food tests

Question 1

what are the 2 types of sugars
2 points

Answer 1

1) reducing
2) non-reducing

Question 2

how can you test for reducing sugars

Answer 2

the Benedict’s test

Question 3

what is the method for Benedict’s test 5 points

Answer 3

1) prepare a food sample and transfer 5cm^3 to a test tube
2) prepare a water bath so that it’s set to 75 ‘C
3) add some Benedict’s solution to the test tube (about 10 drops) using a pipette
4) place the test tube in the water bath using a test tube holder and leave it in there for 5 mins. Make sure the tube is pointing away from you
5) if the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick red

Question 4

what test is used to test for starch

Answer 4

the iodine solution test

Question 5

what is the method for testing for starch
3 points

Answer 5

1) make a food sample and transfer 5cm^3 of your sample to a test tube
2) then add a few drops of iodine solution and gently shake the tube to mix the contents
3) if the sample contains starch, the colour if the solution will change from browny-orange to black or blue-black

Question 6

how do you prepare your food sample
4 points

Answer 6

1) get a piece of food and break it up using a pestle and mortar
2) transfer the ground up food to a beaker and add some distilled water
3) give the mixture a good stir with a glass rod to dissolve some of the food
4) filter the solution using a funnel lined with filter paper to get rid of the solid bits of food

Question 7

how do you test for proteins

Answer 7

using the biuret test

Question 8

what is the method for the finding proteins
3 points

Answer 8

1) prepare a sample for your food and transfer 2cm^3 of your sample to a test tube
2) add 2cm^3 of biuret solution to the sample and mix the contents of the tube by gently shaking it
3) if the food sample contains protein, the solution will change from blue to purple

Question 9

how can you test for lipids

Answer 9

using the sudan III test

Question 10

what is the method for finding lipids
3) points

Answer 10

1) prepare a sample of the food you’re testing (but you don’t need to filter it). transfer about 5cm^3 into a test tube
2) use a pipette to add 3 drops of sudan III stain solution to the test tube and gently shake the tube
3) Sudan III stain solution stains the lipids. if the sample contains the lipids, the mixture will separate out into two layers. the top layer will be bright red.