Skins Comparative Analysis of Collagen Functionality and Peptide Bioactivities from Yak, Cattle, and Donkey Skins

Collagen peptides derived from animal skins are valuable bioactive ingredients with diverse nutritional and functional properties. This study systematically compared the nutritional value, collagen structure function properties, and bioactivities of collagen peptides from six types of animal skins, including yak skins from different altitudes, Pingliang Red cattle skin, Xinjiang Brown cattle skin, and donkey skin. In terms of nutritional value, low-altitude yak skin contained 34.15 g/100 g protein and 1.78 g/100 g fat, exhibiting superior overall performance compared with other samples. Regarding structure-function relationships, low-altitude yak skin showed the highest emulsifying activity (12.05 m²/g) and foaming capacity (26%), which were attributed to its smaller particle size and higher surface hydrophobicity, whereas mid-altitude yak skin demonstrated greater thermal stability (115.3 °C) and a more compact microstructure. In terms of bioactivity, yak leather contains 23,558 to 25,966 peptides, with relatively high activity of antibacterial peptides and anti-diabetic peptides. Pingliang red cowhide and Xinjiang brown cowhide contain 1515 and 2186 polypeptides, respectively, which have strong antihypertensive activity. The antibacterial effect of donkey skin is more obvious, with a total peptide count of 11,678. Collectively, these findings reveal significant differences in the nutritional and processing-related properties of the six skin types and provide potential evidence for expanding their applications in the field of functional foods.