Testing for Carbohydrate in Foods

TESTING FOR CARBOHYDRATE IN FOODSThis presentation illustrates data that you should have seen during the lab investigation.

Results of a Benedict’s Solution TestThe tube on the left is a negative Carbohydrate test result. Color is the original blue of Benedict’s. As you move from left to right, the Benedict’s solution changes from green to orange to red. All three tubes a are a postive test for carbohydrate. The red indicates the presence of the monosaccharide.

• Click on the link and get an explanation of the diagram. How does it relate to the picture in the previous slide?

Why does Benedict's Solution change color?

Something Fun to Look AtRead the list of substances. Are all carbohydrates? Why do the results appear the way they do?

Results for Iodine Test for CarbohydratesOn the right is a test tube of iodine and water. It is a amber color. The test tube on the left contains iodine and a polysaccharide solution. Note the color is no longer amber but a bluish black color.

Why causes the bluish black color?

Check out the results for some common foods and beverages

Post Lab Questions1. Which foods were monosaccharaides?2. Which foods were disaccharides?3. Which foods were polysaccharides?4. What changed color to identify apple juice as a

monosaccharide?5. What test tube(s) can be used to help identify if a food

is a monosaccharide?6. Which test tubes serve as positive controls? Why?7. Did the experiment contain negative controls?8. Write a conclusion for this investigation.