DCMC as a Promising Alternative to Bentonite in White Wine Stabilization. Impact on Protein Stability and Wine Aromatic Fraction

Protein haze in white wine is one of the most common non-microbial defects of commercial wines, with bentonite being the main solution utilized by the winemaking industry to tackle this problem. Bentonite presents some serious disadvantages, and several alternatives have been proposed. Here, an alternative based on a new cellulose derivative (dicarboxymethyl cellulose, DCMC) is proposed. To determine the efficiency of DCMC as a bentonite alternative, three monovarietal wines were characterized, and their protein instability and content determined by a heat stability test (HST) and the Bradford method, respectively. The wines were treated with DCMC to achieve stable wines, as shown by the HST, and the efficacy of the treatments was assessed by determining, before and after treatment, the wine content in protein, phenolic compounds, sodium, calcium, and volatile organic compounds (VOCs) as well as the wine pH. DCMC applied at dosages such as those commonly employed for bentonite was able to reduce the protein content in all tested wines and to stabilize all but the Moscatel de Setúbal varietal wine. In general, DCMC was shown to induce lower changes in the wine pH and phenolic content than bentonite, reducing the wine calcium content. Regarding which VOCs are concerned, DCMC produced a general impact similar to that of bentonite, with differences depending on wine variety. The results obtained suggest that DCMC can be a sustainable alternative to bentonite in protein white wine stabilization.

Potential Contribution of Climate Change to the Protein Haze of White Wines from the French Southwest Region

The aim of this study was to evaluate the role played by climatic conditions during grape ripening in the protein instability of white wines produced in the French southwest region. For this purpose, basic wine analyses were carried out on 268 musts and the corresponding wines, all produced during the 2016, 2017, 2018, and 2019 vintages, with distinctive climatic conditions. Qualitative and quantitative variables were correlated with levels of protein haze determined by heat test (80 °C/2 h) in the wines using analysis of covariance (ANCOVA), principal component analysis (PCA), and classification and regression trees (CART). Our results show that the climatic change, with the increase in temperatures, and the decrease in precipitation during the grape ripening phase, tends to enhance the risk of protein instability in wines. Indeed, the values of pH, titratable acidity, and malic acid concentrations of the musts, which are good indicators of the conditions in which the grapes ripened and of the level of ripeness of the grapes, were also the variables that correlated best with the protein haze. By measuring these parameters at harvest before alcoholic fermentation, it may be possible to predict the risk of protein haze, and thus early and precisely adapt the stabilization treatment to be applied.

Sustainable Replacement Strategies for Bentonite in Wine Using Alternative Protein Fining Agents

Protein stability is an important quality attribute in wines and protein haze will lead to consumer rejection. Traditionally, stability is achieved by bentonite addition; however, environmental concerns and disposal problems mean that alternatives are required to achieve the same goal. In this study, the use of Sacharomyces paradoxus, chitosan, polystyrene, carboxymethyl cellulose, and bentonite were evaluated. Trials in finished wines were agitated for 10 h overnight and analyzed for turbidity and color characteristics spectrophotometrically. Experiments were conducted with wines that are expected to develop protein instabilities, Muscat Canelli, White Zinfandel, Cabernet Sauvignon blanc de noir, Barbera rosé, and Touriga Nacional. Results indicate that S. paradoxus can help with the removal of proteins from wine. Wines with low protein instability can be stabilized with S. paradoxus as well as polystyrene and chitosan to a lesser degree. All fining agents except for bentonite show efficiency variability between white and red wines. With an average protein reduction around 50%, none of the alternative fining methods could reach the efficiency level of bentonite. Experiments in a model system confirm the findings and explain some of the mechanisms involved, for example the specificity of chitosan and challenges related to the use of yeast as a fining agent.

Protection of Wine from Protein Haze Using Schizosaccharomyces japonicus Polysaccharides

Nowadays commercial preparations of yeast polysaccharides (PSs), in particular mannoproteins, are widely used for wine colloidal and tartrate salt stabilization. In this context, the industry has developed different processes for the isolation and purification of PSs from the cell wall of Saccharomyces cerevisiae. This yeast releases limited amounts of mannoproteins in the growth medium, thus making their direct isolation from the culture broth not economically feasible. On the contrary, Schizosaccharomyces japonicus, a non-Saccharomyces yeast isolated from wine, releases significant amounts of PSs during the alcoholic fermentation. In the present work, PSs released by Sch. japonicus were recovered from the growth medium by ultrafiltration and their impact on the wine colloidal stability was evaluated. Interestingly, these PSs contribute positively to the wine protein stability. The visible haziness of the heat-treated wine decreases as the concentration of added PSs increases. Gel electrophoresis results of the haze and of the supernatant after the heat stability test are consistent with the turbidity measurements. Moreover, particle size distributions of the heat-treated wines, as obtained by Dynamic Light Scattering (DLS), show a reduction in the average dimension of the protein aggregates as the concentration of added PSs increases.

Use of gallotannin preparations of different origin in winemaking

Изменения климата нашей планеты приводят к существенным сдвигам качественного состава и количественного содержания компонентов сусла и вина, в т.ч. белковых веществ, принимающих участие в формировании помутнений коллоидной природы. Ранее нами доказано, что высокомолекулярные белки не взаимодействуют с бентонитом и остаются в виноматериале после его обработки. Для удаления таких протеинов необходимо применение галлотанина. Поступление на рынок вспомогательных материалов для виноделия продуктов разного происхождения диктует необходимость изучения их стабилизирующего действия. Исследовано 3 препарата галлотанина: W (из галловых орешков, Китай), W (из галловых орешков, Сирия), W (из стручков дерева Тара, Южная Америка). Исследования проводили на модельных системах - в столовый сухой виноматериал, из которого удалены бентонитом собственные протеины, вносили белки с различной молекулярной массой (лизоцим, яичный альбумин, бычий сывороточный альбумин). В работе использовали таниновый (ТТ) и экспрессный тесты (ЭТ). Установлено, что все препараты активно взаимодействуют с внесенными белками, способность связывать высокомолекулярные протеины более выражена у галлотанинов W и W. Показано, что схемы обработки (1 - бентонит; 2 - желатин-бентонит) не достигают розливостойкости виноматериалов к белковым помутнениям. Применение схемы 3 (галлотанин-желатин-бентонит) обеспечивает стабильность готовой продукции (значения тестов 0,1-0,6 формазинных единиц (ф.е.)). На основании результатов технологической обработки производственных партий виноматериалов установлены дозы вспомогательных веществ в зависимости от показаний тестов. Climate change in our planet leads to significant shifts in the qualitative composition and quantitative content of must and wine components, including proteic substances involved in the formation of haze of colloidal nature. We previously proved that high molecular proteins do not interact with bentonite and remain in the wine material after processing. The use of gallotannin is necessary for removal of such proteins. Presentation on the market of auxiliary materials for winemaking products of different origin dictates the necessity to study their stabilizing action. Three gallotannin preparations were studied: W (from gall nuts, China), W (from gall nuts, Syria), W(from the seedpods of the Tara tree, South America). The studies were carried out on the model systems - proteins with different molecular weight (lysozyme, ovalbumen, bovine albumen) were introduced into table dry wine material with previously removed with bentonite their own proteins. We used tannin (TT) and rapid (RT) tests. It was found that all preparations strongly interact with introduced proteins, the ability to bind high molecular proteins is more expressed in gallotannins W and W. It was shown that treatment schemes (1 - bentonite; 2 - gelatin-bentonite) do not achieve the bottling stability of wine materials to protein haze. The use of scheme 3 (gallotannin-gelatin-bentonite) ensures the stability of the finished product (test values 0.1-0.6 formazine units (f.u.)). Based on the results of technological processing of production batches of wine materials, the amount of additives was established depending on test results.

Yeast Cell Wall Chitin Reduces Wine Haze Formation

ABSTRACT Protein haze formation in bottled wines is a significant concern for the global wine industry, and wine clarification before bottling is therefore a common but expensive practice. Previous studies have shown that wine yeast strains can reduce haze formation through the secretion of certain mannoproteins, but it has been suggested that other yeast-dependent haze protective mechanisms exist. On the other hand, the addition of chitin has been shown to reduce haze formation, likely because grape chitinases have been shown to be the major contributors to haze. In this study, Chardonnay grape must fermented by various yeast strains resulted in wines with different protein haze levels, indicating differences in haze-protective capacities of the strains. The cell wall chitin levels of these strains were determined, and a strong correlation between cell wall chitin levels and haze protection capability was observed. To further evaluate the mechanism of haze protection, Escherichia coli -produced green fluorescent protein (GFP)-tagged grape chitinase was shown to bind efficiently to yeast cell walls in a cell wall chitin concentration-dependent manner, while commercial chitinase was removed from synthetic wine in quantities that also correlated with the cell wall chitin levels of the strains. Our findings suggest a new mechanism of reducing wine haze, and we propose a strategy for optimizing wine yeast strains to improve wine clarification. IMPORTANCE In this study, we establish a new mechanism by which wine yeast strains can impact the protein haze formation of wines, and we demonstrate that yeast cell wall chitin binds grape chitinase in a chitin concentration-dependent manner. We also show that yeast can remove this haze-forming protein from wine. Chitin has in the past been shown to efficiently reduce wine haze formation when added to the wine in high concentration as a clarifying agent. Our data suggest that the selection of yeast strains with high levels of cell wall chitin can reduce protein haze. We also investigate how yeast cell wall chitin levels are affected by environmental conditions.