Browning of fresh-cut lettuce as affected by preprocessing storage and heat treatments

Cut-surface browning is the major problem for fresh-cut lettuce and many treatments have been studied to control it. The aim of the present work was to investigate the effect of storage and heat treatment of plants before processing, on browning of fresh-cut lettuce. Harvested lettuce plants of two cultivars ('Plenty', butterhead and 'Robella', red oak leaf) were stored at 5°C for 0, 3 and 6 days before processing, while harvested lettuce plants of another two cultivars ('Morges', butterhead and 'Quattro stagione' red butterhead) were immersed for 0, 1.5 and 3 min in hot water (HW) at 45 and 50°C before processing. After the above treatments, leaves of each plant were cut vertically to the midrib into pieces of 2×4 cm (length × width), which then were kept in the dark at 10°C and relative humidity >95% and the degree of browning was evaluated subjectively the 3^rd and the 7^th day of storage. The results showed the storage of lettuce plants of two cultivars at 5°C for 3 and 6 days before their processing has no effect on browning of fresh-cut product. On the other hand, although browning was significantly reduced by all HW treatments, the most effective treatment was immersion of plants before processing for 3 min in HW at 50°C.