Polymerization of proanthocyanidins catalyzed by polyphenol oxidase from lotus seedpod.

摘要

This study aimed to investigate the profiles change in proanthocyanidins (PAs) catalyzed by polyphenol oxidase (PPO) from lotus seedpod in a model wine system (MWS). Results showed that PAs from lotus seedpod consisted of dimer (74.00 %) and trimer (22.75 %). PPO could tolerate ethanol concentrations below 20 % (v/v). The optimum temperature of PPO activity was 80 degrees C, and the optimal pH was 9.0. Its molecular weight was approximately 31 kDa, and its secondary structures were alpha-helix (59.0 %), beta-sheet (4.3 %), turns (14.1 %), and random coils (22.6 %). In the MWS, the trimers gradually increased from 22.55 % at 0 h (control) to 100 % at 10 h incubation, while the dimers decreased from 74.33 % (control) to 0 % at 10 h incubation. Moreover, the composition of the precipitate formed at different incubation time points was approximately 16.54 % of monomers, 21.03 % of dimers, and 62.43 % of trimers at 2 h incubation with PPO. The results from this study have provided in vitro evidence for a possible application of PPO in red wine aging