Process of Modelling and optimization the osmotic dehydration pre-treatment for okra drying.
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Date
2017
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University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca , Romania.
Abstract
Okra [Abelmoschus caillei (A. Chev.) Stevels] drying was studied by a factorial experiment under randomized complete block design using a laboratory-scale hot-air dryer. Two osmotic solution concentrations (40 and 60 °Brix of sucrose), three osmotic process durations (60, 120 and 180 min) and four drying temperatures (50, 60, 70 and 80 °C) were considered with each trial conducted in triplicates. Drying rate was determined as the ratio of change in mass of okra to the change in drying time as drying progresses. The ash content, crude fibre, crude fat, crude protein, bulk density, least gelation concentration and water absorption capacity were investigated as quality parameters. Model equations were developed using Essential Regression (ESSREG) analysis and Statistical Package for Social Sciences (SPSS) to relate output parameters to process variables. The results showed that an optimum drying rate of 16.69 g/h could be achieved by subjecting okra to osmotic dehydration pretreatment using a solution of 40 °Brix sucrose for 149.10 min and dried with a temperature of 80 °C. The ash content of 3.76% could be obtained at 40 °Brix, 180 min and 50 °C. An optimum value of 29.65% was obtained for crude fibre at an osmotic solution concentration of 60 °Brix, osmotic process duration of 180 min and drying temperature of 80 °C. Crude fat content of okra has 4.03% as its optimum value and this corresponds to a combination of 60 °Brix osmotic solution concentration, 180 min osmotic process duration and 74.60 °C drying temperature. An osmotic solution concentration of 60 °Brix, osmotic process duration of 60 min and drying temperature of 80 °C should be selected to give the optimum crude protein of 14.12%. Predicted values of drying rate, ash content, crude fibre, crude fat, crude protein and water absorption capacity (WAC) compared favourably with the observed values. This implies the models reliably predicted the drying characteristics of okra very well in terms of these output parameters.
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Keywords
drying rate, duration, hot-air dryer, model equations, temperature, quality parameters