Saccharomyces cerevisiae and grape juice are ‘natural companions’ and make a happy wine marriage. However, this relationship can be enriched by allowing ‘wild’ non‐Saccharomyces yeast to participate ...in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to ‘the next level’ if there are no spoilage yeast present and if the ‘wine yeast’ – S. cerevisiae – is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various ‘matchmaking’ strategies (e.g. cellar hygiene, pH, SO₂, temperature and nutrient management) to keep ‘spoilers’ (e.g. Dekkera bruxellensis) at bay, and allow ‘compatible’ wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowia pulcherrima) to harmonize with potent S. cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a ‘two is company, three is a crowd’ scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour‐active characteristics of those non‐Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present ‘single‐species’ and ‘multi‐species’ ferments in a new light and a new context, and we raise important questions about the direction of mixed‐fermentation research to address market trends regarding so‐called ‘natural’ wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S. cerevisiae, non‐Saccharomyces research can benefit from the techniques and knowledge developed by research on the former.
Sulfur dioxide is the most used additive today for preventing browning in grape musts and wines. However, since wine consumers are increasingly interested in healthier wines, the wine industry is ...keen to reduce its use. Some promising alternatives to sulfur dioxide have been proposed in recent years, including glutathione, both pure and in the form of inactivated yeasts, and
Metschnikowia pulcherrima
used as a bioprotective agent. Some information exists about the protective effect against oxidation of glutathione but there is very few about the use of bioprotection for that purpose. Supplementation with glutathione, regardless of the commercial form, reduced oxygen consumption and browning intensity when laccase was not present in the grape juice.
Metschnikowia pulcherrima
also reduced browning intensity in the absence of laccase but increased the total oxygen consumption. However, in the presence of laccase, glutathione and
Metschnikowia pulcherrima
were not effective enough to adequately prevent the grape juice from browning. Glutathione, both pure and in the form of inactivated yeasts, and
Metschnikowia pulcherrima
are interesting tools for protecting grape must against browning, and thus reducing the use of sulfur dioxide.
To obtain beverages with reduced alcohol content, the use of unripe grapes, with low sugar and high malic acid concentration, was recently explored. Due to the low sugar, ethanol and glycerol ...production is limited during fermentation affecting important sensory aspects such as the palate fullness of these beverages. The high acidity influences their organoleptic quality, as well.
So far, only S. cerevisiae starter, used in conventional fermentations, have been tested in this condition, and no selection has been performed to identify alternative yeasts suitable for unripe grape fermentation. S. bacillaris is known for the low ethanol tolerance, high glycerol and moderate volatile acidity production. Therefore, this non- Saccharomyces yeast have been investigated to improve the quality of low-alcohol beverages. Seven S. bacillaris strains were tested in synthetic musts with different sugar and malic acid levels, mimicking natural ripe and unripe grape musts. In all the tested conditions, S. bacillaris produced higher glycerol than S. cerevisiae. In single-strain fermentation at low sugar and high malic acid no S. bacillaris strains was able to transform all the sugars, although the produced ethanol was lower than that at high sugar condition. Therefore, sequential fermentations with S. cerevisiae were evaluated at low sugar and high malic acid. In this condition all the sugars were consumed and a significant glycerol increase was found. These results were confirmed when sequential fermentations were run in natural unripe grape must. Moreover, an increase in malic acid degradation, with respect to EC1118 single-strain fermentation, was observed.
•At lab condition S. bacillaris showed the best growth when nitrogen was low.•During fermentations at high and low sugar S. bacillaris produced high glycerol.•At low sugar S. bacillaris did not complete the fermentation.•In sequential fermentation with S. cerevisiae all the sugar was consumed.•In unripe grape must fermentation malic acid degradation and high glycerol were found.
Leaf removal (LR) treatments improve the photosynthetic capacity of the remaining leaves and induce flavonoid synthesis as a stress response in the common grapevine (Vitis vinifera L.). However, ...excessive exposure of grape berries to UV‐B radiation as a result of cultural practices in the Mediterranean climate may have negative effects on berry composition. This 2‐year study determined the effects of defoliation on the autochthonous red grape variety ‘Babica’ in a Mediterranean climate (wine‐growing region Dalmatia, Croatia). Six leaves were removed before flowering (FLR) and at the end of véraison (the onset of grape ripening; VerLR) and were compared to the untreated control. Yield parameters, sugar content, grape must pH, total polyphenols (TP), total anthocyanin (TA) content, and individual anthocyanin compounds were measured in grape skin extracts and wines. However, the greater mean daily temperature during the vegetation period and lesser rainfall before harvest in 2018 increased yield per vine, average cluster weights, density, and total acidity, compared to 2017. Both defoliation treatments significantly reduced TP in grape extracts, but these differences were not observed in wine. Compared to the control (NLR), VerLR treatment significantly reduced TA in grape skin extracts and wine. Significantly lesser TP concentrations, in grape skin extracts and wine, as well as TA were noticed during the 2017 season. VerLR treatment reduced the concentration of nine individual anthocyanins compared to the control in grape skin extracts, while this effect was not observed in wine. Season year was a statistically significant source of variability of the individual anthocyanin contents in wine. Under specific environmental conditions LR can decrease polyphenols, especially anthocyanins, and negatively impact grape and wine quality.
This 2‐year study determined the effects of defoliation on the autochthonous red grape variety ‘Babica’ in a Mediterranean climate (wine‐growing region Dalmatia, Croatia). Six leaves were removed before flowering (FLR) and at the end of véraison (the onset of grape ripening; VerLR) and were compared to the untreated control. Yield parameters, sugar content, grape must pH, total polyphenols (TP), total anthocyanin (TA) content, and individual anthocyanin compounds were measured in grape skin extracts and wines.
The aim of the paper was to determine the potential of using grape must and unconventional yeasts in the beer production process. Samples were fermented using non-
Saccharomyces
yeasts (
Dekkera ...bruxellensis
3429,
Wickerhamomyces anomalus
MG971261,
Kluyveromyces lactis
MG971263), and
Saccharomyces cerevisiae
Safale US-05 was used as a control. Grape must was pasteurized and, together with wort, volumetrically introduced into fermentation flasks for fermentation. Mass changes taking place during the process were analyzed. Real extract, alcohol content, free amino nitrogen (FAN) content, titratable acidity, color, and sugar profile were determined in obtained beers. The obtained results have proven that the tested non-
Saccharomyces
yeasts can adapt to fermentation conditions, just like
S. cerevisiae
Safale US-05, and can be used to produce beer-wine hybrid alcoholic beverages. The yeast
K. lactis
MG971263 produced a greater amount of alcohol in beers compared to other yeast strains. There were no significant differences in the color of the obtained beers and in the degree of FAN utilization during the fermentation process. The unconventional yeasts used are capable of producing beers without and with the addition of grape must with parameters similar to beers obtained using
S. cerevisiae
Safale US-05.
-inositol polyalcohol is a characteristic component of natural and concentrated grape musts (CMs), and Regulation (EU) no. 1308/2013 prescribes its presence as a marker of the authenticity of ...rectified concentrated must (RCM). Other polyalcohols besides
-inositol, such as
-inositol or minor sugars, could be considered authenticity markers, but an extensive search in the literature yielded no exhaustively investigated study of their concentration variability in genuine products. The aim of this study was to create an extensive national data bank of minor carbohydrates profiles and investigate the impact of the geographical origin and the different vintages on the concentration of these compounds; to this end, 450 authentic Italian grape musts of different varieties were sampled and analyzed during the harvest season in 2019, 2020, and 2021. The grape musts from the Italian wine-growing areas CII and CIIIb had
- and
-inositol contents always higher than 756 and 39 mg/kg of sugar, respectively. Conversely, also considering other mono- and disaccharides, sucrose, sorbitol, lactose, maltose, and isomaltose showed contents always lower than 534, 1207, 390, 2222, and 1639 mg/kg of sugar, respectively. The general applicability to the CM and RCM of the proposed authenticity thresholds, established in the must, was demonstrated by studying the influence of must concentration on the
- and
-inositol content. Inter-laboratory comparison experiments were also conducted to harmonize and characterize laboratory methods and validate the analytical dataset. Based on the obtained results, the text of the EU legislation (Reg. (EU) 1308/2013), which defines the characteristics of the must and the CRM product, should be revised.
Cereal (rice, barley, emmer and oat) and soy flours and concentrated red grape must were used for making vegetable yogurt-like beverages (VYLB). Two selected strains of Lactobacillus plantarum were ...used for lactic acid fermentation, according to a process which included the flour gelatinization. All VLYB had values of pH lower than 4.0 and both selected starters remained viable at ca. 8.4logcfu/g throughout storage. All VLYB showed high values of apparent viscosity and water holding capacity. During fermentation, lactic acid bacteria consumed glucose, fructose, and malic acid, which was supplied with grape must. Compared to control vegetable yogurt-like beverages (CVYLB), without bacterial inoculum, an increase of total free amino acids (FAA) was found during fermentation and storage. Also the concentration of polyphenolic compounds and ascorbic acid (ASC) was higher in VLYB compared to CVYLB. This was reflected on the antioxidant activity. As determined by Solid Phase Micro-Extraction/Gas-Chromatography/Mass-Spectrometry analysis, several volatile compounds were identified. Beverages made with the mixture of rice and barley or emmer flours seemed to possess the best combination textural, nutritional and sensory properties.
► Lactobacillus plantarum 6E and M6 were suitable starters for non-dairy beverages fermentation. ► The fermented yogurt-like beverages showed improved nutritional and sensory features. ► Ingredients and processing influenced the volatile profiles of the beverages. ► Sensory analysis clearly differentiated the fermented yogurt-like beverages.
The authenticity of grape musts is normally checked through a time-consuming stable isotopic analysis of carbon (
C) after fermentation and distillation by following the official OIV MA AS-312-06 ...method. In this study, the alternative use of a technique based on δ
C isotopic analysis of the major sugars of the grape must by liquid chromatography coupled with isotope ratio mass spectrometry (LC-IRMS) is provided. It allows not only the detection of the fraudulent addition to grape must of exogenous glucose and fructose deriving from C4 plants but also the characterisation of it based on its geographical origin. In order to discriminate between musts from different areas of Italy, a preliminary dataset was considered; the δ
C isotopic ratios of glucose and fructose of around 100 authentic samples were analysed. The two analysed parameters, ranging from -29.8‱ to -21.9‱, are well correlated (R
= 0.7802) and the northern regions showed significantly more negative δ
C values for both sugars than the rest of the dataset.
Saccharomyces cerevisiae starter cultures are largely used in winemaking to repress the wild microorganisms and achieve more predictable and desired outcomes. Notwithstanding, alternative microbial ...resources received increasing attention for their potential to produce wines with more distinctive and typical features. Our previous survey revealed a great inter- and intra-species diversity in an extensive collection of non-Saccharomyces wine yeasts from multiple regions of Italy. This study aimed to explore the detected biodiversity evaluating the quality of wines obtained by sequential inoculation of specific selected strains of the collection (Lachancea thermotolerans or Metschnikowia spp. or Starmerella bacillaris), and S. cerevisiae EC 1118. Fermentations of natural grape must at laboratory scale were followed by microbiological, chemical and sensorial analysis of the wines. The results indicated that each yeast species and strain exerted a distinctive impact on the wine, giving final products clearly separated with Principal Component Analysis. In particular, L. thermotolerans contributed producing relevant amounts of lactic acid and had the highest potential to reduce ethanol content; the presence of S. bacillaris increased the level of glycerol, and, remarkably, reduced acetaldehyde and total SO2; Metschnikowia spp. promoted the formation of higher alcohols and esters, and reduced volatile phenols. The sensory analysis based on the orthonasal aroma confirmed the separation between the wines obtained with the sequential fermentations and the control with single inoculation of EC 1118, although the three non-Saccharomyces species used could not be clearly distinguishable by the panelists. This study indicates that the use of selected native non-Saccharomyces strains in conjunction with S. cerevisiae positively modulates some relevant chemical parameters, and improves the aromatic intensity of wine, therefore justifying investments in non-conventional yeasts as co-starter cultures.
•Non-Saccharomyces yeasts in sequential fermentations significantly improve wine properties.•Effects of non-Saccharomyces yeasts are highly species- and strain-dependent.•L. thermotolerans/S. cerevisiae reduced ethanol and increased wine natural acidity.•S. bacillaris/S. cerevisiae produced more glycerol and less SO2 and acetaldehyde.•Metschnikowia spp./S. cerevisiae positively modulated wine aroma profile.
Muscat of Alexandria is one of the most aromatic grape cultivars, with a characteristic floral and fruity aroma, producing popular appellation of origin wines. The winemaking process is a critical ...factor contributing to the quality of the final product, so the aim of this work was to study metabolomic changes during the fermentation of grape musts at the industrial level from 11 tanks, 2 vintages, and 3 wineries of Limnos Island. A Headspace Solid-Phase Microextraction (HS-SPME) and a liquid injection with Trimethylsilyl (TMS) derivatization Gas Chromatography-Mass Spectrometry (GC-MS) methods were applied for the profiling of the main volatile and non-volatile polar metabolites originating from grapes or produced during winemaking, resulting in the identification of 109 and 69 metabolites, respectively. Multivariate statistical analysis models revealed the differentiation between the four examined time points during fermentation, and the most statistically significant metabolites were investigated by biomarker assessment, while their trends were presented with boxplots. Whilst the majority of compounds (ethyl esters, alcohols, acids, aldehydes, sugar alcohols) showed an upward trend, fermentable sugars, amino acids, and C6-compounds were decreased. Terpenes presented stable behavior, with the exception of terpenols, which were increased at the beginning and were then decreased after the 5th day of fermentation.
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