Creation of a methodology for determining the intensity of moisture evaporation within vacuum drying of fruits

Abstract

The study objects were the Republic of Kazakhstan selection apple sorts: “Baiterek”, “Sarkyt” and “Saya”, also pear sorts: “Syilyk”, “Zhazdyk” and “Nagima”. Study of the process of moisture evaporation within vacuum drying of the fruits has essential value in the nutritional value saving. Basically, the product evaporative capacity is characterized by the evaporation resistance coefficient ‒ µ. Also during moisture removal, thermodynamic state of moisture changes that is described by water activity indicator ‒ aw. Experimental determination of these parameters allows for the analyzing moisture evaporation during vacuum drying process. Studies have established the following evaporation resistance coefficients: µ=2.03±0.07 for apple sorts and µ=2.3±0.05 for pear sorts. Either water activity decreases from 1.0 to 0.62±0.01 for apple sorts and from 1.0 to 0.65±0.04 for pear sorts. Two drying periods are discovered. The first drying period: 5.45–6.10 h for apple sorts; and 6.12–6.25 h. for pear sorts. The second drying period duration: 4.15–3.50 h for apple sorts; and 4.35–4.48 h for pear sorts. The critical humidity value: 27.1±2.1 % for apple sorts; and 30.1±2.5 % for pear sorts. Comparative analysis of calculated and experimental data shows maximum deviations 22.5 % for apple sorts and 23 % for pear sorts. The proposed equation for the calculating a moisture evaporation rate, considering the product properties and the hygroscopic parameters of air, can be used in practice to study the moisture evaporation dynamics from the product surface. The study results allow for the selecting an optimal mode for vacuum drying of apples and pears sorts in order to safe nutritional value and to produce biologically active additives for the food industry

Creation of a methodology for determining the moisture diffusion coefficient within vacuum drying of fruits

“…The positive effect in the using of the study results is the obtaining the dry powders with the maximum preservation of the product original quality. The presented methodology is the logical continuation of the authors' previous published work [1].…”

“…In the previous work [1] the authors have considered the development a methodology for determining the intensity of moisture evaporation from the surface of a product within vacuum drying. Along with the difference in the physical parameters of the product (temperature, pressure, density, concentration, and other parameters) and the environment, moisture moves from the deep layers of the product into its environment.…”

“…The research objects were: the Baiterek apple sort and the Zhazdyk pear sort freshly have picked in the October, 2022 [1].…”

“…In recent years, as a result of the support of small and medium-sized businesses in the agro-industrial sector by the government of the Republic of Kazakhstan, the areas of fruit and berry crops are increasing annually. In the general structure of domestic pome and stone fruit plantations, apple and pear trees are prevail [1].…”

“…Authors have experience in the promising vacuum-sublimation drying of food products at a low temperature [1]. The advantage of this drying method over traditional convection drying is as follows: the tightness of the drying chamber guarantees that the final product is not contaminated by dust from the surrounding air and oxidized by atmospheric oxygen [9].…”