QUALITATIVE AND PHYSIOLOGICAL RESPONSE OF MINIMALLY PROCESSED ROCKET (ERUCA SATIVA MILL.) TO PACKAGE FILLING AMOUNT AND SHELF-LIFE TEMPERATURE

Abstract

Rocket (Eruca sativa Mill.) is a leafy vegetable commonly used for the Mediterranean fresh-cut sector, marketed either single or in mix salads. The aim was to study the effect of package filling amount (50 g, 100 g) and storage temperature (4°C, 12°C) on the physiology and quality of minimally processed rocket during 10 days of shelf-life. The experiment was performed in October 2007. Rocket was grown in 60-cell styrofoam trays using a soilless culture system (ebb-and-flow irrigation system) in greenhouse. After harvest, samples were packaged in polypropylene film bags. Pigments content (chlorophyll and carotenoids), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) activity, ascorbic acid (AA) and dehydroascorbic acid (DHA), total phenolics (TP) content, and antioxidant capacity (AC) were analyzed both at harvest and during shelf-life (at 1, 3, 5, 10 days after packaging). Fresh weight (FW) loss was daily measured during shelf-life. Pigments content decreased over time mainly at 12°C. The total chlorophyll and carotenoids content decreased by 53 and 59%, respectively with 100 and 50 g of package filling amount. PAL, PPO and POD activities, which are tissue browning responsible, increased during shelf-life; however, the enzyme activity values were very low, probably because rocket is packaged and stored as whole canopy and the only possible wounding at the canopy level is the cutting for harvest. Thus, the reduced cut surface could limit the risk of tissue browning. After 10 days, AA decrease was greater at 12°C than at 4°C (47% vs. 32%) reaching 9.39 mg 100 g -1 FW, as it was converted to DHA that increased 6.5-fold the initial value reaching 32.12 mg 100 g -1 FW. TP and AC decreased over time at 12°C, while they did not change at 4°C. Even though the inherent quality of the rocket decreased during shelf-life, after 10 days the leaf turgor was not compromised since the fresh weight loss was less than 1%.