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A Simple Color Test as an Aid in Grading Farm-Separated Cream¹,^,2

Kansas Agricultural Experiment Station, Manhattan

ABSTRACT

1. A simple color test as an aid in grading farm-separated cream at time of purchase is described. Instructions for the preparation of reagents, description of equipment needed and details for the testing procedure are given.
   
2. Although the preparation of reagents and the color standard requires laboratory facilities, the operation of the test is simple and is particularly suitable for field work and cream station conditions.
   
3. The test is based on the depth of color resulting from the addition of 17.6 ml. of 0.1 N NaOH and 1 ml. of crystal violet dye solution of given concentration to 9 ml. of cream in a 2-oz. sample jar. Under the conditions of making the test, the color value obtained primarily is related to the acidity and the physical condition of the cream. Under practical conditions of production the combined acidity and physical condition of cream appear to correlate closely with organoleptic grade.
   
4. Comparison with a prepared color standard of the color value obtained on cream tests permits cream to be graded as first or second grade, and also usually indicates whether it falls in the upper or lower range of the grade.
   
5. The test was used on 780 samples of experimental and commercial cream from stations and creameries during late spring, summer, fall and early winter. Agreement with organoleptic grades was obtained to the extent of 88.8 per cent of the cases. Most of the differences were only borderline variations. In only 1.3 per cent of the samples did the difference represent a whole grade. This was closer agreement than was obtained between organoleptic grades as judged by experienced graders.
   
6. It is expected that the test would be most applicable in those areas where poor cream quality is largely the result of deterioration rather than of flavor defects of other types. Since the test is a partial measure of acidity, the color standard could be modified so that the test would be useful even in states where specific acidity limits are placed on cream grades.
   
7. From the results obtained it appeared that the test offers a means of promoting cream grading in localities where little grading is practiced and where general improvement in quality is needed.
   

¹ Contribution no. 175, Department of Dairy Husbandry.

² This study was supported by a grant from Swift and Company, Chicago, Illinois.