Effect of ultrasound-assisted soaking on the hydration kinetics and physicochemical properties of chickpeas

Abstract

Understanding the behaviour of legumes during soaking results of importance since this might affect subsequent processing steps and thus final product quality. The aim of this study was to determine the effect of different ultrasound-assisted soaking conditions (45.8–108.7 W cm−2 for 10–30 min) on the hydration, physicochemical and nutritional properties of kabuli chickpeas. During sonication, the temperature of the soaking media was either controlled at 20 °C (treatment referred to as US) or allowed to rise (treatment referred to as US + T). Selected temperature treatments without sonication (treatment referred to as T) were also included to identify thermal effects. Results showed that higher sonication intensities enhanced water imbibition up to a moisture content of 74.5% (w/w), being more pronounced in treatments where a temperature rise was allowed. Hydration kinetics were well described by the Peleg model (R2 = 0.961–0.998). Samples treated with temperature (US + T; T) showed high solid (0.8–5.1%), di- (13.2–59.7%) and α-galactosyl-sucrose oligosaccharide (5.4–58.7%) losses. In contrast, high US treatments enhanced oligosaccharides to up to 26.2% as well as pasting properties, while decreasing leaching losses (0.93–3.33%). Nutritional properties of sonicated chickpeas were only slightly affected after cooking following no clear trend. Overall, sonication was an effective pre-treatment to reduce hydration time of up to 90% in chickpeas, especially when combined with temperature, and could be applied to drastically reduce the processing time of chickpea and chickpea flour in the food industry.