Controlled atmosphere preserves quality and phytonutrients in wild rocket (Diplotaxis tenuifolia)

Leaves of wild rocket (Diplotaxis tenuifolia (L.) DC.) are increasingly eaten alone or as part of mixed salads. This species contains a wide range of health-promoting phytonutrients including vitamin C and flavonoids. The effect of controlled atmosphere (CA) containing low oxygen and high carbon dioxide on the sensory and microbiological quality, flavonoids, vitamin C (ascorbic acid + dehydroascorbic acid; AA + DHAA) and antioxidant capacity evaluated by ABTS, DPPH and FRAP assays was studied. Rocket leaves stored in air were compared with those kept in 5 kPa O2 + 5 kPa CO2, 5 kPa O2 + 10 kPa CO2 and enriched air with 10 kPa CO2 for up to 14 days at 4 °C. After 10 days, the sensory and microbiological quality of samples stored in air were not commercially acceptable. On the contrary, CA of 5 kPa O2 + 10 kPa CO2 maintained visual quality and controlled aerobic mesophilic and psychrotropic microorganisms as well as coliforms. The total flavonoid content of wild rocket was approximately 100 mg 100 g−1 fresh weight and remained constant during storage or even increased at the end of the shelf-life in CA, but it was degraded in those samples kept in air. In addition, AA was transformed into DHAA during storage, and the total content of vitamin C was higher in CA-stored samples than those kept in air. A decrease in the total antioxidant capacity was observed during storage and it was particularly marked in samples stored in air. A positive correlation was demonstrated between antioxidant capacity and vitamin C content, whereas a poor correlation was observed with total phenolics. Our data indicate that wild rocket leaves has potential as a good dietary source of phytonutrients when stored under optimal conditions.