Discrimination of reconstituted milk from fresh skim milk by using lactulose and furosine as milk quality indicators

This study aims to develop a novel and rapid method which uses enzymatic spectrophotometric assay and highperformance liquid chromatography (HPLC) for differentiating adulterated milk from pure fresh milk. Furthermore, this study will use the lactulose and Maillard-derived compounds as indicators to distinguish reconstituted milk from fresh milk. In bottle-sterilized milk, lactulose concentration decreased with the increasing addition of reconstituted skim milk. In addition, the content of lactulose in raw, low-temperature long-time (LTLT), and high-temperature short-time (HTST) skim milk samples increased with the proportion of reconstituted milk. Furosine, which had a retention time (RT) of 4.686 min in standard solution, had the RTs of 4.908, 4.926, 4.940, and 4.973 min in raw, LTLT, HTST, and bottle-sterilized milk samples, respectively. The RT peak increased along with the content of reconstituted milk in raw, LTLT, and HTST milk samples but decreased in bottle-sterilized milk. In conclusion, this work represents an important step toward detecting adulterated milk and tightening food safety regulations.