Science Buddies: "Ask an Expert"

I am working on Uncovering Hidden Sugar in Food. As I started answering the wrap up questions for this project, I noticed that one of the formulas was using the equation 10% x 1%= 10%, Analyzing Your Results

Look at the graph you made in the "Testing the Foods for Glucose Concentration Before and After Adding Invertase" section (step 12). Do the glucose readings you took before adding the invertase match what you would expect for these foods?
Which foods had the most glucose before adding the invertase? Which had the least? Did any have no glucose?
Using the data you collected, you can determine the sucrose concentration in each of the foods you tested.
Look at the graph you made in the "Testing Invertase Activity" section. At the linear time point, what was the glucose concentration? If you multiply the glucose concentration at the linear time point by the original sucrose concentration (10%), this will tell you what percentage of the total sucrose was converted to glucose at this time point. We will call this value "Percentage of sucrose converted." You can see this equation written out in Equation 1.
For example, if at the linear time point the 10% sucrose solution had a reading of 1% glucose, then this means that 10% of the total sucrose (10% multiplied by 1%) had been converted to glucose.
Originalsucroseconcentration×Glucoseconcentrationatlineartimepoint=Percentageofsucroseconverted

When I multiply 10% x 1% I do not get 10%. I get .001 which is .1%

Is the formula being used wrong?? Please advise as soon as possible!!!

Another question: If my percentage of original sucrose converted is 7.5% and I'm testing for the original sucrose concentration of food, my figures for original sucrose concentration are coming up much lower than my glucose at linear time point figures. For instance: Green Beans have an original sucrose concentration of 1.5% as opposed to honeycrisp apples which have an original sucrose concentration of .375%

Green Beans equation: 7.5 divided by 5(glucose concentration at linear time point) = 1.5 (original sucrose concentration)

Honeycrisp apples: 7.5 divided by 20(glucose concentration at linear time point) = .375 (original sucrose concentration)

I would of thought that the original sucrose concentration of honeycrisp apples would be higher than green beans. Am I interpreting something incorrectly??

Thank you for your help.

Note from the moderator: I combined your two questions into one post, so the experts who help you can see both questions - the better to help you!

Hi Noah,
You are correct - 1% of 10% is 0.1%. The formula is correct, but there is a typo in the example!
I've submitted a request for this typo to be corrected.

As for your question about the sucrose content of green beans vs Honeycrisp apples, I wonder if you could show us your graphs. Maybe you could upload them as gif files? Or upload your data for those two as word files?

Thank you for catching the typo and thank you for your patience!

Dear Madeline B.:

I am so confused. Please let me explain.

The equation I was given in the experiment asks me to take the original percentage of sucrose converted, which in my case is 7.5%, and then divide it by the glucose concentration at the linear time point for each food. This should give me the original sucrose concentration of each food. Here is my problem:

When I work this out for green beans I get 7.5% divided by 5% = 1.5%

With Honeycrisp Apples I get 7.5% divided by 20% = .375%

For Maple syrup I get 7.5% divided by 15% = .5%

Why would green beans have a higher original sucrose content than Honeycrisp apples and Maple syrup???? Am I working this out correctly? This doesn't make sense to me. Please advise ASAP. I am seriously wondering if the equation is correct.

Thank you so much for all of your help.

Noah

hey noah how did you get 5 for glucose when the highest number is 1% and how did you figure out the equation

Hello Noah,

It would be helpful to see your data table from your lab notebook where you record, for each of the food samples, the two glucose readings: one before adding the invertase and one after, at the linear time point you determined for each food in the "Testing Invertase Activity" section in step 10.b. Could you show us the data as a Word file, or Excel table, or maybe take a picture of your data table with your smart phone?

Also, I'm curious if the percent sucrose converted is 7.5% for each of the foods you tested?

Green Beans: 5 grams
Carrots: 5 grams
Sweet Potatoes: 15 grams
Squash: 2.5 grams
Butternut Squash: 7.5 grams
Peas: 1.75 grams
Prunes: 15 grams
Pears: 10 grams
Apples: 15 grams
Honey Crisp Apples: 20 grams
Beef: 0 grams
Turkey: 0 grams
Chicken: 0 grams
Bananas: 20 grams
Orange Juice: 10 grams
Grape Juice: 20 grams
Apple Juice: 15 grams
Peanut Butter: 0.5 grams
Plain Yogurt: 1 gram
Sour Cream: 0 grams
Coke: 7.5 grams
Maple Syrup: 2.5 grams
Milk: 0 grams

All these results were after invertase. Please respond as soon as possible. Again, Thank You So Much! -- Noah

Noah - unfortunately, there was an error in the section with the equation for this project, and that may have caused some confusion as you worked with your data.

The project has been updated. If you return to: https://www.sciencebuddies.org/science- ... #procedure

You will see updated information in the "Analyzing Your Results" section for the equations, with updated examples for each.

As you work back through your data analysis, if you have specific questions, post back here.

Amy
Science Buddies