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Actinomyces in Milk with Special Reference to the Production of Undesirable Odors and Flavors¹

Laboratories, National Canners Association, Seattle, Washington

ABSTRACT

Actinomyces are often present in market milk samples. In normal samples these organisms constituted about 2.5 per cent of the total organisms present. In abnormal samples, particularly those drawn from cows in dusty stables, this figure may reach 50 per cent.

The principal means of entrance to milk are hay, straw, grain, soil and dust raised from these materials.

Actinomyces may under certain conditions cause an obnoxious bitter-moldy taste to develop in milk after some hours storage. The term "actinomyces taste or odor" is suggested to describe the characteristic taste and odor of actinomyces.

Two outbreaks of bitter-moldy milk in the same dairy were traced to the presence of large numbers of actinomyces. The source of the contamination was probably hay and straw.

Eleven species were identified from the milk. The two most active species concerned were A. griseus group and A. albus. These organisms grow readily in milk and are able to produce profound changes in the casein and whey. The extremely diffusible and volatile substance which causes the odor and taste so characteristic of actinomyces is not known.

Actinomyces may cause stale, musty and moldy odors in such foods as walnuts, dried fish, cereal grains and possibly dried eggs. They occur together with molds in many foodstuffs, especially those in a dried condition.

In studying actinomyces or in attempting to isolate them from foods or other materials, synthetic media combined with long low temperature incubation should be used. The ordinary methods and media with incubation at 37°C., are unsatisfactory.

¹ Work done at N. J. Agr. Exp. Stas., New Brunswick, N. J. Acknowledgment is due Dr. J. G. Lipman, Director, and Mr. L. S. Riford formerly Assistant Dairy Husbandman for criticism and encouragement during the progress of the investigation.