A Critical Study of the United States Public Health Service Definition for Homogenized Milk with Some Recommendations

Homogenized milk was first defined by the United States Public Health Service in the 1939 edition of the recommended Milk Ordinance and Code.In the intervening years this definition has been adopted by some health agencies, made the basis of a modified definition by others and has been used by many milk dealers as a standard for efficient processing with which their product could be compared.There has been, however, no commonly accepted procedure for carrying out the determinations involved in the definition.Several investigators (2, 3, 9, 11, 13) have found that the definition is not easy to comply with and have criticized it for failing to specify a definite method of obtaining the top 100 ee. of a quart bottle of milk for analysis, for not stating the temperature at which the milk should be stored and for failing to specify a method of analysis.They have shown that different methods for removing the upper layer of milk from a quart bottle, after storage, result in varying fat contents but unfortunately different procedures for accomplishing this have been proposed.A.further suggestion on this matter was recently made by Levine and Feingold (7) who recommend the mixing of a sample, its transference to a "Cream-top" type of milk bottle for storage and the use of a specially constructed plunger which allows the top 100 cc. of the milk to be poi~red off without disturbing the remainder.No evidence is presented to show that remixing of the homogenized milk and a second gravitation do not affect the results, or that the peculiar shape of this type of bottle has no influence on gravitation.A microscopic technique for ascertaining the thoroughness of homogenization of milk has been described by Farrall, Walts and Hanson (5).The