Respiration rate and functional quality of rocket leaves as affected by passive modified atmosphere packaging

Fresh-cut wild rocket (Diplotaxis tenuifolia L.) represents a very interesting ready-to eat (RTE) product with a high market value. Scarce information is available on product freshness and on quality attribute deterioration during storage. The aim of this work was to evaluate the respiration rate and functional quality of rocket salad when packaged under passive atmosphere composition in two different permeability bags. Wild rocket was packaged on two different sealed polypropylene bags: macroperforated (P) and a non-permeable (NP) film bag. Bags were stored at 4°C during 15 days and the O2 and CO2 concentrations inside the bags, the respiration rate, the functional quality (ascorbic acid, phenolic compounds, anthocyanins, and chlorophyll) and microbial load of RTE rocket were evaluated at five different time points. Results showed that NP packages generated a passive modified atmosphere, with continuous decrease of O2 concentration (close to anaerobiosis by 14 days) and with increasing CO2 levels up to ca. 8 kPa after 5 days. Rocket preserved in this type of bag showed higher respiration rate in the first 2 days, when compared with rocket packaged in P bags. The evolution of carbon dioxide and oxygen concentration in both systems did not exhibit significant impact in the ascorbic acid and chlorophyll content. A positive effect of oxygen availability inside P packages was observed on total phenolic compounds and total anthocyanin concentration of rocket leaves, but simultaneously higher microbial contamination by day 5 in comparison with NP packages.