INFLUENCE OF MAJOR PROCESS AND FORMULATION PARAMETERS ON MICROFLUIDIZED FAT GLOBULE SIZE DISTRIBUTION AND EXAMPLE OF A PRACTICAL CONSEQUENCE

The influence of certain process variables (pressure and temperature), as well as composition variables (fat, protein and low molecular weig ht emulsifier concentrations) and the emulsification process used, on the size distribution of milk fat globules was studied in a dairy oil- in-water model emulsion and in homogenized milk. In the first case, th e use of a central composite experimental design allowed us to obtain two nonlinear multiple regression equations relating the volume-weight ed average diameter (d(v)BAR) of the fat globules as well as the relat ive width of size distribution (CV) to the emulsification pressure (7. 8-76.3 MPa) and temperature (35-100-degrees-C), and to sodium caseinat e (0.5-3.9 wt.%), butter oil (5.2-14.7 wt.%) and monoglyceride (0.08-0 .88 wt.%) concentrations. These two functions, which account for 93.7 and 81.7%, respectively, of the variation in the average diameter and in the size distribution width of the microfluidized fat globules, wer e used to describe certain interactions between the different variable s affecting the size of the microfluidized fat globules. They were als o used to define the optimal conditions that correspond to the extreme s of the average particle diameter and of the distribution width of th e fat globules. These two functions also allowed us to predict fat glo bule parameters as a function of process and formulation conditions. I n the second case, the microfluidization process lead to an overestima tion (up to 0.3%) of the milk fat content as determined by a infrared analyser.