Optimization of soaking conditions (temperature and time) on physicochemical properties of selected parboiled rice varieties grown in Eastern Ethiopia

This study aimed to optimize soaking temperature and time for better physicochemical properties of parboiled rice varieties grown in Eastern Ethiopia. Two brown rice varieties (NERICA‐4 and NERICA‐6) were collected from the Somali Regional Agricultural and Pastoral Research Center in Gode. The experiment was designed to aid the design expert software using box–behnken experimental design of response surface methodology to optimize the effects of soaking temperature (60–70°C) and soaking time (4–6 h). Relevant physical and chemical composition properties of the parboiled rice varieties were investigated using standard methods. Numerical optimization of the responses was performed using design expert software. The results showed that soaking time and temperature significantly (p < .05) influenced the physicochemical quality of studied brown rice varieties. The optimal soaking temperature and time were 65°C and 6 h, respectively, for NERICA‐4. Under these conditions, the optimum response variables obtained were 375.37 N, 52 min, 12.3%, 1.24%, 13.86%, 2.17%, 3.2942%, 67.1171%, 343.5 kcal/100 g, 274.72 mg/100 g, 318.35 mg/100 g, and 268.31 mg/100 g for hardness, cooking time, moisture, ash, protein, fat, fiber, carbohydrate, energy, magnesium, and potassium and phosphorous content, respectively. However, 65°C and 5 h were optimum soaking temperatures and time for NERICA‐6, giving hardness, cooking time, moisture, ash, protein, fat, fiber, carbohydrate, energy content, magnesium, potassium, and phosphorous of 375.18 N, 52 min, 12.2%, 1.4%, 11.54%, 2.29%, 2.89%, 69.6%, 345.42 kcal/100 g, 156 mg/100 g, 105.9 mg/100 g and 136.9 mg/100 g, respectively. The findings showed that rice varieties, in particular NARICA 4, were processed under optimal parboiling conditions in the study setting for better physical properties, proximate composition, and mineral content.