Detection and Estimation of Cane Sugar in pasteurized Milk by Modified Seliwanoff Method

Principle

Fructose formed in cane sugar reacts with resorcinol in the presence of hydrochloric acid to give red color.

 Reagent

• Dissolve 1.0 g of resorcinol in 100 ml hydrochloric acid (1:1.5)
• 1 volume of concentrated hydrochloric acid of specific gravity 1.18 mixed with 1.5 volume of water.

Note: The resorcinol flakes should be white in color.

Procedure

1. Curdle a known quantity of the milk by adding a little concentrated HCl (for 25 ml of milk usually one ml of concentrated HCl is required). Let stand for about 10 minutes and filter.
2. To 5 ml of the modified resorcinol – HCl reagent taken in a test tube, add 1 ml of the filtered milk serum and mix.
3. Place the test tube in boiling water bath for exactly 1 min. Withdraw the tube and observe the color.
4. Appearance of deep red color indicates presence of sucrose, or a ketoses sugar.

 Result and Interpretation

Visual observation of development of deep red color in the milk sample indicates the presence of cane sugar.

Ref: IS 1479 (Pt I) 1960) Methods of test for Dairy Industry.

(Manual Methods of Analysis for Adulterants and Contaminants in Foods, I.C.M.R., 1990)