Rapid Method for the Determination of Casein in Milk by the Dye Binding Method and for the Detection of Mastitis

Abstract

Casein is isolated from a diluted sample of skimmilk by centrifuging at pH 4.6. The wet casein precipitate is treated with a dye reagent which precipitates the protein quantitatively. The remaining free dye is measured by a spectrophotometer. A nonfat powder of known casein content may be used to construct a standard curve relating absorbance of the free dye to percent casein in the reconstituted powder. The method indicated a highly significant relation between the percent casein in the total protein of the milk and the extent of mastitis as measured by the California Mastitis Test.