Optimization of Egg Yolk Protein Hydrolysis by RSM and Properties of Hydrolysates

Abstract

The effect of temperature, pH, and the enzyme-to-substrate ratio (E/S) on the degree of hydrolysis (DH) of lecithin-free egg yolk (LFEY) protein was optimized by using response surface methodology (RSM). A factorial design was applied to maximize DH and the initial reaction rate (V0). The DH values varied from 16 to 36 % and V0 from 69 to 287 g/L h in the range of tested conditions. The pH was the variable with a major influence on DH and V0. Under the optimized conditions (60°C, pH 9, and E/S=0.35 AU/g) most of the peptides in the hydrolysates had a molecular weight (MW) lower than 12 kDa since the first 10 min of the reaction. Hydrolysates collected after 60 min of the reaction contained mostly oligopeptides (MW<3.5 kDa) with potential antioxidant activity. These hydrolysates might be used as ingredients in high-protein nutritional supplements or the formulation of clinical nutritional products.