Study on Casein Micelles in Raw and Pasteurized Milk in Native State and During the First Stage of the Enzymatic Coagulation by SEM and TEM

In this study changes in microstructure of casein micelles in raw and pasteurized milk were investigated by SEM and TEM. Milk was pasteurized by L.T.L.T. method (Temperature: 63 oC_ Time:30 minute).Samples of raw and pasteurized milk were taken from research pilot plant of The College of Agriculture. Each sample was divided into two parts. One part of each sample was directly prepared for SEM and TEM, whereas the second part were renneted at 2 oC and kept at this temperature for 24 h. and then prepared for evaluation by electron microscopes. Results indicated that in native state, particularly in raw milk casein micelles are in spherical shape with smooth surface and in the single form. The samples, which stored in the cold were under the effect of the rennet, encounter of filamentous status that might be due to the changes occurred in kappa-casein following the action of rennet along with partial removal of beta-casein and micellar calcium phosphate. Micrographs of casein micelles in pasteurized milk indicated that thermal condition during pasteurization had influenced on increasing of casein micelles size.