# Biology IA Yeast Help

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After failing two IA experiments, I have one more week to finish the experiment that my teacher chose for me: expansion of dough.

I tried to make the dough mixed with yeast with following this recipe:

2 grams of all-purpose flour

1.4 ml of distilled water

I am varying instant yeast concentration (0.05, 0.1, 0.15, 0.2, 0.25) and temperature (room temp, 30, 40, 50, 60Â°C)

I tried doing it without sugar but the time taken is wayyyy too long

I want to add sugar to the dough but should I?

And also, how much sugar should I add?

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Two points on this:

1) You're using two independent variables -- keep this in mind for when you're statistically analyzing your results because it WILL cause a huge pain in the derriere when you get to that point. I know because I ended up using two ind. variables for my EE and it took me about 3 days of research to find out how I can reject my null hypothesis using two variables. I'd suggest you limit it to either changing yeast concentration OR temperature.

2) Why shouldn't you add sugar? Yeast needs sugar for fermentation to occur (glucose is the most effective, and if you want to increase fermentation, add a bit of vinegar or any other substance that will lower the pH so that it's more efficient). If you do decide on adding sugar, you're going to have to consider the amount of sugar added. You can't keep this constant because, obviously, the lowest amount of yeast will ferment the quickest because there'll be a higher sugar concentration. I'd suggest finding a way to make sure the yeast:sugar ratio is the same in each (this is only valid if you decide on making your independent variable yeast concentration; otherwise, this bit's irrelevant)

TL;DR I'd suggest making temperature your only independent variable so you can keep yeast concentration and glucose constant without complicating things

Best of luck! Xx

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Like the previous commenter I recommend also just having one independent variable. Changing the amount of sugar is much easier to control compared to temperature. For the amounts I suggest looking at recipes for bread or some other dough (scaling amounts down). This also can add â€œpersonal engagementâ€ to your IA.

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