Abstract
The article studied the patterns of changes in water activity during vacuum drying of apple varieties: Baiterek, Sarkyt and Saya and pear varieties: Syilyk, Zhazdyk and Nagima. Studies have established that in all the studied varieties of apple and pear, the following pattern is observed: in the first four hours of the drying time, the water activity indicator decreases monotonously, and the subsequent drying time drops sharply. This pattern is explained by the fact that after four hours of drying time, part of the remaining weakly bound moisture is gradually removed from the product, and then the bound moisture. Studies have shown that dehydration of fruits, the water activity characterizing the qualitative properties of the product decreases: for apple varieties from 1.0 to 0.62 ± 0.01, for pear varieties this indicator decreases from 1.0 to 0.65 ± 0.04. On the basis of mathematical processing of experimental data, a power-law dependence of water activity on the duration of drying was established. The established pattern of changes in water activity from the duration of drying in subsequent works will be used to determine the optimal drying mode for apples and pears in order to produce high-quality dry powders for the food industry.