Food Tests Flashcards
What do we do a food test?
To find out what type of chemicals are found in each different types
test for starch step 1:
Add a few drops of iodine solution to the food sample
Test for starch step 2:
Look for any colour change ( if present the colour will be blue-black colour) & (if negative it will stay orange-brown)
Variables for starch
Independent: the food that is being tested
Dependent: colour change
Control: the amount of volume of iodine used
Errors that could occur testing for starch
- Using too much iodine may mask the colour change.
- Contaminated equipment may give false results.
Test for sugars step 1:
Add Benedict’s solution to the food sample in a test tube
Test for sugars step 2:
Heat in a water bath at 80°C for a few minutes
Test for sugars step 3:
Look if there is any change in the colour (if present the colours will be green, yellow, orange, or brick red *depending on the concentration of sugar) & (if there isn’t any change it stays blue)
Variables in the test for sugars
- Independent: Type of food tested
- Dependent: Colour change
- Control: Same volume of Benedict’s solution and heating time
Errors that can occur when testing for sugar
- Not heating long enough may lead to false negatives
- Difficult to judge the exact colour change
Test for protein step 1:
Add Biuret reagent (potassium hydroxide + copper sulfate) to the food sample
Test for protein step 2:
Shake gently and observe the colour change (if present the colour will change to purple or lilac colour) & (if there isn’t any change it stays blue)
Variables for the test of protein
- Independent: Type of food tested
- Dependent: Colour change
- Control: Volume of Biuret reagent used
Errors that could occur when testing for protein
- Not mixing properly may prevent reaction
- Contaminated equipment may affect results
