A definite relationship between the somatic cell count of milk and catalase activity was observed when the oxygen liberated was measured accurately with a Warburg apparatus. The somatic cell count could be predicted from the equation: log Y = 2.79 + (1.35 log X), where Y = the somatic cell count in thousands, and X = the microliters of oxygen evolved from 0.5 ml of 1% hydrogen peroxide per milliliter of milk in 40 min at 30 C. The correlation coefficient for this regression is 0.90, and is highly significant.
Catalase activity of milk was maximal over the pH range of 5.64 to 10.74 and at 18 C. Activity was close to the maximum at 15 and 22 C and only slightly less at 10 and 25 C. Milk which contained 590 catalase-producing Staphylococcus aureus organisms per milliliter liberated very little oxygen; such numbers would not influence conclusions from the catalase test.
1Published with the approval of the Director of the Purdue Agricultural Experiment Station as Journal Series Paper No. 2918.
2Present address: The Pillsbury Co., Minneapolis, Minn.