INFLUENCE OF COMBINED DRYING OF COLLOID CAPILLARY-POROUS MATERIALS ON ENERGY EXPENDITURES

Abstract

One of the berry crops that has recently gained popularity among consumers is blueberry (Vaccinium corymbosum L.). The berry is a powerful antioxidant, and besides, it contains fructose in its composition, which automatically refers it to the products of the diabetic diet. Therefore, blueberries become an interesting colloidal capillary-porous drying object. Wax on the skin of berries performs a protective function in the process of ripening, harvesting and transportation, but is a negative factor for the implementation of technological processing by artificial dehydration. The latter causes significant energy costs for the processing process. Therefore, the aim of the work is to determine the effect of combined drying of blueberry on energy consumption. Experimental studies of the drying kinetics of blueberry were carried out on an experimental convective stand with forced recirculation of the coolant and infrared emitters, which was developed in ІEТ of NAS of Ukraine. The effect of pre-developed hygrothermal and infrared treatment of fresh blueberries on the kinetics and change in the drying speed of berries was investigated. The use of infrared radiation made it possible to reduce the total duration of the dehydration process by 1.2 times. The heat of evaporation of moisture from the samples and their heat capacity were investigated using the method created in ІEТ of NAS of Ukraine installations of synchronous thermal analysis DMKI-01, which is intended for the study of colloidal capillary-porous materials. Determination of specific heat capacity was carried out according to the standardized method of step-by-step scanning DSTU ISO 11357–4:2010 in the temperature range from 30 to 95℃. Experimental determination of heat capacity and heat of evaporation of moisture from pre-processed blueberry showed excess energy consumption for a possible phase transition of the waxy shell of the berry during drying and a decrease in the drying efficiency of the material at moisture values Wc ≤ 20%.