ISO 20541|IDF 197:2008 specifies a method for the determination of the nitrate content of milk and milk products by molecular-absorption spectrometry after Griess reaction (preceded by enzymatic reduction).
The method is, in particular, applicable to whole, partly skimmed, skimmed and dried milk, hard, semi-hard and soft cheeses, processed cheese, whey cheese, caseins, caseinates, dried whey and milk protein concentrates.
The method can be used at contents corresponding to a measured concentration in the sample solution (with blank subtracted) of more than 0,2 mg/l.