Food Tests
Iodine Test
Use (x) drops of iodine on experimental area
If iodine is present: Brown > blue-black (Not too sure if terms are interchangeable)
Test For Reducing Sugars
Boil about half a beaker’s worth of water over non-luminous flame (Blue-flame)
When water comes to a boil, place test tubes inside beaker for ±7 mins
| Colour Change | Amount Of Reducing Sugars Present |
|---|---|
| Solution Remains Blue | No Reducing Sugars |
| Blue > Green | Traces Of Reducing Sugars |
| Blue > Yellow/Orange ppt. | Moderate Amount Of Reducing Sugars |
| Blue > Brick-red ppt. | Large Amount Of Reducing Sugars |
- If sample is a large piece, crush it and mix with water. Drain to get rid of the larger pieces and use the water-sample mixture for your experiment (Decant the solution)
Test For Proteins (Biuret Test) (Biuret Solution: Add NaOH, then dilute CuSO4 )
Use equal volume of biuret reagent in a test tube of sample
If solution turns violet, proteins are present. If solution remains blue, proteins are absent.
Test For Fats (Ethanol Emulsion Test)
Sample + Ethanol + Water (In this order!)
If solution turns cloudy, fats are present
If solution remains clear, fats are absent
(For liquid food, you can just do the test straight but for solid food, you need to cut it into small pieces/crush)
Tips In General