Polyphenol composition and qualitative characteristics of fresh-cut lettuce in relation to cultivar, mulching, and storage

The characteristics and nutritional quality of fresh-cut vegetable products during shelf-life depend on the raw material as well as on pre- and post-harvest factors. In this work, three of the commercially most widespread lettuce cultivars ('Montego', 'Great Lakes 118' and 'Salad Bowl'), characterised by different qualitative traits, were cultivated under two different conditions, processed using standard conditions for fresh-cut lettuce, packaged in plastic trays and stored for 9 d at 5 degrees C. Visual and texture analyses were performed, with determinations of polyphenol composition and of anti-oxidant activity. The results showed that the concentration of polyphenols was different in the three varieties, and was highest in 'Salad Bowl'. The main polyphenols found were chlorogenic acid and kaempferol-3-O-glucoside in 'Montego', chlorogenic acid and quercetin-3-O-glucoside in 'Great Lakes', and kaempferol-3-O-glucoside, rutin and dicaffeoyltartaric acid in 'Salad Bowl'. The practice of mulching during the growing period leads to an increase in yield; moreover, it also affects the total quantity of polyphenols, but not the qualitative pattern of polyphenols formed in each variety. During storage, a deterioration in sensory characteristics was observed, but this was not accompanied by any significant change in polyphenol content.