Methodological approach to evaluate freezing points of peach and apple fruits through exotherm study.

Freezing points of peach and apple fruits were investigated through exotherm study. Fruits were harvested at commercial maturity and exposed to freezing temperatures; changing patterns of fruit temperature were analyzed as related to ice formation using data logger devices. Preliminary time-course investigation on the temperature changes of water and sucrose solution during ice formation exhibited clear supercooling and exotherm curve, which were well in accordance with theoretical expectation. According to the exotherm peak, actual freezing points of 'Mibaekdo' peach and 'Fuji' apple fruit seemed to be in the range of -0.7~-1.0 and -1.4~-1.7, respectively. Supercooling points were the same for peach and apple in the range of -2.7~-3.1. The freezing points obtained through exotherm study were virtually identical to those confirmed by real storage experiment. The results of the present study suggest that freezing point of fruit and vegetable crops could be easily estimated through exotherm approach. Based on freezing point, not on the supercooling temperature, postharvest temperature management at above -0.7 and -1.4 is recommended as critical points for peach and apple fruit, respectively.