Qualitative and physiological response of minimally processed garden cress (Lepidium sativum L.) to harvest handling and storage conditions

Author: Li Juan Zhan, Emanuela Fontana, Giorgio Tibaldi and Silvana Nicola ^*

Received 6 May 2009, accepted 28 September 2009.

Abstract

Garden cress (Lepidium sativum L.) has become a new leafy vegetable for the fresh-cut sector. The objective of this work was to study the effects of harvest handling practices (packaged immediately after harvest, S₀; packaged after 1 h of storage at 28°C, S₁) and storage conditions (light; dark) on the physiology and quality of minimally processed garden cress stored at 4°C for five days. Phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) activity, pigments, ascorbic acid (AA) and dehydroascorbic acid (DHA), total phenolics (TP) content, and antioxidant capacity (AC) were analyzed at pre-processing and at 1, 3 and 5 days after packaging. Fresh weight (FW) loss during shelf-life was measured daily. The S₁ harvest handling practice significantly influenced the pigments content which decreased over time, thus highlighting the importance of starting the cold chain as early as possible. PAL changed significantly over time, increased rapidly by 24.5% one day of shelf-life and then leveled off. At preprocessing, the PPO was higher in the S₁ samples than in the S₀ samples, indicating that the S₁ treatment could have induced PPO activity. PPO increased more over time under light than under dark conditions. POD was significantly influenced by both the harvest handling technique and the storage condition over time. POD was higher in the S₁ samples than in the S₀ samples (4.792 and 3.742 ±0.268 ∆A_λ min^-1 g^-1FW, respectively). It increased over time and reached a maximum value earlier under dark than under light conditions. The harvest handling technique significantly influenced the AA and DHA content over time. The S₁ treatment caused ca 13% loss in AA before packaging. AA decreased and DHA increased during shelf-life. The TP content was significantly influenced by the interaction between the harvest handling technique and storage condition over time. The greatest TP content increase was measured in the S₀ samples and in particular in samples stored under light conditions (33.5%). The AC significantly changed over time. Like TP, the AC increased from pre-processing to the first day of shelf-life, and then started to gradually decrease, reaching a reduction of 16.0% of the initial value after five days. The fresh weight loss was minimal (0.21%) at the end of shelf-life. An efficient and rapid harvest handling and storage implementation proved fundamental to reduce quality deterioration during shelf-life.