ZIMSEC O Level Combined Science Notes: Carrying out Food Tests
- It is important to know how much nutrients they contain
- This would be useful to nutritionist and those who are health conscious
Food Testing experiments
- Simple tests can be made on food to determine if they contain a particular food group e.g. proteins
Benedict’s solution/Clinistix, iodine solution, Biuret’s solution/Albustix, ethanol, paper, a variety of foods to be tested, burners, suitable containers.
Testing for sugar/glucose
- Place about 2 ml of food solution in a test tube and add some Benedict’s solution
- Heat the test tubes in a water bath
- Observe the colour change from green/orange to red/brown/ brick red.
- The Benedict’s solution changes from green/orange to brick red if the food contains sugar/glucose
NB. You can also test for the presence of starch using a clinistix by dipping it into a food sample, waiting for about 30 seconds,observing the resulting colour change and comparing the result to a provided colour code.
Testing for starch
- Drop a few drops of iodine solution on the food.
- Or add a food sample to a test tube containing an iodine solution
- The iodine solution turns blue black if starch is present.
Testing for protein
- Add a few drops of Biuret solution to the food sample.
- Add a food sample to a test tube containing Biuret solution
- If the food sample contains proteins the solution will turn blue/ a darker shade of blue.
NB You can also test for the presence of proteins using an albustix by dipping it into a food solution, waiting for about 30 seconds, observe the colour change and comparing it against a provided colour code.
Testing for fats
- Place the food sample (about 2ml) into a test tube.
- Add ethanol and shake thoroughly.
- Am emulsion forms if fat or oil is present
NB. Alternatively a small amount the food can be smeared onto a piece of paper. And left to dry for a couple of minutes, the remaining stain is then observed. If a translucent stain forms then fat is present in the food sample being tested.
A translucent stain is one which allows light to pass but does not allow a person to see through it.
To access more topics go to the Combined Science Notes page.