Practice Questions
1.Describe the food test for sugars
A ground up food sample is added to a test tube along with benedicts reagent or benedicts solution.
The mixture is then heated in a hot water bath for 5 minutes.
If the blue benedicts solution turns red then a sugar is present.
If it stays blue, then sugar is not present.
2. Describe the food test for starch
Iodine solution is a red brown colour, if it stays unchanged then food does not contain starch.
However, if the iodine solution turns blue black, then starch is present.
3. Amy carried our some food tests on a sample of food. The results are shown below in a table
| Food test | Result |
|---|---|
| Add iodine solution to food sample | Blue black colour formed |
| Add benedicts solution to the food sample and heated | Stays blue |
| Added biuret reagent to the food sample | Turns purple |
| Add ethanol to food, mixture shaken and poured into water | White emulsion formed |
3.State which substances are present in the food sample
Starch, protein and lipids.
Sugars are not present.