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

Materials

Benedict’s solution/Clinistix, iodine solution, Biuret’s solution/Albustix, ethanol, paper, a variety of foods to be tested, burners, suitable containers.

Methods

Testing for sugar/glucose

Benedict’s solution. The test tube on the far right is testing positive for glucose

1. Place about 2 ml of food solution in a test tube and add some Benedict’s solution
2. Heat the test tubes in a water bath
3. Observe the colour change from green/orange to red/brown/ brick red.

Results

• 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

1. Drop a few drops of iodine solution on the food.
2. Or add a food sample to a test tube containing an iodine solution

Results

• The iodine solution turns blue black if starch is present.

Testing for protein

Negative (left) and Posative (right) test results for protein. Image credit wordpress.com

1. Add a few drops of Biuret solution to the food sample.
2. Add a food sample to a test tube containing Biuret solution

Results

• 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

Emulsion of fats. Image credit blogspot.com

• Place the food sample (about 2ml) into a test tube.
• Add ethanol and shake thoroughly.

Results

• 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.