Effects of alkaline hydrolysis and storage conditions on the biological activity of ostrich egg white

Abstract

This study aimed to improve the biological activity of ostrich egg white (OEW) using alkaline hydrolysis (0.25 M NaOH at 40°C for 8 hr), and studied the effects of packing materials and temperature on biological and physical properties of OEW hydrolysate (hOEW). The results show that alkaline hydrolysis clearly enhanced several biological activities, including ABTS radical scavenging (61.35%), anti-microbial (51.66% against Bacillus subtilis and 38.58% against Escherichia coli) and anti-angiotensin converting enzyme activity (39.19%). The hydrolysate maintained biological activities after gastrointestinal digestion and showed non-toxicity toward human red blood cells. In storage study, the best storage conditions were packing hOEW powder in an Al-foil-laminated bag at 4°C, resulting in slightly decreased biological activity after 6 months storage and significantly lower moisture content than plastic zipper bag. Additionally, SEM revealed smooth surfaces of hOEW powder for the best condition, while air pores and bridges were found in the worst conditions. Practical applications The alkaline hydrolysis method (incubation in 0.25 M NaOH at 40°C for 8 hr) used in this study can be used to enhance the antioxidant, antimicrobial, and anti-ACE inhibition activity of egg white protein. This study also reports the optimal packaging and storage conditions for egg white hydrolysate powder, which are beneficial for maintaining the antioxidant, antimicrobial, and anti-angiotensin converting enzyme activity as well as the texture of the egg white hydrolysate powder.