Food Tests

Question 1

What is the positive result for the test for starch?

Answer 1

Iodine turns orange to blue/black

Question 2

Describe how to test for the presence of glucose/sugar

Answer 2

• Place food solution in a beaker
• Add drops of Benedict reagent to solution
• Place test tube into a beaker and half fill with hot
  water
• Green - little sugar present
• Yellow - medium amount present
• Brick orange colour - lots of sugar present

Question 3

What types of sugars does the Benedict test work for?

Answer 3

Reducing sugars

Question 4

What is the reagent used to test for starch

Answer 4

Iodine

Question 5

What is the reagent used to test for reducing sugars?

Answer 5

Benedict

Question 6

Explain the results of a test for the presence of a reducing sugar

Answer 6

Green - little sugar present
Yellow - medium amount present
Brick orange/red - lots of sugar present

Question 7

What is the positive result for the test for proteins?

Answer 7

Biuret solution turns Blue to Purple/Lilac

Question 8

What must you do to food before conducting a food test?

Answer 8

Grind the food into a paste using a mortar and pestle, then transfer to a beaker, add distilled water and stir so the food molecules dissolve, then filter to remove suspended food particles.

Question 9

Why don’t you filter the solution before conducting a lipid test?

Answer 9

Lipid molecules can stick to filter paper

Question 10

Describe how to test for the presence of lipids

Answer 10

• Add food solution to test tube
• Add drops of water and ethanol
• White cloudy emulsion occurs in presence of lipids

Question 11

What risk is there when conducting a lipid test?

Answer 11

Ethanol (the reagent) is highly flammable, so make sure no naked flames are present

Question 12

What is the positive result for the test for lipids?

Answer 12

White cloudy emulsion in Ethanol