Comparative proteomic analysis of wines made from Botrytis cinerea infected and healthy grapes reveal interesting parallels to the gushing phenomenon in sparkling wine

Abstract

In addition to aroma compounds also protein composition strongly influences the quality of wines. Proteins of wine derive mainly from the plant Vitis vinifera and may be influenced by abiotic stress as well as fermentation conditions or fining. Additionally, fungal infections can affect the protein content as well by introducing fungal proteins or affecting grape protein composition. An infection of the vine with the plant pathogenic fungus Botrytis (B.) cinerea was shown to cause a degradation of proteins in the resulting wine. Moreover, it influences the foaming properties in sparkling wine. The aim of this study was to compare the protein composition of B. cinerea infected and healthy grapes as well as of wines produced from such grapes in regard to proteins which might play a potential role in the gushing phenomenon of sparkling wine. Therefore, SDS-PAGE and reversed phase HPLC (RP-HPLC) were applied to analyze the protein composition of healthy and botrytized Weißburgunder grapes and the corresponding wines. The fungal infection led to a general decrease of the protein content in infected grapes and wines suggesting a proteolytic activity of B. cinerea. Especially the concentration of a protein with a molecular mass of ~17 kDa underwent a significant reduction in wine from infected grapes as compared to wine made from healthy grapes. Amino acid sequence analysis showed that this protein derives from Vitis vinifera. Other proteins were detected via SDS-PAGE and were shown to occur in the botrytized but not in healthy wines. These unidentified proteins were assumed to be related to the fungal infection, either as induced plant proteins or as proteins produced by the pathogen. Similar results were found when the proteome of non-gushing and gushing sparkling wines were compared. The protein content in gushing sparkling wines was much lower as compared to non-gushing sparkling wines when analyzed by SDS-PAGE and RP-HPLC. Furthermore, in gushing sparkling wine proteins of fungal origin can be found, whereas plant-associated pathogenesis related proteins were enriched in the non-gushing samples. The before mentioned protein (MW: ~17 kDa) was absent or at least reduced in gushing sparkling wine samples. Hence, an infection with B. cinerea led to several proteomic changes in grapes, which were still detectable in the wine made thereof. Degradation of plant proteins and occurrence of fungal proteins were also observed in gushing sparkling wines. These parallels suggest that gushing in sparkling wine might be affected by a degradation of proteins induced by an infection with fungal pathogens.