Organisation RQP- testing for a range of carbohydrates, lipids and proteins

Question 1

how to prepare a food sample

Answer 1

break up using a pestle and mortar, put in a beaker with distilled water, mix and then filter through a funnel with filter paper

Question 2

step 1

Answer 2

• sugar and starch- transfer 5cm3 of food sample to a test tube
• proteins- 2cm3 of food sample
• lipids- 5cm3 of unfilteres food sample

Question 3

step 2

Answer 3

• sugar- prepare a water bath to 75°C and add 10 drops of benedicts solution to the test tube and leave for 5mins
• starch- add a few drops of iodine solution and gently shake
• protein- add 2cm3 biuret solution and gently shake
• lipids- add 3 drops of sudan III stain solution and gently shake

Question 4

step 3

Answer 4

• sugar- if sugar is present, solution will turn from blue to green, yellow or brick red if its a high amount
• starch- if starch is present, solution will turn from browny-orange to black or blue-black
• if protein is present, solution will turn from blue to purple
• if lipids are present, solution will seperate into two layers, the top will be bright red OR if ethanol is used, a cloudy emulsion will form