FoodTests

In order to carry this Experiment out it is a good idea to have many different types of foods. If you and your classmates each bring in a different piece of food we can find out quite a bit about what makes up the different foods.

If you are doing this at home, try a great deal of foods.

Warning

Iodine ingested in pure form is lethal, The tincture you use may also be and so for this experiment you should wear Goggle's, Gloves and wash your hands.

Title

OB3a Testing Food for Starch

Apparatus

Food Sample,

Dropper,

Iodine,

White Tile

Pestle & Morter (to crush the food) .

Safety Concerns

Goggles MUST be warn.

Hands must be washed after handling the iodine. Gloves may be warn.

Method

  1. prepare the food samples, make them small
  2. Put the food on the white tile
  3. Use a dropper add a drop of yellow-brown Iodine to the food sample
  4. leave for a minute
  5. observe the colour of the Iodine on the sample
  6. Write down the colour of the chemical you see

Results / Observations

What did you see or notice, write it down in your table

Conclusions

If the food turns blue-black then starch is present.

If the food goes yellow-brown-red then the food does not contain starch.

Comments

Anything that you did not expect ... or that interested you

We use ________ to test for __________. If it changes colour to _________ colour we know there is ________ present in this food.

OB3d Testing Food for Fat

Apparatus

Food Sample,

Brown Paper

White Tile

Pestle & Morter (to crush the food) .

There are no Safety Concerns with this test, just follow class guidelines.

Method

  1. Prepare the food samples, make them small
  2. On the white tile place the brown paper
    1. Rub the food on brown paper, sqeeze out any liquid

Results / Observations

What did you see or notice, write it down in your table

A translucent stain that remains and will not dry out shows that fat is present.

A stain that is not permanent means that fat is not present.

We use ________ to test for __________. If it changes to _________ we know there is ________ present in this food.

(b) OB3b Testing Food for Reducing Sugar

Apparatus

Method

  1. Grind up the food sample, add it to a test tube
  2. Add blue Benedict’s reagent to the food solution.
  3. Heat, but do not boil, in hot water bath for about 10 minutes.
  4. If the solution goes brick red then reducing sugar is present.
  5. If the solution remains blue then reducing sugar is not present.

How to make Benedicts

We need to make 2 solutions, then mix these together when we need it

Solution A

Dissolve 100g anhydrous sodium carbonate and 173g sodium citrate in 800 cm3 of water

You may need to heat the mixture, and filter it too

Solution B

Dissolve 17.3g of copper (II) sulphate in 100 cm3 of water

Dilute to 150cm3 with water

When required mix both solutions and top up to make 1l

List our differerent foods and now add to the table those that contain sugars.

OB3 (c) Testing Food for Protein

Add blue biuret reagent to the food solution.

Shake to mix the reagent and the food solution.

A colour change from blue to purple indicates that protein is present.

If the solution remains blue then protein is not present.

To make Biuret Reagent

Dissolve 37.4g of Copper (II) Sulphate in 500cm3 of water

Dissolve 330g of solid NaOH with 500cm3 of water and dilute to 1l.

Mix equal measures of these solution when required

Summary Table

Copy this into your Hardback and fill it in

Conclusions

We use ________ to test for __________. If it changes colour to _________ colour we know there is ________ present in this food.

Food Constituent expts