Pathogenesis Related Proteins — Their Accumulation in Grapes during Berry Growth and Their Involvement in White Wine Heat Instability. Current Knowledge and Future Perspectives in Relation to Winemaking Practices

Abstract

Grape growing represents one of the world’s major horticultural enterprises with the vast majority of the production destined for further value-adding through winemaking. An important consideration of grape production is therefore how key constituents of the berry contribute positive and negative attributes to the final bottled wine product. One feature of wine, which is important to the perception of quality, is brilliance and clarity. The presence of “unstable” proteins ranges from 50 to 100 mg/L but occasionally up to several hundred mg/L (Koch and Sajak, 1959; Bayly and Berg, 1967; Somers and Ziemelis, 1973a; Hsu and Heatherbell, 1987a; Murphey et al., 1989; Yokotsuka et al.,1991; Dorrestein et al.,1995; Santoro, 1995; Pocock et al.,1998 a,b; Pocock et al.,1999), and their aggregation to form haze in white wine is a ubiquitous concern for winemakers. Protein haze formation can occur after bottling and is almost certainly due to the slow denaturation of wine proteins. This, in turn, leads to protein aggregation and formation of unattractive suspensions as well as amorphous cloudy precipitates (Paetzold et al., 1990; Waters et al., 1991). Regardless of the taste, consumers will in general reject wines containing hazes or cloudy precipitates due to fears of microbial spoilage having occurred.