Abstract: Heat treatment of postharvest Elizabeth muskmelons was performed respectively using hot water and hot air methods. The effects of operating parameters such as packaging methods, fruit size, cycling medium velocity, temperature and relative humidity on half heating time, three-fourth heating time, seven-eighth heating time and tissue weight loss rate were investigated. The results showed that the length of hot water treatment was only 50%－60% of that of hot air treatment for the same treatment effectiveness (the temperature at the center of a melon sphere reached between 38 ℃ and 53 ℃). The optimum medium velocities in hot water and hot air methods were 0.5－1 m/s and 1.5－2 m/s, respectively. Hot water treatment and high humidity hot air treatment could effectively reduce the tissue weight loss of muskmelon in hot air treatment. Muskmelon grading according to fruit size in advance promoted the uniformity of heat treatment. The optimum operating time was seven-eighth heating time (the dimensionless temperature θ = 0.125).

Key words: muskmelon, heat treatment, operating parameters, weight loss rate