ISO 5542:1984

Is applicable to raw or thermally or mechanically processed whole milk, partly skimmed and skimmed milk provided that the samples are in good condition. In some cases it can also be applied to preserved samples. The principle of determination consists in adding amido black solution to a test portion resulting in the formation of an insoluble dye-protein complex which is removed by centrifuging or filtration, followed by determination of the protein content from the absorbance of the resulting solution containing an excess of dye.