Effects Of Ultrasound Pretreatment On Properties Of Collagen From Grass Carp Skin And Activities Of Its Hydrolysates

Collagen from grass carp skin accounts for about 80%of the total protein in grass carp skin,which is green nutritious,safe and easy to degrade,and can effectively solve the food safety and religious limitations of collagen at present,becoming a promising research hotspot in the international food and biomedical field.In this paper,the effects of ultrasonic pretreatment on the physicochemical properties of grass carp skin collagen and the biological activities of enzymatic hydrolysate were studied.Through the study of polyacrylamide gel electrophoresis,fluorescence spectrum,ultraviolet spectrum,circular dichroism,Raman fitting spectrum,surface micromorphology and surface hydrophobicity of collagen,it was found that the content of the secondary structure components of collagen was changed by ultrasonic treatment.The results showed that the?-helix content of the treated collagen was decreased by 39.19%compared with the untreated group,the?-sheet content was irregularly changed,the irregular coil content was increased by 29.31%,and the?-turn content was increased by 10.38%.The results of spectrum analysis showed that the triple helix structure of collagen was preserved by ultrasonic treatment.Scanning electron microscopy and atomic force microscopy showed that the collagen protein after ultrasonic treatment was more uniform and had multiple small subunits trend to a large subunits.The bioactivity study results of the enzymatic hydrolysate showed that the optimum enzymatic hydrolysis conditions were optimized by the Plackett-Burman experiment,the steepest climbing experiment and the Box-Behnken center combination experiment with the DPPH clearance rate as the index 2.97 h,temperature 46.54?,the amount of enzyme added was 7025.2 U/g.Under these conditions,the DPPH free radical scavenging rate of the enzymatic hydrolysate increased by about 13.0%after ultrasonic treatment.The ability of hydrolysis was increased by 20.6%.The OH radical scavenging rate was increased by18.67%,and the angiotensin converting enzyme(ACE)inhibition rate was increased by17.2%.At the same time,the chelating Fe2~+ability,reducing and cell proliferation rate of collagen hydrolysate from grass carp skin were significantly improved,which was attributed to the increase of the content of peptide components with molecular weight less than 5 ku in the enzymatic hydrolysate.In summary,ultrasonic treatment changes the physicochemical properties of grass carp skin collagen and improves the biological activity of its hydrolysate.