Abstract
The effect of convective drying temperature (Td), air velocity (v), rehydration temperature (Tr), and kind of rehydrating medium (pH) was studied on the following apple quality parameters: water absorption capacity (WAC), volume ratio (VR) color difference (CD). To model, simulate, and optimize parameters of the drying and rehydration processes hybrid methods artificial neural network and multiobjective genetic algorithm (MOGA) were developed. MOGA was adapted to the apple tissue, where the simultaneous minimization of CD and VR and the maximization of WAC were considered. The following parameters range were applied, 50 ≤ Td ≤ 70 °C and 0.01 ≤ v ≤ 6 m/s for drying and 20 ≤ Tr ≤ 95 °C for rehydration. Distilled water (pH = 5.45), 0.5% solution of citric acid (pH = 2.12), and apple juice (pH = 3.20) were used as rehydrating media. For determining the rehydrated apple quality parameters the mathematical formulas were developed. The following best result was found. Td = 50.1 °C, v = 4.0 m/s, Tr = 20.1 °C, and pH = 2.1. The values of WAC, VR, and CD were determined as 4.93, 0.44, and 0.46, respectively. Experimental verification was done, the maximum error of modeling was lower than 5.6%.
Highlights
Drying is one of the most common and the oldest methods of biological materials preservation
The values of water absorption capacity (WAC), volume ratio (VR), and color difference (CD) were 0.45, 0.45, and 5.21, respectively, and they were very close to the values predicted by artificial neural networks (ANN) (0.46, 0.44, and 4.93)
Winiczenko et al [52] carried out optimization of the drying and rehydration processes of apple using multiobjective genetic algorithm (MOGA) algorithm
Summary
Drying is one of the most common and the oldest methods of biological materials (fruits and vegetables) preservation. It consumes between 7 and 15% of total industrial energy production [1]. Two processes occur simultaneously during drying, namely energy transfer (mostly of heat) from the surrounding environment to the wet solid and mass transfer (moisture transfer) from inside of the solid to the surface and its evaporation to the surrounding environment [2]. The objective in drying of biological materials is the reduction of the amount of free-water in the solids to such a level, at which deteriorative processes caused mainly by microbiological growth, chemical reactions, and enzymatic activity are greatly minimalized. Due to the initial moisture content of approximately 74–90% w.b., vegetables and fruits are susceptible to deteriorative processes [3]
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