Year: 1922
Type: article
Abstract: I t 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. In studying the decomposition of cream and butter, this method is used to show the relation of amino nitrogen to the quality of the product. In the manufacture of butter, some of the nitrogenous constituents of the cream are occluded by the fat and remain in the finished product. In order to measure the relative proportion of amino nitrogen in milk, cream, buttermilk and butter, it is desirable to have a procedure that is adaptable to all of these products. Acetic acid~ as used to precipitate the casein in milk will not always work satisfactorily on cream and butter, especially when considerable proteolysis has taken place. In some cases the precipitation of the casein is incomplete and filtration extremely slow and difficult. In the procedure outlined below, picric acid and acetic together have been used satisfactorily te
Source: Journal of Dairy Science
Author: L.W. Ferris
Institution: United States Department of Agriculture
Language: English
Subfield: Food Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: bronze
OpenAlex ID: W1964498265