Temperature of water heat treatments influences tomato fruit quality following low-temperature storage

Mature-green tomato fruit (Lycopersicon esculentum Mill. cv. Sunbeam) were treated in water for 1 h at 27 (ambient), 39, 42, 45, or 48 degrees C, and then either ripened at 20 degrees C (nonchilled) or stored at 2 degrees C (chilled) for 14 days before ripening at 20 degrees C. Treatment at 42 degrees C reduced decay by 60%, whereas the other water temperatures were less effective. Heat treatment had no effect on time required to ripen the fruit, with 11 days required for nonchilled and 27 days required for chilled fruit (including storage time). Ripe, nonchilled tomatoes had higher respiration rates and evolved more ethylene than did chilled fruit. The 48 degrees C treatment increased respiration and ethylene evolution compared with the other treatment temperatures. Red color development was enhanced by heat treatment, and inhibited by chilling. At red ripe, fruit were firmer as a result of storage at the chilling temperature, while heat treatment had no effect on firmness. With the exception of the 45 degrees C treatment, chilled as well as nonchilled fruit previously treated at 39, 42, or 45 degrees C were preferred in terms of taste and texture in informal taste tests over fruit treated at 27 or 48 degrees C. Storage at 2 degrees C led to an increase in electrolyte leakage, particularly in the 48 degrees C treated fruit. Of the 15 flavor volatiles analyzed, the levels of five were decreased and two were increased with increasing temperature of heat treatment. Storage at the chilling temperature reduced the levels of five flavor volatiles. Heat treatments decreased sterols in the steryl ester fraction, several sterols in the free sterol, steryl glycoside, and acylated steryl glycoside fractions. Prestorage heat treatments, with the possible exception of the 48 degrees C temperature, can reduce decay with only minimal adverse effects on tomato fruit quality. (C) 1999 Elsevier Science B.V. All rights reserved.