Food test practical paper 1

Question 1

how to tests for sugars

Answer 1

1. add a few drops of benedicts solution to the food sample
2. heat in a water bath of 70 degrees for around 5 minutes
3. depending on how much sugar is in the sample, the benedicts solution will go from blue to green, yellow, brick red

Question 2

how to test for starch

Answer 2

1. put a fixed amount of the food into a test tube
2. add a few drops of iodine
3. if iodine is present, solution will go from brown/ orange to blue black

Question 3

what sugars would we use bendicts for

Answer 3

reducing sugars

Question 4

how to test for proteins

Answer 4

• take 2cm3 of the food solution
• add 2cm3 of Biuret’s solution
• if protein is present, colour will change from blue to purple/ lilac

Question 5

how to test for fats/ lipids

Answer 5

1. transfer 2cm3 of food solution to a test tube
2. add a few drops of distilled water and a few drops of ethanol
3. gently shake the solution
4. If lipids are present, then a white cloudy emulsion forms

Question 6

why dont we filter solution when testing for lipids

Answer 6

because the lipid molecules might stick to the filter paper

Question 7

dangers of ethanol

Answer 7

highly flammable, make sure no naked flame is present

Question 8

what should we do to the food before every food test

Answer 8

• take the food sample and grind it with distilled water using a mortar and pestle
• mix the solution with more distilled water until the food is dissolved
• filter solution to remove any suspended food partic;es