Extraction optimization and functional properties of muskmelon seed protein concentrate

Optimization of proteins extraction from muskmelon (Cucumis melo) seeds was investigated using a central composite rotatble design involving four factors at five levels: temperature (X1) (40, 45, 50, 55 and 60 °C); pH (X2) (8.5, 9, 9.5, 10, 10.5); extraction time (X3) (30, 40, 50, 60 and 70 min); and solvent/meal (S/M) ratio (X4) (5, 10, 15, 20 and 25 v/w). Protein yield varied from 17.46 to 78.77% for the different combination of four independent factors. Non-significant lack of fit validated the adequacy of the model. The linear factors X1, X2, X3 and X4 along with X13 (temperature and time), X23 (pH and time), X34 (time and S/M) and quadratic coefficient X42 (S/M) showed the significant effect on the response variable. Optimized conditions for protein extraction were 55 °C, pH 10, extraction time 62 min and S/M ratio (v/w) 23. Confirmation study gave the extracted yield of 84.11% which was slightly lower than the predicted value (85.07%) under optimized conditions. Lightness of MPC was lower than the MDSM. Protein content of MDSM was 84.12%. A significant effect of pH was observed on protein solubility, EAI and ESI, foaming capacity and stability. Secondary structure or proteins had more number of β-sheets than random coil and α-helix structures.