Study On Enzymatic Coagulation Properties Of Bovine Milk And The Influencing Factors

Coagulation of milk usually includes two forms, one is acid coagulation and the other is enzymes coagulation. Acid coagulation is the necessary technology of the production of yogurt and some acid cured cheese, and enzyme coagulation is an important process of cheese production. Whether milk coagulating property is good or not directly affects both of the production rate and quality of the product of fermented dairy products such as yogurt and cheese. There are 217 lactation milk samples of different ages, birth order and lactation in different seasons and different scale dairy farms, the physical and chemical indicators of milk samples and the curds time、 curd viscosity and water-retaining capacity after adding chymosin were tested, to study the effects of various factors on the quality of raw materials and curd milk quality;The result of this investigation provided reference for selections of milk in fermented milk production, raw milk classification and improvement of dairy cattle breeding condition.Milk samples from different sources of physical and chemical indicators, coagulation time(the time the formation of curd milk samples after adding rennet), curd viscosity and water retention, were determined, The results showed that: Solidification milk enzyme closely related to the origin and quality of milk samples; with the growth of the age and parity of the cows, the milk curd quality show a downward trend; curd quality mid-lactation after calving than milk Early and late lower; curd quality throughout the year in the best season in autumn; large-scale dairy farming standardized manner will help improve the quality of milk and curd quality.The effect of content and somatic cell count in milk main component of the enzyme coagulation properties of milk, the single factor test showed that: the protein content of milk, the fat content, the amount of calcium chloride and somatic cell count and other factors characteristic of the curd significant effects.Best combination was obtained in combination with the factors interaction analysis: protein content is 4.97%, fat 4.93%, calcium chloride content tendency for 4mmol/L, somatic cell number, the less the better. Under the condition of the curd effect is good and curd time is short. In general protein and fat content in normal milk was 3.3% and 3.5% respectively, lower than the curd optimal value, But in the process of cheese production we can improve the effect of the raw milk curd through the pretreatment of raw milk such as ultrafiltration concentration.The further analysis results of milk samples protein components showed that the enzyme curd quality differences of milk samples associated with the protein components content and genotype distribution, for example, cow milk with a better curd quality usually has a higher content of beta globulin. There are 13 species of differential proteins determined by SDS-PAGE electrophoresis and HPLC which are relatively high in the milk; five types of protein among them have a greater influence on the enzyme curd ability of cow milk such as Κ-CNB, αs1-CNB/C, β-CNB, β-CNC and β-LGB.