OXIDASES ACTIVITIES AND ANTIOXIDANT CAPACITY OF MINIMALLY PROCESSED BABY ROMAINE LETTUCE (Lactuca sativa L. CV. DUENDE) CULTIVATED UNDER DIFFERENT SALINITY CONDITIONS

Browning reactions caused by polyphenol oxidase (PPO) and peroxidase (POD) represent the main cause of shelf-life reduction in minimally processed leafy vegetables. Changes in oxidative activities, as well as in total phenolic content, colour parameters and antioxidant capacity (assayed with ORAC method), were monitored during 15 days of storage at 4 °C of minimally processed baby romaine lettuce (Lactuca sativa L. cv. Duende) cultivated under 3 different salinity conditions (2.8, 3.8, 4.8 dS/m), in order to determine the most suitable condition for further processing. Increasing levels of salinity reduced both oxidases activities immediately after cutting and throughout 7 days of storage. Samples cultivated under high salinity had also the lowest change in colour, expressed as E, and showed the greatest increasing trend in total phenolic content and antioxidant capacity after 3 days of storage. POD seemed to be better correlated with browning of samples than PPO, since its activity rose 3 times in all samples between day 3 and 7 of storage.