Abstract
Shelf life of fresh-cut salad is limited by deterioration of quality characteristics during storage. The objective of this study was to assess the potential of the use of non conventional nitrous oxide gas in maintaining the quality of fresh-cut ‘Iceberg’ lettuce (Lactuca sativa L.) and Wild rocket (Diplotaxis tenuifolia) under modified atmosphere packaging (MAP) in comparison to nitrogen gas. Leaves of rocket and cut ‘Iceberg’ lettuce were washed, dried and packaged fresh in two different non-micro perforated plastic film bags (polypropylene+polyamide, PP+PA and polypropylene + polyethylene terephthalate, PP+PET). The headspace of each pair of two plastic films was filled and sealed with three gas mix treatment compositions: (97 % N2O + 3 % O2), (50 % N2O + 47 % N2 + 3 % O2) and (97 % N2 + 3 % O2) for “Iceberg lettuce” and two gas mix treatments: (95% N2O + 5 % O2) and (95 % N2 + 5 % O2) for rocket leaves. Lettuce and rocket leaves were stored over a period of 9 days and 12 days respectively at 5 oC. Results showed that the two plastic films maintained the nitrous oxide concentration within the bags, with some slight differences in O2 and CO2 concentrations. No significant differences (p<0.05) were observed in texture, colour, and sensory quality (off-odor, off-flavor, texture and overall acceptability). All treatments delayed microbial growth (mesophiles, yeast and mould, psychrophiles and enterobacteria) and compared to control in air, reduced weight losses in both rocket and lettuce. MAP treatments maintained very good quality and freshness of ‘Iceberg’ lettuce for 4 days. Slight increase in off-odor and off-flavor observed during storage were below the moderately acceptable limit even after 9 days. As for rocket, although quality characteristics of the leaves were lessening over the storage period, treatment with nitrogen gas in PP+PA bags seemed to maintain them slightly better than treatment with nitrous oxide gas. The results suggested that nitrous oxide gas does not improve quality compared nitrogen modified atmosphere storage.
