Distribution of Protein in California Milk in 1983

The suitability of California raw milks for the production of cheese was evaluated during 1983 by measuring the distribution of nitrogen in 1417 samples of farm milk from four major dairy regions of California. Both Kjeldahl (431 samples) and the Udy dye-binding procedures (986 samples) were used. True protein concentrations measured by Kjeldahl varied from 2.66 to 4.41% and averaged 3.32%. For samples measured by Udy, true protein concentrations ranged from 2.56 to 3.93% and averaged 3.15%. Casein as a percent of true protein varied from 69.1 to 80.4% and averaged 76.4% for samples analyzed by the Kjeldahl procedure. For samples analyzed by the Udy procedure, casein as percent of true protein ranged from 72.8 to 80.7% and averaged 77.0%. There was close agreement between values obtained by the Udy and Kjeldahl procedures, which suggests that milk can be chosen for cheese production on the basis of its casein content using the Udy procedure.