Physicochemical and biological properties of collagens obtained from tuna tendon by using the ultrasound-assisted extraction

This study aimed to maximize the utilization of tuna tendons, which are by-products of the tuna canning process, to obtain collagen through ultrasound-assisted extraction. Ultrasound was used to assist the extraction of vinegar-, acid-, and pepsin-soluble collagen from tuna tendons, denoted as VUTC, AUTC, and PUTC, respectively. The yield ranged from 10% to 15%, and the collagen solubility was 0.5–0.7 mg protein/mg collagen. The color differed among the collagen samples. Tuna tendon collagens comprised γ-, β-, α1-, and α2-chains, in accordance with type I calf skin collagen. Regarding the amino acid composition, there were high amounts of glycine, proline, glutamic acid, alanine, hydroxyproline, and aspartic acid. Salt concentration and pH effects on the solubility of collagen were evaluated. The samples were less soluble at higher salt concentrations and had good solubility at low pH. Fourier transform infrared spectroscopy showed the presence of a triple helix. Fractional viscosity and differential scanning calorimetry (DSC) analysis indicated a degradation temperature of 30–36 °C and 167–171 °C, respectively. Finally, tuna tendon collagen had antioxidant and immune-enhancing activities and did not exert cytotoxicity