Protein evolution during the early stages of white winemaking and its relations with wine stability

Abstract

Background and Aims: Grape proteins are responsible for the appearance of haziness in white wines during storage after bottling. However, only a few studies have approached the analysis of the fate of must proteins throughout the alcoholic fermentation. This study aimed to systematically investigate the daily variations in protein type and content during the fermentation in order to understand its influence on hazing potential and to attain some basic information to improve the practical management of grape proteins involved in the hazing of white wines. Methods and Results: The evolution of total soluble protein and individual protein fractions was studied in samples taken before, during and after alcoholic fermentation of a white grape must. The results were then related to variations in protein instability as measured by the heat test. Both the quantity of soluble protein and the protein instability increased during fermentation and then decreased after 1-month storage of the wine. Protein composition did not vary during fermentation as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and anion exchange chromatography (AEC). However, variations in the relative proportions of the six protein fractions obtainable by AEC were noted in the different samples. The contribution of each AEC protein fraction to wine instability was determined by considering both the intrinsic instability and the relative quantity of each of the individual protein fractions in the wine. It was demonstrated that the grape thaumatin-like protein VVTL1, as identified by mass spectrometry, showed the largest increase during fermentation and accounted for almost 40% of the heat-induced haze of the final wine. Moreover, the decreased protein instability noted after one month storage of the wine could be attributed to the stabilizing effect of polysaccharides released by the yeast cells. Conclusions: The quantity and relative proportion of soluble proteins vary during and after the alcoholic fermentation, as does their heat instability in wine. Grape VVTL1, constituting a large proportion of the total proteins in wine, seems to play a major role in protein haze formation. The release of yeast polysaccharides is related to an increased heat stability of total wine protein, despite the increase in the relative proportion of their most unstable component VVTL1. Therefore, the hazing potential of a white wine seems to be affected by variations in the relative proportions of its macromolecular components occurring in the early stages of winemaking. Significance of the Study: This study addressed for the first time the issue of the protein changing during the fermentation of white wine. The results obtained here offer useful information to aid understanding of the contribution of individual proteins to white wine instability, which can be applied for the improvement of the winemaking process. AbbreviationsAEC anion-exchange chromatography; KDS potassium dodecyl sulfate; MS mass spectrometry; MW molecular weight, PAS periodic aci...

Effect of using bentonite during fermentation on protein stabilisation and sensory properties of white wine

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The challenging SO2-mediated chemical build-up of protein aggregates in wines

“…Although testing all protein fractions in wine and not individual ones, our work extends beyond this hypothesis since the aggregation of the major protein fraction was shown to be induced by the addition of sulfur dioxide at concentrations normally found in wines. Although we did not characterize the proteins present in fraction H5, it is well established in the literature that TLPs and chitinases are the most abundant proteins in wines (Marangon, Van Sluyter, et al, 2011;Monteiro et al, 2001;Vincenzi, Marangon, Tolin, & Curioni, 2011).…”

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“…Wine proteins are relatively small, with molecular weights (MWs) between 9.6 and 60 kDa, and acidic, with isoelectric points between 3.5 and 7.6 . The major proteins in wine are thaumatin‐like proteins (MW around 24 kDa), chitinases (MW around 30 kDa) and invertase (MW around 60 kDa) . However, all proteins do not contribute equally to the foaming properties of wines.…”