Food Tests

• Prepare Your 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
• Sugars


  Non-reducing and reducing
• Use the Benedict's Test to Test for Sugars


  1. Prepare a food sample and transfer 3 cm² to a test tube

  2. Prepare a water bath so that it's set to 25 °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
• Use Iodine Solution to Test for Starch


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

  2. Then 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
• Foods containing starch


  • Pasta, rice and potatoes
• Use the Biuret Test to 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
• Foods containing protein


  • Meat and cheese
• Use the Sudan III Test to 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 cm³ 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
• Foods containing lipids


  • Olive oil, margarine and milk
• Sudan (III)


  Test for lipids. Positive test is seperate red layer on the top.
• Biuret Test


  Test for Proteins. Positive test changes from blue to purple.
• Benedicts solution 


  Test for sugars. Positive test will turn from blue to green to yellow to red depending on how much sugar it contains
• Iodine solution 


  Test for starch. Positive test is brown to blue-black.