Shelf-life of rocket leaves stored in argon enriched atmospheres

The aim of this work was to monitor the effect of storage in non-conventional modified atmospheres on sensory, nutritional, and microbiological quality of rocket leaves during refrigerated storage. Rocket leaves (Diplotaxis tenuifolia) processed according to industry procedures were stored for 10 days in a humidified flow of air (as a control), and of the following atmosphere mixtures: 97% Ar + 3% O2, 50% Ar + 3% O2 (in nitrogen), and 3% O2 (in nitrogen). The effect of atmosphere composition on respiration rate was evident only at 6 days of storage when both Ar-enriched atmospheres were more effective than air and 3% O2 in nitrogen in slowing down respiration rate. Moreover, Ar-enriched atmospheres were more effective in controlling color changes of the leaves, as resulted by a lower hue angle variation at 10 days of storage, compared to 3% O2, whereas samples stored in air showed intermediate variation. The gas mix 50% Ar + 3% O2 induced an increase of phenolic compounds, which was higher than in those stored in 97% Ar + 3% O2, the latter also showing a sensible decrease after 10 days of storage. As for microbial control, the atmospheres with 50% Ar + 3% O2 and 3% O2 (in nitrogen) showed lowest microbial counts, after 10 days of storage. Moreover, samples stored in 50% Ar + 3% O2 showed the lowest yeast and mould growth rate after 10 days. There was no significant difference for quality parameters such as texture, antioxidant capacity and ascorbic acid. In conclusion, results obtained indicated a slight benefit induced by the atmosphere with 50% Ar + 3% O2 compared to conventional modified atmosphere with 3% O2 in nitrogen, although further investigations are needed to confirm these findings.