Can Pawpaw Fruit be Cold-stored for Extended Periods?

Pawpaw [Asimina triloba (L.) Dunal] is a highly perishable climacteric fruit, softening rapidly once ripening commences which may limit its marketability. In studies to determine the optimum cold storage temperature and maximum storage life of the fruit, pawpaw fruit were stored at -2, 2, and 6 °C for 1, 2, 4, 8, and 12 weeks, and then ripened upon removal to ambient temperature. Through 4 weeks, fruit exhibited adequate firmness upon removal from cold storage, but at 8 and 12 weeks fruit held at 2 and 6 °C were very soft. Irrespective of storage temperature, at 8 weeks fruit showed a delay in a climacteric-like respiratory increase, and by 12 weeks a respiratory climacteric was not apparent. An ethylene climacteric was evident after all temperature and storage periods except those held at 6 °C for 12 weeks. Significant symptoms of cold injury were found by 8 weeks of 2 °C cold storage. In addition to a delayed respiratory climacteric, pawpaw fruit stored for 8 and 12 weeks exhibited flesh browning within 48 h of moving to ambient temperature. A change in fruit aroma volatile profile suggested injury might have been developing by 4 weeks of cold storage even though other symptoms were not evident. Immediately after harvest, methyl octanoate was the dominant volatile ester followed by methyl hexanoate. By 4 weeks of postharvest cold storage, ethyl hexanoate was the dominant ester followed by ethyl octanoate, but methyl octanoate production was still substantial. At 8 weeks, volatile ester production was generally lower with ethyl hexanoate the major volatile followed by ethyl octanoate. These symptoms indicate that pawpaw fruit can suffer cold injury during extended periods of cold storage.