Raman spectroscopy as a modern tool for lactose determination

Digestion of lactose, the milk disaccharide, makes problem to a large number of the population. Therefore, the lactose intolerant individuals are limited in the intake of milk and dairy products. The lactose – free products offers a solution for the diet. Raman spectroscopic analyses were performed for a purpose of rapid assessment of lactose content in bovine milk, lactose-free milk, mixtures of bovine milk and lactose-free milk, and bovine milk with additions of lactose. Based on characteristic vibrations, Raman spectra of lactose, glucose and galactose exhibit enough differences to distinguish the content of lactose in milk. C-O-H bending mode at 1087 cm -1 is used for lactose quantification. Two different substances – phenylalanine contained generally in the milk and crystal violet used as an internal standard, were studied for the evaluation of the spectroscopic data. The content of phenylalanine in samples was verified by IEC. Better accuracy exhibits the phenylalanine normalization. The contents of lactose and more easily digestible monosaccharides glucose and galactose from the mixtures of milk and lactose-free milk were analysed by HPLC, Raman spectroscopy provided corresponding results. The study shows that Raman spectroscopy is an effective method for the feedback control of lactose. Key-Words: Lactose intolerance, lactose content, lactose-free milk, Raman spectroscopy, milk, phenylalanine, crystal violet, quantitative analysis