Topic 2 - Food Tests

Question 1

how do you test for glucose?

Answer 1

the benedicts test

Question 2

how do you carry out the benedicts test?

Answer 2

1. prepare a food sample and transfer 5cm³ to a test tube
2. prepare a 75⁰c water bath
3. add some benedicts solution to the test tube
4. place the test tube in the water bath
5. if the food sample contains glucose, the solution will change colour

Question 3

if a solution contains glucose, what colours can the solution change to after the benedicts test?

Answer 3

it will change from blue to green/yellow in low concentrations and red in high concentrations

Question 4

what do you use for testing a solution for starch?

Answer 4

iodine solution

Question 5

how do you use iodine solution to test for starch?

Answer 5

1. make a food sample and transfer 5cm³ to a test tube
2. add a few drops of iodine solution and gently shake to mix

Question 6

if a solution contains starch, what colour will the solution change after the iodine test?

Answer 6

it will change from browny-orange to black or blue-black

Question 7

what do you use to test for proteins?

Answer 7

the biuret test

Question 8

how do you do the biuret test?

Answer 8

1. prepare a food sample and transfer 2cm³ to a test tube
2. add 2cm³ of biuret solution to the sample and mix by shaking

Question 9

if a solution contains protein, what colour will it change to after the biuret test?

Answer 9

the solution will change from blue to pink or purple

Question 10

what is the test for lipids?

Answer 10

The Sudan III test

Question 11

how do you carry out the Sudan III test?

Answer 11

1. prepare a food sample and transfer 5cm³ to a test tube
2. add 3 drops of Sudan III solution with a pipette to a test tube

Question 12

how does the colour change if a solution contains lipids after the Sudan III test?

Answer 12

the mixture will separate into two layers, where the top layer will be bright red