Bovine spongiform encephalopathy caused a situation of crisis leading the public and winemakers to lose their confidence in the use of gelatin as a fining agent and to reject animal proteins in general. Therefore, we started the search for a substitute for gelatin and egg protein by comparing gluten with these fining treatments currently used. This study concerned the fining of a Burgundy red wine (Rully, Controlled Appellation). For 6 g/hL, enzymatically hydrolyzed glutens (EHG) gave better efficiencies than deamidated glutens. The efficiency of the egg proteins treatment was situated between those of the hydrolyzed glutens and deamidated glutens. For 12 and 18 g/hL, turbidities of the wine treated by five glutens were 67 to 86% less than that of the control wine. Better results were obtained with egg proteins for short kinetics particularly. Wine fining with gluten was always better than gelatin treatments. The differences between the five glutens became very small when the dose incorporated in the wine increased. The volumes of lees generated by fining with gluten are situated between the values obtained with egg proteins and gelatin. After fining, immunodetection with gluten polyclonal antibodies failed to detect residual deamidated gluten.
Qualitative effects of Botrytis cinerea infection on a must protein fraction were studied by comparing the electrophoretic patterns of musts obtained from healthy grapes or from grapes highly infected by B. cinerea. Evidence was obtained that proteins secreted by B. cinerea can degrade grape proteins. Most of the proteins present in the healthy must, between 20 and 30 kDa and a major glycoprotein at 62/64 kDa, disappeared in the infected must. Moreover an immunochemical technique, using polyclonal antibodies raised against B. cinerea-secreted proteins, was developed to specifically detect proteins originating from B. cinerea in the infected must. This is of particular interest when considering that some of the grape proteins participate in the foaming properties of Champagne wines.
The objective of this study was to analyze the origin of proteins of a Chardonnay wine. Three various polyclonal antibodies raised against must, yeast, and bacteria proteins were produced. For microorganisms, only the secreted macromolecules were used. To this end, yeast and bacteria were cultured in a model medium under conditions close to those of winemaking. Results obtained using these specific antibodies indicate that most of the wine proteins came from grapes and many of them were glycoproteins. Some proteins of this Chardonnay wine came from the yeast; they were released during the alcoholic fermentation and consisted of high molecular weight mannoproteins. In contrast, no bacteria proteins were detected in this Chardonnay wine.
We describe here techniques to detect and quantify lysozyme in Pinot noir and Chardonnay Champagne wines. Using a dot-blot technique, lysozyme antibodies were able to recognize their antigens even when the concentration of lysozyme in wine was 75 mg/L. SDS-PAGE was the second technique used. After Coomassie Brilliant Blue (CBB) staining or antibody immunostaining was performed, the wine originating from the lysozyme-treated must gave only one band corresponding to the lysozyme. It is then possible to precisely determine the concentration of lysozyme in a must or a wine by densitometric measurement of this band. The control wine gave no band with the CBB staining, such as with the immunostaining. The quantification of lysozyme with HPLC is another useable technique because the lysozyme elution time is largely superior to that of all of the wine compounds. In wines, losses of lysozyme were higher when the enzyme was added at one time to the must (-34% for the Pinot noir and -37% for the Chardonnay) than when lysozyme is added in 2-fold both in the must and in the wine (around -26% for the two wines). The lowest diminution is observed when lysozyme was added to the wine only (-18%) in comparison to the addition to the must at 300 mg/L (-43%).
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