Protein digestibility of pigskin and bovine tendon in rats

Abstract

Summary.The protein nutritional value of pigskins and bovine tendons, with collagen contents of 75 and 95% respectively, was evaluated using amino acid analyses and nitrogen balance experiments on rats. Pigskins contain somewhat higher amounts of tryptophan, meth‐ionine, cystine and tyrosine than tendons. The amounts of several essential amino acids were low. The true digestibilities were for young (4 month old), unscalded pigskin 96.1%, old (5 year old), unscalded pigskin 92.5%, calf tendon 97.3% and cow tendon 92.4%. Small but statistically significant differences due to the animal age were observed. Insoluble collagen, extracted from bovine tendon, had a digestibility of 95.2%. Wet heat treatment of old pigskin and cow tendon samples at 74â°C for 30 min significantly increased the digestibilities to 96.3 and 97.3% respectively. The results indicate that prior denaturation of collagen, as obtained by, for example, heat treat‐ment, is not necessary for the digestion of pigskin and tendon in rats.