Effect of Temperature, Alkali Concentration, Mixing Time and Meal/Solvent Ratio on the Extraction of Watermelon Seed Proteins—a Response Surface Approach

Watermelon seeds are a byproduct of juice manufacture and contain good-quality extractable proteins. The effect of temperature, alkali concentration, mixing time and solvent/meal ratio was studied on the extraction of watermelon (Citrullus lanatus Cv Mateera) seed protein. A central composite design was used with four variables: temperature (40, 45, 50, 55 and 60 °C); alkali concentration (0·3, 0·6, 0·9, 1·2, and 1·5% w/v); extraction time (5, 10, 15, 20 and 25 min); and solvent/meal ratio (30:1, 40:1, 50:1, 60:1 and 70:1). The experimental values of protein yield ranged between 75·49% and 86·08%. The second-order model obtained for protein yield revealed coefficient of determination of 0.846. Protein yield was primarily affected by alkali concentration and solvent/meal ratio. Maximum yield was obtained when alkali concentration, solvent/meal ratio, temperature and extraction time were 1·2% w/v, 70:1, 40 °C and 15 min, respectively. These results help in designing the process of optimal protein extraction from watermelon seeds.