Science Buddies: "Ask an Expert"

My son is doing - Sucrose, Fructose and Glucose - oh my uncovering hidden sugars - project for science fair, and is in the process of analyzing the data. (https://www.sciencebuddies.org/science- ... p035.shtml)
For coke and orange juice (with 1:10 dilution) the glucose levels were 1.0 before adding invertase and 1/2 at linear point (15 mins) after adding invertase. He was expecting the numbers to go up and not sure why the numbers went down? Is this expected? For other foods the numbers were low before and high later.

Thanks.

Hello pn66,

You are right to expect the glucose level to rise in orange juice when invertase is added. It should roughly double since orange juice contains enough sucrose to provide about as much added glucose after invertase is added as was present in the juice before invertase.

I don't know why the reading dropped in your experiment. One possible factor is that the test strips don't read beyond 2%. Maybe something unexpected occurred when the strip was immersed in the more concentrated sugar. You might try diluting the juice 1:20 and repeating the experiment with the more dilute liquids.

Good luck, WW