Test for Glucose All the monosaccharides (e.g. glucose) and many of the disaccharides are classed as reducing sugars. Benedict’s test is used to determine the reducing properties of the different sugars. Benedict’s solution is a turquoise/blue solution.

Test for Glucose A solution containing equal quantities of food solution and Benedict’s solution are placed in a boiling tube and heated in a water bath for several minutes. A change of colour through green, then yellow to ‘brick red’ indicates the presence of a reducing sugar such as glucose. The ‘brick red’ colour is the definitive result.

Test for Glucose When a Benedict's test is performed on pure solutions of glucose and sucrose (table sugar), the following results are obtained... Sucrose Result Glucose Sucrose is a non-reducing sugar Glucose is a reducing sugar

Test for Glucose: Make a solution of your food to be tested(add some water) Add ten drops of Benedict’s Reagent to a solution of the food to be tested in a boiling tube. (excess of Benedicts ensures all the glucose reacts) Place the test tube containing the food to be tested into the boiling water (water bath in beaker). A colour change from blue to orange/red indicates that sugar is present. (This can be demonstrated using a solution of glucose.) . (This can be demonstrated using a solution of glucose.)

Test for Starch When iodine in potassium iodide solution is added to starch, the iodine molecules pack inside the starch molecules to give a blue-black colour. When iodine reacts with the starch in this piece of potato, the blue-black colour develops.

Test for Protein (Biuret test) A purple/violet colour indicates the presence of a protein protein A solution of the material to be tested is placed in a test tube. A little sodium hydroxide solution is added to clear the solution. A small amount of weak copper sulphate solution is added down the side of the test tube.

Test for Protein: Make a solution of your food to be tested (add some water) Add 2cm3 (2 pipettes) of Biuret reagent to a solution of the food to be tested and shake well. A colour change from blue to violet/purple indicates the presence of protein. This can be demonstrated using some egg albumen solution (egg white).

Test for Lipid - Emulsion Test The material to be tested is placed in a test tube. Approximately 2cm3 of ethanol is added and the tube is shaken. The ethanol layer is poured off into a second test tube. Approximately 2cm3 of water is added to the ethanol. A milky emulsion confirms the presence of a fat or oil

Test for Lipid - Paper Test This is a simple test used to detect fats and oils in food. Paper stays translucent when fats or oils are absorbed - even after drying.