Preparation And Characterization And Functional Evaluation Of Collagen From Haddock And Pollock Processing By-product

Collagen produced from aquatic products has been attracting more attention. Fish, a typical kind of poikilotherms, has the unique collagen which is different from that of terrestrial animals. The fish collagen has unique amino acid composition as well as some special properties. To use the aquatic products by-product, acid-soluble collagen (ASC) has been extracted from haddock and Pollock processing by-product. The extraction method has been optimized and hydrolysates are obtained by acid and enzymatic hydrolysis. The relationship between hydrolysis process and average molecular weight (MW) of the hydrolysate has been investigated. Function properties of the ASC from the skin of haddock and Pollock and their hydrolysates are evaluated afterwards via a series of in vivo and in vitro experiments.Using mechanical shear, microwave and ultrasonic methods as the pretreatments, ASC has been extracted from the raw material at a temperature gradient in the acetic acid solution. According to the quality and yield of the products, the optimized preparation method is extraction at 20℃after half-time ultrasonic pretreatment. The yields of haddock and pollock skin ASC are 15.05% and 13.11%, respectively. The characteristics of the product are typical as collagen and the original molecular structure has been preserved.The two kinds of ASC have been characterized by some physical and chemical methods. They have only one UV-vis absorption peak at 233 nm and 230 nm, respectively. FTIR spectra show the existence of helical arrangements in their structures. Amino acid composition analysis shows the contents of Glycine in the two ASCs are 21.1% and 19.8% while that of Hydroxyproline are 7.8% and 6.9%, respectively. This model of composition has similarities of some other fish collagen reported. The SDS-PAGE patterns suggest the two kinds of collagen have at least two differentαchains. Thus, the collagens should be classified as type I collagen. It has a distinctive thermal stability. Their denaturation temperatures are close which are both lower than that of mammalian collagens. The thermal stability is related to the proportion of Hydroxyproline in the molecule.Three different kinds of acid treatments and other three enzymatic treatments are employed in hydrolysis of the two sorts of ASC. The average MW of the haddock skin ASC acid hydrolysate ranged from 3.5 kDa to 53.4 kDa while that of pollock skin ASC acid hydrolysate ranged from 2.6kDa to 46.4kDa. In the enzymatic hydrolysis process, the relationship between enzymatic activities, reaction time and average is more complicated than that in acid hydrolysis. The random nature of acid hydrolysis makes the average MW of the product more stable and predictable. Two series of hydrolysates named Hydrolysate1-4 are selected from the two groups of ASC hydrolysates and then introduced into function evaluation experiments together with the two ASCs.For the function experiments in vivo, haddock and pollock skin ASC and their high average MW hydrolysates show hemostatic function. Haddock skin ASC and its Hydrolysate1 reduce the clotting time by 26.5% and 22.9% while pollock skin ASC and its Hydrolysate1 reduce that by 27.0% and 19.1%, respectively. In the wound healing time determination, haddock skin ASC reduces the healing time by 30.4%. Pollock skin ASC and its Hydrolysate1 reduced that by 26.1% and 21.7%. For the scald repair experiments, all the ASC and hydrolysates show positive effects to varying degrees. Nevertheless, Hydrolysate3 and 4 are the most effective of all the treatments. Haddock ASC and its Hydrolysate1 and Pollock ASC have stimulatory effects on angiogenesis in chick embryo chorioallantoic membrane (CAM). The way they performed is to enhance the branch of small vessels in capillary bed area while the chick embryos remain intact.For the function experiments in vitro, strength and elongation of human hair have been obviously improved after treated with Hydrolysate3 and 4 of haddock skin ASC. However, Hydrolysate3 and 4 of Pollock skin ASC treatments show improvements only after applied for more than 2 h. In the blood hemagglutination test in vitro, haddock and Pollock skin ASC have great influence in blood clot. They form fibrous blood clots while their Hydrolysate1 form similar but smaller ones. Better moisture keeping capacityies are performed by the two ASCs. However, the capacity is lower when the average MW of hydrolysate drops.