Yeast Modulation of Wine Flavor

Volatilomics of Cabernet Sauvignon grapes and sensory perception of wines are affected by canopy side in vineyards with different row orientations

This study aimed to clarify how microclimate diversity altered volatilomics in Cabernet Sauvignon grapes and wines. Four row-oriented vineyards were selected, and metabolites of grapes and wines were determined from separate canopy sides. Results showed that shaded sides received 59% of the solar radiation and experienced 55% of the high-temperature days compared to the exposed sides on average. Grape primary metabolites were slightly affected by the canopy side. Herbaceous aromas were consistently more abundant in grapes and wines from shaded clusters. Heat-stressed canopy sides accelerated terpenoid loss and increased norisoprenoid levels in grapes, while β-damascenone in north-side wines was 13%-32% higher than that in south-side wines of the east-west vineyard. The northeast-southwest vineyard showed the most notable variation in taste and aroma sensory scores, with four parameters significantly different. There were 32 aroma series identified in wines, and banana, pineapple, and strawberry odors were highly correlated with aroma sensory score.

Quantitative genetic analysis of attractiveness of yeast products to Drosophila

An attractive perfume is a complex mixture of compounds, some of which may be unpleasant on their own. This is also true for the volatile combinations from yeast fermentation products in vineyards and orchards when assessed by Drosophila. Here, we used crosses between a yeast strain with an attractive fermentation profile and another strain with a repulsive one and tested fly responses using a T-maze. QTL analysis reveals allelic variation in four yeast genes, namely PTC6, SAT4, YFL040W, and ARI1, that modulated expression levels of volatile compounds [assessed by gas chromatography-mass spectrometry (GC-MS)] and in different combinations, generated various levels of attractiveness. The parent strain that is more attractive to Drosophila has repulsive alleles at two of the loci, while the least attractive parent has attractive alleles. Behavioral assays using artificial mixtures mimicking the composition of odors from fermentation validated the results of GC-MS and QTL mapping, thereby directly connecting genetic variation in yeast to attractiveness in flies. This study can be used as a basis for dissecting the combination of olfactory receptors that mediate the attractiveness/repulsion of flies to yeast volatiles and may also serve as a model for testing the attractiveness of pest species such as Drosophila suzukii to their host fruit.

Volatilomics of Fruit Wines

Volatilomics is a scientific field concerned with the evaluation of volatile compounds in the food matrix and methods for their identification. This review discusses the main groups of compounds that shape the aroma of wines, their origin, precursors, and selected metabolic pathways. The paper classifies fruit wines into several categories, including ciders and apple wines, cherry wines, plum wines, berry wines, citrus wines, and exotic wines. The following article discusses the characteristics of volatiles that shape the aroma of each group of wine and the concentrations at which they occur. It also discusses how the strain and species of yeast and lactic acid bacteria can influence the aroma of fruit wines. The article also covers techniques for evaluating the volatile compound profile of fruit wines, including modern analytical techniques.

The Use of Hanseniaspora opuntiae to Improve 'Sideritis' Wine Quality, a Late-Ripening Greek Grape Variety

In view of climate change and the increasingly antagonistic wine market, the exploitation of native genetic resources is revisited in relation to sustainable wine production. 'Sideritis' is a late-ripening Greek grape variety, which is quite promising for counteracting wine quality issues associated with the annual temperature rise. The aim of this study was to improve the quality and to enhance the aroma of 'Sideritis' wine through the use of native yeasts. To improve vinification, Hanseniaspora opuntiae L1 was used along with Saccharomyces cerevisiae W7 in mixed fermentations (SQ). The addition of H. οpuntiae significantly altered the chemical profile of the wine compared to the single-inoculated fermentations with W7 (IS). H. opuntiae increased all the acetate esters, except for hexyl acetate and (Z)-3-hexen-1-ol acetate. The concentration of 2-phenylethyl acetate, which imparts flowery and sweet notes, exhibited a 2.6-fold increase in SQ as compared to IS wines. SQ also showed higher levels in several ethyl esters, including ethyl butyrate, ethyl heptanoate and ethyl 7-octenoate, which are associated with fruity notes compared to IS. H. opuntiae produced citronellol, a terpene associated with rose and green notes, and increased the overall acceptance of the wine. Present results are thus quite promising for improving 'Sideritis' wine quality towards a sustainable wine production in Greece in view of global warming.

CRISPRi-induced transcriptional regulation of IAH1 gene and its influence on volatile compounds profile in Kluyveromyces marxianus DU3

Mezcal is a traditional Mexican distilled beverage, known for its marked organoleptic profile, which is influenced by several factors, such as the fermentation process, where a wide variety of microorganisms are present. Kluyveromyces marxianus is one of the main yeasts isolated from mezcal fermentations and has been associated with ester synthesis, contributing to the flavors and aromas of the beverage. In this study, we employed CRISPR interference (CRISPRi) technology, using dCas9 fused to the Mxi1 repressor factor domain, to down-regulate the expression of the IAH1 gene, encoding for an isoamyl acetate-hydrolyzing esterase, in K. marxianus strain DU3. The constructed CRISPRi plasmid successfully targeted the IAH1 gene, allowing for specific gene expression modulation. Through gene expression analysis, we assessed the impact of IAH1 down-regulation on the metabolic profile of volatile compounds. We also measured the expression of other genes involved in volatile compound biosynthesis, including ATF1, EAT1, ADH1, and ZWF1 by RT-qPCR. Results demonstrated successful down-regulation of IAH1 expression in K. marxianus strain DU3 using the CRISPRi system. The modulation of IAH1 gene expression resulted in alterations in the production of volatile compounds, specifically ethyl acetate, which are important contributors to the beverage's aroma. Changes in the expression levels of other genes involved in ester biosynthesis, suggesting that the knockdown of IAH1 may generate intracellular alterations in the balance of these metabolites, triggering a regulatory response. The application of CRISPRi technology in K. marxianus opens the possibility of targeted modulation of gene expression, metabolic engineering strategies, and synthetic biology in this yeast strain.

Yeast Starter Culture Identification to Produce of Red Wines with Enhanced Antioxidant Content

Grape variety, quality, geographic origins and phytopathology can influence the amount of polyphenols that accumulate in grape tissues. Polyphenols in wine not only shape their organoleptic characteristics but also significantly contribute to the positive impact that this beverage has on human health. However, during the winemaking process, the total polyphenol content is substantially reduced due to the adsorption onto yeast wall polymers and subsequent lees separation. Despite this, limited information is available regarding the influence of the yeast starter strain on the polyphenolic profile of wine. To address this issue, a population consisting of 136 Saccharomyces cerevisiae strains was analyzed to identify those with a diminished ability to adsorb polyphenols. Firstly, the reduction in concentration of polyphenolic compounds associated to each strain was studied by assaying Total Phenolic Content (TPC) and Trolox Equivalent Antioxidant Capacity (TEAC) in the wines produced by micro-scale must fermentation. A total of 29 strains exhibiting a TPC and TEAC reduction ≤ 50%, when compared to that detected in the utilized grape must were identified and the nine most-promising strains were further validated by larger-scale vinification. Physico-chemical analyses of the resulting wines led to the identification of four strains, namely ITEM6920, ITEM9500, ITEM9507 and ITEM9508 which showed, compared to the control wine, a TPC and TEAC reduction ≤ 20 in the produced wines. They were denoted by a significant (p < 0.05) increased amount of anthocyanin, quercetin and trans-coutaric acid, minimal volatile acidity (<0.2 g/L), absence of undesirable metabolites and a well-balanced volatile profile. As far as we know, this investigation represents the first clonal selection of yeast strains aimed at the identifying "functional" fermentation starters, thereby enabling the production of regional wines with enriched polyphenolic content.

Vineyard soil heterogeneity and harvest date affect volatolomics and sensory attributes of Cabernet Sauvignon wines on a meso-terroir scale

To produce premium wines in a specific region is the goal of local oenologists. This study aimed to investigate the influence of soil properties and harvest date on the volatolomics of wine to provide a better insight into single-vineyard wines. Six Cabernet Sauvignon vineyards were selected in a semi-arid region to produce their wines at three harvest ripeness levels ranging from 23°Brix-28°Brix in three seasons (2019-2021). Results showed that among all six vineyards, the vineyard with the highest soil pH produced wines with lower C6 alcohols and herbaceous aroma. Moderate nutrition in soils was beneficial for the accumulation of β-damascenone and enhanced fruity and floral aroma in wines while over-fertile soil produced wines with the lowest sensory score. As the harvest ripeness elevated, the wine's fruity and floral aroma intensity decreased. Through advanced network analysis, the key volatiles such as β-damascenone, ethy1 lactate, and isoamyl octanoate, and their interaction in affecting wine sensory scores were evaluated. Our study provided a concept for producing premium single-vineyard wines.

Endogenous CO2 Overpressure Effect on Higher Alcohols Metabolism during Sparkling Wine Production

Higher alcohols produced by yeast during the fermentation of sparkling wine must have the greatest impact on the smell and taste of wine. At present, the metabolic response to methanol and higher alcohols formation of Saccharomyces cerevisiae under endogenous CO₂ overpressure has not been fully elucidated. In this work, a proteomics and metabolomics approach using a OFFGEL fractionator and the LTQ Orbitrap for the protein identification, followed by a metabolomic study for the detection and quantification of both higher alcohols (GC-FID and SBSE-TD-GC-MS) and amino acids (HPLC), was carried out to investigate the proteomic and metabolomic changes of S. cerevisiae in relation to higher alcohols formation under a CO₂ overpressure condition in a closed bottle. The control condition was without CO₂ overpressure in an open bottle. Methanol and six higher alcohols were detected in both conditions, and we have been able to relate to a total of 22 proteins: 15 proteins in the CO₂ overpressure condition and 22 proteins in the control condition. As for the precursors of higher alcohols, 18 amino acids were identified in both conditions. The metabolic and proteomic profiles obtained in both conditions were different, so CO₂ overpressure could be affecting the metabolism of higher alcohols. Furthermore, it was not possible to establish direct correlations in the condition under CO₂ overpressure; however, in the condition without pressure it was possible to establish relationships. The data presented here can be considered as a platform that serves as a basis for the S. cerevisiae metabolome-proteome with the aim of understanding the behavior of yeast under conditions of second fermentation in the production of sparkling wines.

Oenological characteristics of two indigenous Starmerella bacillaris strains isolated from Chinese wine regions

To broaden knowledge about the oenological characteristics of Starmerella bacillaris, the influence of two Chinese indigenous S. bacillaris strains on the conventional enological parameters and volatile compounds of Cabernet Sauvignon wines were investigated under different inoculation protocols (single inoculation and simultaneous/sequential inoculation with the commercial Saccharomyces cerevisiae EC1118). The results showed that the two S. bacillaris strains could complete alcohol fermentation alone under high sugar concentrations while increasing the content of glycerol and decreasing the content of acetic acid. Compared with wines fermented by EC1118 single inoculation, S. bacillaris single inoculation and S. bacillaris/EC1118 sequential inoculation increased the contents of isobutanol, ethyl isobutanoate, terpenes, and ketones and decreased the contents of isopentanol, phenylethyl alcohol, fatty acids, acetate esters, and total ethyl esters. Furthermore, for S. bacillaris/EC1118 simultaneous inoculation, the concentrations of ethyl esters were increased, contributing to a higher score of "floral" and "fruity" notes in agreement with sensory analysis. KEY POINTS: • S. bacillaris single and simultaneous/sequential inoculation. • Conventional enological parameters and volatile compounds were investigated. • S. bacillaris/EC1118 simultaneous fermentation increased ethyl esters.

Manipulating the severe shoot topping delays the harvest date and modifies the flavor composition of Cabernet Sauvignon wines in a semi-arid climate

This study aimed to mitigate the adverse effects of global warming by applying severe shoot topping (SST) to grapevines in a semi-arid climate. A three-year study (2018-2020) was performed to investigate the impact of SST on wine flavor composition. Results showed that SST effectively delayed the grape harvest date, which was more evident in the dry and warm vintage (7-11 d). SST significantly increased the concentration of myricetin-based flavonols in wines which were 18% higher than in untreated wines. Through orthogonal partial least squares discriminant analysis (OPLS-DA), SST wines were characterized by more abundant phenolic compounds and higher sensory scores. The carry-over effect of applying SST in consecutive years in the same vines could be reflected in wine color. The correlations among wine metabolites, color and aroma parameters, and sensory parameters were evaluated through multiple analyses. This study provided an idea for delaying grape ripening in a semi-arid climate.

Impact of Assimilable Nitrogen Supplementation on Saccharomyces cerevisiae Metabolic Response and Aromatic Profile of Moschofilero Wine

The concentration of nitrogen in must is critical to yeast fermentation efficiency and wine aroma profile. The present work determined the effect of the amount of yeast assimilable nitrogen (YAN) on fermentation kinetics, aroma production, and gene expression patterns of the wine yeast Saccharomyces cerevisiae. Fermentations were performed under two different YAN concentrations of must. Acetate esters, linalool, and nerol appeared to be clearly affected by the different YAN levels. Real-time-PCR results revealed that the genes involved in ethyl and acetate esters production recorded, in general, higher transcript levels under high nitrogen supplementation. In addition, an up-regulation of the BGL2 and EXG1 genes, which are related to terpenes production, was observed in the case of high nitrogen content and it is well corresponded to the terpenol concentration found. Our study revealed the impact of nitrogen supplementation on yeast metabolism and its importance to adjust wine's aromatic composition and sensory profile.

Characterization of Nero Antico di Pretalucente Wine and Grape Fungal Microbiota: An Expression of Abruzzo Region Cultivar Heritage

The aim of this study was to characterize the ampelographic and genetic profiles of Vitis vinifera L. cv. Nero Antico di Pretalucente and to describe the grape-borne fungal communities. The oenological characteristics and the aroma profile of wine obtained by spontaneous fermentation were also investigated. Microsatellite profiles and ampelographic traits indicated that this cultivar presented a unique profile, and therefore it can be considered a cultivar in its own right and autochthonous of Gessopalena village. Next-generation sequencing analysis revealed that Aureobasidium spp. was the main genus detected on grapes. At the species level, Aureobasidium pullulans was the main species, followed by Alternaria alternata. Wines were characterized by a final ethanol content of 12.75% (v/v), a pH of 3.4, a volatile acidity lower than 0.6 g/L, a content of glycerol of 8.56 g/L, and a concentration of polyphenols and anthocyanins of 977 GAE/L and 266 mg/L, respectively. The intensity and tonality of the wine as well as the active odor compounds found were described. The results obtained could improve the knowledge concerning the agronomic traits and the wine obtained from this ancient and autochthonous grapevine variety cultivated in a foothill area, in order to offer consumers a wine with unique traits.

Engineering a fermenting yeast able to produce the fragrant β-ionone apocarotenoid for enhanced aroma properties in wine

Wine is composed of multitudinous flavour components and volatile organic compounds that provide this beverage with its attractive properties of taste and aroma. The perceived quality of a wine can be attributed to the absolute and relative concentrations of favourable aroma compounds; hence, increasing the detectable levels of an attractive aroma, such as β-ionone with its violet and berry notes, can improve the organoleptic qualities of given wine styles. We here describe the generation of a new grape-must fermenting strain of Saccharomyces cerevisiae that is capable of releasing β-ionone through the heterologous expression of both the enzyme carotenoid cleavage dioxygenase 1 (CCD1) and its substrate, β-carotene. Haploid laboratory strains of S. cerevisiae were constructed with and without integrated carotenogenic genes and transformed with a plasmid containing the genes of CCD1. These strains were then mated with a sporulated diploid wine industry yeast, VIN13, and four resultant crosses-designated MQ01-MQ04-which were capable of fermenting the must to dryness were compared for their ability to release β-ionone. Analyses of their fermentation products showed that the MQ01 strain produced a high level of β-ionone and offers a fermenting hybrid yeast with the potential to enhance the organoleptic qualities of wine.

Aromatic Characteristics of Passion Fruit Wines Measured by E-Nose, GC-Quadrupole MS, GC-Orbitrap-MS and Sensory Evaluation

This study investigated the volatile composition and aromatic features of passion fruit wines using a combination of gas chromatography-quadrupole mass spectrometry (GC-qMS), gas chromatography-Orbitrap-mass spectrometry (GC-Orbitrap-MS), electronic nose (E-nose) and sensory evaluation. The results showed that these passion fruit wines possessed different aromatic features confirmed by E-nose. Seventeen sulfur compounds and seventy-eight volatiles were detected in these passion fruit wines using GC-Orbitrap-MS and GC-qMS, respectively. Forty-four volatiles significantly contributed to the overall wine aroma. These wines possessed passion fruit, mango, green apple, lemon and floral aromas confirmed by sensory evaluation. The partial least squares regression analysis indicated that sulfides, esters and terpenes, and terpenes mainly correlated to the passion fruit, mango and green apple aroma, respectively. Sulfur compounds significantly affected the aroma of passion fruit wine. The findings in this study could provide useful insight toward the quality control of passion fruit wine.

Chitosan Film as a Replacement for Conventional Sulphur Dioxide Treatment of White Wines: A 1H NMR Metabolomic Study

Chitosan–genipin (Ch-Ge) films have been proposed for the replacement of sulfur dioxide (SO₂) in white wines preservation to circumvent the adverse health consequences caused by SO₂ intake. To assess the effects of different-sized Ch-Ge films (25 and 100 cm²) on wine composition compared to SO₂-treated and untreated wines, nuclear magnetic resonance metabolomics was applied. Relative to SO₂, 100 cm² films induced significant changes in the levels of organic acids, sugars, amino acids, 5-hydroxymethylfurfural, among other compounds, while 25 cm² films appeared to induce only small variations. The observed metabolite variations were proposed to arise from the mitigation of fermentative processes, electrostatic interactions between acids and the positively charged films and the promotion of Maillard and Strecker reactions. Qualitative sensory analysis showed that wines maintained overall appropriate sensory characteristics, with 100 cm² film treated wines showing slightly higher attributes. Based on these results, the possibility of using Ch-Ge films as a replacement for SO₂ treatment is discussed.

Adaptive evolution in the Saccharomyces kudriavzevii Aro4p promoted a reduced production of higher alcohols

The use of unconventional yeast species in human-driven fermentations has attracted a lot of attention in the last few years. This tool allows the alcoholic beverage industries to solve problems related to climate change or the consumer demand for newer high-quality products. In this sense, one of the most attractive species is Saccharomyces kudriavzevii, which shows interesting fermentative traits such as the increased and diverse aroma compound production in wines. Specifically, it has been observed that different isolates of this species can produce higher amounts of higher alcohols such as phenylethanol compared with Saccharomyces cerevisiae. In this work, we have shed light on this feature relating it to the S. kudriavzevii aromatic amino acid anabolic pathway in which the enzyme Aro4p plays an essential role. Unexpectedly, we observed that the presence of the S. kudriavzevii ARO4 variant reduces phenylethanol production compared with the S. cerevisiae ARO4 allele. Our experiments suggest that this can be explained by increased feedback inhibition, which might be a consequence of the changes detected in the Aro4p amino end such as L₂₆ Q₂₄ that have been under positive selection in the S. kudriavzevii specie.

Effects of Purified β-Glucosidases from Issatchenkia terricola, Pichia kudriavzevii, Metschnikowia pulcherrima on the Flavor Complexity and Typicality of Wines

The aim of this study was to investigate the effects of purified β-glucosidases from Issatchenkia terricola SLY-4, Pichia kudriavzevii F2-24, and Metschnikowia pulcherrima HX-13 (named as SLY-4E, F2-24E, and HX-13E, respectively) on the flavor complexity and typicality of wines. Cabernet Sauvignon wines were fermented by Saccharomycescerevisiae with the addition of SLY-4E, F2-24E, and HX-13E; the fermentation process and characteristics of wines were analyzed. The addition of SLY-4E, F2-24E, and HX-13E into must improved the contents of terpenes, higher alcohols, and esters, and decreased the contents of C₆ compounds and fatty acids, which enhanced the fruity, floral, and taste aspects, reducing the unpleasant green of wines with no significant difference in their appearance. β-glucosidases from different yeast species produced different aroma compound profiles which presented different flavor and quality. F2-24EW had the best effect on flavor and quality of wine followed by SLY-4EW and HX-13EW. These research results can provide references for the use of β-glucosidases from non-Saccharomyces yeasts to improve the flavor complexity, typicality, and quality of wines.

Diversity of Volatile Aroma Compound Composition Produced by Non-Saccharomyces Yeasts in the Early Phase of Grape Must Fermentation

There is a lack of studies evaluating the metabolic contribution of non-Saccharomyces yeasts in early fermentation phases. This study aimed to investigate the volatile aroma profiles produced by various non-Saccharomyces yeasts just before sequential inoculation with Saccharomyces cerevisiae to provide an insight into the particular effects they induce at this stage. The grape must of Malvazija istarska was inoculated with monocultures of Torulaspora delbrueckii, Metschnikowia pulcherrima, Pichia kluyveri, Lachancea thermotolerans, and Schizosaccharomyces pombe, alongside a S. cerevisiae control. Eighty volatile compounds were quantified via headspace solid-phase microextraction and gas chromatography–mass spectrometry, and the data were statistically elaborated. Volatile profiles of non-Saccharomyces yeasts differed significantly from the S. cerevisiae control. Most treatments caused increases in linalool and β-damascenone, decreases in higher alcohols and fatty acids, and improved synthesis of odoriferous esters. Torulaspora delbrueckii and M. pulcherrima produced compounds not commonly found in S. cerevisiae fermented wines. Multivariate statistical analysis linked the investigated yeasts to specific, particularly abundant compounds. Future studies should explore to what degree these contributions persist after sequential inoculation with S. cerevisiae in diverse grape must matrices.

A Preliminary Study of Yeast Strain Influence on Chemical and Sensory Characteristics of Apple Cider

During the fermentation of apple juice, yeast metabolism creates complex biosynthetic pathways which produce a range of compounds responsible for the organoleptic qualities of cider. In this study, basic cider quality parameters were measured to investigate the influence of six yeast strains on cider made from three apple varieties (‘Pink Lady’, ‘Sturmer’, and ‘Bulmer’s Norman’). Measurement of pH, titratable acidity, and total phenolic content revealed that yeast can influence cider attributes, albeit variety and season dependent. Descriptive sensory analysis using a trained sensory panel was conducted on cider made from ‘Pink Lady’ apples and the same six yeast strains. The sensory panel significantly differentiated the yeast strains on the attributes of ‘fresh apple’, ‘earthy’ and ‘pear’. Identifying the variety specific influence of individual yeast strains on chemical and sensory characteristics of apple cider will provide cider makers with an enhanced understanding when choosing yeast strains.

Characterization of Saccharomyces Strains Isolated from “Kéknyelű” Grape Must and Their Potential for Wine Production

Novel wine yeast strains have the potential to satisfy customer demand for new sensorial experiences and to ensure that wine producers have strains that can produce wine as efficiently as possible. In this respect, hybrid yeast strains have recently been the subject of intense research, as they are able to combine the favourable characteristics of both parental strains. In this study, two Saccharomyces “Kéknyelű” grape juice isolates were identified by species-specific PCR and PCR-RFLP methods and investigated with respect to their wine fermentation potential. Physiological characterization of the isolated strains was performed and included assessment of ethanol, sulphur dioxide, temperature and glucose (osmotic stress) tolerance, killer-toxin production, glucose fermentation ability at 16 °C and 24 °C, and laboratory-scale fermentation using sterile “Kéknyelű” must. Volatile components of the final product were studied by gas chromatography (GC) and mass spectrometry (MS). One isolate was identified as a S. cerevisiae × S. kudriavzevii hybrid and the other was S. cerevisiae. Both strains were characterized by high ethanol, sulphur dioxide and glucose tolerance, and the S. cerevisiae strain exhibited the killer phenotype. The hybrid isolate showed good glucose fermentation ability and achieved the lowest residual sugar content in wine. The ester production of the hybrid strain was high compared to the control S. cerevisiae starter strain, and this contributed to the fruity aroma of the wine. Both strains have good oenological characteristics, but only the hybrid yeast has the potential for use in wine fermentation.

Native Non-Saccharomyces Yeasts as a Tool to Produce Distinctive and Diverse Tamjanika Grape Wines

The enological potential of two previously characterized indigenous yeast isolates, Hanseniaspora uvarum S-2 and Candida famata WB-1, in pure and sequential inoculation with commercial yeast Saccharomyces cerevisiae QA23 were analyzed in industrial-scale vinification of the grape variety Tamjanika. Their contribution to the quality and aroma profile was investigated by quantifying volatile compounds and wine sensory evaluation. Both yeast isolates were able to complete alcoholic fermentation, to reduce ethanol concentration up to 1.06% v/v (in monoculture) in comparation to S. cerevisiae QA23, and to enhance aroma and sensory profile. Based on calculated odor activity values (OAV), p-cymene, ethyl hexanoate, ethyl octanoate, and ethyl decanoate were the major aroma volatile compounds in all Tamjanika wine samples. Analyzed yeast strains significantly affected relative contribution of volatile compounds and can be considered responsible for the differences and uniqueness of the obtained wine samples. Besides confirmation of good enological and fermentative characteristics, selected isolates can be characterized as high ester-producing strains with potential to enhance the floral and fruity aromas of wine. The present study represents a further step toward the use of indigenous yeast isolates at industrial-scale fermentation in order to ensure the regional signature of Tamjanika wine.

Role of Yeasts on the Sensory Component of Wines

The aromatic complexity of a wine is mainly influenced by the interaction between grapes and fermentation agents. This interaction is very complex and affected by numerous factors, such as cultivars, degree of grape ripeness, climate, mashing techniques, must chemical−physical characteristics, yeasts used in the fermentation process and their interactions with the grape endogenous microbiota, process parameters (including new non-thermal technologies), malolactic fermentation (when desired), and phenomena occurring during aging. However, the role of yeasts in the formation of aroma compounds has been universally recognized. In fact, yeasts (as starters or naturally occurring microbiota) can contribute both with the formation of compounds deriving from the primary metabolism, with the synthesis of specific metabolites, and with the modification of molecules present in the must. Among secondary metabolites, key roles are recognized for esters, higher alcohols, volatile phenols, sulfur molecules, and carbonyl compounds. Moreover, some specific enzymatic activities of yeasts, linked above all to non-Saccharomyces species, can contribute to increasing the sensory profile of the wine thanks to the release of volatile terpenes or other molecules. Therefore, this review will highlight the main aroma compounds produced by Saccharomyces cerevisiae and other yeasts of oenological interest in relation to process conditions, new non-thermal technologies, and microbial interactions.

Effects of the Irrigation of Chelva Grapevines on the Aroma Composition of Wine

Climate change scenarios are predicting an increase in temperature as well as more scarce and torrential rainfall episodes. Due to this, an imbalance between grape technological and phenolic maturity is being observed, which detrimentally affects the grapes’ composition. In semi-arid areas, irrigation management is a main field practice used to influence grape ripening. The goal of the present study was to investigate the influence of vine irrigation on the aroma composition and sensory characteristics of La Mancha Chelva wines. Volatile compounds were studied by gas chromatography–mass spectrometry (GC/MS). A total of 75 aroma compounds were identified and quantified in Chelva wines elaborated with grapes of irrigated and non-irrigated vines. The results show that the application of irrigation during vine cultivation produced small changes in the concentration of wine volatile compounds. Nevertheless, it increased, in general, the intensity of the attributes of the main aroma sensory profile of the wines. According to the results, the vine irrigation of Chelva cultivated in the La Mancha region can be used as a method to increase the aroma of wines.

Application Potential of Baijiu Non-Saccharomyces Yeast in Winemaking Through Sequential Fermentation With Saccharomyces cerevisiae

To explore the potential application of non-Saccharomyces yeasts screened from Baijiu fermentation environment in winemaking, the effect of four Baijiu non-Saccharomyces yeasts (two Zygosaccharomyces bailii and two Pichia kudriavzevii) sequentially fermented with Saccharomyces cerevisiae on the physicochemical parameters and volatile compounds of wine was analyzed. The results indicated that there was no obvious antagonism between S. cerevisiae and Z. bailli or P. kudriavzevii in sequential fermentations, and all strains could be detected at the end of alcoholic fermentation. Compare with S. cerevisiae pure fermentation, Z. bailii/S. cerevisiae sequential fermentations significantly reduced higher alcohols, fatty acids, and ethyl esters and increased acetate esters; P. kudriavzevii/S. cerevisiae sequential fermentations reduced the contents of C6 alcohols, total higher alcohols, fatty acids, and ethyl esters and significantly increased the contents of acetate esters (especially ethyl acetate and 3-methylbutyl acetate). Sequential fermentation of Baijiu non-Saccharomyces yeast and S. cerevisiae improved the flavor and quality of wine due to the higher ester content and lower concentration of higher alcohols and fatty acids, non-Saccharomyces yeasts selected from Baijiu fermentation environment have potential applications in winemaking, which could provide a new strategy to improve wine flavor and quality.

Differences between Kazak Cheeses Fermented by Single and Mixed Strains Using Untargeted Metabolomics

Mixed fermentation improves the flavor quality of food. Untargeted metabolomics were used to evaluate the impact of mixed fermentation and single-strain fermentation on the volatile and non-volatile compound profiles of Kazak cheese. Lacticaseibacillus paracasei SMN-LBK and Kluyveromyces marxianus SMN-S7-LBK were used to make mixed-fermentation cheese (M), while L. paracasei SMN-LBK was applied in single-strain-fermentation cheese (S). A higher abundances of acids, alcohols, and esters were produced via mixed fermentation. Furthermore, 397 differentially expressed non-volatile metabolites were identified between S and M during ripening. The flavor compounds in mixed-fermentation cheese mainly resulted from ester production (ethyl butanoate, ethyl acetate, ethyl octanoate, and ethyl hexanoate) and amino acid biosynthesis (Asp, Glu, Gln, and Phe). The metabolites were differentially expressed in nitrogen metabolism, D-glutamine and D-glutamate metabolism, phenylalanine metabolism, D-alanine metabolism, and other metabolic pathways. The amount of flavor compounds was increased in M, indicating that L. paracasei SMN- LBK and K. marxianus SMN-S7-LBK had synergistic effects in the formation of flavor compounds. This study comprehensively demonstrated the difference in metabolites between mixed-fermentation and single-strain-fermentation cheese and provided a basis for the production of Kazak cheese with diverse flavor characteristics.

Characterization of the flavor and nutritional value of coconut water vinegar based on metabolomics

Tender Coconut water is popular for its deliciousness and nutrition. Mature coconut water, usually discarded as waste in the coconut kernel-based food industry due to its unpleasant flavor, was used as a raw material to make vinegar by liquid-state fermentation. The compounds in fresh coconut water with high odor activity values (OAVs) were isovaleric acid and acetic acid, with pungent sour tastes. The compounds with high OAVs in aged coconut water vinegar were phenylethyl acetate, isoamyl acetate and benzaldehyde, with almond, banana or pear-like aromas. Coconut water vinegar was rich in essential amino acids, especially phenylalanine. Through pathway analysis, seventeen key metabolic pathways and three key metabolic substrates (aspartate, glutamate and pyruvate) were found. According to sensory evaluation, the aged vinegar tastes better. Coconut water vinegar is delicious and nutritious, so reprocessing mature coconut water into vinegar is an appropriate way to reuse waste coconut water.

Effects of three indigenous non-Saccharomyces yeasts and their pairwise combinations in co-fermentation with Saccharomyces cerevisiae on volatile compounds of Petit Manseng wines

The combined use of selected Saccharomyces cerevisiae and non-Saccharomyces strains is becoming an effective way to achieve wine products with distinctive aromas. The purpose of this study was to further improve the wine aroma complexity through optimizing inoculation protocols of multi-starters. The three indigenous non-Saccharomyces strains (Torulaspora delbrueckii, Hanseniaspora vineae, and Lachancea thermotolerans) and their pairwise combinations (co-inoculation) were sequentially inoculated with S. cerevisiae in Petit Manseng grape must, respectively. Results evidenced a higher divergence in aroma compounds produced by two different non-Saccharomyces species compared to single species. Especially for the combination of T. delbrueckii and L. thermotolerans, the concentrations of most ethyl esters were further increased, contributing to a higher score of 'pineapple' note in agreement with sensory analysis. Our results highlighted that the inoculation of more than one non-Saccharomyces species is a potential strategy to improve the aroma diversity and quality of industrial wines.

Evaluation of Four Indigenous Non-Saccharomyces Yeasts Isolated from the Shangri-La Wine Region (China) for Their Fermentation Performances and Aroma Compositions in Synthetic Grape Juice Fermentation

This study investigated the fermentation performances and aroma compositions of synthetic grape juice that was fermented by four indigenous non-Saccharomyces yeast isolates that were obtained from the Shangri-La wine region (China): Meyerozyma guilliermondii (AD-58), Saccharomycopsis vini (BZL-28), Saturnispora diversa (BZL-11), and Wickerhamomyces anomalus (DR-110), in comparison to those of Saccharomyces cerevisiae (EC1118). The four indigenous non-Saccharomyces yeasts showed a lower fermentative capacity and a lower conversion rate of sugar to alcohol, but a higher yield of volatile acidity. W. anomalus (DR-110) had a greater ability to produce numerous esters and short-chain fatty acids and the representative flavors of its fermented medium were fruity and fatty. Sac. vini (BZL-28), interestingly, exhibited great capacity in the formation of many monoterpenes, particularly (Z)-β-ocimene, E-β-ocimene, linalool, citral, and geraniol and its fermented medium was characterized by a strong fruity (citrus-like) and floral flavor. M. guilliermondii (AD-58) and Sat. diversa (BZL-11) only mildly affected the aroma profiles of their resultant fermented media, since the concentrations of most of the volatiles that were produced by these two isolates were much lower than their sensory thresholds. The four indigenous non-Saccharomyces yeasts exhibited distinctive fermentation performances and aroma production behaviors. In particularly, W. anomalus (DR-110) and Sac. vini (BZL-28) have shown good potential in enhancing the aromas and complexity of wine.

Comparison of Ultrasound Type and Working Parameters on the Reduction of Four Higher Alcohols and the Main Phenolic Compounds

In this paper, studies were conducted by a series of single-factor experiments to investigate the effects of ultrasound types and working parameters on the higher alcohols (HA), phenolic compounds, and color properties of red wine, so as to highlight the importance of the comprehensive consideration on its application. The results indicate that ultrasound devices and working parameters do have some definite influences on the HA of wine; moreover, the ultrasound bath (SB-500DTY) is better than the SCIENTZ-950E and the KQ-300VDE. With the SB-500DTY employed to further investigate its effects on phenols and color properties other than on HA, unexpectedly, some variations of color parameters are opposite to the results ever obtained from other ultrasound conditions. In summary, all these results suggest that both the ultrasound type and parameters should be fully considered or neutralized so as to have a comprehensive evaluation about its application, instead of some contradictory results.

Characterization and Evolution of Volatile Compounds of Cabernet Sauvignon Wines from Two Different Clones during Oak Barrel Aging

Xinjiang is a major wine-making region in China, but its hot climate in summer and intense sun exposure negatively affect the aroma quality of Cabernet Sauvignon wine. The aim of this study was to characterize and differentiate the volatile composition of Cabernet Sauvignon wines from two clones (169 and 191) in Xinjiang, and to study their aromatic profile evolution during 12-month oak barrel aging period. Results showed that before aging, clone 169 wine contained higher concentrations of several alcohols and ethyl esters, while acetate esters and furanic compounds were higher in clone 191 wine. After aging, levels of many terpenes, norisoprenoids, volatile phenols and phenolic aldehydes were significantly higher in clone 169 wine than 191 wine. Aroma series analysis revealed that clone 169 wine exhibited higher floral and roasty aromas after aging, while clone 191 wine had stronger chemical aroma. Principal component analysis indicated that aging process played a primary role in the alteration of volatile profile in these wines. Clone played a secondary role and oak barrel had a tertiary contribution to the variation. The present work indicates that clone 169 is a better choice for producing high-quality aged Cabernet Sauvignon wine with intense and elegant aroma in Xinjiang.

Screening and Identification of Yeasts from Fruits and Their Coculture for Cider Production

Coculturing non-Saccharomyces yeasts with Saccharomyces cerevisiae could enrich the aromatic complexity of alcoholic beverages during cider brewing. Therefore, the present study performed rapid strain screening via selective culture medium and aroma analysis and adopted a response surface methodology to optimize fermentation conditions to produce 2-phenylethyl acetate (PEA), which presents a rose and honey scent. The effects of coculturing yeasts on cider quality were evaluated through hedonic sensory analysis and the check-all-that-apply (CATA) method. Hanseniaspora vineae P5 and S. cerevisiae P1 produced ciders with high levels of PEA and 2-phenylethanol, respectively. The optimal fermentation process consisted of sequential inoculation with a 31 h delay between inoculations, followed by fermentation for 14.5 d at 18.7 °C, yielding 17.41 ± 0.51 mg/L of PEA, which was 4.6-fold higher than that obtained through the unoptimized fermentation process. Additionally, the CATA results revealed that the cider produced through coculturing was associated with descriptors such as “smooth taste”, “honey”, “pineapple”, and “fruity”, which can be attributed to the high ethyl acetate and PEA levels in the cider.

Impact of Yeast Selection on Volatile Phenol Levels of Wines Produced from Smoked-Exposed Juice

Grapes exposed to smoke can result in wines that have unacceptable high levels of volatile phenols. High volatile phenols levels have a negative impact on wine quality. This study aimed to determine the levels of volatile phenols in wines produced from smoke-exposed juice by a selection of commercial wine yeasts and to determine if yeast selection affected the perception of smokiness in wine. Commercial white and red wine yeasts were screened for the production of volatile phenols in smoke-exposed Chenin Blanc and Merlot juice. Volatile phenol levels were determined by GC-MS/MS and wines were also subjected to sensory evaluation. Volatile phenol levels in smoked wines varied and was affected by yeast strain. The highest guaiacol levels in Chenin Blanc were found in wines fermented with QA23, while Merlot wines that underwent spontaneous alcoholic fermentation contained the highest levels. The levels of volatile phenols differed significantly between the smoked and unsmoked wines, and the sensory results supported the chemical data. Volatile phenols had a negative effect on Chenin Blanc flavor profiles even when the levels were below odor detection thresholds. Yeast selection is important and can affect the volatile phenol levels and flavor profiles of wines.

Effect of a yeast autolysate produced by high pressure homogenization on white wine evolution during ageing

The enological characteristics and the performances of a yeast autolysate produced by high pressure homogenization (HPH-YD) were investigated for the first time in white wine and model solution, in comparison with a thermolysate (T-YD) and a commercial yeast derivative (COMM). In wine-like medium, HPH-YD showed a significant release of glucidic colloids (on average, slightly higher than the other products), also leading to a greater glutathione solubilization with respect to T-YD. Concerning the volatile composition of the autolysates, HPH-YD was characterized by the highest concentration of alcohols and esters, while showing an average amount of fatty acids, carbonyls and heterocyclic compounds lower than COMM. These features are potentially linked to a more favorable impact of this product on the composition of wine aroma, should these compounds be released into the wine itself. HPH-YD determined minor modifications on wine volatile profile when added for short contact times, without releasing unwanted compounds and with a slightly lower binding capacity towards wine esters. The effects of the three yeast derivatives (YDs) on wine color during ageing was also investigated in comparison with sulfur dioxide (SO₂). HPH-YD was the most efficient preparation, limiting wine color changes due to oxidation during four months and behaving more similarly to SO₂. The use of HPH for the production of yeast autolysates for winemaking may represent an interesting alternative to thermal treatments, improving the enological characteristics of these additives, particularly their antioxidant capacity, leading anyhow a significant release of colloidal molecules and a limited impact on wine aroma composition.

Evaluation of Autochthonous Non-Saccharomyces Yeasts by Sequential Fermentation for Wine Differentiation in Galicia (NW Spain)

Non-Saccharomyces yeasts constitute a useful tool in winemaking because they secrete hydrolytic enzymes and produce metabolites that enhance wine quality; in addition, their ability to reduce alcohol content and/or to increase acidity can help to mitigate the effects of climatic change on wines. The purpose of this study was to evaluate the oenological traits of non-Saccharomyces yeast strains autochthonous from Galicia (NW Spain). To do that, we carried out sequential fermentation using 13 different species from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (Evega) and Saccharomyces cerevisiae EC1118. The fermentation kinetics and yeast implantation were monitored using conventional methods and genetic techniques, respectively. The basic chemical parameters of wine were determined using the OIV official methodology, and the fermentative aroma compounds were determined by GC–FID. The results evidenced the limited fermentative power of these yeasts and the differences in their survival after the addition of S. cerevisiae to complete fermentation. Some strains reduced the alcohol and/or increased the total acidity of the wine. The positive effect on sensory wine properties as well as the production of desirable volatile compounds were confirmed for Metschnikowia spp. (Mf278 and Mp176), Lachancea thermotolerans Lt93, and Pichia kluyveri Pkl88. These strains could be used for wine diversification in Galicia.

Oenological Characteristics of Four Non-Saccharomyces Yeast Strains With β-Glycosidase Activity

Non-Saccharomyces yeast with β-glucosidase activity might positively contribute to the flavor and quality of wines. The contribution of four non-Saccharomyces yeast strains Issatchenkia terricola SLY-4, Pichia kudriavzevii F2-24, P. kudriavzevii F2-16, and Metschnikowia pulcherrima HX-13 with β-glucosidase activity to the flavor and quality of wine making was studied. Compared with those of S. cerevisiae single fermentation, the four non-Saccharomyces yeast strains could grow and consume sugar completely with longer fermentation periods, and with no significantly negative effect on chemical characteristics of wines. Moreover, they produced lower content of C6 compounds, benzene derivative, and fatty acid ethyl ester compounds and higher content of terpene, β-ionone, higher alcohol, and acetate compounds. Different yeast strains produced different aroma compounds profiles. In general, the sensory evaluation score of adding non-Saccharomyces yeast-fermented wine was better than that of S. cerevisiae, and I. terricola SLY-4 fermentation received the highest one, followed by P. kudriavzevii F2-24, P. kudriavzevii F2-16, and M. pulcherrima HX-13 from high to low. The research results provide a theoretical basis for the breeding of non-Saccharomyces yeast and its application in wine making.

Simultaneously deleting ADH2 and THI3 genes of Saccharomyces cerevisiae for reducing the yield of acetaldehyde and fusel alcohols

The reduced yields of acetaldehyde and fusel alcohols through fermentation by Saccharomyces cerevisiae is of significance for the improvement of the flavor and health of alcoholic beverages. In this study, the ADH2 (encode alcohol dehydrogenase) and THI3 (encode decarboxylase) genes of the industrial diploid strain S. cerevisiae XF1 were deleted. Results showed that single-gene-deletion mutants by separate gene deletion of ADH2 or THI3 led to a reduced production of the acetaldehyde or fusel alcohols, respectively. In the meantime, the double-gene-deletion mutant S. cerevisiae XF1-AT was constructed by deleting the ADH2 and THI3 simultaneously. An equivalent level of the ethanol production by the S. cerevisiae XF1-AT could be achieved but with the yields of acetaldehyde, isoamyl alcohol and iso-butanol reduced by 42.09%, 15.65% and 20.16%, respectively. In addition, there was no interaction between the ADH2 deletion and THI3 deletion in reducing the production of acetaldehyde and fusel alcohols. The engineered S. cerevisiae XF1-AT provided a new strategy to alcoholic beverages brewing industry for reducing the production of acetaldehyde as well as the fusel alcohols.

Lebanon's Native Oenological Saccharomyces cerevisiae Flora: Assessment of Different Aspects of Genetic Diversity and Evaluation of Winemaking Potential

A total of 296 isolates of Saccharomyces cerevisiae sampled from naturally fermenting grape musts from various locations in Lebanon were typed by interdelta fingerprinting. Of these, 88 isolates were compared with oenological strains originating from various countries, using microsatellite characterization at six polymorphic loci. These approaches evidenced a large diversity of the natural oenological Lebanese flora over the territory as well as in individual spontaneous fermentations. Several cases of dominance and perenniality of isolates were observed in the same wineries, where fermentations appeared to involve lineages of sibling isolates. Our work thus evidenced a “winery effect” on strains’ relatedness. Similarly, related or identical strains were also detected in vicinal wineries, suggesting strain circulation within small geographical areas and a further “vicinity effect”. Moreover, and despite its diversity, the Lebanese flora seemed interrelated, on the basis of microsatellite loci analysis, in comparison to worldwide communities. We finally tested the ability of 21 indigenous strains to act as potential starters for winemaking. Seven of them passed our pre-selection scheme and two of them at least may be good candidates for use provided pilot-scale assays confirm their suitability.

Inoculation of grape musts with single strains of Saccharomyces cerevisiae yeast reduces the diversity of chemical profiles of wines

Anecdotal evidence suggests that spontaneous alcoholic fermentation of grape juice is becoming a more popular option in global wine production. Wines produced from the same grape juice by inoculation or spontaneous fermentation usually present distinct chemical and sensorial profiles. Inoculation has been associated with more similar end-products, a loss of typicity, and lower aroma complexity, and it has been suggested that this may be linked to suppression of the local or regional wine microbial ecosystems responsible for spontaneous fermentations. However, whether inoculated fermentations of different juices from different regions really end up with a narrower, less diverse chemical profile than those of spontaneously fermented juices has never been properly investigated. To address this question, we used grape juice from three different varieties, Grüner Veltliner (white), Zweigelt (red), and Pinot noir (red), originating from different regions in Austria to compare spontaneous and single active dry yeast strains inoculated fermentations of the same grape samples. The chemical analysis covered primary metabolites such as glycerol, ethanol and organic acids, and volatile secondary metabolites, including more than 40 major and minor esters, as well as higher alcohols and volatile fatty acids, allowing an in depth statistical evaluation of differences between fermentation strategies. The fungal (mainly yeast) communities throughout fermentations were monitored using automated ribosomal intergenic spacer analysis. The data provide evidence that inoculation with single active dry yeast strains limits the diversity of the chemical fingerprints. The fungal community profiles clearly show that inoculation had an effect on fermentation dynamics and resulted in chemically less diverse wines.