea thermotolerans species, known for the formation of lactic acid, was tested in sequential fermentation with three different Saccharomyces cerevisiae strains. At the end of the fermentation process, implantation control for S. cerevisiae strains (interdelta sequence profile analysis) was performed, oenological parameters were determined according to the OIV protocols, and the volatile compounds produced were measured by gas chromatography-mass spectrometry (GC/MS). Finally, all produced wines were evaluated by quantitative descriptive analysis by two groups of experts; the Greek team of oenologists from Santorini Island specialized in Assyrtiko wines, and the French team of oenologists specialized in wine from Bordeaux. As expected, the inoculated strain was the one that dominated the fermentation process, but nine S. cerevisiae indigenous strains were also identified in the produced wines. Lachancea thermotolerans produced 1 g/L of lactic and also modulated the volatile profile of the wines independently of the S. cerevisiae strain used. The origin of the panelists played an important role in bringing up sensorial traits, such as acidity. Our results led to a new interesting application of L. thermotolerans for white wine production adapted to climate change claims.

Wine aroma modification by Hanseniaspora uvarum: A multiple-step strategy for screening potential mixed starters

Hanseniaspora uvarum is a prevalent yeast species in vineyards. However, its application in grape wine fermentation remains limited. This study used culture-dependent and -independent approaches to investigate the dynamics of H. uvarum during the spontaneous fermentation of Cabernet Sauvignon grapes. The results revealed that H. uvarum constituted 77.49 % of the non-Saccharomyces yeast population during fermentation. An indigenous strain, QTX-C10, was isolated from the 148 H. uvarum strains using a multistep screening strategy. The 1:1 co-inoculation of QTX-C10 with Saccharomyces cerevisiae proved to be an optimal strategy for mixed fermentation, resulting in a 48.54 %-59.55 % increase in ethyl esters in Cabernet Sauvignon wine and a 96.94 %-110.92 % increase in Chardonnay wine. Furthermore, this approach reduced the acetic acid levels by 12.50 %-17.07 % for Cabernet Sauvignon wine and 10.81 %-17.78 % for Chardonnay wine. Additionally, increased ethyl ester content may enhance the tropical fruit flavor of Cabernet Sauvignon wines.

Metagenomic analysis of the relationship between the microorganisms and the volatiles' development in the wines during spontaneous fermentation from the eastern foothills of the Ningxia Helan mountains in China

BACKGROUND

The natural fermentation of multispecies microbial communities is responsible for unique flavors of winery regions of the eastern foothills of the Ningxia Helan Mountains in China. However, the participation of different microorganisms in the metabolic network for the development of important flavor substances is not clearly defined. Microbial population and diversity on different fermentation phases of Ningxia wine were analyzed by metagenomic sequencing approach.

RESULTS

Gas chromatography-mass spectrometry and ion chromatography were used to identify flavor components, and 13 esters, 13 alcohols, nine aldehydes and seven ketones were detected in volatile substances with odor activity values > 1, and eight organic acids were detected as important flavor components in young wine. Thus, 52 238 predicted protein-coding genes from 24 genera were identified in the Kyoto Encyclopedia of Genes and Genomes level 2 pathways of global and overview maps, and the genes were primarily involved in amino acid metabolism and carbohydrate metabolism. Major microbial genera (Saccharomyces, Tatumella, Hanseniaspora, Lactobacillus, and Lachancea) were closely related to self-characteristic compound metabolism and further contributed to wine flavor.

CONCLUSION

This study clarifies the different metabolic roles of microorganisms in flavor formation during Ningxia wine spontaneous fermentation. Saccharomyces, dominant fungi involved in glycolysis and pyruvate metabolism, produces not only ethanol but also two important precursors, pyruvate and acetyl-CoA, which are necessary for the tricarboxylic acid cycle, fatty acid metabolism, amino acid metabolism, and flavor formation. Lactobacillus and Lachancea, dominant bacteria involved in lactic acid metabolism. Tatumella, dominant bacteria involved in amino acid metabolism, fatty acid metabolism, and acetic acid metabolism to produce esters in the Shizuishan City region samples. These findings provide insights into the use of local functional strains to generate unique flavor formation, as well as improved stability and quality, in wine production. © 2023 Society of Chemical Industry.

Quality Characteristics and Antioxidant Activities of Six Types of Korean White Wine

The cultivation of European grape cultivars suitable for winemaking in Korea presents challenges due to factors such as climate, soil conditions, precipitation, and sunlight. Consequently, Korea has traditionally resorted to adding sugar to its wine production to counteract the low sugar content in Korean grapes, yielding lower-quality wines. However, recent success in the cultivation of five European grape cultivars and the development of the domestic grape cultivar Cheongsoo have increased the possibility of achieving high-quality Korean wines. This study aimed to explore the potential of European grape cultivars and Cheongsoo as wine grapes in Korea. This study also conducted sensory evaluation and analyzed the physicochemical properties of the grapes and wines, including antioxidant capacity and color. Despite originating from the same vineyard, the composition of grapes and wines, including volatile aromatic compounds, significantly differed among the grape cultivars. In particular, Vidal wine exhibited superior antioxidant capacity compared with other wines. Moreover, Cheongsoo wine showed higher levels of essential volatile aromatic compounds, such as monoterpenes, than other wines. Sensory evaluation of these two wines also revealed excellent results. In conclusion, these findings hold promise for enhancing the diversity of Korean white wine and fostering growth in the wine industry.

Impact of Candida railenensis during fermentation on the aromatic profile of Vidal blanc icewine

Mixed culture fermentation with non-Saccharomyces yeasts and Saccharomyces cerevisiae as multi-starters has more advantages than spontaneous fermentation, and wine products with distinctive and pleasant aromas can fulfill the diverse demands of consumers. This study was carried out to illuminate the effect of sequential inoculation of indigenous Candida railenensis and S. cerevisiae on alcoholic fermentation behavior and chemical and aromatic characteristics of Vidal blanc icewine. During the mixed culture fermentation, C. railenensis was present in the initial and middle stages but was absent after 14 days. The results of basic chemical parameters showed that the glycerol content in the mixed culture-fermented icewine was higher than that of the pure fermented icewine, but the acetic acid content was the opposite. In terms of volatile aroma compounds, C. railenensis in the mixed culture fermentation reduced some metabolites such as lower alcohols, 1-hexanol, 3-methylthiopropanol, and their unpleasant notes and increased the production of some desired volatile aroma compounds such as benzaldehyde, β-damascenone, 2-furanmethanol, and 5-methyl furfural associated with rose, honey, nut, and caramel characteristics. Furthermore, C. railenensis also changed the sensory performance of icewine by participating in the fermentation of S. cerevisiae. These findings suggest that C. railenensis with positive enological properties has the ability to be used in icewine production, which has never been reported before.

Profiling potential brewing yeast from forest and vineyard ecosystems

The brewing ability of wild yeast strains obtained from forest and vineyards ecosystems was analysed and compared with commercial yeast strains. The selection of new yeast strains as a way to create new beer aromas and flavours and to use local strains to promote the proximity ingredients in brewing is a topic of interest in the craft beer sector. Seventy-six wild Saccharomyces and non-Saccharomyces isolates and eighteen control strains were evaluated for their enzymatic activity and brewing capacity. The early screening system was set up to profile their enzymatic activity, utilisation of wort sugars and the effect of hop acids and ethanol on yeast growth. The microvolume screening method allows a large number of samples to be studied at the same time, permitting an affordable and rapid characterization in a relatively short period of time. Twenty-eight strains were selected using this method and tested in small-scale fermentations. Finally, three of these strains, all belonging to the species Lachancea thermotolerans, showed great potential and adaptability to ferment different wort styles, although further studies will be necessary to test their possibilities as beer starters. Understanding yeast enzymatic profiles and the influence of beer ingredients on their fermentation activity provides a platform to select strains for further consideration in brewing research.

Inside Current Winemaking Challenges: Exploiting the Potential of Conventional and Unconventional Yeasts

Wine represents a complex matrix in which microbial interactions can strongly impact the quality of the final product. Numerous studies have focused on optimizing microbial approaches for addressing new challenges to enhance quality, typicity, and food safety. However, few studies have investigated yeasts of different genera as resources for obtaining wines with new, specific traits. Currently, based on the continuous changes in consumer demand, yeast selection within conventional Saccharomyces cerevisiae and unconventional non-Saccharomyces yeasts represents a suitable opportunity. Wine fermentation driven by indigenous yeasts, in the various stages, has achieved promising results in producing wines with desired characteristics, such as a reduced content of ethanol, SO₂, and toxins, as well as an increased aromatic complexity. Therefore, the increasing interest in organic, biodynamic, natural, or clean wine represents a new challenge for the wine sector. This review aims at exploring the main features of different oenological yeasts to obtain wines reflecting the needs of current consumers in a sustainability context, providing an overview, and pointing out the role of microorganisms as valuable sources and biological approaches to explore potential and future research opportunities.

Sequential culture with aroma-producing yeast strains to improve the quality of Kyoho wine

Despite many non-Saccharomyces yeasts being considered spoilage microorganisms, they can increase aroma and flavor diversity in alcoholic beverages. The purpose of this study was to investigate nontraditional inoculation strategies using aroma-producing yeast strains for Kyoho wine fermentation, followed by an instrumental analysis and sensory evaluation. The winemaking process was carried out using Saccharomyces cerevisiae Gr112, Hanseniaspora uvarum Pi235, and Pichia kluyveri Pe114. Multiple inoculation strategies were explored. In instrumental analysis results, mixed culture could promote the formation of esters (5.9-folds) and glycerol (1.3-folds) and reduce the content of ethanol (-0.5% [v/v]) in wine. The sensory analysis results suggested that the three yeast strains sequential inoculation treatment was associated with the aroma attributes "floral," "red fruity," and "tropical fruity." Co-cultivation contributed to an increase in complexity and aromatic intensity, with the three-strain inoculation treatment presenting a more distinctive appearance. PRACTICAL APPLICATION: The inoculation of S. cerevisiae improved the accumulation of volatile acids and esters by inhibiting the growth of non-Saccharomyces yeast strains. Inoculation of H. uvarum and P. kluyveri would effectively solve the defect of excessive content of higher alcohols in wines produced by S. cerevisiae. The suitable inoculation strategy between non-Saccharomyces yeasts could improve the overall quality of Kyoho wine whose starter might be widely used in fermentation industry.

Assessment of Tannin Tolerant Non-Saccharomyces Yeasts Isolated from Miang for Production of Health-Targeted Beverage Using Miang Processing Byproducts

This research demonstrated an excellent potential approach for utilizing Miang fermentation broth (MF-broth), a liquid residual byproduct from the Miang fermentation process as a health-targeted beverage. One hundred and twenty yeast strains isolated from Miang samples were screened for their potential to ferment MF-broth and four isolates, P2, P3, P7 and P9 were selected, based on the characteristics of low alcoholic production, probiotic properties, and tannin tolerance. Based on a D1/D2 rDNA sequence analysis, P2 and P7 were identified to be Wikerhamomyces anomalus, while P3 and P9 were Cyberlindnera rhodanensis. Based on the production of unique volatile organic compounds (VOCs), W. anomalus P2 and C. rhodanensis P3 were selected for evaluation of MF-broth fermentation via the single culture fermentation (SF) and co-fermentation (CF) in combination with Saccharomyces cerevisiae TISTR 5088. All selected yeasts showed a capability for growth with 6 to 7 log CFU/mL and the average pH value range of 3.91-4.09. The ethanol content of the fermented MF-broth ranged between 11.56 ± 0.00 and 24.91 ± 0.01 g/L after 120 h fermentation, which is categorized as a low alcoholic beverage. Acetic, citric, glucuronic, lactic, succinic, oxalic and gallic acids slightly increased from initial levels in MF-broth, whereas the bioactive compounds and antioxidant activity were retained. The fermented MF-broth showed distinct VOCs profiles between the yeast groups. High titer of isoamyl alcohol was found in all treatments fermented with S. cerevisiae TISTR 5088 and W. anomalus P2. Meanwhile, C. rhodanensis P3 fermented products showed a higher quantity of ester groups, ethyl acetate and isoamyl acetate in both SF and CF. The results of this study confirmed the high possibilities of utilizing MF-broth residual byproduct in for development of health-targeted beverages using the selected non-Saccharomyces yeast.

Development of mixed starter culture for the fermentation of Ethiopian honey wine, Tej

Ethiopian honey wine is one of the country's most popular spontaneously fermented traditional alcoholic beverages. However, the final product of this natural fermentation system is frequently of poor and inconsistent quality. Furthermore, it makes the process difficult to predict, control, and correct. Thus, the main aim of this study was to develop a direct fermentation system for Ethiopian honey wine, Tej. After isolating fermentative microbial strains from Tej samples, they were subjected to intensive screening to fit to its purpose. Later, phenotypic and genotypic characterization, and inoculation of isolates to honey-must were performed sequentially. Finally, microbial interaction and physicochemical analysis, including volatile compounds profiling, were done for the inoculated samples. The identified isolates were strains of Saccharomycetaceae and Lactobacillaceae families. These strains showed a good ability to tolerate osmotic stress and a lower pH environment. Tej sample produced by mixed culture inoculation of Saccharomyces and Lactobacillus species showed similar physicochemical, volatile compounds, and sensory attributes values with that of the control sample. Thus, a mixture of Saccharomyces and Lactobacillus strains could be used as a starter culture to produce Ethiopian honey, Tej, without scarifying of its major quality attributes.

Impact of Torulaspora delbrueckii During Fermentation on Aromatic Profile of Vidal Blanc Icewine

Non-Saccharomyces yeasts usually have a positive effect on improving the diversity of wine aroma and increasing the differentiation of wine products. Among these non-Saccharomyces yeast species, Torulaspora delbrueckii is often studied and used in winemaking in recent years, but its application in icewine has not been reported yet. In this study, indigenous T. delbrueckii strains (TD1 and TD2) and Saccharomyces cerevisiae strains (commercial yeast SC1 and indigenous icewine yeast SC2) were sequentially inoculated for icewine fermentations; meanwhile, pure S. cerevisiae (SC1 and SC2) fermentations were used as the control; TD1, TD2, and SC2 strains used were screened from spontaneous fermentations of Vidal blanc icewine. The aim was to investigate the effect of T. delbrueckii on the aroma complexity of icewine, which is of great significance to the application of T. delbrueckii in icewine production. The results showed that T. delbrueckii was completely replaced by S. cerevisiae at the middle and later fermentative stages in mixed culture fermentations. Compared with the icewine fermented with pure S. cerevisiae, mixed culture fermented icewines contained lower acetic acid and ethanol, and higher glycerol. The inoculation of T. delbrueckii greatly impacted the levels of several important volatile compounds, and more 2-phenylethyl alcohol, isoamyl acetate, linalool, D-limonene, p-cymene and cineole were produced, and the fruity, flowery, and sweet characteristic was intensified. Moreover, the relevance of strain-specificity within T. delbrueckii to aroma compound differences was shown. To our knowledge, this study is the first to investigate the application of T. delbrueckii in Vidal blanc icewine fermentation, and volatile aroma compounds in the icewine fermented by T. delbrueckii and S. cerevisiae.

Exploring Use of the Metschnikowia pulcherrima Clade to Improve Properties of Fruit Wines

Mixed fermentation using Saccharomyces cerevisiae and non-Saccharomyces yeasts as starter cultures is well known to improve the complexity of wines and accentuate their characteristics. This study examines the use of controlled mixed fermentations with the Metschnikowia pulcherrima clade, Saccharomyces cerevisiae Tokay, and non-conventional yeasts: Wickerhamomyces anomalus and Dekkera bruxellensis. We investigated the assimilation profiles, enzyme fingerprinting, and metabolic profiles of yeast species, both individually and in mixed systems. The chemical complexity of apple wines was improved using the M. pulcherrima clade as co-starters. M. pulcherrima with S. cerevisiae produced a wine with a lower ethanol content, similar glycerol level, and a higher level of volatilome. However, inoculation with the Dekkera and Wickerhamomyces strains may slightly reduce this effect. The final beneficial effect of co-fermentation with M. pulcherrima may also depend on the type of fruit must.

Development of Korean Indigenous Low-Temperature-Tolerant Yeast for Enhancing the Flavor of Yakju

Yakju, a traditional fermented beverage in Korea, is prepared using various raw materials and methods, and, hence, exhibits various characteristics. Low-temperature-fermented yakju can inhibit the growth of undesirable bacteria and is known for its unique flavor and refreshing taste. To increase the production of volatile aromatic compounds in yakju, strains with strong resistance to low temperatures and excellent production of volatile aromatic compounds were screened from indigenous fruits (grape, persimmon, plum, aronia, wild grape) and nuruk in Korea. One Saccharomyces cerevisiae and three non-Saccharomyces strains were finally screened, and yakju was fermented at 15 °C through mono/co-culture. The analysis of volatile aromatic compounds showed that S. cerevisiae W153 produced 1.5 times more isoamyl alcohol than the control strain and reduced the production of 2,3-butanediol by a third. Similarly, a single culture of Pichia kudriavzevii N373 also produced 237.7 mg/L of ethyl acetate, whereas Hanseniaspora vineae G818 produced ~11 times greater levels of 2-phenethyl acetate than the control. Alternatively, Wickerhamomyces anomalus A159 produced 95.88 mg/L of ethyl hexadecanoate. During principal component analysis, we also observed that the co-culture sample exhibited characteristics of both volatile aroma compounds of the single cultured sample of each strain. Our results suggest that yakju with unique properties can be prepared using various non-Saccharomyces strains.

Ability of Yeast Metabolic Activity to Reduce Sugars and Stabilize Betalains in Red Beet Juice

To lower the risk of obesity, diabetes, and other related diseases, the WHO recommends that consumers reduce their consumption of sugars. Here, we propose a microbiological method to reduce the sugar content in red beet juice, while incurring only slight losses in the betalain content and maintaining the correct proportion of the other beet juice components. Several yeast strains with different metabolic activities were investigated for their ability to reduce the sugar content in red beet juice, which resulted in a decrease in the extract level corresponding to sugar content from 49.7% to 58.2%. This strategy was found to have the additional advantage of increasing the chemical and microbial stability of the red beet juice. Only slight losses of betalain pigments were noted, to final concentrations of 5.11% w/v and 2.56% w/v for the red and yellow fractions, respectively.

The Antimutagenic and Antioxidant Activity of Fermented Milk Supplemented with Cudrania tricuspidata Powder

In this study, Cudrania tricuspidata (CT) containing abundant phytochemicals, such as xanthones and flavonoids, was evaluated as an additive to fortify the functionality and organoleptic quality of fermented milk. The physicochemical, functional, and sensory properties of fermented milk supplemented with different concentrations of CT powder were investigated. Increasing amounts of CT powder elevated the malic acid concentration, increasing the total acidity and decreasing the pH of fermented milk supplemented with CT powder. The viable cell count and free sugar contents of fermented milk indicated that supplementing with CT powder improved lactic acid fermentation slightly. The color of fermented milk supplemented with CT powder was darker, redder, yellower, and more pleasing than the control fermented milk. The total phenolic and flavonoid contents of fermented milk supplemented with CT powder rose as the concentration of supplemented CT powder increased, resulting in enhanced antioxidant and antimutagenic activities. The CT powder improved the functionality of the fermented milk; still, at 2% or more, it had some unfavorable sensory properties, such as sourness, taste, and texture, which reduced the overall consumer preference. Therefore, a CT powder concentration of 0.5% or 1% may be acceptable to consumers.