| Poultry eggs production of China are very large. Compared with developed countries, there are some deficiencies in Chinese egg processing industry, such as low processing capacity, low-depth processing and lack of species etc. There is large number of high value-added substances in eggs, particularly in egg yolk. Egg yolk oil is one kind of such substance. Extraction of egg yolk oil by enzymatic method has high value to industrialize. By- products of this process– the solution of egg yolk protein is of high value and nutrient-rich. This paper was conducted to make good use of the part of egg yolk protein resources, and provide academic bases for comprehensive utilization of egg yolk.Firstly, the composition and existence state of the solution of egg yolk protein were analyzed. Then our research was revolve around enhancing calcium-binding capacity of the solution of egg yolk protein. Single factor experiment and central composite design was used to find the optimum condition, and the optimum condition is: temperature for trypsin is 45℃, enzyme dosage is 5.2%, pH 9.1, hydrolysis time is 132 min. SAS software was used to analyze variance of regression equation. It was found that the enzyme regression equation forecast the results very well and the verification experiment also proved the accuracy of the equation. After enzymolysis of trypsin, the calcium-binding capacity of the solution of egg yolk protein was enhanced form 54 mg/100g.pr to 116 mg/100g.pr. Hydrolysate of egg yolk protein with the molecular weight of 1800Da to 2500Da had the highest calcium binding capacity.Secondly, procession research was conducted to purify the solution of egg yolk protein by membrane separation technology, and egg yolk protein polypeptide powder was prepared. This solution was pretreated by degreasing, mechanical filtration and microfiltration. Then the solution was treated by the ultrafiltration membrane with Molecular Weight Cutoff of 100,000Da. Then nanofiltration with 300Da Molecular Weight Cutoff was chosen to retain and enrich bioactive peptide. In this procedure, 92% bioactive peptide of ultrafiltration permeates with the ability to promote absorption of mineral was cut off by nanofiltration. Retentate of nanofiltration was freeze-dried into egg yolk protein polypeptide powder.The calcium binding capacity of egg yolk protein polypeptide powder is 258 mg/100g.pr. Ingredients of this powder is, protein content: 75%, ash: 13%, salt content: 9%. The ratio of salt in this powder was reduced from 15% to 9%. This egg yolk protein polypeptide powder is a mixture, which molecular weight is mainly distributed between 3200Da and 1000Da.Lastly, the preparation of enzymolysis egg yolk protein powder was studied. Fishy smell elimination became the focus of our study. The solution of egg yolk protein was defatted to decrease the amount of fishy smell substance in fat. Among several ways of fishy smell elimination, the technology ofβ-CD embedding was chosen to carry further research. The optimum condition ofβ-CD embedding was optimized by single factor experiment, that is,β-CD dosage : 4%; water bath temperature : 70℃; water bath time: 30 min. The solution of egg yolk protein containingβ-CD was spray drying into enzymolysis egg yolk protein powder. The composition of enzymolysis egg yolk protein powder containingβ-CD is, protein: 56%; fat: 2%; ash: 19%; salt: 12%. There is large amount of ash and salt in the enzymolysis egg yolk protein powder. Compared to the solution of egg yolk protein, the activity of this powder decreased to a certain degree. In GC-MS, the results showed that volatile substances of enzymolysis egg yolk protein powder, such as aldehydes and ketones, was greatly decreased after fishy smell elimilation.
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