Oxidized starch-metal ion microgels: A novel approach for efficient delivery of bioactive peptides

The encapsulation of peptides can effectively improve their bioavailability and commercial application. In this research, oxidized starch-metal ion microgels were prepared to encapsulate soybean antihypertensive peptides by ionic gelation method and to explore the encapsulation mechanism of the peptides. The study revealed that both oxidized starch-calcium ion microgels (WOS-Ca-P) and oxidized starch-zinc ion microgels (WOS-Zn-P) demonstrated effective encapsulation of soybean peptides. Moreover, a higher degree of starch oxidation leads to an increase of carboxyl content, providing more groups for cross-linking with metal ions, thus enhancing cross-linking density and encapsulation efficiency (EE) Both WOS-Ca-P and WOS-Zn-P microgels exhibited the ability to delay the burst release of soybean peptides in a simulated low-pH gastric environment, reducing the release by approximately 40%, and maintained distinct sustained-release characteristics in subsequent simulated intestinal environments. During simulated gastrointestinal digestion, the WOS-Ca-P and WOS-Zn-P microgels effectively preserved the antihypertensive function of soybean peptides from degradation. After simulated digestion, Angiotensin Converting Enzyme (ACE) activity inhibition efficiency remained at around 60%, resulting in a 2-fold increase in the activity of free soybean peptides. Additionally, after a 30-day storage period, the ACE activity inhibition rate still remained above 50% and continued to exhibit a masking effect on unpleasant odor.