Yeast Lees Research Articles

Monitoring of glutathione concentration during winemaking by a reliable high-performance liquid chromatography analytical method

Background and Aims: Glutathione (GSH) is valued in winemaking as an effective antioxidant in must and white wine if its concentration exceeds a few milligrams per litre. We report the further improvement of a previous analytical method for GSH quantification and its application to the analysis of grapes and wines. Methods and Results: Glutathione was derivatised with p-benzoquinone and detected by HPLC/UV. The analytical method was sensitive (limit of quantification, 0.43 mg/L), linear (R2 > 0.997), accurate (recovery, 101% in grape juice and white wine) and repeatable (relative standard deviation, 3.1). The monitoring of vinifications at commercial wineries showed that Saccharomyces cerevisiae was a main source of GSH in wine, since the GSH of the grape was poorly preserved following juice preparation. Glutathione concentration decreased during wine aging on yeast lees. Conclusion: Glutathione concentration varied considerably during winemaking, and thus monitoring is essential for improving wine flavour and preventing oxidation. This method is suitable for this purpose. Significance of the Study: The analytical method proposed is reliable, fast and easy-to-apply and allows the assessment of the GSH in grape, must and wine. The strong role of the yeast on the GSH concentration in wine is reported.

Formation of biogenic amines in wine production

Factors and conditions for the formation of biogenic amines in wine production were studied. It was shown that amino acids were decarboxylated during alcoholic fermentation and biological acidic reduction in the presence of enzymes of yeast and lactic acid bacteria. The pH value, the presence of phenolic compounds, tartaric and malic acid, the duration of the contact between the wine material and yeast lees, and the rate of their autolysis were found to influence the intensity of the decarboxylation process.

Wood impregnation of yeast lees for winemaking

This study develops a new method to produce more complex wines by means of an indirect diffusion of wood aromas from yeast cell-walls. An exogenous lyophilized biomass was macerated with an ethanol wood extract solution and subsequently dried. Different times were used for the adsorption of polyphenols and volatile compounds to the yeast cell-walls.The analysis of polyphenols and volatile compounds (by HPLC/DAD and GC–MS, respectively) demonstrate that the adsorption/diffusion of these compounds from the wood to the yeast takes place. Red wines were also aged with Saccharomyces cerevisiae lees that had been impregnated with wood aromas and subsequently dried. Four different types of wood were used: chestnut, cherry, acacia and oak. Large differences were observed between the woods studied with regards to their volatile and polyphenolic profiles.Sensory evaluations confirmed large differences even with short-term contact between the wines and the lees, showing that the method could be of interest for red wine making. In addition, the results demonstrate the potential of using woods other than oak in cooperage.

Antioxidant properties of different products and additives in white wine

Different winemaking products (ascorbic acid, glutathione, yeast lees and a yeast autolysate) were tested in comparison with sulphur dioxide, concerning radical scavenging activity (measured by DPPH assay), oxygen consumption capacity and ability to reduce wine colour and predisposition to browning. Trials were performed in white wines and model solution. SO2 was the most active in reducing wine colour development. Fresh lees and ascorbic acid were very effective in oxygen and free radical scavenging, but they both induced browning during wine storage, the former, by releasing phenolic compounds. Glutathione was also able to scavenge DPPH in wine, but less effective against oxygen, and it induced browning during storage. Surprisingly, the yeast derivative preparation was the treatment that behave more similarly to sulphiting; it was very active in scavenging DPPH, and, even without modifying oxygen consumption rate, it protected quite well wine colour over an 8months storage time.

Decontamination of ochratoxin A by yeasts: possible approaches and factors leading to toxin removal in wine.

Biological decontamination of mycotoxins using microorganisms is one of the well-known strategies for the management of mycotoxins in foods and feeds. Yeasts are an efficient biosorbant, used in winemaking to reduce the concentration of harmful substances from the must which affect alcoholic fermentation (medium-chain fatty acids) or which affect wine quality in a negative way (ethyl phenols and sulphur products). In recent years, several studies have demonstrated the ability of yeasts to remove ochratoxin A (OTA) by live cells, cell walls and cell wall extracts, yeast lees. In spite of the physical and chemical methods applied to remove the toxin, the biological removal is considered a promising solution, since it is possible to attain the decontamination without using harmful chemicals and without losses in nutrient value or palatability of decontaminated food. In addition, adsorption is recognized as economically viable, technically feasible and socially acceptable. This paper intends to review the current achievements of OTA removal mediated by yeasts, the recent updates in the selection of strains acting at the same time as starters and as biological tools to remove OTA and the factors affecting the removal process.

Wine: looking ahead

Not available.

Changes in Polysaccharide Composition during Sparkling Wine Making and Aging

The evolution in polysaccharide composition and molecular weights during sparkling wine making and aging was studied for the first time in this work. Different autochthonous grape varieties from Spain (Verdejo, Viura, Malvası́a, Albarı́n, Godello, Garnacha and Prieto Picudo) were used to elaborate sparkling wines following the champenoise method. Principal component analysis showed differentiation of wines according to polysaccharide families. This differentiation was due to the process of aging on yeast lees, but not to the variety employed. The content of mannoproteins during aging was positively correlated (r = 0.792) with total polysaccharides from grapes. After six months of aging the highest content of mannoproteins and polysaccharides rich in arabinose and galactose was obtained. Also a shift to lower molecular weights was observed. The combination of these two characteristics could imply a better foam stability and thus sensory quality of sparkling wines.

Umami in wine

The positive effects of umami on flavour are widely documented, but as far as the author is aware, wines are not mentioned in umami-related literature; vice versa, in wine-related scientific publications, references to umami were not found. In the fermentation and subsequent ageing of wines there is ample opportunity for umami compounds to develop. Umami refers to the taste of free glutamic acid (Glu), an amino acid that can be present in the taste of wine as a result of the grapes used and the applied vinification techniques. Some techniques are likely to enhance the presence of Glu in wines, especially fermentation on yeast lees, a common procedure in the manufacture of many prestigious Chardonnay wines. During the malolactic fermentation, the relative content of Glu is also likely to increase. Sweet wines like Port and Madeira are also reported to have considerable amounts of Glu. In dairy fermentations, such as in cheese, there is sophisticated knowledge about the specific flavours and textures that are formed by different starter lactic acid bacteria. They provide desired enzymes which yield small peptides and free amino acids that give a certain cheese its specific character. As amino acids are also precursors of various volatile flavour compounds such as aldehydes and alcohols the development of specific wine yeasts that could impart specific desirable characteristics to a wine could prove to be an important venture in the production of successful wines.

Biotechnological Strategies for Controlling Wine Oxidation

Apart from the controversial positive effects of moderate wine consumption on human health, wine antioxidant capacity plays a key role in winemaking technology. From juice extraction to bottle storage, oxygen management is one of the most critical points for making quality wines. In the past, the protection of juice and wine from oxidations was based on the sole use of sulfur dioxide; more recently, the toxicity and the allergenic potential of this additive, together with the increased knowledge on wine oxidation mechanisms, have given rise to new biotechnological approaches and producing trends, leading to a significant reduction of sulfites in winemaking. The aim of this paper is to review the oxidation mechanisms of grape juice and wine and to discuss the opportunities to reduce as much as possible sulfur dioxide addition by a proper management of alcoholic and malolactic fermentation and by the supplementation of some important yeast nutritional factors (e.g., thiamine). The use of natural antioxidants complementing the activity of sulfites (i.e., ascorbic acid, glutathione, yeast lees, and yeast derivatives) is also discussed.

Wastewater polishing by a channelized macrophyte-dominated wetland and anaerobic digestion of the harvested phytomass

Constructed wetlands (CW) offer a mechanism to meet increasingly stringent regulatory standards for wastewater treatment while minimizing energy inputs. Additionally, harvested wetland phytomass subjected to anaerobic digestion can serve as a source of biogas methane. To investigate CW wastewater polishing activities and potential energy yield we constructed a pair of secondary wastewater-fed channelized CW modules designed to retain easily harvestable floating aquatic vegetation and maximize exposure of water to roots and sediment. Modules that were regularly harvested averaged a nitrate removal rate of 1.1 g N m−2 d−1; harvesting, sedimentation and gasification were responsible for 30.5%, 8.0% and 61.5% of the N losses, respectively. Selective harvesting of a module to maintain dominance of filamentous algae had no effect on nitrate removal rate but lowered productivity by one-half. The average monthly productivity for unselectively harvested modules was 9.3 ± 1.7 g dry wt. m−2 d−1 (±SE). Cessation of harvesting in one module resulted in a significant increase in nitrate removal rate and decrease in phosphate removal rate. Compared to the influent, the effluent of the harvested module had significantly lower levels of estrogenic activity, as determined by a quantitative PCR-based juvenile trout bioassay, and significantly lower densities of E. coli. In mixed vertical-flow reactors anaerobic co-digestion of equal dry weight proportions of harvested aquatic vegetation, wine yeast lees and dairy manure was greatly improved when the manure was replaced with the crude glycerol by-product of biodiesel production. Remaining solids were vermicomposted for use as a soil amendment. Our results indicate that incorporation of constructed wetlands into an integrated treatment system can simultaneously enhance the economic and energetic feasibility of wastewater and organic waste treatment processes.

Sparkling Wines Produced from Alternative Varieties: Sensory Attributes and Evolution of Phenolics during Winemaking and Aging

Spanish grape varieties that have been traditionally used to produce still wines were examined for their potential to make white and rosé sparkling wines. Sparkling wines manufactured from <i>Vitis vinifera</i> cv. Verdejo, Viura, Malvasía, Albarín, Godello, Garnacha, and Prieto varieties were examined for sensory attributes and for the evolution of monomeric and polymeric phenolics during different stages of winemaking and aging. Stabilization and clarification of the base wines significantly decreased the concentrations of anthocyanins and proanthocyanidins. During the initial months of aging on yeast lees, all types of polyphenols decreased, although some were released back into the wine during the final months. Garnacha rosé and Albarín white wines had high phenolic potential. Garnacha rosé sparkling wines had particularly high hydroxycinnamic acid concentrations, while Prieto Picudo rosé sparkling wines had the highest color intensity and anthocyanin concentrations. Among white sparkling wines, Albarín had the most catechin, proanthocyanidins, and, together with Viura, hydroxycinnamates. In sensory profiling, Prieto Picudo had more visual color intensity, red tones, olfactory intensity, freshness sensations, and foam quality than Garnacha wines. Albarín and Verdejo had more visual color and olfactory intensity than the other white wines, and Verdejo had better foam quality. Prieto Picudo, Albarín, and Verdejo were the most promising varieties for the production of high-quality sparkling wines.

Foamability of Prosecco wine: Cooperative effects of high molecular weight glycocompounds and wine PR-proteins

Five Macromolecular fractions differing in molecular weight (M.W.) and composition were separated from a Prosecco wine by ultrafiltration and Size Exclusion Chromatography (SEC) before and after 1 and 18 months of wine ageing on yeast lees. The SEC fractions, combined or alone, were back added to the ultrafiltered wine in order to assess their contribution to wine foamability. The results indicated that the highest M.W. fraction, containing the wine glycocompounds and comprising the yeast mannoproteins was that giving the highest foamability, whereas the wine proteins deriving from the grape berry did not foam. However, the combination of all the fractions gave a foamability higher than that provided by the glycocompounds, indicating a cooperative effects between these latter and the proteins of grape origin. This result can be explained by hypothesizing a molecular interaction leading to the formation of macromolecular complexes able to interact with the gas–wine interface.

Effect of Winery Yeast Lees on Touriga Nacional Red Wine Color and Tannin Evolution

Red wine aging on lees is a winemaking practice used to achieve more rounded and less astringent wines. In two different trials, external yeast lees were added to a red wine and their effects on wine color and tannin evolution during aging were studied. Results indicated that the addition of yeast lees did not affect color stabilization during the studied period. Color compounds and condensed tannins were rapidly adsorbed to the yeast lees at the beginning of the experiment. There was a retarding effect on proanthocyanidin polymerization reaction by the addition of yeast lees, leading to the maintenance of low and medium molecular weight tannins in solution. Two different interactions were observed: first, proanthocyanidin adsorption by the yeast lees, primarily ones with the highest polymerization degree, and second, the retarding of proanthocyanidin polymerization, likely by the mannoproteins released by yeast lees. The age of the yeast lees was a factor in mannoprotein release and its effect in wine.

Interactions of phenolic and volatile compounds with yeast lees, commercial yeast derivatives and non toasted chips in model solutions and young red wines

Ageing of wines on lees, the use of commercial yeast derivative products and the addition of oak chips to wine permit the release of different compounds such as mannoproteins and polysaccharides into wines during yeast autolysis. These compounds released can interact with phenolic compounds and/or aromatic compounds, also modifying wine sensory perception. For that reason, the aim of this work was to evaluate the interaction of phenolic and volatile compounds of wines with yeast lees, non-toasted oak wood chips and different commercial yeast derivative preparations in model wine solutions and in a real red wine. The results found in this study have shown that most of the phenolic and volatile compounds studied are adsorbed by wood and bound by lees in model wine solutions. However, in the model wines in general, the commercial yeast derivative products studied only interacted with the volatile compounds but not with the phenolic compounds. The adsorption of the phenolic compounds occurred in the first 15 days of treatment, remaining constant for 2 months; however, in the case of volatile compounds, these compounds initially displayed a retention effect, but after 30–60 days, the release of the previously bound compounds was instigated. The adsorption effect on the phenolic and volatile compounds in the model wine solution was not always the same as in the red wine studied, which highlights the important presence of other wine compounds in these interactions.

Evaluating the Influence of Malolactic Fermentation Inoculation Practices and Ageing on Lees on Biogenic Amine Production in Wine

Biogenic amines are compounds, produced primarily by lactic acid bacteria (LAB) that negatively affect the wholesomeness of wine. Standard winemaking practices can greatly influence the levels of biogenic amines in wine. The aim of this study was to determine the relative contribution of different malolactic fermentation (MLF) practices and ageing of wines on fermentation lees to the final levels of biogenic amines. Wines were made on small scale over two harvest seasons with two red grape cultivars. Treatments included spontaneous MLF, co-inoculated MLF, MLF inoculated after alcoholic fermentation (conventional inoculation) and 4 months of ageing in the presence and absence of fermentation lees of all MLF treatments. Biogenic amine concentrations were measured by high-performance liquid chromatography at key winemaking stages and statistically analysed for the effects of MLF treatment and winemaking stage. Results indicate that the presence of indigenous LAB increased the risk of biogenic amine formation. Inoculation proved to reduce biogenic amine production over time compared to spontaneous MLF and co-inoculation even more than conventional inoculation. The presence of yeast lees during ageing generally led to higher final concentrations of biogenic amines in wines than the absence of lees. This study confirms other works that conclude that spontaneous MLF and uncontrolled ageing on yeast lees are generally unpredictable and pose a risk of biogenic amine contamination in finished wines.

Chips, lees, and micro-oxygenation: influence on some flavors and sensory profile of a bottled red Sangiovese wine

Wine samples of Red Sangiovese wines were aged for 3 months using three different techniques (chips, lees, and micro-oxygenation) separately or combined. Later, their evolution in bottle was monitored for 5 months. At the end of aging, the main effect on selected volatile compounds was related to chips addition: as a matter of fact, chips increased aromatic compounds derived from oak, such as vanilla and burnt/toasted aromas. Micro-oxygenation induced a lower amount of 4-ethyl guaiacol than in its control. The combined use of micro-oxygenation and yeast lees led to a lower amount of guaiacol and vanillin than in its control. Wine evolution in bottle was significantly affected by the up-cited aging techniques. The use of chips led to a decrease in 4-ethyl guaiacol than in control. Micro-oxygenation reduced guaiacol and whisky lactone decrease and the increase in 4-ethyl guaiacol. The combined use of chips, micro-oxygenation, and yeast lees reduced the decrease in whisky lactone in a not significant way, instead of all the other trials. A descriptive analysis of wines put in evidence that micro-oxygenation combined with the use of chips and yeast lees reduced astringency, increased balance, and enhanced vanilla perception.

Proteomic response of LAP-activated RAW 264.7 macrophages to the anti-inflammatory property of fungal ergosterol

Ergosterol is the principal fungal sterol in edible mushrooms and yeast lees in wine. In this study, the immunoregulatory action of ergosterol was evaluated by a proteomic approach using two-dimensional gel electrophoresis to identify proteins with modified expression in LPS-challenged RAW 264.7 macrophages treated with ergosterol. By comparing the proteome signatures, alterations of multiple proteins were observed, including NF-κB cascade-related proteins, Rho family GTPase protein, and cytoskeleton-related proteins. The down-regulation of NF-κB cascade-associated proteins coincided with the inhibition of TNF-α production and COX-2 expression in the ergosterol-treated RAW 264.7 cells. Western blotting analysis indicated that ergosterol inhibits LPS-induced inflammation in RAW 264.7 macrophages by suppressing the NF-κB signalling pathway.

Variation of Some Fermentative Sulfur Compounds in Italian “Millesimè” Classic Sparkling Wines during Aging and Storage on Lees

Fermentative sulfur compounds are recognized as strongly affecting wine aroma, mainly as off-flavors, but recently also as possible positive contributors to wine quality and typicity in still wines. Nevertheless, no evidence has been provided for the influence of these molecules on sparkling wine aroma, except for peculiar volatile thiols found in French Champagne. According to the traditional method, the second fermentation, occurring in sealed bottles, is the essence of the procedure. After this fermentation, sparkling wine is aged on yeast lees for a period ranging from a few months to several years so that yeast autolysis can take place. So far, no evidence is provided for the effect of yeast contact duration on the level of sulfur compounds. Following a HS-SPME/GC-MS method, 13 sulfur compounds, that is, ethylmercaptan, dimethyl sulfide, diethyl sulfide, dimethyl disulfide, diethyl disulfide, methyl thioacetate, ethyl thioacetate, 2-mercaptoethanol, 2-(methylthio)-1-ethanol, 3-(methylthio)-1-propanol, 4-(methylthio)-1-butanol, benzothiazole, and 5-(2-hydroxyethyl)-4-methylthiazole, were quantified in several Italian sparkling wines, produced according to the traditional method in two wineries from Trentino-South Tyrol, region. Additionally, the influence of winemaking technology differences and vintage effects on the evolution of the quoted sulfur compounds was considered. This investigation was carried out by coupling the HS-SPME data with those obtained by SPE method and relevant to other volatile compounds, which are considered as winemaking markers. This work furnished the first evidence of the effect of aging and lees contact at different storage temperatures on the levels of these analytes in sparkling wines. Significant increments were observed for dimethyl sulfide, diethyl sulfide, 2-(methylthio)-1-ethanol, 3-(methylthio)-1-propanol, and 4-(methylthio)-1-butanol during aging with a different variation slope possibly due to the remarkably different storage temperatures. No clear influence of lees contact duration was found for the majority of the sulfur compounds considered.

Genetically modified wine yeasts and risk assessment studies covering different steps within the wine making process

The use of gene technology to modify the genome of wine yeasts belonging to the species Saccharomyces cerevisiae began in the early 1990s. From a purely scientific point of view, many yeast constructs [genetically modified organisms (GMO)] have been made so far, covering more or less all stages of the wine making process in which microorganisms or commercial enzymes play a key role. The range of theoretical applications is summarised in this report. So far, only two wine-producing countries worldwide allow the use of engineered wine yeasts; the changing situation in Germany regarding consumers’ attitudes towards gene technology, and foodstuffs thus produced, will be outlined here. Experiments at the Geisenheim Research Center have highlighted the essential stages of the wine making process where yeasts are involved by using engineered wine yeasts in comparison with non-engineered yeast strains. Greenhouse simulations revealed the persistence of genetically modified (gm) yeasts when these were used as fertilizers, as vintners do with yeast lees after the fermentation process. Furthermore, the persistence of engineered yeast was also monitored in fermentations, after bottling, and after biological treatment of winery waste water. It turned out that engineered wine yeast strains behave like non-engineered wine yeasts. They also persist in the winery interior and installations as well as becoming part of the yeast flora on grape vines in a vineyard with annual fluctuations in the composition of the yeast populations.

Effect of Yeast Mannoproteins and Grape Polysaccharides on the Growth of Wine Lactic Acid and Acetic Acid Bacteria

Polysaccharides constitute one of the main groups of wine macromolecules, and the difficulty in separating and purifying them has resulted in them being less studied than other wine macromolecules. In this study, the biological activity of a number of polysaccharide fractions obtained from yeast lees, must, and wine has been analyzed against a large collection of both lactic acid bacteria (LAB) and acetic acid bacteria (AAB) of enological origin. Results showed that a high proportion of AAB strains (60-88%) was inhibited by concentrations lower than 50 mg/L polysaccharide fractions containing intermediate- (6-22 kD) and small-molecular-weight (<6 kD) mannoproteins and oligosaccharide fragments derived from cellulose and hemicelluloses. Results also showed that, in contrast, yeast mannoproteins in concentrations up to 200 mg/L activated the growth of 23-48% of the studied LAB strains when ethanol was present in the culture broth. Specially, yeast commercial mannoproteins of intermediate molecular weight (6-22 kD) were active in increasing Oenococcus oeni growth (81.5% of the studied O. oeni strains) in the presence of ethanol in the culture broth. These effects of wine polysaccharides on bacterial growth provide novel and useful information for microbiological control of wines and winemaking biotechnology.