Optimum conditions for extracting collagen from the tunica albuginea of immunologically castrated pig testes and the functional properties of the isolated collagen

•We showed that pig tunica albuginea has high collagen content.•We optimized the method for extraction of collagen from pig tunica albuginea.•We obtained a product with high content of collagen called isolated collagen.•The functional properties of the isolated collagen were better than bovine skin collagen.•The isolated collagen can be used in pharmaceutical and food emulsion products.

This study evaluated alternative methods for extracting collagen from the tunica albuginea of pig testes and characterized the functional properties of the isolated collagen. Using the statistical tools of factorial design (24-1) and a central composite rotatable design (23), it was concluded that the best conditions were 0.83 mol L− 1 acetic acid, 0.24% pepsin and 28 h of hydrolysis to isolate 82.54 g of collagen per 100 g of sample. This purified collagen had improved functional properties in relation to bovine skin collagen, including water solubility, water-holding capacity, emulsifying capacity and emulsion stability. These results suggest that isolated collagen from the tunica albuginea can be used in pharmaceutical and food products.