Study On The Chelating Ability Of Restricted Hydrolyzed Zein To Zn²⁺ And Fe²⁺

Zein is rich in glutamine,which can be hydrolyzed into glutamic acid by specific enzymes to obtain bioactive peptides with good chelating ability of divalent metal ions.At present,the study of bivalent metal ions chelated by bioactive peptides is still weak and needs to be further explored.In this study,Zein was used as the raw material.Firstly,the single factor test confirmed that Zein had good chelating capacity of Zn²⁺and Fe²⁺,secondly,the chelate was characterized by ultraviolet and infrared.The double-enzyme hydrolysate was separated by Sephadex G-15and the amino acid composition was determined.,then the binding result of Zn²⁺,Fe²⁺with functional groups of Zein hydrolysate were analyzed.Finally,some functional properties of the hydrolysate and the antioxidant activity of the chelate were determined.The main findings are as follows:1.Under the pH 12 reaction system,Zn²⁺chelation ability and Fe²⁺chelation ability was used as the evaluation index respectively,single factor experiment was carried out to study the effect of alkaline proteinase,proteinase K and double enzyme restriction hydrolysis based on enzyme sequence on the Zn²⁺chelating ability and Fe²⁺chelating ability of Zein.The results showed that Zein had the best Zn²⁺chelation ability and Fe²⁺chelation ability when proteinase K was added first and then added alkaline proteinase.The optimal hydrolysis conditions with Zn²⁺chelation ability as the evaluation index were proteinase K:reaction time 2 h,substrate concentration 10 mg/mL,enzyme addition amount 2.4 U/mg,reaction temperature 60°C,Alkaline proteinase:reaction time 3 h,substrate concentration 10 mg/mL,enzyme addition amount 8.0×10⁵ U/mg,reaction temperature 50°C;Zn²⁺chelation ability was 13.72 mg/g Zein,corresponding hydrolysis degree was 28.91%.The optimal hydrolysis conditions with Fe²⁺chelation ability as the evaluation index were proteinase K:reaction time 4 h,substrate concentration 10 mg/mL,enzyme addition amount 2.4 U/mg,reaction temperature 55°C,alkaline proteinase:reaction time 4 h,the substrate concentration is 10 mg/mL,the enzyme addition amount is 1.4×10⁶ U/mg,and the reaction temperature is 55°C,Fe²⁺chelation ability was 37.11?g/g Zein,and the corresponding hydrolysis degree is 36.11%.2.In order to determine the Zn²⁺,Fe²⁺and Zein of restricted hydrolyzed to form a new substance with chelating reaction,the Zein hydrolysate and chelate prepared under the optimal chelating hydrolysis conditions of Zn²⁺and Fe²⁺was subjected to ultraviolet and infrared scanning,respectively.Meanwhile Sephadex G-15 was used to separate the double enzyme hydrolyzate and determine the amino acid composition of the separated components.The results showed that the position and intensity of UV-infrared absorption peaks of Zein hydrolysate and chelate changed significantly?P<0.05?,the Zein hydrolysate separation component which first added with proteinase K and then added hydrolyzed by alkaline proteinase-restricted hydrolysis.The protein hydrolysate separation component mainly contains acidic amino acids,and comprehensive analysis of Zn²⁺and Fe²⁺is coordinated with-COOH and-NH₂ in the Zein hydrolysate to form a new substance.3.Enzymatic hydrolysis caused a substantial change in the structure of Zein.The functional properties of the hydrolysate prepared under the optimal hydrolysis conditions with best Zn²⁺chelation ability and Fe²⁺chelation ability were compared.The antioxidation of Zn²⁺chelate and Fe²⁺chelate was studied.The results showed that the Zein had better emulsifying activity than the hydrolysate,and the emulsification stability of the hydrolysate was better than Zein.The enzymatic hydrolysis of Zein had better foaming characteristics and it can increase molecular flexibility.The content of free sulfhydryl groups decreased,and Zn²⁺chelate and Fe²⁺chelate have better DPPH,·OH,ABTS+·scavenging effects.