The Physical Properties and Renneting Characteristics of the Synthetic Membrane on the Fat Globules of Microfluidized Milk

¹ Department of Food Science, University of Guelph, Guelph, ON, Canada N1G 2W1

The effect of particle size on the renneting properties of the synthetic fat globules that were formed in full fat homogenized milk were investigated using microfluidization. A decrease in the average hydrodynamic diameter of the fat globules from 390 to 313 nm had no apparent effect on the casein load on the synthetic membrane of the fat globules. However, fat globules with smaller diameters decreased the rennet coagulation time and the curd firming rate. The integrity of the curd microstructure also showed signs of deterioration as the diameters of the fat globules were decreased. Rennet curd was also produced from milk after the cream was separated from the milk, washed, and emulsified with whey proteins by microfluidization before being remixed with the skim milk. The resulting curd showed no significant change in coagulation time or firming rate as the fat globule diameter varied from 265 to 640 nm. There was also no significant change in the microstructure of the curds. We concluded that the changes in the properties of curd made from microfluidized milk were caused by restructuring in the micellar casein during microfluidization rather than by the change in size of the fat globules.

Key Words: milk • microfluidization • rennet • microstructure

Submitted on October 21, 1997
Accepted on March 25, 1998