Food Test - Practical

• Food Tests


  Clever ways to identify what type of food molecule a sample contains
• Preparing a food sample

  1. Get a piece of food and break it up using a pestle and mortar

  2. Transfer the ground up food to a beaker and add some distilled water

  3. Give the mixture a good stir with a glass rod to dissolve some of the food

  4. Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
• Benedict's Test for Reducing Sugars


  1. Prepare a food sample and transfer 5 cm³ to a test tube

  2. Prepare a water bath so that it's set to 75 °C

  3. Add some Benedict's solution to the test tube (about 10 drops) using a pipette

  4. Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes

  5. If the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick-red
• Iodine Solution Test for Starch

  1. Make a food sample and transfer 5 cm³ of your sample to a test tube

  2. Add a few drops of iodine solution and gently shake the tube to mix the contents

  3. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
• Biuret Test for Proteins

  1. Prepare a sample of your food and transfer 2 cm³ of your sample to a test tube

  2. Add 2 cm³ of biuret solution to the sample and mix the contents of the tube by gently shaking it

  3. If the food sample contains protein, the solution will change from blue to purple
• Sudan III Test for Lipids

  1. Prepare a sample of the food you're testing (but you don't need to filter it) and transfer about 5 cm into a test tube

  2. Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube

  3. If the sample contains lipids, the mixture will separate out into two layers with the top layer being bright red
• Sugars are found in all sorts of foods such as biscuits, cereal and bread
• There are two types of sugars: non-reducing and reducing
• Foods like pasta, rice and potatoes contain a lot of starch
• Meat and cheese are protein rich foods
• Lipids are found in foods such as olive oil, margarine and milk