Degradation kinetics of postharvest quality attributes of rocket leaves grown under different nitrogen rates

Diplotaxis tenuifolia L. cv Dallas (rocket leaves) is one of the most widely consumed fresh-cut salad vegetables in Europe, especially in southern Italy, being appreciated for its pungent taste and health promoting phytochemicals. However, its short postharvest shelf-life is still a major drawback. In this study rocket plants were grown in pots using a soilless peat/perlite substrate (3:1, v/v) under glasshouse conditions and irrigated with nutrient solutions containing six nitrogen (NO₃ ^- and NH₄ ⁺) concentrations (0.005-0.015 mol L^-1) and the quality characteristics and shelf-life of rocket leaves were evaluated. Samples were kept at 5 °C in passive modified atmosphere packaging with clamshells in 99% relative humidity for 18 days. Quality parameters such as vitamin C, chlorophyll, firmness, microbial load (mesophilic aerobic bacteria, yeasts and moulds) and general sensory acceptability parameters were monitored at regular intervals. Degradation kinetics were explained by primary (first-order and lag-exponential) and secondary models and predicted sensory shelf-life at a threshold score value 3 for marketability.

Results showed that low to moderate nitrogen levels had significantly higher vitamin C content and sensory quality. In contrast, greater nitrogen levels (> 0.013 mol L^-1) promoted nutrient loss at faster rates and surpassed the European safety levels for nitrates. Shelf-life prediction models showed that they fit well (R² > 0.90) and indicated a trade-off between quality preservation and nitrate safety.

Moderate nitrogen fertilization (corresponding to 0.005-0.007 mol L^-1) favoured both the quality retention and the compliance with the regulations, in favour of sustainable agricultural practices. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.