Food tests Flashcards
How do we prepare a food sample?
Crush the food with a pestle and mortar.
2. Add a few drops of distilled water and mix well.
Which solution do we use to test for sugars?
Benedict’s solution
Which solution do we use to test for starch?
Iodine solution
What colour is Benedict’s solution when it contains no simple sugars?
Blue
What colour is iodine solution when there is no starch present?
Orange
What colour is iodine solution in the presence of starch?
Blue/Black
What is distilled water?
Pure water (it contains no other chemicals)
How do we test for starch?
Add a few drops of iodine solution to a food sample.
2. If solution turns blue/black starch is present.
How can you test for SOLID lipids?
Rub the piece of food on filter paper.
Hold paper to light source.
If paper turns translucent - lipids are present.
What does translucent mean?
Slightly see-through
How can you test for lipid in a food solution (LIQUID)
Add a few drops of ethanol to the food solution.
Shake tube and leave for 1 minute.
Pour ethanol into a tube of water.
If solution turns cloudy - lipids are present.
How do you test for simple sugars?
Add a few drops of Benedict’s solution to the food sample.
Heat the test tube in a water bath.
If the solution turns orange/red the food contains simple sugars.
How do you test for protein?
Add a few drops of copper sulfate to food solution.
Add a few drops of sodium hydroxide.
If solution turns purple - proteins are present.
What colour is copper sulfate solution?
Blue
