Abstract

Introduction. Pectin-based protective coatings can produce a perfect biodegradable edible film. Secondary watermelon raw materials are a promising resource for this type of food coating as it contains 13.4% of pectin components, of which 8.1% is protopectin. The present research objective was to find the density and thermophysical characteristics of the pectin extract in order to optimize the drying process.
Study objects and methods. The research featured a pectin extract from watermelon rind. Its thermophysical properties were defined according to the thermocouple inertia method. The calorimetric method was used to change the aggregation state, while the pycnometric method was applied to calculate the density. The method of criterion equations helped to define the heat transfer coefficient.
Results and discussion. The average density of the final film material was 652 kg/m³ and that of the liquid semi-finished product was 1,028 kg/m³. The research also revealed the dependence of physical density and humidity W, heat capacity, thermal diffusivity, and thermal conductivity. For different W, averaged were 3393, 3225, 3137, and 3113, respectively. The study also provided the criterion dependence for determining the heat transfer coefficient and modified α on the speed of the air coolant for artificial convection at conventional coolant temperature (≈ 100°C) in contact with the food product surface (≈ 80°C).
Conclusion. The article introduces the thermophysical characteristics and physical density of watermelon gel for various humidity and thermal agent parameters, as well as a modified criterion dependence for determining the heat transfer coefficient. The research results can be used to design dehydration operations, other thermophysical processes, and their equipment.

Keywords

Watermelon raw materials, rind, pectin extracts, protective film, thermophysical parameters, structural and mechanical characteristics, drying

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