SORPTION CAPACITY OF SUBLIMATED FRUIT AND BERRY RAW MATERIALS

The aim of the study is to investigate the rehydration processes of sublimated fruit and berry raw materials when determining their sorption capacity with respect to free and bound moisture. To study the ability of raw materials to be restored after drying, it is necessary to study the sorption capacity and determine the types of moisture absorbed during rehydration. For popular market dried items (avocado (Persēa americana), garden strawberry (Fragaria ananassa Duch. variety Pegasus), apricot (Prunus armeniaca, variety Vodolay)) experiments were conducted on their sublimation dehydration and the conditions and parameters of restoration were determined. Drying was carried out in a Vikumer BFD-10 freeze dryer in stages: lyophilization of samples to a temperature of 45 °C, at a pressure in the working chamber of 200 Pa, heating the contact surface of the shelves to 20 °C; then, over the course of three hours, the pressure in the working chamber was reduced to 100 Pa under the same parameters; At the final stage, the shelf surface temperature was increased to 25 °C while maintaining the pressure in the working chamber no higher than 75 Pa (abs.) for 8 hours. The ability to restore lyophilized raw materials was studied experimentally by quantitatively assessing the sorption capacity depending on the temperature in the range from 5 to 80 °C for 10 minutes. An original approach to determining the sorption capacity of raw materials is proposed, estimated by a modified rehydration efficiency coefficient, which shows how much free moisture the product can absorb. The rehydration efficiency index is nonlinear, the highest coefficient was obtained for strawberries – 86.15 % at a temperature of 5 °C, for apricots – (79.59 ± 94) % at 45 °C, for avocados – (66.42 ± 80) % at 80 °C. The obtained empirical data and recommendations can be used in confectionery industry enterprises and by end consumers of freeze-dried raw materials.