Date of Award:

1962

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Department name when degree awarded

Dairy Manufacturing

Abstract

The addition of the Streptococcus lactis culture in the pasteurized milk was studied, in an attempt to find the effects of the culture in prolonging shelf life of the milk. Various concentrations of the culture were tried to find the optimum concentration that would give favorable effect on keeping quality of the milk. It was found that the addition of Streptococcus lactis culture at the rate of 0.0001 percent has shown promising effects in prolonging shelf life of the milk at the storage temperature of 40 F.

In addition to the above study, effects of added acid in the pasteurized milk, were studied. The adjustment of pH with the addition of the citric acid used in these studies, had no effect in extending the keeping quality of the pasteurized market milk. The acid treatment of the milk showed spoilage earlier than the control samples of the milk.

Two temperatures, 40 F and 50 F were studied to find suitable temperature for storage of the milk. It was observed that the 50 F is not a desirable temperature for storage of pasteurized milk. A 40 F temperature was found better for storage of the milk.

Bacteriological studies done simultaneously, on pasteurized milk stored at 40 F, showed that the coliform organisms did not multiply at that temperature.

The initial bacterial counts on psycrophilic organisms were negative; but after seven days their presence was in large number.

The number of organisms as determined by the Standard Plate Count, was not a reliable indicator of the keeping quality during storage temperature of 40 F.

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