Using True Protein In Cheese Yield Formulas
Using True Protein In Cheese Yield Formulas
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USDA has adopted TRUE PROTEIN as the protein measure to be used under Federal Order reform. Currently, almost all of the US dairy industry uses TOTAL or CRUDE PROTEIN for pricing milk. The primary exception is New York State, where most protein premiums have been based on true protein for more than a decade. USDA stated several reasons for adopting true protein over total protein. First, true protein is a better measure of the actual protein in milk, because it does not include the non-protein nitrogen (NPN) that is included in Crude Protein. Since NPN plays no role in product yields, it is of little, if any, economic value to processors. Second, true protein is already measured by modern infrared laboratory equipment. In fact, the current machines used to measure crude protein actually measure true protein, then adjust up for the NPN factor. Because true protein better measures useable milk protein, and modern lab equipment already measures true protein, the movement to true protein is a logical one by USDA, and supported by most of the industry. Research shows that the relationship between true and total protein is usually an additive one, although individual herds and cows vary. Work at Cornell University found that milk generally contains about 0.19 pounds non-protein nitrogen per cwt. A Federal Order market study from Texas confirms this relationship. In fact, it finds the relationship to be very consistent at 0.18 lbs. per cwt., regardless of season or herd protein test. Thus the research shows that true protein concentration is usually 0.18 to 0.20 pounds per cwt. lower than crude protein. Plants paying on cheese yield that adopt the true protein measurement will need to modify their cheese yield formulas to reflect the change. Casein comprises a greater portion of true protein than total protein. This greater casein concentration will increase the casein recovery factor when true protein measures are used in cheese yield formulas. The calculations for this adjustment are demonstrated below:
If Total Protein = 3.2, then True Protein = 3.01 (based on estimated average of 0.19 lbs. non-protein nitrogen per cwt.)
If crude protein contains 78% casein, then true protein would contain 78% x 1.063 or 82.9% casein. NOTE: This casein percentage adjustment will also be necessary when determining casein-to-fat ratio in milk based on true protein, and adjusting for excess fat, if any, in milk.
Comparison of Cheese Yield Formulas for True and Crude Protein. Under Crude Protein, the Cheese Yield formula for Cheddar used by many cheese plants usually looks like this: (% Fat x 90% Recovery + CRUDE Protein x 78% Casein - 0.1) x 1.09 With true protein, the casein factor needs to increase to 82.7% to adjust for the higher concentration of casein in true protein: (% Fat x 90% Recovery + TRUE Protein x 82.9% Casein - 0.1) x 1.09 Example for cheese yield for milk containing 3.7% fat and 3.2% crude protein or 3.02% true protein:
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