Sustainable protein extraction from spent coffee grounds using response surface methodology
摘要
Spent coffee grounds (SCGs) were produced as a significant byproduct during coffee production. They contain valuable compounds such as proteins. This study investigates sustainable protein extraction from them using both acid extraction with alkaline precipitation and alkaline extraction with acid precipitation. Response surface methodology (RSM), specifically the Box-Behnken design, was employed to optimize the extraction conditions of proteins from SCGs. The optimized conditions for protein content (%) were determined to be pH 5 with 0.05 M HCl + 0.05 M NaCl solution for an extraction time of 6 h using the acid extraction with alkaline precipitation method while 0.4 M Na3PO4·12H2O solution to adjust pH 12 for an extraction time of 1.5 h using the alkaline extraction with acid precipitation. The optimized conditions for protein recovery (g protein/100 g dry SCGs) were determined to be pH 9 with 0.2 M HCl + 0.2 M NaCl solution for an extraction time of 24 h using the acid extraction with alkaline precipitation method while 1.0 M Na3PO4·12H2O solution to adjust pH 12 for an extraction time of 0.5 h using the alkaline extraction with acid precipitation. The regression equation for acid extraction with alkaline precipitation shows that approximately 84.5% of the variance in protein recovery was explained by independent variables, while alkaline extraction with acid precipitation had about 75.9% of the protein content. The study demonstrates that SCGs could be effectively valorized into a sustainable source of protein through optimized extraction processes. It enables the transformation of coffee waste into value-added products and increases the valorization of coffee wastes.