Optimization and Scale-Up Preparation of Egg White Hydrolysate with Angiotensin I Converting Enzyme Inhibitory...

Angiotensin I converting enzyme (ACE) plays an important role in regulation of blood pressure as it converts angiotensin I into angiotensin II (a potent vasoconstrictor). Food protein-derived ACE inhibitory peptides have been considered as a safer alternative to antihypertensive drugs. In our previous study, three ACE inhibitory peptides were characterized from egg white ovotransferrin and their antihypertensive activity has been validated in spontaneously hypertensive rats. However, it is too costly to prepare these peptides from purified egg white ovotransferrin. The aims of the study were to determine the feasibility of preparing these peptides using egg white and then to optimize the conditions of preparing egg white hydrolysate. Taguchi's method was used to design experiments for optimization, which was established as follows: substrate %, pH of thermoase, time of thermoase digestion, ratio of pepsin to substrate, pH of pepsin, temperature of pepsin, and time of pepsin digestion were 7.5%, pH 8, 90 min, 1%, pH 2.5, 55 °C, and 180 min, respectively. The ACE inhibitory activity (IC₅₀ value) and peptide yield obtained under optimal condition were 30 ± 2 μg/mL and 77.5% ± 0.3%, respectively, which were comparable to the predicted values. Hydrolysate prepared at 150 L reactor showed comparable activity but low peptide yield. Results of this study demonstrated the feasibility of using egg white protein as the starting material to prepare a functional ingredient with potent ACE inhibitory activity.