Food quality in modified atomosphere heat pump drying

Abstract

In order to make best use of heat pump dryer, inert gas was used to improve drying process in this research. The effect of nitrogen and carbon dioxide on drying kinetics, energy efficiency and quality of heat pump dried apple, guava, potato, papaya and ginger were investigated extensively.They were cut into 1cm cubes or 3mm slices. Results showed that inert gas did contribute to some improvement. For the dried products, there are less browning and smaller colour changes; lower shrinkage and more porous structures were observed, which resulted in faster rehydration rate; vitamin C retention of nitrogen dried guava is as high as 1.64 times of normal air drying; and ginger flavour (6-gingerol) is even better than freeze drying. For drying kinetics, the effective diffusivity in nitrogen drying of guava is increased by 73.2% compared with normal air drying