Extraction and Properties of Acid-Soluble Collagen and Pepsin-Soluble Collagen from Silver Carp (Hypophthalmichthys molitrix) Scales: Prerequisite Information for Fishery Processing Waste Reuse

As a waste of the fish processing industry, scales cause the disposal of large amounts of solid waste into the environment. How to turn such waste into a useful product is an important issue. In this study, acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted from silver carp (Hypophthalmichthys molitrix) scales using a new acid-enzyme combined method. The results showed that the extraction yields of ASC and PSC were 5.09% and 12.06%, respectively. Then amino acid analysis, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD) and ultra-sensitive differential scanning calorimetry (US-DSC) were used to study their composition, properties and structure. Amino acid analysis indicated that ASC and PSC were type I collagens with 34% glycine and 20% imino acid (Pro and Hyp). The results of SDS-PAGE and FT-IR analysis showed that ASC and PSC were similar to those of the standard type I collagen. CD indicated that the triple helical structure of both ASC and PSC were still retained. And the transition from triple helix to random coil of ASC and PSC were 34.26 degrees C and 34.47 degrees C, respectively. For the first time, the collagen yields of silver carp scales were calculated. Meanwhile, their composition, properties and structure were characterized. These results may offer theoretical support for the development of silver carp scales related to reusing technology to control waste.