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Journal of Dairy Science Vol. 29 No. 1 33-40
© 1946 by American Dairy Science Association ®
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Lactic Acid in Dairy Products. IV. Effect of Storage of Evaporated Milk on Lactic and Formic Acid Production, on Ph, and on Acidity and Formol Titrations1

I. A. Gould2, Earl Weaver and R. S. Frantz

Agricultural Experiment Station, Michigan State College, East Lansing, Mich.

ABSTRACT

Increases in lactic acid in evaporated milk stored at 35°, 70° and 100° F. for seven months averaged 1.1, 1.7 and 2.4 mg. per 100 gm. respectively.

These small increases are, for all practical purposes, insignificant. However, storage of the milk at 120° F. for six months resulted in an average lactic acid increase of 14.6 mg. per 100 gms., but at this time the milk had deteriorated far beyond the marketable stage.

In an additional experiment in which evaporated milk was stored at 100° P. for seven months, lactic acid changes were again insignificant, but marked increases occurred in titrable acidity and formic acid, accompanied by a decrease in pH. Titrations of oxalated samples indicated much larger acid-ity increases than were revealed by the standard titration procedure. For-mol titrations were essentially unaffected by storage.

Formic acid constitutes a significant portion of the total acid produced in evaporated milk as a result of storage. Under the conditions of this ex-periment, and when the recovery of formic acid is corrected for retention, the increase in formic acid during storage was equivalent to 71.3 per cent of the total acidity increase as determined by titration.

Limitations of the methods and possible applications of the findings are discussed.

FOOTNOTES

1 Journal Article No. 772, new series, from the Michigan Agricultural Experiment Station

2 Now at the University of Maryland, College Park, Maryland.






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Copyright © 1946 by the American Dairy Science Association ®.