Characterization of acid-soluble collagen (ASC) derived from walleye pollock and silver carp skin and comparison them with the collagen from pig and duck skin

•The acid-soluble collagen (ACS) was extracted from four different sources.•The extraction yield and efficiency of fish skin collagen were high.•There were slight differences in physicochemical properties of four ACSs.•The thermal stability of ASC from land animals was higher than from fish skin. The acid-soluble collagens (ASC) extracted from the skins of walleye pollock and silver carp were compared with ASCs from skins of duck and pig in physicochemical properties. The dry weight extraction rates of ASCs from walleye pollock and silver carp were 14.10 % and 10.30 %, which were significantly higher than those of pig and duck (4.53 % and 3.14 %). It was found that the ASCs from skins of pig, walleye pollock and silver carp were all type I collagen with intact triple helix structure, while ASC from duck skin was a mixture of type I and type II collagen.The PI of the four ASCs was in the weakly acidic range (5.49–6.84), but ASCs from two fish skins were less thermally stable than that from pig and duck. The dynamic frequency scanning showed that collagen from porcine skin always maintained elastic behavior, while the other three ASCs changed from viscous behavior to elastic behavior with the increasing of frequency. The collagen from two fish skins had a less dense microstructure. The high extraction rate proved that two fish skins were high-quality raw materials for collagen, and the differences in physicochemical properties allowed fish skin collagen to have different applications than terrestrial animal collagen.