Ultrasound-assisted hydration with sodium bicarbonate solution enhances hydration-cooking of pigeon pea

Abstract

This work studied the effect of ultrasound power and sodium bicarbonate (NaHCO3) concentration during soaking process on the hydration and cooking kinetics of pigeon pea (Cajanus cajan). The pigeon pea grains were hydrated using 0, 1, 1.5, and 2% m/m NaHCO3 solutions without and with ultrasound assistance (17 W/L; 40 kHz and 43 W/L; 40 kHz) at 27 °C. Cooking process was studied using softening kinetics. Grains were cooked in boiling water and their softening was evaluated with a texturometer. Both hydration and softening kinetics were fitted to suitable models and their parameters were used for evaluating the effect of ultrasound power and salt concentration. Ultrasound accelerated hydration kinetics but did not affect the cooking process. Soaking in NaHCO3 solution, delayed hydration kinetics, but accelerated the softening kinetics. The synergetic effect of ultrasound (17 W/L) and NaHCO3 solution (1% m/m) accelerated both hydration and cooking kinetics by approximately 3 h. In fact, hydration is a long process, which requires more than 6 h, and cooking requires boiling temperature, which increases energy use and cost. Using ultrasound technology and adding sodium bicarbonate in soaking water can improve grain processing. Studying other grains and salts solutions on hydration-cooking process in the future is recommended.