Wild wall rocket (Diplotaxis erucoides L.) leaves functionality and postharvest quality as affected by cut and cold storage

In the last few years, fresh-cut industry has largely spread due to the growing demand for ready-to-eat vegetables. Consumers are now searching for meals easy to prepare but, at the same time, they pay great attention to sensory quality and health-related properties. Among ready-to-eat food, rocket is highly appreciated as a salad vegetable. Moreover, it is a source of glucosinolates, carotenoids, and phenolic compounds, which are well-known as healthy phytochemicals and determinants of the nutraceutical quality of these species. The aim of this work was to evaluate the effects of cut on the quality and storability of white wall rocket (Diplotaxis erucoides L. 'Wasabi') leaves. White wall rocket was grown in hydroponics, and leaves were harvested at the commercial stage for the minimally processing industry. About 10 g of entire and cut leaves were placed in airtight jars and stored in dark conditions at 8±1°C for up to 7 days. The analysis of the headspace gas composition (CO2, O2, and RH%) was performed in each jar after 7 days of storage for estimating the respiration rate possibly induced by the cut. Chlorophyll a fluorescence-related parameters were measured in the entire and cut leaves, at harvest and after storage, in order to evaluate the possible changes in the efficiency of the photosystem II (PSII). Phenolic compounds were determined at harvest and after 7 days of storage as well. No significant difference was found in respiration-related parameters. The significant differences in all chlorophyll a fluorescence related-parameters, showed a progressive increase of stress conditions during storage, especially for cut leaves, at the end of the storage period. Moreover, a significant increment was found in the phenolic compounds (phenolic index) between samples at harvest and after the storage period. In conclusion, the results of the present work show the sensibility of chlorophyll a fluorescence related-parameters in detecting stress conditions of leaf tissues, and a strong correlation between stress condition and the increase of secondary metabolites.