Bio1 - Food tests

Question 1

What are the three beginning steps within the practical Food tests?

Answer 1

1. Take food sample and grind with distilled water using a mortar and pestle- to make a paste.
2. Transfer paste to a beaker + add more distilled water, stir so chemicals dissolve in the water.
3. Filter solution to remove suspended food particles.

Question 2

What is the method to test for carbohydrates? (Starch)

Answer 2

Steps 1 - 3
4. Pour 2cm ³ of food solution into test tube and add iodine solution
If starch is present it will turn a blackish blue colour and if it’s not present it remains orange.

Question 3

What is the method to test for sugars (glucose) ?

Answer 3

1-3
4. Place 2cm ³ food solution into test tube
5. Add 10 drops of Benedict’s solution (blue), place test tube into a beaker half full with hot kettle water.
6. Leave for 5 minutes and should change colour if sugar is present.

Question 4

What are the three colours Benedict’s solution can change to if sugars are present and what does each colour mean in terms of yield in sugar?

Answer 4

Green - small amount of sugar
Yellow - medium amount of sugar
Brick red - strong amount of sugar

Question 5

What is the method to test for protein?

Answer 5

1-3.
4. Pour 2cm ³ into test tube and add 2cm ³ of biuret solution.
5. The colour should change to a purple / lilac colour and if not it will remain blue.

Question 6

What is the method to test for lipids?

Answer 6

1-2
3. Food solution isn’t filtered as lipid molecules can stick to filter paper.
4. Pour 2cm ³ into tube and add a few drops of distilled water + a few ethanol drops.
5. Gently shake the tube.
6. If lipids are present, a cloudy white emulsion forms.