Food Tests

• Why is it important to prepare a food sample before carrying out tests?

  To ensure accurate results when identifying biological molecules.
• What is the purpose of filtering the solution using a funnel lined with filter paper?


  To get rid of the solid bits of food.
• What are the steps to prepare a food sample for a food test?

  1. Get a piece of food and break it up using a pestle and mortar.
  2. Transfer the ground food to a beaker and add distilled water.
  3. Stir the mixture with a glass rod to dissolve some of the food.
  4. Filter the solution using a funnel lined with filter paper.
• What type of biological molecule is made up of simple sugars?

  Carbohydrates
• What are the chemical elements that proteins are made up of?

  Carbon, hydrogen, oxygen, and nitrogen
• What is the significance of knowing the composition of carbohydrates, proteins, and sugars?

  • Important for understanding digestion.
  • Essential for identifying biological molecules in food tests.
• What types of foods can glucose be found in?

  Biscuits, cereal, and bread.
• What test is used for Glucose?

  Benedicts Test
• How do you carry out the Benedict's Test?


  • prepare a food sample and transfer 5cm^3 to a test tube
  • prepare a 75 degree celcius water bath
  • add around 10 drops of benedict's solution to the test tube using a pipette
  • place the test tube in the water bath
  • leave it there for 5 minuets
  • see what colour it has turned to find out the results
• What colour does the benedict's solution turn if glucose is present?


  it will change from its usual blue colour to :

  • yellow/green in low concentrations of glucose
  • brick red is high concentraitions of glucose
• what test is used for starch?

  Iodine Test
• what types of food can starch be found in?

  pasta, rice and potatoes
• how do you carry out the iodine test?


  • make a food smaple and transfer 5cm^3 to a test tube
  • add a 2-3 drops of your iodine solution
  • gently shake the tube to mix the contents
  • look to see what colour it turns to fiure out the results
• what colour does the iodine test turn in the presence of starch?


  it will change from its usual colour of browny-orange to blue-black or black
• what test is used for proteins?

  Biuret test
• what types of food can protein be found in?


  meat and cheese are rich in protein
• how do you carry out the biuret test?


  • prepare a food sample and transfer 2cm^3 to a test tube
  • add 2cm^3 of biuret solution to the sample
  • gently shake to mix the contents
  • look to see what colour it changes to get your results
• what colour will the biuret solution turn in the presence of protein?


  it will change from its usual colour of blue to pink or purple
• what test do you use for lipids?

  the Sudan III Test
• what foods are lipids found in?


  olive oil, margarine and milk
• how do you carry out the Sudan III test?


  • prepare a food sample but don't filter it
  • transfer 5cm^3 to a test tube
  • use a pipette to add 3 drops of Sudan III stain solutions to the test tube
  • gently shake to mix the contents
  • look to see the results
• what will happen in the Sudan III Test if lipids are present?


  • Sudan III solution stains lipids
  • if the sample contains lipids, the misture will seperate into two layers
  • the top layer will be bright red
  • if no lipids no layers or colours will form