Food Tests

Question 1

Describe the test for proteins?

Answer 1

• Biuret test
• Place food sample in a test tube
• Add an equal volume of Biuret solution
• If proteins are present, solution will turn from blue to purple

Question 2

For reducing sugars

Answer 2

• Add Benedict’s reagent
  -Heat mixture in a water bath
• If reducing sugars present, mixture will change from a blue solution to brick red precipitate
• Orange colour detects a medium concentration

Question 3

For non reducing sugars

Answer 3

• Carry out the test for reducing sugars
• Add sample to some dilute HCl
• Heat mixture in water bath
• Neutralise mixture by adding sodium hydrogencarbonate solution
• Retest sample using reducing sugar test

Question 4

For starch

Answer 4

• Add iodine solution to sample
• If starch present, solution turns from orange to blue/black

Question 5

For lipids

Answer 5

• Place sample in test tube
• Add ethanol
• Shake
• Add distilled water
• Milky white emulsion forms if lipids are present