Effect of Wounding on Phenolic Enzymes in Six Minimally Processed Lettuce Cultivars upon Storage

9 pages, 6 figures, 4 tables.-- Online version published Nov. 2000.The effect of wounding on polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) was studied in six minimally processed lettuce (Lactuca sativa L.) cultivars upon storage for 7 days at 5 °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 time range from 3.7 days (LGS) to 6.3 days (RC). However, total PPO activity (active plus latent) remained constant. Isoform pattern of PPO changed upon storage probably because of posttranslational processes. POD activity linearly increased with induction of new POD isoenzymes. PAL activity presented a typical bell-shaped induction pattern in four cultivars. Only IM and IGQ showed a second induction response which has not been previously described in the literature. IM was the cultivar most susceptible to browning and RC was the cultivar least susceptible. However, no clear correlation was observed between browning and any of the biochemical and physiological attributes investigated (PPO, PAL, and POD activities, total and individual phenols accumulation, and ascorbic acid content).This work has been partially supported by a grant from the Comisión Interministerial de Ciencia y Tecnología (CICYT), Spain, project CICYT-ALI97-0681. E.C. is holder of a grant from the Movilidad de Investigadores y Tecnólogos program under the action Mit-Becas; Modalidad F2. J.C.E. is holder of a Marie Curie contract HPMF-CT-1999-00023 from the European Commission under the framework of the program titled Improving the Human Research Potential and the Socio-Economic Knowledge Base.Peer reviewe