Abstract: The FAST method is based on quantification of protein denaturation by means of Trp fluorescence (FTrp) and accumulation of fluorescent Maillard products (FAMP) in the pH 4.6-soluble fraction of the milk. The fluorescence of raw milk, pasteurized milk ,and milk power was determined. Trp fluorescence was much lower in reconstituted milk compared to fresh milk, whereas the fluorescence of advanced Maillard products(FAMP) increased during heat treatment applied to fresh milk. As the proportion of reconstituted milk increased in fresh milk , the FTrp decreased linearly and FAMP increased linearly. The FAST method can be an effective way in determination of the presence of reconstituted milk in fresh or Pasteaurized milk.