Preparation And Characterization Of Calcium Chelated Corn Polypeptide

Corn gluten meal,rich in protein,is the main by-product of wet production of corn starch.However,corn gluten meal has some shortcomings,such as rough taste,poor water solubility,special smell and color,especially the lack of essential amino acids,such as lysine,tryptophan and so on.These disadvantages affect its application in the food industry,thus,corn gluten meal is usually used as feed or thrown away.In this experiment,corn gluten meal was used as raw material to purify and concentrate corn protein,and then corn protein polypeptide was prepared by enzymolysis under certain conditions with hydrolysis degree as index.The result showed that the hydrolysis effect of trypsin was the best,and the hydrolysis degree was 28.5±0.056%.The extraction conditions of corn protein polypeptide were optimized through L₉?3⁴?orthogonal tests,considering the effects of hydrolysis time,hydrolysis temperature,enzyme dosage and pH on the hydrolysis of corn polypeptide.The optimum extraction conditions were as follows:pH 7.5,enzyme dosage 1.6%,temperature 40?and time 3 hours.At this time,the degree of hydrolysis was 28.21%.The solution of corn protein polypeptide prepared under the optimum process was chelated with CaCl₂ to prepare corn polypeptide chelated calcium under certain conditions with the chelating rate as index,considering the effects of chelating temperature,chelating time,peptide-calcium ratio and multiple addition of absolute ethyl alcohol on the chelating rate.On the basis of single-factor experiment,the experimental conditions of corn protein polypeptide calcium were optimized through L₉?3⁴?orthogonal tests.The optimum chelating conditions were determined as follows:chelating time 30mins,chelating temperature 30?,peptide-calcium ratio 10:1,multiple addition of absolute ethyl alcohol 8,chelating rate up to 79.33%and the corn polypeptide with molecular mass<3kDa.Under this condition the corn polypeptide was easier to combine with calcium.The structure of corn polypeptide chelated calcium was characterized by ultraviolet spectroscopy,Fourier transform infrared spectroscopy,SEM scanning electron microscope and X-rays diffraction.The results showed that the chemical structure of corn polypeptide and polypeptide chelated calcium changed to a certain extent by the analysis of UV,IR and X-rays diffraction.This result indicated that corn polypeptide formed a new chelation with calcium.