ENHANCEMENT OF POLYPHENOLIC COMPOUNDS IN READY-TO-EAT VEGETABLES BY POST-HARVEST UV-B APPLICATION

Low-dosage UV radiation is known to enhance the vegetable quality, improving their polyphenolic healthy-related content, during the growing period. We aimed at testing the occurrence of this process in postharvest by UV-B irradiation of ready-to-eat salads (RTES). Fresh leaves of RTES (lettuce - Lactuca sativa and rucola - Diplotaxis tenuifolia) in PET vessels, packed in BOPP bags, were submitted to two lightening conditions during 6-days of storage (144h): control (PAR = 20 ?mol m-2 s-1) and supplemental UV-B radiation (PAR + UV-B 9h/day for 3-days at 1-1.5 W m-2, followed by 3-days of PAR). Flavonols (FlavI) and chlorophyll (ChlI) indices were measured by the Multiplex® sensor each day from T0 to T144, when leaves were weighted and measured for their chlorophyll fluorescence. In the UV-B treated leaves of both species FlavI increased from T48 to T96, remaining high until T144. Therefore, UV-B triggered the production of UV-absorbing compounds that were maintained 72h after the end of the treatment. ChlI did not change throughout the storage, while the fresh weight decreased (1.5-4.5%), especially in lettuce due to a higher transpiration. The maximal (Fv/Fm) and actual (?PSII) efficiency of PSII photochemistry were maintained during the storage, indicating the lack of damage at the photosynthesis apparatus in both UV-treated and control samples. In conclusion, postharvest UV-B applications represent a promising tool to enhance the healthy-related compounds in RTES. Further analyses will be conducted to characterize the UV-induced polyphenolic profile and to evaluate their effect on the quality and shelf life of RTES vegetables.