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Some Observations on the Freezing Point of Cream and its Use in Detecting Added Water

F. J. Doan

Dairy Husbandry Department, Pennsylvania State College, State College, Pennsylvania

ABSTRACT

A very brief review of literature, only, is included since no published data was found bearing directly on the subject of this paper.

From data presented it is concluded that cream and skimmilk have the same freezing points as the original sample of milk from which they are separated. If this is so then the normal range must be from –0.530°C. to –0.566°C. as for milk, with an average of –0.550°C.

Winter's formula as given in the "official methods" of the A.O.A.C. is theoretically incorrect and while this fact does not make it entirely inapplicable for whole milk or skimmilk it shows a great degree of inaccuracy when applied to samples of cream, the degree increasing as the cream samples become richer in fat. Data is given showing the inaccuracies when it is applied to a series of diluted cream samples.

A modified formula is given which is theoretically more accurate and when applied to the same samples of cream mentioned above gives fairly close results as compared with actual amounts of water known to have been added.

The amount of added water found in a cream sample or a skimmilk sample does not correspond with the amount added to the original whole milk, in case such diultion was made before separation; but the latter can be calculated by the formula shown if the weights or volumes of both the cream and skimmilk portions are known together with the respective amounts of water in each, as found by cryoscopic examination and the use of the "serum" formula.

Published by permission of the Director of the Agricultural Experiment Station. Contribution from the Department of Dairy Husbandry. The Pennsylvania State College, No. 415.