food tests

• What should you be able to describe by the end of the video on chemical tests?

  How to carry out the chemical tests for carbohydrates, proteins, and lipids
• Why is it important to wear safety goggles during the chemical tests?

  Because all of the chemicals used are potentially hazardous
• What are the key things to learn for the chemical tests of food groups?

  • Chemicals used to test for each food group
  • Positive results of the tests
• What is the first step in preparing a food sample for testing?

  Grind the food sample with distilled water using a mortar and pestle
• What is done after grinding the food sample with distilled water?

  The paste is transferred to a beaker and more distilled water is added
• What is the purpose of filtering the solution after preparing the food sample?

  To remove suspended food particles
• What are the two types of carbohydrates mentioned?

  Starch and sugars such as glucose
• How do you test for starch in a food solution?

  Add a few drops of iodine solution to 2 cm³ of the food solution
• What color change indicates the presence of starch when using iodine solution?

  The iodine solution turns blue-black
• What happens to the iodine solution if no starch is present?

  The iodine solution remains orange
• How do you test for sugars such as glucose?

  Add 10 drops of Benedict solution to 2 cm³ of the food solution and heat it
• What does the color change of the Benedict solution indicate?

  It indicates the amount of sugar present
• What color indicates a small amount of sugar in the Benedict test?

  Green
• What color indicates a large amount of sugar in the Benedict test?

  Brick red
• What type of sugars does the Benedict test work for?

  Reducing sugars such as glucose
• What is the procedure for testing for proteins?

  Add 2 cm³ of Biuret solution to 2 cm³ of the food solution
• What color change indicates the presence of protein in the Biuret test?

  The Biuret solution changes from blue to purple or lilac
• How do you test for lipids?

  Add a few drops of distilled water and ethanol to the food solution and shake
• Why do we not filter the solution when testing for lipids?

  Because lipid molecules can stick to filter paper
• What indicates the presence of lipids in the test?

  A white cloudy emulsion forms
• Why is it important to avoid naked flames when testing for lipids?

  Because ethanol is highly flammable
• What resources can students use to find questions on testing for chemicals in foods?

  • Vision workbook
  • Link provided in the video