Starch ( iodine test)
Method
1. Place a spatula of starch onto a clean watch glass
2. Using a dropper, place a few drops of iodine solution onto the starch sample. Note the colou
change onto the table.
3. Repeat with unknown food samples record your observation
Results
sample/food Iodine test
Starch Dark blue
Glucose No colour change
Sucrose No colour change
Sucrose with acid No colour change
Albumin (egg white) Yellow/orange
milk No colour change
Fructose No colour change
, Protein (biuret test)
Method
1. place a sample in a test tube (around 2ml if liquid) then add 2ml of distilled water, stir and
2. Add an equal amount of potassium hydroxide solution, mix by stirring.
3. Add 3 drops of copper sulphate solution and stir for 2 minutes. The colour change can be
subtle.
4. Record the colour change on the table.
5. Repeat with food samples.
Results
Sample/ food Biuret test
Starch blue
Glucose blue
Sucrose blue
Sucrose with acid Light blue
Albumin (egg white) Purple
Milk Dark purple
fructose green
Method
1. Place a spatula of starch onto a clean watch glass
2. Using a dropper, place a few drops of iodine solution onto the starch sample. Note the colou
change onto the table.
3. Repeat with unknown food samples record your observation
Results
sample/food Iodine test
Starch Dark blue
Glucose No colour change
Sucrose No colour change
Sucrose with acid No colour change
Albumin (egg white) Yellow/orange
milk No colour change
Fructose No colour change
, Protein (biuret test)
Method
1. place a sample in a test tube (around 2ml if liquid) then add 2ml of distilled water, stir and
2. Add an equal amount of potassium hydroxide solution, mix by stirring.
3. Add 3 drops of copper sulphate solution and stir for 2 minutes. The colour change can be
subtle.
4. Record the colour change on the table.
5. Repeat with food samples.
Results
Sample/ food Biuret test
Starch blue
Glucose blue
Sucrose blue
Sucrose with acid Light blue
Albumin (egg white) Purple
Milk Dark purple
fructose green
