Modelling the Hydration kinetics of kidney beans (Phaseolus vulgaris) in sodium salts using Response surface methodology

Abstract

The present work investigated the effect of salt solutions of sodium chloride, and sodium bicarbonate on the water uptake by kidney beans (Phaseolus vulgaris) at different temperatures (30, 45 and 60 0C). Thirty-five soaking solutions were prepared using NaCl and NaHCO3 to find the optimum soaking treatment and time to maximise the hydration. Hydration kinetics of kidney beans was studied in different concentrations of the salt solutions and at different temperatures by the method of weight gain until equilibrium conditions were attained. Response surface methodology was used to design the experiments and to optimize the levels for minimum soaking time and to maximize the hydration. The soaking solutions affected the mass transfer in both seed coat and cotyledon, demonstrating changes on both proteins and polysaccharides.  Increasing the temperature from 30 to 60 0 C in sodium chloride solution and sodium bicarbonate solution (0.5, 1.0 and 1.5% concentration) decreased the soaking time from >225min and 225 min to 82.5 min and 73.5 min respectively to achieve around 80% hydration. Beans soaked in sodium bicarbonate solution exhibited higher hydration rates than in distilled water followed by sodium chloride solution at the same salt concentration. Soaking for about three hours at 300C resulted in maximum hydration.  The optimum soaking treatment was found to be in a salt solution containing 1.10% NaCl and 0.92% NaHCO3 at 300C which resulted in a soaking time of 193.45 min.  This work demonstrated a simple and non-tedious approach for enhancing the hydration process of grains.