Nitrogen fertilisation determines the shelf-life of fresh-cut rocket leaves

Fresh-cut rocket leaves are highly valued in the European ready-to-eat salad market, but their short shelf-life remains one of their main limitations.

A study published in the Journal of the Science of Food and Agriculture analyses how nitrogen rates applied before harvest influence the postharvest quality, food safety and shelf-life of rocket leaves (Diplotaxis tenuifolia L. cv. Dallas).

The research evaluated plants grown in soilless substrate under greenhouse conditions and irrigated with nutrient solutions containing six nitrogen concentrations, ranging from 0.005 to 0.015 mol L⁻¹. After harvest, the leaves were stored at 5 ºC in clamshell containers under passive modified atmosphere packaging and 99% relative humidity for 18 days. During storage, parameters such as vitamin C, chlorophyll, firmness, microbial load and sensory acceptability were monitored.

Moderate nitrogen rates help preserve quality

The results show that low to moderate nitrogen levels led to higher vitamin C content and better sensory quality. In contrast, higher nitrogen rates, above 0.013 mol L⁻¹, accelerated nutrient loss and exceeded European nitrate safety limits.

The study concludes that moderate fertilisation, especially between 0.005 and 0.007 mol L⁻¹, helps preserve postharvest quality while complying with regulations, supporting more sustainable agricultural practices.

Excess nitrogen shortens shelf-life

According to the authors, preharvest nitrogen fertilisation significantly affects the quality, safety and shelf-life of fresh-cut rocket leaves. The kinetic models developed in the study showed that high nitrogen supply accelerated chlorophyll and sensory degradation, reducing shelf-life to approximately 7.6 days. In contrast, nitrogen levels of 0.005 to 0.009 mol L⁻¹ maintained sensory acceptability for up to 17.8 days.

These results confirm that nitrogen management influences not only crop yield, but also product stability during storage. The study highlights that moderating nitrogen inputs can help reduce postharvest losses, increase product value and lower the environmental burden associated with excessive fertiliser use.

Sources

Journal of the Science of Food and Agriculture, article “Degradation kinetics of postharvest quality attributes of rocket leaves grown under different nitrogen rates”, by Aysha Saleem, Maria Luisa Amodio, Pramod V. Mahajan, Maria Gonnella, Lucia Bonelli and Giancarlo Colelli.