Required practical: food testing

Question 1

Step 1

Answer 1

Take food sample and grind it with distilled water using mortar and pestle

Question 2

Step 2

Answer 2

Transfer the paste to a beaker with more distilled water, stir until chemicals in the food are dissolved

Question 3

Step 3

Answer 3

Filter solution to remove suspended food particles

Question 4

Testing for starch

Answer 4

Place 2cm³ of food solution into test tube
Add few drops of iodine solution
If starch is present iodine orange ——> blue/black

Question 5

Testing for protein

Answer 5

Add 2cm³ of food solution to 2cm³ of biuret solution
changes blue —-> purple

Question 6

Testing for sugars

Answer 6

Place 2cm³ of food solution into test tube
Add 10 drops of Benedict solution which is blue
Place tube in a beaker containing hot water
Green tells us small amount of sugar
Yellow tells us a fair amount is
Red tells us a lot is

Question 7

Testing for lipids

Answer 7

We do not filter paper here as lipid molecules stick to filter paper
Add 2cm³ of food solution then drops of distilled water and ethanol
Shake solution, and if a white cloudy emulsion forms lipids are present

Question 8

What sugars does Benedict solution test for?

Answer 8

Reducing sugars like glucose
But not sucrose

Question 9

What tests for starch?

Answer 9

Iodine solution

Question 10

What colour does iodine go if starch is present?

Answer 10

Orange ——> blue black

Question 11

What tests for sugars?

Answer 11

Benedict’s solution

Question 12

What colour does Benedict’s solution go if sugars are present?

Answer 12

Blue ——> green if not much
Yellow if fair amount
Red if a lot

Question 13

What tests for proteins?

Answer 13

Biuret solution

Question 14

What colour does biuret solution change if protein present?

Answer 14

Blue ——> purple

Question 15

What tests for lipids?

Answer 15

Distilled water and ethanol shaked

Question 16

What colour forms if lipids are present?

Answer 16

White colours emulsion