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Pasteurization Efficiency of the Vacreator when Used on Ice Cream Mix

Department of Food Technology, University of Illinois, Urbana

H. C. Lingle

Research Laboratories, Cherry-Burrell Corporation

ABSTRACT

As the amount of steam used in the Vacreator was reduced, the average time required for the test liquid (water) to pass through the first chamber was increased from 0.75 to 0.89 sec. Under set conditions, as the pump capacity was increased from 1,800 to 5,300 lb. per hour the time required for the test liquid to pass through the first chamber was decreased from 0.74 to 0.61 sec. The time required for complete travel through the Vacreator varied from 5.63 to 7.16 sec., depending upon the capacity at which the machine was operated. The 170° F. temperature ordinarily used in the second effect was found to be high enough to have considerable lethal effect.

If, from a Public Health angle in the case of mix pasteurization, it is desirable to require the temperature effect of the first chamber treatment to be the equivalent of or better than that obtained with pasteurization at 155° F. for 30 min., then, according to the results obtained, the temperature carried in the first effect should not be less than 194° F.

Dropping the preheating temperature from the standard temperature of 110 to as low as 49° F. did not alter the efficiency of pasteurization. When the infeed pump speed was increased above the rated capacity of 3,000 lb. per hour, there was no change in the efficiency of pasteurization.

When the amount of the steam used in the first chamber was reduced from 500 lb. to approximately 200 lb. per hour, the efficiency of pasteurization remained the same. Partial clogging of the spray jets in the first chamber or removal of the spray pan did not result in a change in the effectiveness of the pasteurization process.

Overloading the Vacreator as much as 50 per cent above the rated maximum capacity did not result in unsatisfactory pasteurization of the mix.

Reducing the steam pressure to below that recommended for proper operation of the Vacreator reduced the velocity of the product passing through the first chamber so that there was sufficient time for proper pasteurization.

When the Vacreator is operated so that a minimum temperature of 194° F. is maintained in the first chamber, results will be obtained that will equal or better the Public Health protection afforded ice cream mix pasteurized at 155° F. for thirty min. in a sealed glass tube.

¹ Now associated with the Dean Milk Co., Research Laboratories, Rockford, Illinois.