Improved protein extraction for mung beans using a deep eutectic solvent-based extraction technology: process optimization using response surface methodology

Abstract: Proteins extracted from plant sources are important in food and non-food applications, including food ingredients, nanodelivery, food packaging, adhesives, and biomaterials. The techno-functional properties play a vital role in developing these value-added applications. Mung beans contain 20-25% protein content which shows a high potential to use in the above areas due to proven superior functional properties such as emulsification and foaming. However, due to undesirable chemicals and protein denaturation, traditional extraction methods limit its application. Deep eutectic solvent-based protein extraction (DESs) is an emerging technique that uses non-toxic chemicals and can potentially extract protein at higher purity while retaining protein functionality. The current study aimed to optimize protein extraction for mung bean using a DES system of glycerol and choline chloride (molar ratio = 1:2 (w/w)). A Box Behnken design was used to optimize the solid-to-liquid ratio (1:5-1:25 w/w), water content (40-90% w/w), and extraction time (0.5-2 hours) while keeping the extraction temperature constant at 50 °C. The model showed 92.27% R-sq, 89.33% R-sq-adj, 83.95% R-sq-pred, and 0.284 (p >0.5) Lack-of-fit values indicating the suitability of the model for process optimization. According to the optimized conditions, a maximum protein yield of 170.16 mg/g of flour (DW) can be obtained at a 1:25 solid: liquid ratio, 90% water content, and 1.3 hours extraction time. Changing the time to 0.5 hours slightly reduced the predicted yield to 162.37 mg/g of flour (DW). Considering industrial/large-scale production, the extraction time of 0.5 hours was selected over 1.3 hours for the validation. Under selected optimized conditions (solid: liquid = 1:25, water content = 90%, extraction time = 0.5 hours), the protein was extracted at a 167.71 ± 2.9 mg/g of flour (DW) yield. Therefore, this method can potentially extract 70-75% of proteins from the initial protein content, which is economical compared to conventional extraction studies.