STUDY OF THE INFLUENCE OF GAINER LIQUID COMPOSITION ON THEIR DRYING KINETICS IN THE “DROPLET–VAPOR–GAS MEDIUM” SYSTEM

Abstract

Considering today’s wartime conditions in Ukraine, dry concentrates of sports nutrition (gainers) with a powerful protein–carbohydrate complex are advisable to use in the general therapy of severely wounded servicemen to increase the effectiveness of their treatment and accelerate recovery. Obtaining them by spray drying makes it possible to minimize thermal effects on thermolabile biologically active substances, particularly those derived from fresh fruit raw materials. The proteins and carbohydrates used in the proposed formulations, including pumpkin puree, represent insufficiently studied multicomponent heterogeneous systems, which should be additionally investigated as objects of spray drying.

The aim of the study was to examine the kinetic regularities of drying in the “droplet–steam–gas medium” system for liquid gainer compositions in order to determine the rational heat-technology parameters of their spray drying.

Research methods. The study used liquid gainer compositions that included proteins, fats, and carbohydrates in different proportions. The required consistency, containing particles of insoluble fractions ≤150–180 μm from pumpkin puree (30% content in the compositions), was achieved by processing in a cylindrical-type rotary-pulsation apparatus. The drying kinetics of single droplets of the compositions were studied in the “droplet–steam–gas medium” system using an experimental setup in a heat-carrier flow heated to 150 °C, 165 °C, and 185 °C. Based on experimental drying data (critical points and thermogram patterns), the corresponding kinetic dependences were constructed.

Results. The dehydration process of all three compositions occurred in the high-temperature drying period, which included the stages of crust formation, boiling, and final drying. According to the kinetic dependences of droplet heating rate: during crust formation, the heat–moisture transfer process in droplets of samples No. 2 and No. 1 proceeded under milder conditions, while during the final drying stage, sample No. 1 was able to dry at an accelerated rate. Shortening of the crust formation and boiling stages reduced the relative duration of dehydration up to the critical point cr.3 to values of 0.35–0.45 and significantly extended the final drying stage to 0.55–0.65, which is typical for colloidal systems. Rapidly formed dense shells on the droplet surface resisted moisture transfer, leading to the formation of hollow, thin-walled particles of enlarged size, especially at temperatures ≥180 °C, with a high probability of elevated moisture content and increased adhesiveness in the hot state.

Conclusions. The study showed that, as with typical colloidal systems, the proposed compositions are characterized by the low diffusion capacity of poorly permeable surface shells of drying droplets, which hinders moisture transfer and increases the risk of obtaining powder with elevated moisture content and adhesiveness in the hot state. The hollow structure of enlarged particles reduces the bulk density of the powder.

It was experimentally established that, among all the tested compositions, composition No. 1 was the most suitable for obtaining high-quality powder by spray drying. According to its kinetic characteristics, its structural protein–carbohydrate potential ensured reduced deformation of the particle shape during drying and smaller final particle size at 165–175 °C, while structural strengthening and the disappearance of adhesiveness were achieved after cooling due to the vitrification of sugary substances.