Extraction Optimization of Red Kidney Bean (<i>Phaseolus vulgaris</i> L.) Protein using Response Surface Methodology

Red kidney beans valued globally for their nutritional content, health benefits, and culinary versatility. Response surface methodology was used to determine the optimum conditions for the extraction of protein from red kidney bean seeds. By using a central composite design, the effects of three independent variables, namely pH (8, 9, 10, 11, and 12), temperature (20, 40, 60, 80, and 100oC), and time (15, 30, 45, 60 and 75 min) were investigated on the selected response variable i.e. percent protein recovery. The second-order model obtained for protein recovery revealed a good coefficient of determination (98.79%). Maximum protein recovery was obtained when pH, temperature, and extraction time were 10.1, 31.4oC, and 75 min, respectively. Additional experiments were performed at optimum conditions to confirm the suitability of the model. The results revealed that the range of protein recovery from red kidney bean flour was 68.7% to 83%, with temperature, pH, and extraction time having a significant impact. Strong agreement between predicted and experimental values was demonstrated by the second-order regression model, which had a high fitness (R2 = 98.79%). The highest protein recovery of 85.1% was obtained under ideal extraction conditions (pH 10.1, 31.4°C, 75 min). The experimental values for protein recovery were in close agreement with that of the predicted results, thus signifying the appropriateness of the model used. The study can instigate the production of protein isolates or concentrates from red kidney beans for use as promising food ingredients in the industry.