Effects of temperature and time in cool storage on the ripening and storage life of pears

Abstract

Packham's Triumph and Beurre Bosc pears were stored for various times at various temperatures from -1.1� to 5�C and then ripened at 20�C. The concept that the cool storage life of pears might be defined by a characteristic number of heat units (degree-days) above a particular base temperature was examined in detail. The heat units accumulated during cool storage and subsequent ripening were examined in relation to storage temperature, time in storage, variety, and season. There was no general characteristic number of heat units that could express the storage life of either variety, but for a particular combination of variety, season, and storage temperature, the heat units accumulated at low temperature until the end of cool storage life were similar for pears from different growers. The time to ripen after removal from storage was related to the time in storage and to the temperature of storage, the effect of time being more marked at the higher temperatures. Maximum storage life was related to temperature of storage in such a way that small decrements of temperature increased storage life more at the lower levels in the range of -1.1� to 5�C. The more rapid softening of pears and their shorter life at higher temperatures both emphasize the importance of maintaining exported pears at low temperatures before shipment and during transport to prevent them being 'too forward' at discharge.