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Old 08-14-2012, 02:48 AM   #1
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Default Science Experiment with yeast

I want to do a science experiment with my kids this weekend and I was thinking about using some cheap yeast to show how different types of sugars ferment or do not ferment. I didn't see anything that had a break down of the different types of sugars and how yeast would interact. Is there already a post on this or could someone smarter than me explain. I would like to explain the chemical break down of the sugars a little and what components caused the different reactions. I planned on using simple bakers yeast so that I don't waste any of the good stuff on water bottles and ballons. Any help will be appreciated.
Thanks, Nick

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Old 08-14-2012, 11:14 PM   #2
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You don't have too many sugars available to you: maltose and glucose from the LHBS, sucrose from the grocery store which might also have fructose (in the form of high fructose corn syrup), and perhaps invert sugar (Lyles Syrup) so it will be hard to illustrate that, for example, lager and ale yeasts ferment rafinose and mellibiose differently.

For the chemical process of fermentation (which is really quite involved) look up glycolysis in any biochem text or try the Wikipedia article.

With bakers yeast and table sugar I'm not sure you could do much except note how the reaction starts slowly, picks up speed and drops off, show how colder temperatures slow it down, demonstrate (by using grape juice for example) that the sweetness drops and other flavors emerge, distill off some of the alcohol (you can buy little stills from novelty catalogs). Bakers yeast will doubtless rip through glucose faster than an equivalent amount of sucrose as glucose enters EMP (the glycolytic pathway) directly where as the yeast have to synthesize a transportase to get sucrose into the cell, invert it and then send the fructose down a separate (partially) pathway.
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Old 08-14-2012, 11:18 PM   #3
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John Palmer breaks it down pretty well in his book "How To Brew".

There is a free version online at www.howtobrew.com
"Wisdom isn't "thinking hard". It's experience." - PassedPawn
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