Volatile composition of partially fermented wines elaborated from sun dried Pedro Ximénez grapes

In this work, we used a cell immobilisation system consisting of Penicillium chrysogenum fungi (GRAS) bound to the osmotolerant yeast strains Saccharomyces cerevisiae X4 and X5 for the partial fermentation of raisin musts. The resulting wines were compared with others obtained by partial fermentation of musts with free yeasts and with a traditionally produced sweet wine (i.e. without fermentation of the must). The analysis of volatile compounds grouped by aroma series showed the partially fermented musts had a more complex aroma than the traditional wine. Specially prominent among aroma series was that of ripe fruit, followed by the milky and chemical series. The volatiles with the greatest impact on wine aroma as assessed in terms of odour activity were ethyl hexanoate, ethyl octanoate, butyrolactone, isoamyl alcohols, acetaldehyde, ethyl acetate, 2,3-butanediol, acetoin and 2,3-butanedione. A cluster analysis according to the Ward method was performed to assess the similarity between the traditional sweet wine and those obtained by partial fermentation with free and immobilised yeasts revealed small differences between the wines obtained with free and immobilised yeasts, and marked differences between partially fermented and traditionally obtained sweet wine. The wines provided by immobilised yeasts were the most appreciated in the sensory analysis (especially those obtained with X4 yeasts).     

Impact of yeast starter formulations on the production of volatile compounds during wine fermentation

The most diffused starter formulation in winemaking is actually represented by active dry yeast (ADY). Spray‐drying has been reported as an appropriate preservation method for yeast and other micro‐organisms. Despite the numerous advantages of this method, the high air temperatures used can negatively affect cell viability and the fermentative performance of dried cells. In the present study, 11 wine S. cerevisiae strains (both indigenous and commercial) were submitted to spray‐drying; different process conditions were tested in order to select the conditions allowing the highest strain survival. The strains exhibited high variability for tolerance to spray‐drying treatment. Selected strains were tested in fermentation at laboratory scale in different formulations (free fresh cells, free dried cells, immobilized fresh cells and immobilized dried cells), in order to assess the influence of starter formulation on fermentative fitness of strains and aromatic quality of wine. The analysis of volatile fraction in the experimental wines produced by selected strains in different formulations allowed identification of > 50 aromatic compounds (alcohols, esters, ketones, aldehydes and terpenes). The results obtained showed that the starter formulation significantly influenced the content of volatile compounds. In particular, the wines obtained by strains in dried forms (as both free and immobilized cells) contained higher numbers of volatile compounds than wines obtained from fresh cells. Copyright © 2014 John Wiley & Sons, Ltd.     

Production of white wine by Saccharomyces cerevisiae immobilized on grape pomace

White wine was produced with Saccharomyces cerevisiae cells immobilized on grape pomace, by natural adsorption. The support, the main solid waste from the wine industry, consisted of the skins, seeds and stems. Immobilization was tested using different media, namely complex culture medium, raw grape must and diluted grape must. Grape pomace was revealed to be an appropriate support for yeast cell immobilization. Moreover, grape must was shown to be the most suitable medium as immobilized cells became adapted to the conditions in the subsequent alcoholic fermentation in the wine‐making process. The wines produced, either with immobilized cells or with free cells, were subjected to chemical analysis by HPLC (ethanol, glycerol, sugars and organic acids) and by gas chromatography (major and minor volatile compounds); additionally, colour (CIELab) and sensory analysis were performed. The use of immobilized systems to conduct alcoholic fermentation in white wine production proved to be a more rapid and a more efficient process, especially when large amounts of SO₂ were present in the must. Furthermore, the final wines obtained with immobilized cells demonstrated improved sensory properties related to the larger amounts of ethanol and volatile compounds produced. The more intense colour of these wines could be a drawback, which could be hindered by the reutilization of the biocatalyst in successive fermentations. Copyright © 2012 The Institute of Brewing & Distilling     

Discrimination of sweet wines partially fermented by two osmo-ethanol-tolerant yeasts by gas chromatographic analysis and electronic nose

Some special sweet wines are obtained by partial fermentation of musts from off-vine dried grapes containing large amounts of sugars. This process is very slow and subject to serious stop problems that can be avoided by using osmo-ethanol-tolerant yeasts. Musts containing 371 g/l of sugars were partially fermented with selected Saccharomyces cerevisiae strains, X4 and X5, to 12% (v/v) and the wines obtained with X5 exhibited a higher volatile acidity but lower concentrations of higher alcohols, carbonyl compounds and polyols than those obtained with X4. A principal component analysis (PCA) of the data provided by an electronic nose (E-nose) afforded discrimination between fermented and unfermented musts, but not between wines obtained with X4 or X5. The PCA applied to the major volatile compounds and polyols shows similar results, but a clear discrimination between wines is obtained by removing the polyols glycerol and 2,3-butanediol from the PCA.     

Raspberry wine fermentation with suspended and immobilized yeast cells of two strains of Saccharomyces cerevisiae

The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212. Copyright © 2014 John Wiley & Sons, Ltd.     

Continuous Fermentation of Worcestershire Sauce by Trickle Bed Bioreactor Using Comb-Shaped Ceramic Carriers

A two-step fermentation process using Saccharomyces cerevisiae OC-2 (wine yeast) was studied. The first step, to multiply and immobilize yeast cells, was carried out by batch method (7 days) in a trickle bed bioreac-tor. In a second step, the substrate was continuously fermented by immobilized and free yeast cells in the same bioreactor. Continuous fermentation resulted in retention of 3% (W/V) of ethanol, 50 mg/L of isoamyl alcohol and 6 mg/L of β-phenethyl alcohol (the major aromatic components of fermented Worcestershire sauce). Maximum ethanol productivity was retained at 4.1–4.2 g/L/hr under continuous operation with immobilized yeasts, 3.2-fold higher than with the batch system.     

Influence of different yeasts on the growth of lactic acid bacteria in wine

The influence of various yeasts on the growth of lactic acid bacteria in wine was tested by inoculating Lactobacillus hilgardii, L. brevis and two strains of Leuconostoc mesenteroides into experimental wines made with twelve different yeasts of the genus Saccharomyces. Wines made from juice which had been infected with several spoilage yeasts and then fermented with a wine yeast were also tested in this way. It was found that the yeasts differed considerably in their effects on bacterial growth. In some of the experimental wines bacterial growth was delayed or failed altogether. Generally, the unfavourable influence of any yeast on bacterial growth was much reduced if the wines were left in contact with the yeast cells for some weeks after the fermentation. The significance of these results in relation to the occurrence of malo-lactic fermentation in commercial wineries is discussed.     

Production of Table Wine from Processed Tea Bags Using Different Strains of Saccharomyces cerevisiae

Wine samples were produced from locally available tea infusions (Lipton tea, Top tea and Highland tea) using baker’s yeast (Saccharomyces cerevisiae By1) and yeast cultures from pineapple (S. cerevisiae Py6) and cocoa (S. cerevisiae CY43). Physicochemical analyses and microbial evaluation were undertaken during fermentation. Lipton tea wine produced, using baker’s yeast, pineapple yeast and cocoa yeast had highest alcoholic contents of 7.88%, 6.25% and 7.20%, respectively. Top tea wine produced using the same set of yeasts had highest alcoholic contents of 9.78%, 5.43 and 8.15% respectively, while Highland tea wine produced highest alcoholic contents of 9.78%, 7.07% and 7.61% respectively. Physicochemical analyses for all the wines produced showed that the specific gravity, total solids and pH of the must decreased as fermentation progressed while the titratable acidity remained constant throughout the must fermentation. Colony counts showed a high biomass of yeast cells that decreased as it tended towards the end of fermentation. Sensory analysis of the wines showed that Lipton and Top tea are the most acceptable organoleptically when compared with the commercial wine used as control although the three tested teas were not significantly different statistically. Baker’s yeast was rated as the best yeast for wine fermentation irrespective of the type of tea used. All the wines produced were generally accepted as they were scored above average. This study highlights the potential of using different tea infusions as alternatives to grape and other fruit musts in wine making. It also confirms that commercial yeasts such as baker’s yeast can be used in homemade wine production.     

Contribution of wild yeasts to the formation of volatile compounds in inoculated wine fermentations

The aim of this work was to study the contribution of wild yeasts to the volatile composition of wine in inoculated fermentations. To do so, Parellada must, sterilized and inoculated with Saccharomyces cerevisiae strain Na33 (pure inoculated fermentation), inoculated Parellada must (mixed inoculated fermentation) and Parellada must that fermented with its wild yeasts (control fermentation) were used. From the results obtained in the pure inoculated fermentation it can be seen that S. cerevisiae produced appreciable quantities of isoamyl acetate, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. However, the wild yeasts also contributed to the synthesis of esters since the total concentration of these substances was higher in the mixed inoculated fermentation than in the pure inoculated fermentation. 2-Phenylethyl acetate was only synthesized by wild yeasts when they did not compete with S. cerevisiae. The concentration of total alcohols was similar in the three samples; the important production of isobutanol and 2-phenylethanol in the control fermentation is noteworthy. As regards the acids, the greatest concentration corresponded to the mixed inoculated fermentation. The wild yeasts contributed to the synthesis of these compounds to a significant extent and S. cerevisiae synthesized appreciable amounts of short-chain fatty acids.     

The aromatic volatile composition of Lonicera edulis wines produced with three different strains of Saccharomyces cerevisiae

Three different strains of Saccharomyces cerevisiae – D₁₅, Dibosh and 71B – were evaluated in the fermentation of Lonicera edulis wines. Volatile aromatic components were analysed by gas chromatography–mass spectrometry coupled with headspace solid‐phase microextraction. In all, 81 volatile compounds were identified in L. edulis wines, including 43, 48 and 38 individually found in wines fermented with D₁₅, Dibosh and 71B. There were 17 common volatile aromatic components found in all the three L. edulis wines. The main volatile compounds in wines fermented with D₁₅ and Dibosh yeasts were 2‐methyl‐1‐butanol (24.8%) and hexane (20.6%). Pentanol was the primary volatile aromatic compound in wines produced with S. cerevisiae 71B, accounting for 40.8% of total volatile aromatic compounds. Combining the sensory analysis, S. cerevisiae D₁₅ was suggested to be the most suitable strain for producing L. edulis wine. © 2018 The Institute of Brewing & Distilling     

Discovering a chemical basis for differentiating wines made by fermentation with 'wild' indigenous and inoculated yeasts: role of yeast volatile compounds

Background and Aims:  Winemakers are constantly searching for new techniques to modulate wine style. Exploiting indigenous yeasts present in grape must is re-emerging as a commercial option in New World wine regions. Wines made with indigenous or 'wild' yeasts are perceived to be more complex by showing a greater diversity of flavours; however, the chemical basis for the flavour characteristics is not yet defined. In order to evaluate techniques for making wine with the 'wild yeast fermentation' character more reliably, it is necessary to define the salient chemical characteristics of such wines.
Methods and Results:  Pairs of Chardonnay wines were prepared from the same must and subjected to similar fermentation conditions in the wineries of origin, except for the mode of inoculation. Reference wines were made by inoculation with a Saccharomyces cerevisiae starter culture, whereas companion wines were allowed to undergo fermentation with the indigenous microflora. Of all wine chemicals analysed, only yeast-derived volatile fermentation products showed significant differences between the yeast treatments.
Conclusions:  Inoculated wines were associated with the esters ethyl hexanoate and 3-methylbutyl acetate and formed a clear cluster by principal component analysis. By comparison with inoculated wines, 'wild' yeast fermented wines showed high variability in volatile compounds that contribute to wine aroma, with higher concentrations of 2-methylpropanol, 2-methylbutanoic acid, ethyl 2-methylpropanoate, ethyl decanoate and ethyl dodecanoate potentially being sensorially important.
Significance of the Study:  This study shows that yeast-derived volatile fermentation products are a key difference between inoculated and uninoculated ferments and provides a chemical basis for the 'wild yeast fermentation' character.     

产香酵母的分离鉴定及对不同原料酿造甜酒香气成分的影响

该研究从传统颗粒甜酒曲中筛选分离产香酵母菌,结合形态学观察及分子生物学技术鉴定分离菌株,采用顶空-气相色谱（HS-GC）法对筛选菌株产香能力进行分析,并考察产香酵母对不同原料酿造甜酒香气成分的影响。结果表明,共分离筛选出6株酵母,其中5株菌（编号为YRNN1～YRNN5）被鉴定为扣囊复膜酵母（Saccharomycopsis fibuligera）,1株菌（编号为YRJM）被鉴定为酿酒酵母（Saccharomyces cerevisiae）。菌株YRNN5发酵米汁产β-苯乙醇最高（22.98 mg/L）,将其作为甜酒增香菌株应用于不同原料酿造甜酒。甜酒香气成分分析结果表明,籼米甜酒的β-苯乙醇和乙酸苯乙酯含量分别为771.38 mg/L、2.90 mg/L,显著高于籼糯米甜酒（P＜0.05）,且籼米甜酒和籼糯米甜酒的酒精度分别为15.15%vol和12.80%vol。菌株YRNN5和籼米可以作为甜酒发酵的产香酵母和优良原料。     

Optimization of the Operating Conditions for Color Correction in White Wines Based on the Use of Yeast as Fining Agent

ABSTRACT: Sherry-type pale white wines were subjected under different stirring times to color correction treatments based on the use of variable concentrations of free yeast and a single concentration of yeast immobilized on carrageenan gel. At all concentrations tested, the free yeasts decreased the A420 of the initial wine. The immobilized yeast showed slightly lower effectiveness to retain browning compounds of the wine and exhibited no significant differences among the treatment times assayed. Choosing the most unfavorable conditions (24 h), significant decreases in the concentrations of low-molecular-weight phenolic compounds were observed. The sensory properties of the wines treated with the immobilized yeast were shown to be similar to those of wines treated with activated charcoal for flavor, better for color, and slightly worse for aroma. Keywords: browning, immobilized yeast, white wines, fining agents     

Chemical and volatile composition of lychee wines fermented with four commercial Saccharomyces cerevisiae yeast strains

This study evaluated the chemical and volatile composition of lychee wines fermented with four commercial yeast strains of Saccharomyces cerevisiae: EC‐1118, R2, 71B and MERIT.ferm. Yeast cell population, pH, malic acid, ammonia and some amino acids had significant differences between strain 71B and other strains. There were strain variations with regard to degradation and retention of some juice volatiles as well as formation of new volatile compounds such as most esters and certain terpene compounds. Ethyl octanoate had the highest odour activity value (OAV of 500–1100), followed by ethyl hexanoate (about 50–85), among the common odorants in all lychee wines. Ethyl octanoate reached its highest OAV (1077) in the lychee wine fermented with strain EC1118, whereas ethyl hexanoate had the highest OAV (85) in the wine fermented with strain MERIT.ferm. Cis‐rose oxide, the character‐impact volatile in lychee juice with highest OAV (161), was dramatically reduced to trace levels after fermentation.     

以甘蔗固定化酵母发酵低醇葡萄酒的研究

试验以甘蔗为载体材料,研究了用甘蔗块固定化酵母在低醇贵人香葡萄酒发酵中的表现,检测了其对发酵时间,酒精度,稳定性及发酵批次等的影响,同时定量分析了固定化前后酵母发酵低醇酒在香气成分上变化.结果发现,以甘蔗为载体固定化酵母应用到低醇酒发酵,可以有效地控制低醇葡萄酒的理想酒精度,增加产品的稳定性.而且甘蔗固定化酵母减少了酒中高级醇的含量,增加了低醇葡萄酒的复杂香气和口感.     

Co-inoculation of different Saccharomyces cerevisiae strains and influence on volatile composition of wines

Wine is the result of the performance of different yeast strains throughout the fermentation in both spontaneous and inoculated processes. 22 Saccharomyces cerevisiae strains were characterized by microsatellite fingerprinting, selecting 6 of them to formulate S. cerevisiae mixed cultures. The aim of this study was to ascertain a potential benefit to use mixed cultures to improve wine quality. For this purpose yeasts behavior was studied during co-inoculated fermentations. Aromatic composition of the wines obtained was analyzed, and despite the fact that only one strain dominated at the end of the process, co-cultures released different concentrations of major volatile compounds than single strains, especially higher alcohols and acetaldehydes. Nevertheless, no significant differences were found in the type and quantity of the amino acids assimilated. This study demonstrates that the final wine composition may be modulated and enhanced by using suitable combinations of yeast strains.     

Effects of seven yeast strains on the volatile composition of Palomino wines

The must obtained from Palomino grapes was inoculated with seven different commercial yeast strains (three Saccharomyces cerevisiae cerevisiae– MO5, CEG and IOC BR 8000 and four Saccharomyces cerevisiae bayanus– ALB, KD, REIMS and IOC 2007) and fermented under identical conditions. Standard chemical analyses were done on the final industrial wines and the major volatile compounds extracted and analysed by gas chromatography coupled to mass spectrometry. No differences were found in gross chemical composition, but the wines had significantly different volatile characteristics and the results demonstrated that large sensory differences were generated by the different yeast strain that had been used in the vinification. The major constituents that contributed to the volatile composition in this wine were the higher alcohols, ethyl esters, acetates, fatty acids and volatile phenols. In terms of floral and fruity odours, the best results were obtained for the wines inoculated with IOC 2007, ALB and REIMS S. cer. bayanus strain.     

不同酵母对赤霞珠桃红葡萄酒香气的影响

利用CY3079、Zymaflore X16、TXL和STR四种不同类型的商业酵母发酵赤霞珠新鲜桃红葡萄酒,采用顶空固相微萃取（HS-SPME）结合气相色谱质谱（GC-MS）联用技术,分别对酒精发酵结束和瓶储陈酿一年的葡萄酒样品进行香气物质的定性与定量分析。结果表明,4种酵母发酵的赤霞珠桃红葡萄酒中香气物质的种类相似,但其含量差异显著。酒精发酵结束阶段,CY3079和Zymaflore X16酵母发酵的桃红葡萄酒中脂肪酸乙酯的含量高于其他酵母发酵的酒样,使它们具有更加浓郁的果香、甜香和花香;而Zymaflore X16和STR酵母产生乙酸异戊酯和乙酸苯乙酯的能力较强。经过一年的瓶储陈酿,所有处理的桃红葡萄酒中脂肪酸乙酯和高级醇乙酸酯的含量显著下降,导致其果香的强度降低,同时减少了不同酵母发酵酒样之间的差异。