The method is applicable to products having carbonyl compounds contents between 0.00025 % (m/m) and 0.01 % (m/m). The principle is based on reaction in acid medium of the carbonyl compounds in a test portion with 2,4-dinitrophenylhydrazine. Formation of the corresponding 2,4-dinitrophenylhydrazones which, after making the solution alkaline, take on a red coloration. Photometric measurement of this red coloration at a wavelength of about 445 nm. - International Standards ISO 1388/1 to 1388/12 cancel and replace ISO Recommendation R 1388-1970 of which they constitute a technical revision.