MICROFLUIDIZATION OF DAIRY MODEL EMULSIONS .1. PREPARATION OF EMULSIONS AND INFLUENCE OF PROCESSING AND FORMULATION ON THE SIZE DISTRIBUTION OF MILK-FAT GLOBULES

The influence of certain process variables (pressure and temperature) as well as composition variables (fat, protein and low molecular weight emulsifier concentrations) on the size distribution of milk fat globules was studied in a dairy model emulsion (oil-in-water) produced by microfluidization, a mechanical emulsification technique. The use of a central composite experimental design allowed us to obtain 2 nonlinear multiple regression equations relating the volume-weighted average diameter of the fat globules (d(v)BAR) as well as the relative size distribution width (cv) to the emulsification pressure (7.8-76.3 MPa) and temperature (35-100-degrees-C), and to sodium caseinate (0.5-3.9 wt%), butter oil (5.2-14.7 wt%) and monoglyceride (0.08-0-88 wt%) concentrations. These 2 functions account respectively for 93.7 and 81.7% of the variation in the average diameter and in the size distribution width of the microfluidized fat globules and were used to explain certain interactions between the different variables affecting the size of the microfluidized fat globules. They were also used to demonstrate the existence of the optimal conditions that correspond to the extremes of the average particle diameter and of the distribution width of the fat globules. Finally, these 2 functions allowed us to predict fat globule size parameters as a function of process and formulation conditions.