2.1. Milk samples
Pasteurized whole and skim milk (4% and 0.30% fat content,respectively) were obtained from the Washington State University Creamery.
Pasteurized milk was used to minimize any competitive flora effect during processing. Milk was characterized for initial microbial load and was kept under refrigerated conditions (4 C)until used, no longer than 24 h.
The pH and electrical conductivity of milk samples were determined with a pH/conductivity Orion 4-Star Meter (Beverly, MA, USA) at 21 C. For skim milk, pHwas 6.56 (0.01) and conductivitywas 5.12 (0.01) mS cm1; for whole milk, pH was 6.31 (0.02) and conductivity was 4.90 (0.01) mS cm1.