Describe the tests used to identify the presence of starch, reducing sugars, non-reducing sugars, and proteins in a food sample.

Here's how to test for the food substances: i) Starch or carbohydrate Test: Iodine test Procedure: Add a few drops of iodine solution to the food sample. Positive Result: A blue-black* colour indicates the presence of starch. ii) Reducing sugar Test: Benedict's test Procedure: Add Benedict's solution to the food sample and heat the mixture gently in a water bath. Positive Result: A colour change from blue to green, yellow, orange, or brick-red precipitate* indicates the presence of a reducing sugar. iii) Non-reducing sugars Test: Hydrolysis followed by Benedict's test Procedure: 1. Add dilute hydrochloric acid to the food sample and boil gently for a few minutes to hydrolyze the non-reducing sugar into reducing sugars. 2. Neutralize the solution with sodium bicarbonate or sodium hydroxide. 3. Then, perform the Benedict's test as described above (add Benedict's solution and heat). Positive Result: A colour change from blue to green, yellow, orange, or brick-red precipitate* after hydrolysis and Benedict's test indicates the presence of a non-reducing sugar. iv) Proteins Test: Biuret test Procedure: Add sodium hydroxide solution to the food sample, then add a few drops of dilute copper(II) sulphate solution. Shake gently. Positive Result: A purple (violet)* colour indicates the presence of protein. v) Fats and oils Test: Emulsion test or Translucency test Procedure (Emulsion test): Add ethanol to the food sample, shake well, then pour the ethanol into a test tube containing water. Positive Result (Emulsion test): A white emulsion* (cloudy appearance) indicates the presence of fats or oils. Procedure (Translucency test): Rub a small amount of the food sample onto a piece of filter paper and let it dry. Positive Result (Translucency test): A translucent spot* on the paper indicates the presence of fats or oils. Last free one today — make it count tomorrow, or type /upgrade for unlimited.