Characteristics of acid soluble collagen and pepsin soluble collagen from scale of spotted golden goatfish (Parupeneus heptacanthus)

Acid soluble collagen (ASC) and pepsin soluble collagen (PSC) were extracted from scale of spotted golden goatfish (Parupeneus heptacanthus) with the yields of 0.46% and 1.20% (based on dry weight basis), respectively. Both ASC and PSC were characterised as type I collagen, containing α1 and α2 chains. β and γ components were also found in both collagens. Based on FTIR spectra, the limited digestion by pepsin did not disrupt the triple helical structure of collagen. ASC and PSC contained glycine (336–340 residues/1000 residues) as the major amino acid and had imino acids of 186–189 residues/1000 residues. Maximal transition temperatures (Tmax) were 41.58 and 41.01 °C for ASC and PSC, respectively. From zeta potential analysis, net charge of zero was found at pH 4.96 and 5.39 for ASC and PSC, respectively. Both collagens exhibited high solubility in acidic pH (2–4) and were soluble in the presence of NaCl at concentration up to 20 and 30 g/l for ASC and PSC, respectively.