Effect Of Emulsifier On The Stability Of Casein-stabilized Emulsions

Emulsifier is an important component of food emulsions, which has essential effect on the stability of food emulsion system. Monoglycerides and sucrose ester, two kind of multi-dimensional alcohol ester emulsifiers, are the largest quantity of food emulsifiers used in emulsions. In this paper, the effects of monoglycerides, sucrose esters and associative emulsifiers on the casein emulsion were investigated, containing particle size distribution, creaming rate, rate of partial coalescence of fat, liquid protein concentration, emulsifier concentration in the interface, microstructure, and so on. The functional mechanism of emulsifier on the casein emulsion stability was also studied. The main conclusions are as follows:(1) GC-MS and HPLC-UV were employed to detect BS-2000. The composition of fatty acids of BS-2000 was investigated, and the compounds were well separated. HPLC-UV, HPLC-RI and HPLC-ELSD were compared to measure the monoglycerides and sucrose esters, and the ELSD was found to the most suitable. Therefore, HPLC-ELSD was employed to determine the standard recovery of interface emulsifier concentration of monoglycerides and sucrose esters. As a result, the average recoveries were 92.9% and 92.3%, respectively. The relative standard deviations were 2.1 and 1.1, respectively. The variation coefficients were 2.2% and 1.2%, respectively. The results showed that the repeatability of the measure method was favorable, which achieved the requirement of the analysis methodology.(2) With the increase in the amount of monoglycerides, D[3, 2] and D[4, 3] values of the emulsion decreased first and increased later. The minimum appeared when the monoglycerides load was 0.60%. The change tendency of creaming rate was similar as the particle size, indicating that both have a good correlation. Moreover, the fatty part coalescence rate declined until a stable value. The interface monoglycerides concentration increase first, then decreased, and at last increased again. The liquid phase protein concentration gradually increased. The microscopy result showed that with the increase in the amount of monoglycerides, the fatty ball decreased first and then increased, and the minimum size was in the amount of 0.60% monoglycerides. It was proved that the fatty ball size changed with the different amounts of monoglycerides. (3) With the increase in the amount of sucrose esters, D[3,2] and D[4,3] values of the emulsion decreased overall. A similar decline tendency of the creaming rate was also found as well as the fat partial coalescence rate. What's more, the liquid protein concentration increased. When the amount of casein was 0.25%, the interface concentration of sucrose esters decreased first and then increased. However, when the amount of casein was 0.50~1.00%, the interface concentration of sucrose esters increased. The microscopy of emulsions indicated the size had changed with the different amounts of sucrose esters.(4) As to the associative emulsifiers, with increasing the amount of sucrose esters, D[3,2] and D[4,3] values decreased first and then increased. The creaming rate showed a similar change tendency as the particle size. The liquid phase protein concentrations increased. The interface monoglyceride concentration revealed a declining tendency, and the maximum and minimum were 10.64 mg/m~2 and 7.36 mg/m~2, respectively. On the contrary, the interface concentration of sucrose esters showed an increase tendency, the maximum and minimum of which were 9.93 mg/m~2 and 1.63 mg/m~2. The result of microscopic analysis demonstrated that the fatty ball size decreased first and then increased. When the ratio of associative emulsifiers was 1:1, the fatty balls were well-distributed and the size reached the minimum.