| Milk is a complex colloidal system. It often appears fat float and protein flocculation phenomena during manufacture process and influence product quality and stability, which is a major problem that puzzled Dairy Enterprises. Thus it becomes necessary for the research of characteristics of main components in dairy system. During practical manufacture process, Dairy Enterprises often enhance system stability by adding emulsifiers and thickeners. But the choosing of additives and adding amounts are empirical and stochastic, which lack theoretical guidance.Casein micelles, whey protein and fat globules were acquired by centrifuge in this research. The changing of stability with different acidity of caseins and whey proteins were researched and analyzed from the microscopic. Method of combining Zeta potential with surface tension was first used to research the mechanism between three main components and two emulsifiers. The results were as follows:1. When the pH values of casein solution was less than 7, the reduction of pH resulted in dissolve of colloid calcium phosphate and diminishes of average particle size. Zeta potential value (absolute value) and conductance value decreased gradually, which indicated that the static exclude strength diminished and caseins became coagulated. So the average particle size increased and systems became instability. Scanning results of TURBISCAN LAB showed that solutions with the pH between 5.8 and 6.6 were more stable. Casein solution had the minimal average particle size 26.03nm at pH 6.2.2. Zeta potential value (absolute value) of whey protein solutions decreased with the fall of pH. Viscosity first increased and then decreased, while surface tension and average particle size first decreased and then increased and had the least value 55.04mN/m and 20.286nm at pH6.6. Whey protein solutions with the pH between 5.8 and 6.6 were more stable and had the best stability at pH6.6, System keep stable with the effect of spatial effect, static exclude strength and other forces. When pH decreased,molecular structure expensed and strengthened spatial effect, which made up for the decreases of static exclude strength. So system could also keep stabilize when pH>5.8. But the further decrease of pH, decrease of repulsion potential made the protein molecules aggregates, which decreased the stability of system.3. Influence of HLB and adding amount of emulsifiers to characteristics of fat globule solutions was researched. The results showed that the optimum adding HLB of emulsifier was 9.0 and the optimum adding amount was 0.08% based on this HLB value. After the adding of emulsifiers to fat globule solutions, emulsifier molecules could adsorb onto fat globules surface and formed a compact thin film layer, which kept the emulsion stabilize. Molecules with HLB value 9 could adsorb onto fat globules surface more effectively and enhanced with the increase of adding amount. Conductance value, surface tension value and zeta potential of solutions reached balance when adding amount≥0.08%. Further adding of emulsifiers increased particle amount of system for superfluous emulsifier molecules assembled each other and formed micelles.4. Mechanism of monoglycerid and sucrose ester with caseins was studied. The results showed that Zeta potential of casein and conductance value increased first and then decreased as the increase of adding amount. Surface tension value reached the maximum value with monoglycerid adding amount 0.02% and sucrose ester adding amount 0.01%. Then it decreased rapidly as the further increase of adding amount. Viscosity increased all the time.5. No matter water soluble sucrose ester or oil soluble monoglycerid, when added to whey protein solution, could inhibit aggregate of protein molecules effectively. Zeta potential of whey protein and conductance value increased first and then decreased as the increase of adding amount. Surface tension value reached the maximum value when adding amount was 0.01% and then decreased rapidly as the increase of adding amount.
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