Food Tests

Question 1

What are the 5 food tests

Answer 1

1. Test for reducing sugars
2. Test for non-reducing sugars
3. Test for starch
4. Test for lipids
5. Test for proteins

Question 2

What is the test for reducing sugars

Answer 2

1. Add 2cm of the food sample to a test tube
2. Add an equal amount of benedicts reagent
3. Heat the mixture gently in a water bath for 5 minutes
4. Brick red precipitate = Reducing sugar presence

Question 3

What is the test for non-reducing sugars

Answer 3

1. Add 2cm of the food sample to a test tube
2. Add an equal amount of benedicts reagent
3. Heat the mixture gently in a water bath for 5 minutes
4. No colour change = Reducing sugar not present
5. Add another 2cm of food sample to 2cm of HCL. HCL hydrolyses any disaccharide
6. Add sodium hydrogen carbonate to neutralise pH. Benedicts doesnt work in acidic conditions
7. Re-test with benedicts in a water bath for 5 minutes, brick red = Non-reducing

Question 4

What is the test for starch

Answer 4

1. Add 2cm of the food sample to a test tube
2. Add 2 drops of iodine and shake
3. Starch = Blue/Black colouration

Question 5

What is the test for lipids

Answer 5

1. Add 2cm of the food sample to 5cm of ethanol in a clean test tube
2. Shake the test tube to dissolve lipids
3. Add 5cm of water and shake
4. Cloudy emulsion = Lipid
5. Repeat with water for a control

Question 6

What is the test for proteins

Answer 6

1. Place food sample in a test tube
2. Add an equal amount of sodium hydroxide solution
3. Add a few drops of dilute copper(II) sulfate solution and mix gently
4. Purple colouration = Protein, blue = No protein.