Abstract
The design of a thermal-radiation single-drum roll dryer with a combined method of heat supply, application and cutting of the dried layer of raw materials was developed. The dryer allows obtaining a powder fraction of a semi-finished product with a solids content of 3...5 %. Such a design solution will make it possible to obtain a high-quality semi-finished product due to low-temperature drying.
 The effective viscosity of the studied pastes produced by blending apple, sea buckthorn, black chokeberry, beet and pumpkin purees was determined. Adding different percentages of raw materials to apple paste increases the effective viscosity by 9...18 %. According to the results of the organoleptic evaluation, the sample with the following composition turned out to be the best: apple – 30 %, sea buckthorn – 20 %, black chokeberry – 15 %, beet – 15 % and pumpkin – 20 %. The drying time of the blended paste with a solids content of 45 % at a temperature of 65 °C and different layer thicknesses of application to the working surface (8, 6 and 4 mm) is 75, 60 and 56 min, respectively.
 All the samples of pastes have a reddish-purple color with a wavelength of 610.5...614.5 nm and a tone purity of 66.5...78.8 %. The wavelength of the dried fraction is 495...615.3 nm with a tone purity of 34.3...34.8 %, from bluish-red to bluish-purple. The brightness of the samples after drying decreases within 3...4 %. The obtained color change values and drying time of the samples confirm the possibility of using the improved dryer to obtain high-quality vegetable semi-finished products of the dried fraction. The experimental data will be useful in design calculations and testing of the developed dryer in order to obtain its maximum efficiency
Highlights
An important component of the food industry of European countries is the provision of healthy nutrition based on organic raw materials in the fresh form and after gentle processing for obtaining various high-quality semi-finished products [1]
When drying blended pastes from organic raw materials in the thermal-radiation single-drum roll dryer, it is necessary to determine the mechanism of formation of the raw material layer on the working surface of the roll (Fig. 1, pos. 3). 240 This can be done if the structural and mechanical properties of blended concentrates, for example, organic pastes of apple, 210 sea buckthorn, black chokeberry, beet and pumpkin, are determined, according to their proposed formulation ratio 180 for puree (Table 1)
The blend 1c is characterized by a bluish-purple color, as it has a tone purity of 34.3 %
Summary
An important component of the food industry of European countries is the provision of healthy nutrition based on organic raw materials in the fresh form and after gentle processing for obtaining various high-quality semi-finished products [1]. The use of combined organic powdered semi-finished products with high physiological and functional properties and the immune component will provide optimal conditions for the production of healthy food [2]. Causing the need to improve the engineering and technological component and searching for innovative ways to intensify thermal-radiation drying on the basis of low-temperature regimes, taking into account the properties of complex blends of organic raw materials, ensuring high quality of the products. An urgent task is to develop and implement modern engineering and technological solutions for improving thermal-radiation single-drum roll dryers for drying concentrates of blended organic raw materials (pastes) into powdered semi-finished products. Intensification of the method of heat supply, application and cutting of the dried layer of raw materials will ensure hardware and technological competitiveness in obtaining high-quality powdered semi-finished products, a high degree of readiness for further introduction in food and pharmaceutical technologies
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