Science Buddies: "Ask an Expert"

Hi, guys! So I've got kind of a problem here:
I was assigned to do an experiment: make 3 yeast-doughs and put sugar in 2 of them, always using yeast, water and flour. Leave one sugar free. I put saccharose in dough 2, dextrose in dough 3, dough 1 is sugar free. Then I put all of them in a nice warm bath and needed to watch which dough swims up to measure the production of carbon dioxide.

Now my problems are:
1. Dough 1 came up first, and that's the dough WITHOUT sugar who shouldn't even be able to do yeast fermentation. Why is that? How does it produce CO2? There was no sugar in the water either, it was just normal tap water. And I watched out not to mix it with the other doughs.

2. Dough 2 (saccharose) came up before dough 3 (dextrose). Why is that? Is saccharose more sugar-y than dextrose?

I'd love to get your guys answers, the experiment is due to Sunday!!

Hi there,

I would first suggest completing several trials to see if this unexpected outcome repeats itself. If it does, then make sure dough 1 doesn't get cross-contaminated with any of the sugar, which you most likely have already done.

Are all of the doughs placed in one large bath or are they each placed in separate containers? Make sure the water also doesn't get contaminated between the different types of doughs. Also, make sure everything you are working with (yeast, water, and flour) is the same amount throughout all of the doughs. Keep the amounts of all ingredients constant. The only explanation I have for dough 1 to be rising first is for some type of error or inconsistency to be occurring between each of the doughs.

Since saccharose contains both fructose and dextrose, it is considered sweeter (or more sugary) than dextrose by itself. Therefore, it will rise up before dough 3.

I hope these possible explanations help and let me know if anything changes after completing the experiment for several trials. If you have any questions, please feel free to ask!