| Corn protein powder is the main one of by-products that produce the starch in corn wet-milling process. It implies more than 60% protein and the major protein fractions are zein (68%). It is insoluble in water. The content of essential amino acids is higher than soybean and wheat. But the content of Lys and Trp is low. These drawbacks limit its application to the food fields. Now, most of starches factories regard it as the animal feed to sell in low price. Facing lack protein resources in the world , the corn protein is used as the animal feed can not satisfied with the requirement that deal with the by-products of starch industries-corn protein powder. Only using modern high and new techniques to deal with the corn protein powder deeply, we can increase its additional value and increase the economic benefit of the business. Thus it will improve total utilization rate of the corn resources.The modern nutrition research discovers that the protein is digested and absorbed mainly in low peptide but not in amino acids after enzymes hydrolyzing. And the amino acids what is consisted of low peptide may not be essential amino acids. In additional to having the easily absorption characteristic, these low peptide still have many good functions characteristic and the physiological activity. They can be used widely in the food field.Corn peptide is the mixture of short peptides that the corn protein is hydrolyzed by enzymes and again is refined. Japan takes the first place in the field of corn peptides' research. Corn peptide food has appeared on market early. In our country, this field still is placed in the starting stage and only has theories reports. There are few corn peptide products in the market. Corn protein is hydrolyzed only by one enzyme in their researches and properties of corn peptide are researched more but the physiological activity studies are researched less.Two kinds of protein enzymes have been used to hydrolyze corn protein to produce corn peptide in this article. Through the single factor experiments and orthogonal test, the optimum hydrolyzing conditions have been determined: Temperature is 55 癈 ,pH value is two enzymes' optimum pH value(pH of an alkaline protease is 8.5 and pH value of pepsin is 7.5). After hydrolyzing 1.5 hours adding alkaline protease with the 4% enzyme concentration, corn protein powder iscontinuously hydrolyzed 1.5 hours again adding pepsin with 3.5% enzyme concentration. In this condition Nitrogen Solubility Index (X) and degree of hydrolysis (DH) are respectively 81.06% and 80.97%. The effect of factors on hydrolysis has been analyzed. Then the hydrolysis is refined by removing bitterness, color, decompression condensing and ice drying and the process parameters to produce corn peptide powder has been determined. At last corn peptide powder is gained and its gotten rate is about 65% and protein content is about 75%. The constitution, physical and chemical properties and physiological function of corn peptide powder are studied. The results show that the corn peptide is abundant in Glu and Leu and most of molecular weight distributions is below about 5000Da. The solubility in water is improved and is not changeable with the changing of pH. It has low viscosity in high concentration. Further more corn peptide has many physiological activity: anti-oxidation promoting yeast fermentation activity anti-fatigue, promoting the alcohol metabolism activity and has quantity and effect connection.Using enzyme-engineering techniques, corn protein powder is produced deeply into corn peptide what is a new generation function factor. Corn peptide makes up the drawbacks of corn protein such as unbalanced amino acids constitution and insolubility in water. Better solubility can make corn peptide present many good characteristic and physiological activity at the same time. It will be extensively applied to the raw material of heath food. As people's consciousness of health is building up, the development of corn peptide will have the vast market foreground necessarily. |
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