End Of Alcoholic Fermentation Research Articles

Chromatic characteristics and anthocyanin profile of a micro-oxygenated red wine after oak or bottle maturation

Micro-oxygenation (MOX) was applied to a red wine for 5 months following the end of alcoholic fermentation and then both a non-oxygenated control wine and the micro-oxygenated wine were matured in oak barrels or bottles. The concentration of anthocyanin and anthocyanin-derived compounds and the chromatic characteristics of the control and micro-oxygenated wines after the maturation period were studied. Anthocyanin and anthocyanin-derived compounds composition were determined by liquid chromatography-mass spectrometry; and, together with monomeric anthocyanins, compounds including direct anthocyanin-flavanol adducts, ethyl-linked anthocyanin-flavanol compounds, and pyranoanthocyanins were identified. The results showed that the improvements in the chromatic characteristics obtained by applying the MOX technique to Monastrell wines were maintained after an aging period in bottle or barrel. The color intensity of wines increased during maturation in oak barrels, whereas the color of the bottled wines decreased, although MOX wines always showed higher color intensity than the respective control wines. Bottled wines also showed a higher increase in tint and a lower quantity of compounds resistant to SO2 discoloration than oak matured wines, indicating that the formation of these compounds is favored by the oxidative conditions in oak barrels.

Interactions between Brettanomyces bruxellensis and other yeast species during the initial stages of winemaking

Wine is the product of complex interactions between yeasts and bacteria in grape must. Amongst yeast populations, two groups can be distinguished. The first, named non-Saccharomyces (NS), colonizes, with many other micro-organisms, the surface of grape berries. In the past, NS yeasts were primarily considered as spoilage micro-organisms. However, recent studies have established a positive contribution of certain NS yeasts to wine quality. Amongst the group of NS yeasts, Brettanomyces bruxellensis, which is not prevalent on wine grapes, plays an important part in the evolution of wine aroma. Some of their secondary metabolites, namely volatile phenols, are responsible for wine spoilage. The other group contributing to wine aroma, which is also the main agent of alcoholic fermentation (AF), is composed of Saccharomyces species. The fermenting must is a complex microbial ecosystem where numerous yeast strains grow and die according to their adaptation to the medium. Yeast-yeast interactions occur during winemaking right from the onset of AF. The aim of this study was to describe the interactions between B. bruxellensis, other NS and Saccharomyces cerevisiae during laboratory and practical scale winemaking. Molecular methods such as internal transcribed spacer-restriction fragment length polymorphism and polymerase chain reaction and denaturing gradient gel electrophoresis were used in laboratory scale experiments and cellar observations. The influence of different oenological practices, like the level of sulphiting at harvest time, cold maceration preceding AF, addition of commercial active dry yeasts on B. bruxellensis and other yeast interactions and their evolution during the initial stages of winemaking have been studied. Brettanomyces bruxellensis was the most adapted NS yeast at the beginning of AF, and towards the end of AF it appeared to be more resistant than S. cerevisiae to the conditions of increased alcohol and sugar limitation. Among all NS yeast species, B. bruxellensis is better adapted than other wild yeasts to resist in must and during AF. Moreover, B. bruxellensis appeared to be more tolerant to ethanol stress than S. cerevisiae and after AF B. bruxellensis was the main yeast species in wine. Brettanomyces bruxellensis interacts with other yeast species and adapts to the wine medium as the dominant yeast species at the end of AF. Contamination of B. bruxellensis might take place at the beginning of malolactic fermentation, which is a critical stage in winemaking.

Oxygen measures and consumption in must and wine

The aim of this work is to point out a system of oxygen measure on real scale and to estimate the oxygen concentrations in must in red winemaking, in particular during maceration and alcoholic fermentation. The experimental vat had two different controlled aeration systems of must: during pumping-over or during the re-circulation of a fraction of the liquid. For the evaluation of the oxygen dissolved during maceration, the vat was equipped with devices to carry out the measure in the must before the aeration, in the must aerated during the re-circulation, after the pumping-over and in the total mass. The measure of dissolved oxygen were made with an instrument based on the Clark electrode, provided with automatic compensation for the temperature and the salinity. In order to obtain the consumption kinetics, the measures were made in the time range necessary to reach the values determined before aeration. During maceration, the oxygen concentration returns to the initial value in variable times, ranging from few minutes to 20 min. In the first 2–3 min the oxygen dissolved in the total mass is reduced of 50–60% during the tumultuous fermentation and of the 35–50% at the end of alcoholic fermentation. Subsequently the decrease is gradual and slower and the oxygen concentration was closed to the instrumental detection limit. The consumption kinetics, apart from the mechanism, can be represented by an exponential equation.

Stilbenes: Quantitative extraction from grape skins, contribution of grape solids to wine and variation during wine maturation

With the objective of studying the relationship between stilbenic composition in grape skins and that in corresponding red wine, we have firstly optimized a method for quantitative extraction and purification of stilbenes from grape skins, used for posterior HPLC analysis. Stilbene levels in grape skins of three Vitis vinifera varieties (Castelão, Syrah and Tinta Roriz) and in their corresponding wines made by traditional winemaking technologies were analyzed. Stilbene composition in grape skin varied considerably, depending on the grapevine variety. The contents of trans-resveratrol in grape skins of the three varieties were not significantly different. However, their contents of trans-piceid on dry skin were very significantly different (67.24, 10.43 and 11.57 mg kg −1, respectively). Moreover, cis-piceid, which was absent in Syrah and Tinta Roriz grape skins, was detected in Castelão grape skin with an important amount (58.9 mg kg −1 on dry skin). The high concentrations of stilbenes were found in stem tissue (cv. Castelão): 145.52 mg kg −1 of trans-resveratrol, 61.43 mg kg −1 of trans-piceid and 143.85 mg kg −1 of cis-piceid (on dry stem), while only trans-resveratrol was quantified in the grape seeds with a low concentration (6.8 mg kg −1 on dry seed). Simulated maceration of each solid part of grapes using model wine solution indicated that both stem and seed have little contribution of stilbenes to wines while skins are the major source of these compounds in wine. On the other hand, cis-piceid was not detected in the corresponding wines made by these grapevine varieties, but its isomer trans-piceid was detected in an important concentration, suggesting that cis-piceid, once extracted, isomerized to its trans-form. The evolution of these compounds during the elaboration of wines (from the end of alcoholic fermentation until second racking, i.e., just before bottling) showed that in general, trans-resveratrol concentration decreases gradually, trans-piceid kept constant, while cis-resveratrol increases slightly. The important finding of this work is that there was a significant correlation between the concentration of total piceid in grape skins and that in the respective wine. On the contrary, no such relationship was found for resveratrol.

Influence of yeast strain on ochratoxin A content during fermentation of white and red must

The aim of this work was to examine whether the yeast strains, responsible for alcoholic fermentation, have an influence on the concentration of ochratoxin A (OTA) in wine. Before the fermentation, OTA was added to musts up to a concentration of about 2 μg/l. OTA content was determined in white and red wines resulting from respective musts and in methanolic extract of the yeast lees (MEL). Data showed a significant reduction of OTA at the end of alcoholic fermentation. However, depending on the yeast strain involved in the fermentation, there was a difference in the content of OTA in the wines. The percentage of OTA removal during the fermentation was between 46.83% and 52.16% in white wine and between 53.21% and 70.13% in red wine. The absence of degradation products suggested an adsorption mechanism. OTA concentration in MEL resulting from red must fermentation was higher than in white. A significant amount of OTA was not recovered either from wine or from MEL.

Effect of antioxidant protection of must on volatile compounds and aroma shelf life of Falanghina (Vitis vinifera L.) wine.

Two vinification methods involving different degrees of antioxidant protection of Falanghina must during prefermentative steps, and referred as HAMP (high antioxidant must protection) and LAMP (low antioxidant must protection), were compared in terms of fermentation performances of four different yeast strains, composition of the volatile fraction of wines at the end of alcoholic fermentation, and shelf life of wines during storage. The use of HAMP technology resulted in wines with lower volatile acidity and higher concentrations of medium-chain fatty acid ethyl esters, acetates, and volatile fatty acids. For two of the four strains a lower concentration of isoamyl alcohol was also observed. HAMP wines also revealed increased shelf life because of the higher concentration of odor active esters at the end of storage and better preservation of varietal aromas.

Influence of different pH values and inoculation time on the growth and malolactic activity of a strain of Oenococcus oeni

The present study was undertaken to evaluate the influence of medium pH and inoculation time on the growth and malolactic activity of an Oenococcus oeni culture. Samples of a commercial white grape juice adjusted to pH 3.2, 3.4 or 3.6, and inoculated with Saccharomyces cerevisiae strain CY3079, were inoculated with a malolactic culture (Oenococcus oeni strain 31) at the beginning, middle, and end of alcoholic fermentation. The results obtained from this single case study show that it is possible to inoculate the bacterial culture at the three different times during alcoholic fermentation without slowing down or stopping alcoholic fermentation or causing failure of MLF. However, pH and timing of bacterial inoculation were critical to how rapidly MLF starts. At pH 3.2 a lowering of bacterial viability was observed, but a more important reduction was recorded at all tested pH levels when the bacteria were inoculated halfway through alcoholic fermentation. When inoculation was carried out at the end of alcoholic fermentation, the presence of yeast seemed to favour bacterial viability and activity and bacteria performed MLF even in difficult conditions such as pH values around 3. In all wines malolactic fermentation was accompanied by total degradation of malic and citric acids and production of L-lactic acid, D-lactic and acetic acids.

Maintenance and Protection of Yeast Morphology by Contact with Wine Polyphenols During Simulation of Wine Aging on Lees

ABSTRACTScanning electron microscopy was used to monitor yeast cell morphology during simulated wine aging. Although yeast cells in lees in the absence of wine polyphenols rapidly reach a flat shape after the end of alcoholic fermentation, they keep a spherical (and almost intact) shape in the presence of wine polyphenols. We confirmed these visual observations by calculating the dynamic viscosity of the corresponding lees. Because yeast autolysis is not affected by the contact with wine polyphenols, such maintenance of yeast morphology maybe the consequence of protection of some constitutive parts of yeast cell walls by wine polyphenols toward the action of hydrolytic enzymes.

Use of encapsulated yeast for the treatment of stuck and sluggish fermentations

<p style="text-align: justify;">In this work, encapsulated whole cells of <em>S. cerevisiae</em> in calcium-alginate gel (<em>S. cerevisiae</em>-CAG) were used for the treatment of sluggish and stuck fermentation in vinification. <em>S. cerevisiae</em>-CAG can be applied into the must grape and then they can be withdrawn easily at the end of alcoholic fermentation. For the treatment of sluggish and stuck fermentations, <em>S. cerevisiae</em>-CAG were applied following two steps: firstly <em>S. cerevisiae</em>-CAG were introduced into permeable bags and they were activated in a liquid medium; secondly, after an activation period of eight hours, the immobilized yeast cells were introduced into the fermentation tank. In this work, the obtained results for the treatment of sluggish and stuck fermentations in several French and Portuguese wineries are presented. Preliminary results obtained in micro-vinification conditions have shown that the use of immobilized yeast was better than traditional method (which uses free cells) for the treatment of stuck and sluggish fermentations. The large success rate of immobilized yeast can be explained by one adaptation step of yeast cells to high ethanol concentrations during the immobilization process. The application of immobilized cells of <em>S. cerevisiae</em> under real conditions of vinification has shown a consumption rate of 2.8 g/L per day of reducing sugar with a concentration of 5 million of viable cells per mL. It was never observed any increase of the volatile acidity or of other undesirable compounds.</p>

The hexose transporters of Saccharomyces cerevisiae play different roles during enological fermentation.

We investigated the role of hexose transporters in a Saccharomyces cerevisiae strain derived from an industrial wine strain by carrying out a functional analysis of HXT genes 1-7 under enological conditions. A strain in which the sugar carrier genes HXT1-HXT7 were deleted was constructed and the HXT genes were expressed individually or in combination to evaluate their role under wine alcoholic fermentation conditions. No growth or fermentation was observed in winemaking conditions for the hxt1-7 delta strain. The low-affinity carriers Hxt1 and Hxt3 were the only carriers giving complete fermentation of sugars when expressed alone, indicating that these carriers play a predominant role in wine fermentation. However, these two carriers have different functions. The Hxt3 transporter is thought to play a major role, as it was the only carrier that gave an almost normal fermentation profile when produced alone. The hxt1 carrier was much less effective during the stationary phase and its role is thought to be restricted to the beginning of fermentation. The high-affinity carriers Hxt2, Hxt6 and/or Hxt7 were also required for normal fermentation. These high-affinity transporters have different functions: hxt2 is involved in growth initiation, whereas Hxt6 and/or Hxt7 are required at the end of alcoholic fermentation. This work shows that the successful alcoholic fermentation of wine involves at least four or five hexose carriers, playing different roles at various stages in the fermentation cycle.

Comparative Analysis of Concentrations of trans- and cis-Resveratrol in Must and Wine from Eleven Different Grapevines Grown in Hokkaido, Northern Japan.

It has been suggested that resveratrol (RT) has a protective effect against cardiovascular diseases. We analyzed the concentration of RT in must and wine samples made from nine varieties of red and two of white grapes grown in Hokkaido, Japan, by a combination of normal and reverse phase high-performance liquid chromatography. The sum of trans-and cis-RT concentrations in the must differed significantly among the grapes, ranging from 0.04 to 0.41 mg/L. After alcoholic fermentation, the RT concentrations in the red wines increased to 0.50∼2.76 mg/L due to maceration with skin, but those in the white ones scarcely changed. The ratios of trans-RT to the cis-form in the must samples were in the range of 3.0 to 12.0, but an increasing level of cis-RT was usually observed in the wine samples. In red wine samples, after malolactic fermentation, the RT concentrations were found to be increased 1.1-to 1.9-fold compared with those measured at the end of alcoholic fermentation. In contrast, the amounts of piceid (RT glucoside), quantified as the RT equivalent after β-glucosidase digestion, decreased in the wines. It was therefore assumed that the increase in RT might have resulted from the hydrolysis of piceid during malolactic fermentation.

Indução da fermentação maloláctica em vinho tinto com a cultura láctica viniflora oenos

A fermentação maloláctica é responsável pela redução da acidez total, muitas vezes elevada em vinhos tintos jovens, ao mesmo tempo que proporciona maior estabilidade biológica e complexidade de aroma e sabor. No Estado do Rio Grande do Sul, a fermentação maloláctica se torna uma necessidade devido a freqüente elevada acidez das uvas, no entanto a indução por inoculação bacteriana não tem sido prática comum. Este trabalho teve como objetivo principal avaliar o comportamento de uma cultura láctica na indução da fermentação maloláctica, em relação as bactérias nativas. Um mosto da Vitis vinífera Cabernet Sauvignon foi vinificado e inoculado com a cultura comercial de Leuconostoc oenos, Viniflora Oenos, em diferentes níveis de açúcar residual: 34,1 - 13,8 - 1,7 e 1,5g/l. As inoculações, com duas repetições, foram comparadas com a fermentação maloláctica espontânea (controle). A degradação do ácido málico foi acompanhada através de cromatografia em papel. Os ácidos orgânicos foram determinados através de cromatografia líquida de alta eficiência. Foram também analisados os açúcares redutores (AR), °Brix, pH, acidez total e álcool. Os vinhos inoculados no estádio 34,1 g/l AR fermentaram em 14 dias,enquanto os controles levaram em média 28,5 dias. Nos estádios com 13,8 e 1,7g/l AR, Viniflora Oenos completou a degradação do ácido málico em torno de 13 e 11 dias, enquanto os controles levaram 20,5 e 16,5 dias, respectivamente. No estádio 1,5g/l AR, os vinhos inoculados e os controles não demonstraram diferença significativa e fermentaram entre 8 e 10 dias. Viniflora Oenos completou a fermentação maloláctica em menos tempo que o controle, demostrando que a inoculação pode ser realizada antes do término da fermentação alcoólica com bons resultados. Na maioria dos tratamentos, não houve diferença significativa na produção de ácido acético entre a cultura e o controle. O comportamento dos ácidos málico, acético, láctico, pirúvico e tartárico foi demonstrado.

Resveratrol in Wine: Extraction From Skin During Fermentation and Post-fermentation Standing of Must From Gamay Grapes

Resveratrol (<i>cis</i>- and <i>trans</i>-isomers) was analyzed in skin, seeds and must of grape berries of Gamay from starting must to skin separation and in wine after malolactic fermentation. Its concentration increases in must while decreasing in skin and remains quite constant in seeds during alcoholic fermentation. Extraction from the skin correlates well with the increase of ethanol concentration in must up to day 6. After malolactic fermentation, the amount of resveratrol is about twice that measured at the end of alcoholic fermentation indicating a pool of resveratrol probably in the form of glucosides and (or) as on oligomeric form from which free resveratrol could be liberated by enzymatic activity of malolactic bacteria.

Lower Fructose Uptake Capacity of Genetically Characterized Strains ofSaccharomyces bayanusCompared to Strains ofSaccharomyces cerevisiae:A Likely Cause of Reduced Alcoholic Fermentation Activity

Four strains of the (sparkling) wine yeast <i>Saccharomyces bayanus</i> were identified and characterized by growth tests and chromosomal karyotyping. Physiological properties of these strains were determined in sugar uptake experiments performed with ¹⁴C-labeled glucose and fructose. The total uptake capacity of both sugars, glucose and fructose, varied from strain to strain. High sugar uptake seems to be correlated to the structure of hexokinase encoded sequences. At the end of fermentation all four strains had markedly lower fructose than glucose uptake capacities, which is in contrast to investigated <i>S. cerevisiae</i> strains. The lower fructose uptake capacity of <i>S. bayanus</i> towards the end of alcoholic fermentation with an excess of residual fructose may thus be responsible for the occurrence of decreased alcoholic fermentation activity.

Etude d'un nouveau procédé de déclenchement de la fermentation malolactique

&lt;p style="text-align: justify;"&gt;A method is described, by wich the malolactic fermentation is induced through direct inoculation with an industrial preparation of &lt;em&gt;L. plantarum&lt;/em&gt; (CHL2). When inoculated into must, this homofermentative lactobacillus metabolizes very little sugar, and is unable to produce acetic acid. The inoculated population of bacteria has a high malolactic activity even at low pH values, which is closely related to cell viability. The decarboxylation of malic acid starts immediately after inoculation and proceeds at a high rate during the first days of alcoholic fermentation. As the alcohol concentration rises, the lactobacilli are gradually eliminated, so inoculation with the malolactic culture has to be done very early in the vinification process, in order to achieve a complete malolactic fermentation. At the end of alcoholic fermentation, the malolactic fermentation is finished, and the bacterial inoculum has been completely killed of.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The efficiency of this new process is demonstrated in laboratory experiments and field trials with different types of must and different vinification procedures. The advantages of the method, which the winemakers would particularly appreciate, include the direct inoculation mode and considerable gain in terms of production time.&lt;/p&gt;

THE ANALYSIS OF BURGUND RED WINES POLYPHENOLS CONTENT OBTAINED IN MINIS AND MURFATLAR VINEYARDS

The researchers that were done regarded the evolution of phenolic compounds at superiors red wines from Burgund variety, obtained in Minis and Murfatlar vineyards during five years period of time. &#x0D; In the purpose to obtain extractive wines and intensely coloured, external enzymatic mixtures was experienced during the maceration and fermentative processes, and for some technological phases improvement for primary wine making process. &#x0D; During the hole period of study physical and chemical analyses were done to superior red wines obtained from Burgund variety, beginning with the end of alcoholic fermentation, malolactic fermentation, at 3 months, 6 months, 9 months, 12 months, 18 months and after that yearly, as for the wines obtained with external enzymatic mixtures used during the maceration – fermentation process, as for the one which weren’t treated with enzymes.&#x0D; Through external enzymatic mixtures utilisation the antocians and total poliphenols to superior red wines obtained is the biggest contribution which contribute the their quality improvement, especially to colours and extractive character.