Wednesday, September 1, 2010

Say What!!! That's in My Food???

Today we tested common household foods for the biomolecules they contain.  The tests were as follows:


Simple Sugars -- Use Benedict's solution.  If the original blue color changes to blue/green, green, yellow, orange, or red after sitting in a warm water bath, then you had an item that was positive for simple sugars.  The degree of color change indicates the amount/type of simple sugar present.

Starch -- Use iodine.  When iodine was added to cause a change from brown/red to a dark black/brown color, then your food item tested positive for starches.


Drop a small amount of your food item on a piece of newspaper.  When your paper dries, you might be able to see light pass through the paper.  This property is known as translucence. If your paper allows light to pass through, then your food tested positive for lipids. 


Add Biuret reagent to see if protein is present.  If you see a vivid to pink to purple color appear, then you have a food filled with protein. 

What group of organic molecules did we not search for during our lab?

Why would this test be unneeded when it comes to living organisms?

Below is a link to an online version of this food lab.  Once you are at the page, click on the words "Organic Molecules." Review each step and observe the additional test for lipids.

Online Food Lab

Be sure that you are able to determine which test is necessary to find a particular type of molecule as well as read the results of each test.


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