Changes in Chitinase and Thaumatin-like Pathogenesis-Related Proteins of Grape Berries during the Champagne Winemaking Process

Plant defense proteins (pathogenesis-related, or PR, proteins) have been implicated in allergenic reactions in humans. Grape PR-proteins are also known to be responsible for heat-induced haze and are susceptible to precipitation in the bottle. Changes in two defense proteins, a chitinase (CHV5) and a thaumatinlike (TL), were followed during the Champagne winemaking process, using Vitis vinifera L. cv. Pinot noir grape berries. Determination of chitinase activity indicated that the extraction yield of chitinases is at least 22% in the must with low pressing to make Champagne and that chitinase activity regularly diminishes during the winemaking process. SDS-PAGE electrophoresis of the must revealed that CHV5 and TL are the major proteins found in grape berries cv. Pinot noir. Using specific antibodies, changes in these two proteins during the Champagne winemaking process were followed. Western blotting indicated a regular disappearance of CHV5 and TL. TL did not seem to precipitate or hydrolyze but was absent in Champagne wine. CHV5 was likely fixed on the cell wall of Saccharomyces cerevisiae yeast (yeast lees) after alcoholic fermentation and on the cell wall of Oenococcus oeni bacteria after malolactic fermentation. Fragments of low molecular weight linked to CHV5 were observed, probably indicating that CHV5 had undergone proteolysis. This observation is in good agreement with the occurrence of an acid protease activity during the Champagne winemaking process.