Detection of Vegetable Oils in Milk and Milk Fat by a Rapid Method

The elevation of butyrorefractometer (BR) reading of milk fat by addition of different vegetable oils was used to detect adulteration of milk. (i) Skim milk, (ii) standardized milk with 2% milk fat and (iii) standardized milk with 4% milk fat using cow, mixed and buffalo milks were used. The average BR reading of groundnut, cottonseed, corn, sesame, sunflower, mustard, soya and castor oils were 59.81, 62.43, 64.50, 64.88. 65.25, 65.64, 66.00 and 73.00, respeetively. The BR reading of pure cow, buffalo and mixed milk fat varied from 40.5 to 44.0. The BR readings of clear fat of different milk systems outside this range can be taken as cut off point for establishing the presence of vegetable oil(s). The mean BR readings of fat isolated from skim milk blended with I, 2, 4 and 6% cottonseed oil were above 50.0 in all cases and significantly higher. The adulteration of 2% of cottonseed oil or such other oils (BR reading higher than 59.0) to cowlbuffalo/mixed milk can be deteeted.