Estimation of sugars in milk by HPLC and its application in detection of adulteration of milk with soymilk

A high-performance liquid chromatography method is described for the detection of adulteration of milk with soymilk, based on separation of sugars on NH₂ column and their detection by refractive index detector. Sugars were extracted with 20% acetonitrile in the presence of Carrez solutions and quantified. Recovery of added raffinose to soymilk was 96.3%. Owing to relative high concentration of lactose in milk or adulterated milk, lactose peak was very broad and spread to retention time corresponding to sucrose and raffinose. However, stachyose peak remained well separated. Presence of stachyose peak in milk can be used for the detection of adulteration of milk with soymilk and the method can detect upto 5% soymilk in milk.