Food tests

• What is the first step in preparing a food sample for testing?

  Grind up food samples using pestle and mortar
• Why do you mix the ground food sample with water?

  To create a solution for testing
• What equipment is used to filter the food sample mixture?

  Funnel and filter paper
• What reagent is added to test for reducing sugars?

  Benedict’s reagent
• What is the next step after adding Benedict’s reagent to the sample?

  Boil test tube in a hot water bath
• What indicates the presence of reducing sugar in the sample?

  A brick red precipitate forms
• What reagent is used to test for starch?

  Iodine solution
• What color change indicates the presence of starch?

  From brown to blue-black
• What is the first step in testing for lipids?

  Add ethanol to the sample
• What should you do after adding ethanol to the lipid sample?

  Add water to the sample
• What indicates the presence of lipids in the sample?

  A white emulsion is formed
• What reagent is used to test for proteins?

  Biuret reagent
• What is the composition of Biuret reagent?

  Potassium hydroxide and copper (II) sulphate
• What color change indicates the presence of protein?

  From blue to purple
• How do the tests for reducing sugars and proteins differ in their indicators?

  Reducing sugars form a brick red precipitate, proteins turn purple
• What is the significance of filtering the food sample mixture?

  To separate solid particles from the liquid
• If a sample remains blue after adding Benedict’s reagent, what does this indicate?

  No reducing sugar is present
• Why is it important to shake the mixture after adding Biuret reagent?

  To ensure proper mixing for accurate results
• What is the purpose of adding water after ethanol in the lipid test?

  To form a white emulsion if lipids are present
• What does a blue-black color change signify in the starch test?

  Presence of starch in the sample
• How do the tests for starch and lipids differ in their procedures?

  Starch uses iodine, lipids use ethanol and water
• What would you conclude if a sample turns purple after adding Biuret reagent?

  Protein is present in the sample
• What is the role of the pestle and mortar in food sample preparation?

  To grind food samples into smaller pieces
• What color does iodine solution start as before testing for starch?

  Brown
• Why is it necessary to boil the test tube in the reducing sugar test?

  To facilitate the reaction with Benedict’s reagent
• What is the significance of the color changes in these biochemical tests?

  They indicate the presence of specific biomolecules