A novel strategy for ultrasound-assisted immobilized enzyme hydrolysis for the preparation of yak bone collagen peptides: Process optimization, structure and antioxidant mechanisms

In recent years, food-derived antioxidant peptides have garnered growing interest within the food industry, owing to their remarkable bioavailability and safety profiles. In this study, collagen peptides derived from yak bone (YCP) were prepared using an ultrasound-assisted immobilized enzyme hydrolysis system (US + IP-EH), and a comprehensive investigation was conducted into their structural characteristics, stability, and underlying antioxidant mechanisms. The results revealed optimal extraction conditions as follows: an ultrasonic power of 415 W, an enzymatic hydrolysis temperature of 49 °C, a hydrolysis duration of 8.4 h, an immobilized enzyme dosage of 3.6 %, and hydrolysis degree (DH) reaching 22.36 % in the validation experiment. Notably, the US + IP-EH approach significantly enhanced the yield, structural integrity, and antioxidant capacity of YCP, enabling them to retain robust antioxidant stability even under challenging conditions such as high temperatures, extreme pH (strong acids or alkalis), light exposure, and gastrointestinal digestion. Furthermore, ten novel antioxidant peptides were successfully identified, demonstrating non-allergenic and non-toxic properties. Among these, peptides P1, P4, and P10 exhibited favorable interactions with Keap1 by occupying its primary binding sites, thereby effectively disrupting the Keap1-Nrf2 complex structure. This research provides a solid theoretical and practical foundation for the development of yak bone collagen into natural functional foods and health products.