EFFECT OF MINIMAL PROCESSING ON BOTH POLYPHENOL OXIDASE AND PEROXIDASE FROM LETTUCE UPON COLD STORAGE

摘要

The effect of wounding on both polyphenol oxidase (PPO) and peroxidase (POD) was studied in six minimally processed lettuce (Lactuca sativa L.) cultivars upon storage for 7 days at 4°C (Iceberg Mikonos (IM), I. Green Queen (IGQ), I. Asdrúbal (IA), Little Gem Sandra (LGS), Romaine Cazorla (RC) and R. Modelo (RM)). Wounding of lettuce tissue midribs (because of minimal processing) caused an exponential increase in PPO activity due to the activation process from latent to fully active PPO by following first order kinetics in the range time from 3.7 days (LGS) to 6.3 days (RC). However, total PPO activity (active + latent) remained constant. Isoform pattern of PPO changed upon storage probably due to post-translational processes. POD activity linearly increased with induction of new POD isoenzymes. IM was the most susceptible cultivar to browning and RC was the least. However, no clear correlation was observed between browning and PPO or POD activities.