Post-harvest performance of ready-to-eat wild rocket salad as affected by growing period, soilless cultivation system and genotype

Abstract

The present study focuses on the effect of growing period (autumn-winter and winter-spring), soilless cultivation system (floating system and ebb and flow system) and genotype (‘Naturelle’ and ‘Nature’) on the post-harvest performance of wild rocket salad.Changes in bio-physical characteristics (weight losses, main colour indices, the concentration of dry matter and chlorophylls), physiological characteristics (relative water content, osmotic potential, electrolytic leakage), antioxidant compounds (vitamin C, phenolic compounds, carotenoids), glucosinulates, and activity of antioxidant enzymes (CAT-catalase; APX-ascorbate peroxidase; SOD-superoxide dismutase; GR-glutathione reductase) were evaluated in wild rocket salad after 7 days of cold storage.Wild rocket salad grown under winter spring conditions and in a floating system was more prone to post-harvest quality decay as highlighted by higher electrolyte leakage and osmotic potential, and lower relative water content, greater weight losses due to respiration activity, and a rapid breakdown of colour to yellowness. A higher shelf-life of the product grown under less photo-thermal stressing condition (autumn-winter cycle) was attributable to less physiologically stressed raw material and to a rise in non-enzymatic antioxidant compounds, namely carotenoids, phenols, and vitamin C (ascorbic acid), all effective at contrasting oxidative stress during storage. The higher shelf-life of the product grown in an ebb and flow system (lower losses of mass and lower visual decay) and of ‘Nature’ (a higher retention of the green colour) under autumn-winter conditions, seems to be imputable both to a higher efficiency of antioxidant enzyme activity (APX and CAT) and to a greater content of antioxidant compounds, mainly carotenoids. The role of individual glucosinolates in delaying senescence was only observed as a genotype-specific response of ‘Nature’ to the root oxygen limitation occurring with the floating system.