Help with science project - fermentation

My brother is doing a science project comparing apples and oranges.

He wants to ferment apples (and then oranges) and eventually distill the product and measure the ethanol produced. He needs to know how to get the fermentation part done.

If anyone has any experience in this area (maybe making ciders or wines?), maybe you could explain the procedure to me? It’s important, though, that he uses an identical method for the apples and the oranges, so that he can compare them in the end.

Probably the easiest way to do the fermentation would be to go to a wine-making supplies store (or order on-line) and get the appropriate yeast. Although I do not make my own wine, I know from listening to a friend who does that some things (like grapes) are way easier to ferment than others (like oranges). pH is a factor, as is level of fermentable sugar in the juice. Part of the fermentation can be done in an aerobic environment, but part has to be done anaerobically, too. Have your brother get a book about winemaking from the library or check out the kajillion websites about it.
This is actually a pretty interesting project, but one that will require him to invest a few bucks in equipment and some time in reading beforehand if he expects to get useful results.

Regular old yeast, Fleischmann’s or Redstar, will work fine for fermenting apples and oranges. You can get it in the baking goods section of any grocery store. Your brother should run a control fermentation by putting 10 grams of sugar in 250 mls water, along with a teaspoon of yeast. That’ll give him a known sugar content to compare with his apples and oranges.

Wait, he has to distill the stuff? Distillation tends to be frowned on by the powers that be, though there may be exceptions if it’s a science project.

There are all sorts of airborne yeasts and bacterial that can ferment the juice. Leave the stuff exposed to the air by a window for a day or two to allow the wild yeasts to take up residence. He can then put an airlock on each bottle and wait a week or so.

That said I’ll second the recommendation to get to a wine/beer making store, buy a couple of air locks that would fit his containers and pick up some wine yeast. It’ll add a measure of control to his project.

Everything will be done in the chemistry lab, under supervision. The distillation part has been approved, and nobody’s going to be drinking ANY of it. He’s doing the distillation (i think) to be able to isolate the ethanol at the end and measure it. Although I know there are easier ways to measure that, this is the way he and his partners want to do it - mayhem in the chem lab.

He’s been looking into winemaking and cidermaking sites but most assume you already know something about the process - for example, do you mash up the fruit first? Do you use the juice? I suggested tossing whole fruit into a blender, and getting, say, 500mL of mush from each type of fruit (to keep it equal), and then using that. Would that work?

The blender idea is good though I would say freeze it afterwards to burst the cell walls, thaw and heat it to ~150 F for 20 minutes to pasteurize it. Then let it cool to ~60-70F and add yeast. You don’t need to but it should inhibit any wild yeast naturally occuring on the fruit. Shake vigorously to oxygenate the mush and cap with the air lock. Wait 1-2 weeks. He may want to decant the fermenting juice after 3-4 days to get it off the bed of fruit flesh.

Oh, and use wine yeast not beer yeast. I say this only because wine yeast tends to deal with higher alcohol levels better and let’s face it, with only 500ml sample he’s going to need the extra help to get a meaningful sample.