Biochemical tests are essential for identifying the presence of different types of carbohydrates such as reducing sugars and starch. The two main tests used are the Benedict's Test for sugars and the Iodine Test for starch.

Method for Benedict's Test:

1. Preparation: Ensure that the food sample is in liquid form. If the sample is solid, dissolve it in water to create a solution.

2. Add Sample: Place 2 cm³ of the food sample in a test tube.

3. Add Benedict's Reagent: Add 2 cm³ of Benedict's reagent (an alkaline solution of copper(II) sulfate) to the test tube.

4. Heat the Sample: Place the test tube in a water bath set to gently heat the mixture for 5 minutes.

5. Observe the Colour Change:

• If a reducing sugar is present, the solution will gradually turn from blue (the colour of the reagent) to brick red (orange-brown) due to the formation of copper(I) oxide.
• The intensity of the colour change can indicate the amount of reducing sugar present. If little sugar is present, the colour may turn green or yellow before becoming red as more sugar is detected.

Method for Iodine Test:

1. Place a small amount of the food sample into a test tube.
2. Add a few drops of iodine solution (iodine dissolved in potassium iodide) to the sample.
3. Observe the colour change:

• If starch is present, the iodine solution will change from orange-brown to blue-black.
• If there is no starch, the iodine solution will remain orange-brown.