2. Test for Starch Place a little starch powder in a depression on a spotting tile. Add a few drops of iodine. Positive Result : Blue/Black colour Negative results: Browncolour
3. Test for Glucose Take 10ml of glucose solution in a test tube. Add 5 drops of Benedict’s solution to the test tube. Lower the test tube into a water bath kept at 70oC.
4. Test for Glucose Strong Positive Result : Brick Red precipitate Medium Positive Result Yellow orange precipitate Weak Result Green colour Negative results: Blue colour
5. Test for proteins Dissolve a little milk powder in a test tube. Add a few drops of Biuret reagent Positive Result : Purple Colour Negative results: Blue colour
6. Test for oil and fat Place about 1cm3 of ethanol in a test tube. Add a few drops of oil and mix by shaking. Add an equal amount of water and shake again. Positive Result : A cloudy emulsion forms Negative results: Liquid remains clear Note Food with solid fats can be tested by crushing them in ethanol.
