Heat-induced tolerance to internal browning of pineapple (Ananas comosus cv. 'Mauritius') under cold storage.

摘要

A study was conducted to evaluate the ability of postharvest hot water treatment to induce cold tolerance in pineapple fruit to reduce the development of internal browning during prolonged cold storage. Pineapple (cv. Mauritius) fruit, under low temperature (10 degrees C) and 85% RH storage, developed internal browning symptoms. Fruit acidity, polyphenol oxidase and peroxidase enzyme activities increased sharply, and phenylalanine ammonia-lyase activity increased slightly during low temperature storage, concurrent with the development of internal browning. Harvesting fruit early reduced both the incidence and severity of internal browning. Postharvest heat treatment, in the form of a hot water dip, induced pineapple fruit tolerance to cold injury and, in turn, reduced internal browning during prolonged low temperature storage. Several temperature-time combinations were effective, but the best was 38 degrees C for 60 minutes. Pineapple fruits treated at 38 degrees C for 60 minutes developed 70 and 45% less browning than the untreated controls in the flesh and core regions, respectively. The results also indicate that an internal tissue temperature of 37 degrees C is a prerequisite for the induction of cold tolerance. Heat treatment, however, slowed down fruit ripening and increased water loss. Wrapping heat-treated fruits in polyethylene, exposing only the crown, prior to cold storage reduced internal browning by a further 10% and water loss by 8.5%, giving fruit a better appearance..