Food tests

Question 1

Test for starch

Answer 1

1. Add iodine to food sample
2. Positive result: turns blue-black
3. Negative result: stays orange

Question 2

Test for reducing sugars

Answer 2

1. Add benedicts solution to food sample
2. Place in water bath and let sample heat
3. Positive result: turns brick-red
4. Negative result: stays light-blue

Question 3

Test for lipids

Answer 3

1. Add ethanol to food sample
2. Add water to sample and mix well
3. Positive result: white emulsion formed on top of sample
4. Negative result: solution stays colourless

Question 4

Test for proteins

Answer 4

1. Add biuret’s solution to sample
2. Positive result: purple/lilac
3. Negative result: stays blue

Question 5

Using solid food samples

Answer 5

1. Crush in pestle and mortar
2. Dissolve in warm, distilled water (Must use soluble foods)