Quality changes of lamb’s lettuce during postharvest storage

Lamb's lettuce (Valerianella olitoria L. (Valerianella locusta (L.) Laterr.)) is one of the most important leafy vegetables used in the minimally processed industry. The aim of this work was to evaluate the quality changes of lamb's lettuce harvested from two different greenhouses in which organic fertilization was performed one or two years before. The lamb's lettuce was stored at 4 or 10°C for 12 days. The quality of the lettuce was evaluated by measuring ascorbic acid, anthocyanins, chlorophyll, carotenoids and phenols every three days. Stress conditions were determined by chlorophyll α fluorescence and ethylene production. JIP analysis was performed at the intermediate points of the fluorescence induction curve. Results showed that the higher storage temperature had only a slight effect on lamb's lettuce leaf quality. Storage had no effect on the ascorbic acid content, chlorophyll, carotenoids anthocyanins and total phenols. The ethylene concentration inside the bags increased with storage time. The ethylene levels were higher at 10°C, only in samples grown on soils fertilized with manure one year before. Among the calculated JIP indexes, the PI was able to highlight differences at harvest and during storage. The organic fertilization during the growing cycle affected the quality of the produce. Ascorbic acid content had higher levels in lamb's lettuce grown on soils fertilized one year before. Opposite results were observed for total phenols and anthocyanins.