Extraction and characterization of acid-soluble and pepsin-soluble collagen from skin of loach (Misgurnus anguillicaudatus).

Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) were extracted from loach skin. The yields of ASC and PSC were 22.42% and 27.32%, respectively. Sodium dodecyl sulfate-polyacrylamide-gel electrophoresis and peptide mass fingerprint analysis revealed that loach skin contained type I collagen. There were 212 imino acids/1000 residues in ASC and 193 imino acids/1000 residues in PSC. Fourier transform infrared spectrometry analysis, UV measurements and circular dichroism confirmed that loach skin collagen had a triple helical structure. The denaturation temperatures of ASC and PSC were 36.03°C and 33.61°C, respectively. Zeta potential analysis revealed that net zero charge values of ASC and PSC were 6.42 and 6.51, respectively. Therefore, loach skin collagen may be an alternative to terrestrial mammalian collagen and may enhance the added value of this fish species.