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A Study of the Churn Cleaning Methods Used by Plants Producing Butter of Various Yeast and Mold Counts¹

Division of Dairy Husbandry, State College of Washington, Pullman, Wash.

ABSTRACT

The methods regularly employed for washing the churns in seventeen different creameries in the State of Washington were studied in the light of the yeast and mold counts of the butter of these plants covering samples obtained during 14–28 different months.

Although there are many possible causes of high yeast and mold counts in butter, the consistently low counts of some of these plants indicate that their methods of churn treatment were satisfactory.

The methods of the seven plants having a consistently low yeast and mold content in their butter are given. From a study of these methods, the following factors appear to be important:

1. The use of ample quantities of washwater amounting to at least one third to one-half the capacity of the churn.
   
2. A high temperature of the washwater, preferably 180°–200° F.
   
3. The use of 0.1–0.2 per cent of washing powder solution gives added protection by assisting in the removal of the grease, improving germicidal power and improving the odor of the churn.
   
4. Washing or rinsing with an alkaline crystalline hypochlorite solution of about 50 parts per million of chlorine together with hot water treatment also insured satisfactory results. Only four plants reported the use of this product, but three of these—Nos. 11, 4 and 19—were among the seven plants with the best yeast and mold records.
   
5. Keeping the hot water in contact with the revolving churn for at least 15 minutes.
   

Some fault could be found with the methods used by most of the other plants outside of the seven leaders, although, of course, the poor results obtained may have been due to other causes as well. Five plants mentioned rinsing the churn with cold or lukewarm water immediately after washing. Such a practice is undesirable because it does not leave the churn dry and a wet churn promotes microbial multiplication. In three plants too little water was used in washing. The small amount of water cools rapidly and thus loses its germicidal effect. In four plants the churns were in contact with the hot water for only 5 minutes, which is an insufficient period. One plant using steam sterilization did not produce satisfactory results.

Considering individual samples and the samples from individual plants, no direct relationship was found between yeast and mold counts and the quality and keeping quality of the butter held one month at 36–41° F. However, when grouping the plants in accordance with their median yeast and mold counts, the average scores of each group, both when fresh and after storage for a month at 36–41° F., decreased and the average score losses during storage increased as the median yeast and mold counts increased. Although the results do not prove any direct effect of yeast and mold content on the quality and keeping quality of commercial salted butter, the relationships found are of considerable significance.

It is apparent that in many of our commercial plants more attention might profitably be paid to a more painstaking care of the churn.

¹ Published with the approval of the Director of the Washington Agr. Exp. Sta. as Scientific Paper No. 333, College of Agriculture and Agr. Exp. Sta., State College of Washington, Pullman, Wash.

This article has been cited by other articles:

				. (a) The Cleansing and Sterilizing of Dairy and Ice-cream Plant, by J. G. DAVIS, D.SC., PH.D., F.R.I.C. (Member), Director (Technical), the Express Dairy Co., Ltd The Journal of the Royal Society for the Promotion of Health, January 1, 1948; 68(5): 547 - 556. [PDF]