Summary GCSE Biology Required Practical 4: Food Tests

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Aim:
Use qualitative reagents to test for a range of carbohydrates, lipids and proteins. To
include: Benedict’s test for sugars, iodine test for starch and Biuret reagent for protein.
BENEDICT’S TEST FOR SUGARS:
Equipment:
 Benedict’s reagent  Warm water Bath  Pipette
 Sample  Test tube
Method: Results:
1. Put the sample in the test tube.  If the sample turns brick-red, sugar
2. Add a few drops of Benedict’s reagent to is present
the sample using a pipette.  If the sample turns, yellow or
3. Place the sample into a warm water green, sugar is present but in
bath. smaller amounts
4. After 5 minutes remove the sample  If the sample remains blue, sugar is
from the warm water bath. not present.
IODINE TEST FOR STARCH:
Equipment: Results:
 Iodine  Spotting Tile
 If the sample turns blue-black,
 Sample  Pipette
starch is present
Method:  If the sample remains the same,
1. Put the sample on the spotting tile.
starch is not present.
2. Add a drop of iodine to the sample.
BIURET TEST FOR PROTEIN:
Equipment:
 Test tube  Biuret reagent (mixture of sodium hydroxide (NaOH) and copper sulfate (CuSO4))
 Sample  Pipette