SELECTING LAYER THICKNESS IN FREEZE DRYING OF HIGH-VALUE BIOLOGICAL PRODUCTS

The efficiency of freeze-drying for obtaining dry food products with high quality indicators is considered. Freeze-drying allows preserving the original properties of the product, including its shape. The thickness of the drying layer has a significant effect not only on the process kinetics, but also on the product quality. The objects of the study were microalgae, honey, salmon caviar and royal jelly. The graphs demonstrate change in the relative mass, the rate of relative mass change of spirulina and chlorella, and the product temperature during freeze-drying with variation of product layer thickness. Lyophilized spirulina was a finely dispersed powder of dark green colour. Lyophilized honey had a dense consistency. Freeze-dried caviar mostly retained its original shape. After freeze drying, royal jelly had a loose powdery consistency and appeared offwhite with a cream tint. For caviar, a layer thickness of 15 mm is recommended, and for other products, it should be 20 mm. This variation is due to the fact that, layer thickness most significantly affects the caviar quality compared to other products.