This International Standard specifies a method for the quantitative determination of B*-lactoglobulin (B*-LG) content, soluble at pH 4,6 in liquid milk. The method has been tested over a range between 0 mg and 3500 mg of B*-lactoglobulin (B*-LG) per litre of milk. It is suitable for distinguishing different categories of heat-treated liquid milk.