Detection Of Undenatured Whey Protein And It’s Effect On Product Properties

Whey protein is a kind of nutritional value and high quality protein of milk because of its essential amino acids complete kinds, abundant and proportion and appropriate. And it plays an important role in sustaining the health of the body bowel, muscle tissue and oxidation system health.Firstly, Study the detection method of undenatured whey protein in milk with colorimetric method. In the study, the formula of the biuret’s method and Coomassie Brilliant Blue G-250 were optimized by orthogonal test. Under the condition of the optimal, contrast the precision and the rate of recycle, the result dedicated that the method of Coomassie Brilliant Blue G-250 was better. The optimal preparation method is that we should add 100mg G-250 powder,60mL 85% phosphoric acid, 100mL95% ethanol. Finally, put the capacity to 1000ml with distilled water. In the condition, the standard curve of the S value is 0.419, the test of recovery was 98.64%, the coefficient of test repeatability RSD was 0.814%, accurate test results. The result is wanted.After different heat treatment, whey protein in milk can present different degrees of degeneration. Choose colorimetric method to determine undenatured whey protein content. And pH, solution protein hydrophobicity, sulphur content, colour and lustre, sensory characteristics, turbidity, thermal stability and particle size as an index, were studied. The results showed that the processing temperature is higher, its protein denaturation degree enhanced. The content of undenatured whey was from 4.573 mg/mL to 0.328 mg/mL; Degeneration rate of undenatured whey protein content and protein hydrophobicity and sulfhydryl content is inversely proportional, turbidity and the stability have a positive correlation with it.After different temperature preheating the milk, we get different samples. Make different yoghurt using the preheating milk. Then, measure viscosity, whey exhalation rate (water), pH, colour and lustre, the sensory score as an index to research different heat treatment conditions about the whey protein content on the yogurt and the influence of the quality during storage. The results showed that 80-100 ℃ handling raw materials, the yogurt sensory score, colour and lustre is better, and it has high viscosity, high water-based (whey exhalation rate low), and to maintain a good stability and flavor characteristics during the storage.Powder of different thermal classification of the basic indexes determination, combined with microscopic scanning and the nature of the different thermal grading powder particle size analysis, we can provide theoretical basis for further experimental study. The results showed that low temperature powder solubility is better than the solubility of high and medium temperature powder; Low temperature of powder particle size is smaller; Scan results shows that low temperature powder surface smooth, full and high temperature in the powder surface in different degrees of depression and fold, and clustering, which reduces the solubility.