Study On The Preparation And Biological Activities Of Zinc Chelating Small Peptides From Silver Carp Protein

The undeveloped processing technology of freshwater fish is a big obstacle in the way of the development of freshwater fishery. Therfore, studies on new processing technology of freshwater fish become more and more important. Small peptides obtained from enzymatic hydrolysis of fish protein not only has lots of functional properties, but also can improve the absorbability of zinc. It has been proved that amino acid chelated zinc has many biological activity which can promote animal growth and improve immunity of animals. There are many researches about the preparation and application of amino acid chelated zinc, but studies on the preparation and activity of zinc chelating small peptides are very limited. This paper studied the preparation of small peptides using controlled-enzymatic hydrolysis of silver carp protein and zinc chelating small peptides as well as the biological activity of zinc chelating small peptides in mice. The main results were shown as follows:1 preparation of small peptides by using controlled-enzymatic hydrolysis of silver carp proteinThrough single factor test, suitable conditions were obtained as follows: In conditions of continuous mixing, firstly using alkaline protease as hydrolysis enzyme, at silver carp protein concentration of 3.3%, enzyme dosage of 5018u/g, hydrolyzing at 55℃with initial pH9.5, inactive enzyme after 3h of hydrolysis. Then adding flavor enzyme at dosage of 5018u/g , and hydrolyzing at 55℃for 3h. The main hydrolysis products were confirmed to be small peptides with molecular weight distribution between 508.745 and 195.704Da by GPC analysis.2 preparation conditions and characterization of zinc chelating small peptides from silver carp proteinThe optimum condition for preparing zinc chelating small peptides was as follows: the concentration of protein hydrolysates was 7%, the mol ratio of hydrolysates to zinc was 2:1, at 70℃pH 6.0, and the chelating time was 20min, the chelating rate of zn²⁺ was 55.15% at the optimum conditions. To avoid interference from zinc hydroxide formation, the pH value should be strictly controlled in accordance with reaction conditions during the preparation of zinc chelating small peptides.The optimum condition for preparing zinc chelating small peptides in acetone aqueous system was as follows: the acetone concentration of 45%, the mol ratio of hydrolysates to zinc was 3:1, reaction temperature 70℃, and reaction time was 10min, the chelating rate of zn²⁺ was 49.92%. Acetone can undermine the role of zinc ion hydration and suppress the formation of zinc hydroxide. and pH value can be ignored on the effects of chelation reaction to simplify the preparation process, but the chelating rate of zn²⁺ in solvent-water mixtures is slightly lower than that in aqueous phase.UV and IR analysis and DSC analysis showed that the product was small peptides chelating zinc.3 Biological activity of zinc chelating small peptidesZinc chelating small peptides can markedly improved zinc content in mice liver and serum; under the same dosage of zinc , zinc content in mice liver and serum and akp vitality in the groups supplied with high doses of zinc chelating small peptides was significantly higher than that of supplied with the same dosage of gluconate zinc and sulfate zinc groups , which meaned that zinc chelating small peptides has a significant effect of zinc supplementation, and is more effective than the same dose of zinc gluconate or zinc sulfate.Oral administered with zinc chelating small peptides can significantly reduce liver MDA content of mice, improve the activity of T-AOC of mice, which indicated that zinc chelating small peptides had antioxidant activity. Compared to zinc gluconate and zinc sulfate, zinc chelating small peptides showed more significant antioxidant activity in mice at the same dose.