Food tests

Question 1

test for lipids

Answer 1

emulsion

Question 2

test for proteins

Answer 2

biuret test

Question 3

test for starch

Answer 3

iodine test

Question 4

test for carbohydrates/reducing sugars

Answer 4

Benedict’s solution

Question 5

process for the emulsion test

Answer 5

the sample is mixed with ethanol. if a white emulsion forms on top a lipid is present

Question 6

process for the iodine test

Answer 6

iodine is dissolved in potassium iodide and then the sample is added. if it changes from yellow to blue/black then starch is present

Question 7

process for the Benedict’s test

Answer 7

the sample is placed in a boiling tube and an equal volume of Benedict’s solution is added. the mixture is heated in a water bath. reducing sugars will make the water turn from blue to brick red. if it is a non-reducing sugar it will remain blue but a red precipitate

Question 8

process for the Benedict’s test

Answer 8

the sample is placed in a boiling tube and an equal volume of Benedict’s solution is added. the mixture is heated in a water bath. reducing sugars will make the water turn from blue to brick red. if it is a non-reducing sugar it will remain blue but a red precipitate will form

Question 9

testing carbohydrates using a colorimeter

Answer 9

1 - filter is placed in the colorimeter and calibrated using distilled water
2 - the Benedict’s test is performed on a range of known conc
3 - resulting solutions were filtered to remove precipitate
4 - the % transmission of each solution of glucose is measured using colorimeter
5 - using this info, calibration curve was plotted, steps 2-5 repeated using the solution with unknown iconic of glucose