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A Method for the Determination of Amino Nitrogen and Ammonia in Cream and Butter¹

Food Control Laboratory, Bureau of Chemistry, United States Department of Agriculture

ABSTRACT

It is the general opinion of dairy chemists that the nitrogenous constituents of milk and cream undergo certain changes which begin at an early stage, the degree of change depending, principally, upon the kind and amount of contamination and the temperature at which the product is held. These changes may be caused by the action of enzymes and bacteria upon the proteins with the production of intermediary products of more or less complexity, the simplest being the amino acids. The more favorable the conditions for enzymic and bacterial activity, the greater should be the number of amino groups formed from the original protein. A determination of the amino nitrogen reacting with nitrous acid in a solution from which the undecomposed proteins have been removed by filtration, will be a measure of the proteolysis that has taken place except for the nitrogen that has been synthesized into protein by the microorganisms present.

¹ Published by the permission of the Secretary of Agriculture