Abstract
For the purpose of SO2 reduction and stabilizing ice wine, a new antibacterial technique was developed and verified in order to reduce the content of sulfur dioxide (SO2) and simultaneously maintain protein stability during ice wine aging process. Hazardous bacterial strain (lactic acid bacteria, LAB) and protein stability of Italian Riesling ice wine were evaluated in terms of different amounts of lysozyme, SO2, polyphenols, and wine pH by single-factor experiments. Subsequently, a quadratic rotation-orthogonal composite design with four variables was conducted to establish the multiple linear regression model that demonstrated the influence of different treatments on synthesis score between LAB inhibition and protein stability of ice wine. The results showed that, synthesis score can be influenced by lysozyme and SO2 concentrations on an extremely significant level (P < 0.01). Furthermore, the lysozyme-combined antibacterial system, which is specially designed for ice wine aging, was optimized step by step by response surface methodology and ridge analysis. As a result, the optimal proportion should be control in ice wine as follows: 179.31 mg L−1 lysozyme, 177.14 mg L−1 SO2, 0.60 g L−1 polyphenols, and 4.01 ice wine pH. Based on this system, the normalized synthesis score between LAB inhibition and protein stability can reach the highest point 0.920. Finally, by the experiments of verification and comparison, it was indicated that lysozyme-combined antibacterial system, which was a practical and prospective method to reduce SO2 concentration and effectively prevent contamination from hazardous LAB, can be used to stabilize ice wine during aging process.
Highlights
Wine is a product made from a series of complex metabolism processes driven by different microbial species
In the absence of oxygen yeast converts the sugars of wine grapes into alcohol and carbon dioxide through the process of alcoholic fermentation (AF), and lactic acid bacteria (LAB) are in charge of decarboxylation of L-m alic acid to form L -lactic acid which provides the elegant and round taste during malolactic fermentation (MLF) (Tchelistcheff et al 1971; Ribéreau- Gayon et al 2006; Lopez et al 2009)
150 mg L−1 lysozyme significantly affected LAB activity, which reduced by 57.3% as comparing with 100 mg L−1 lysozyme
Summary
Wine is a product made from a series of complex metabolism processes driven by different microbial species. Among these species, yeast and lactic acid bacteria (LAB) are the most important microorganisms initially present in vineyards and thrive throughout fermentation until packaging (Ribéreau-G ayon et al 2006). In the absence of oxygen yeast converts the sugars of wine grapes into alcohol and carbon dioxide through the process of alcoholic fermentation (AF), and LAB are in charge of decarboxylation of L-m alic acid to form L -lactic acid which provides the elegant and round taste during malolactic fermentation (MLF) (Tchelistcheff et al 1971; Ribéreau- Gayon et al 2006; Lopez et al 2009). Several LAB species, such as L. brevis, L. plantarum, and P. damnosus could elicit negative effects on wine quality (Fugelsang and Edwards 2006). Because of broad-spectrum antimicrobial and antioxidant activities, sulfur dioxide (SO2) is always regarded as a conventional and effective preservative which is necessary for LAB inhibition and MLF control in winemaking
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