ABSTRACT
The protein instability with haze formation represents one of the main faults occurring in white and rosé wines. Among the various solutions industrially proposed, aspergillopepsin I (AP-I) supplementation coupled with must heating (60-75 °C) has been recently approved by OIV and the European Commission for ensuring protein stability of wines. This study investigates the impact of AP-I either applied independently or in combination with flash pasteurization on the chemical composition of grape must and wines derived from Sauvignon Blanc and Gewürztraminer. The efficacy on protein stability of a complete treatment combining heat (70 °C) and AP-I (HP) was confirmed through heat test and bentonite requirement, although no differences were observed between must heating and HP treatments. However, high-performance liquid chromatography analysis of unstable pathogenesis-related proteins revealed that AP-I supplementation reduced chitinases and thaumatin-like proteins compared to the non-enzymed samples, with and without must heating. Amino acid increase was reported only in HP musts, particularly in Sauvignon Blanc. The concentration of yeast-derived aroma compounds in Gewürztraminer wines was increased by must heating; compared to controls, flash pasteurization rose the overall acetate esters content of 85 % and HP of 43 %, mostly due to isoamyl acetate. However, heat treatments -with or without AP-I- reduced terpenes up to 68 %. Despite the different aroma profiles, no differences were observed for any descriptor for both varieties in wine tasting, and only a slight decrease trend was observed for the floral intensity and the typicality descriptors in heated wines.
