Empirical study of durian fruit slices hygroscopic parameters

The use of various drying methods to reduce water activity allows preserving the native properties of any plant material, including tropical fruits. The object of the study was the tropical fruit durian (Durio zibethinus L.), which is widespread in Southeast Asia and has high antioxidant activity compared to analogues. For tropical fruits, the best drying strategy is their dehydration at moderate temperatures. For example, when drying delicate fruits, which include durian, it is recommended to use convective energy supply or the sublimation method. Dried durian slices have a long shelf life, but are highly hygroscopic, and powders from them are prone to agglomeration due to their hydrophilic nature. The authors studied isotherms of equilibrium moisture content in dry durian slices to identify the hygroscopic properties of them. That allows us to estimate the preservation potential of dehydrated products. The purpose of the study is to analyze the experimentally obtained sorption isotherms of durian slices dried by convective dehydration. Based on the study of hygroscopic properties, static patterns and the nature of variation of interdependent equilibrium parameters, such as temperature and humidity of the contacting phases, were identified and mathematically described, and isotherms of moisture sorption by durian slices were constructed. The sorption limits of dried durian slices were determined at different temperature conditions of 298–318 К (Wp = 0.34 kg/kg), the final rational moisture content of durian slices during convective drying was revealed (W = 0.1 kg/kg), which at a relative humidity of the environment of 60% guarantees high-quality preservation of the final product. The obtained data will form the basis for a thermodynamic analysis of the statics of the process of drying durian slices in order to model and evaluate the energy intensity of this operation.