Abstract: Pre-cooling is the key factor in the modern circulation system of pre-cooling fruits and vegetables. It is also the first operation in the cold chain, and is essential for perishable produce in nature. Rapid cooling has been clearly shown to prolong the storage life of freshly harvested produce. Forced-air cooling is the most versatile and widely used among all cooling methods. A forced-air pre-cooling experimental unit was thus established. The Litchi temperature characteristic curves of forced-air pre-cooling process in different experimental conditions were obtained. The pre-cooling time of Litchi was discussed under the influence of different cool-air temperature, flow rate and litchi position in fruit box. The test results showed the reasonable air velocity obtained for Litchi pre-cooling, so as to provide foundation and theoretical basis for design of forced-air pre-cooling system-less than 1 m/s.

Key words: pre-cooling, forced-air cooling, litchi, fresh keeping