Bromelain from pineapple stem in alcoholic–acidic buffers for wine application

Abstract

Bromelain from pineapple stem has been studied in unexplored model wine buffer (pH 3.2 tartaric acid and ethanol) in order to evaluate its applicability for white wine protein stabilisation. Bromelain proteolytic activity was studied against several synthetic peptide substrates in McIlvaine buffer covering a wide pH range. Among different synthetic substrates, Bz-Phe-Val-Arg-pNA turned out to be the most suitable one to test bromelain activity at the average minimum pH value of wine (3.2). The protease activity was significantly increased by the presence of 5 mM cysteine while no influence was exerted by EDTA. The inhibiting effect of ethanol was investigated in the range 0–25% (v/v), resulting in being rather limited at the average minimum concentration found in wine (10% v/v). The kinetic parameters were estimated in both McIlvaine (as reference) and model wine buffers. This study showed that stem bromelain worked well at the average minimum pH value of wine, and had a significantly higher activity in model wine buffer ( K a increased of 42%). These results are the basis for suggesting a future biotechnological application of this protease in winemaking.