Adventures in Ethics and Science

A conversation that bubbled up at the dinner table last night, some time after the Free-Ride offspring were informed that the cassoulet they were eating had, as one of its ingredients, white wine.

Younger offspring: Why do they call booze “spirits”?

Dr. Free-Ride’s better half: I think that goes back to the early days of distillation. Do you know what distillation is?

Elder offspring: Ummm…

Dr. Free-Ride’s better half: OK, to distill something, you have a container of the thing it is you’re distilling. You apply heat to that container, and it’s attached to a tube that’s usually surrounded by something like cold water. As you’re heating the stuff in the container, some of it turns into vapor, and when the vapor gets into the tube surrounded by the cold water it cools down —

Elder offspring: And condenses?

Dr. Free-Ride’s better half: Yes! And that tube where the vapor is condensing is hooked up to a collection container, so it drips down into that container instead of going back to the container with the original stuff you were heating.

Younger offspring: I still don’t understand what this has to do with “spirits”.

Dr. Free-Ride’s better half: Well, using this distilling, you could take a substance that looked pretty muddy and yucky and still collect distillate — that vapor that condensed — that was clear. So people thought that the clear liquid they could collect was the “spirit” of the muddy, yucky stuff.

Younger offspring: Oh.

Dr. Free-Ride: Of course, you can also distill stuff that isn’t muddy and yucky. For example, you can distill wine to make brandy.

Younger offspring: But brandy is brownish.

Dr. Free-Ride’s better half: That’s because it’s been aged in oak casks after it’s distilled.

Elder offspring: So, do they use distillation to make beer and wine, too?

Dr. Free-Ride: Nope. You make beer and wine and hard cider —

Dr. Free-Ride’s better half: And sake!

Dr. Free-Ride: — and sake through fermentation.

Younger offspring: Huh?

Dr. Free-Ride: Fermentation happens when yeast in your grape juice or apple juice or grain munch on the sugars and make alcohol.

Elder offspring: Oh yeah! The yeast eat the sugar and they poop out alcohol and carbon dioxide?

Dr. Free-Ride’s better half: What they do actually depends on whether they have a lot of oxygen around. So, why are the yeast eating sugar?

Younger offspring: To get energy.

Dr. Free-Ride’s better half: That’s right. And in conditions with plenty of oxygen, the yeast will get a lot of energy out of the sugar and give off carbon dioxide as a waste product. But when they’re deprived of oxygen, they can still get energy out of the sugar — not quite as much, but they manage. And then, they give off alcohol as a waste product. Here, let me show you. (writing on some scrap paper)

i-b65e991507463ca912c07dd56dcf61e1-Fermentation.jpg

Dr. Free-Ride’s better half: Sugar — well, glucose, anyway — has six carbons and a bunch of hydrogens and oxygens. And in grape juice or apple juice there’s plenty of H2O around. So, if the yeast have lots of oxygen to work with, how many CO2 can they make from each sugar?

Dr. Free-Ride: Just think about the carbons here …

Elder offspring: Six?

Dr. Free-Ride’s better half: That’s right. OK, and here’s alcohol — the kind we drink is actually ethyl alcohol —

Dr. Free-Ride: Which nowadays we call ethanol.

Elder offspring: Hey, don’t some cars use that for fuel?

Dr. Free-Ride: Yes.

Dr. Free-Ride’s better half: — which has two carbons, six hydrogens, and an oxygen. So if the yeast don’t have access to lots of oxygen as they’re eating their sugar, how many alcohols can they make from each sugar?

Elder offspring: Umm, three?

Dr. Free-Ride’s better half: That’s right. Now here’s what’s interesting: just with fermentation, the alcohol level can’t get very high. Do you know why?

Younger offspring: The yeast find oxygen?

Dr. Free-Ride’s better half: No. Alcohol is a poison.

Younger offspring: It is?

Dr. Free-Ride: Uh huh. And that means, once there’s a certain level of it floating around in the juice where the yeast have been munching the sugar –

Elder offspring: It poisons the yeast?

Dr. Free-Ride: That’s right. They’re swimming in their own waste products and after a certain point, those waste products kill them.

Elder offspring: Kind of like us swimming in our own waste products as the planet gets more and more polluted.

Dr. Free-Ride’s better half: Um, yeah.

(There followed a brief interlude in which the Free-Ride offspring made their best gruesome “yeast poisoned by its own waste products” faces. They were pretty gruesome.)

Dr. Free-Ride: So, if fermentation only gets you to the concentration of alcohol that kills the yeast, distillation is a way to get a higher alcohol concentration.

Younger offspring: Distillation makes alcohol, too?

Dr. Free-Ride: No, the yeast make the alcohol, but distillation lets you concentrate it by separating it from the water. And the reason you can do that is, as you’re heating what it is you’re going to distill —

Elder offspring: Like wine?

Dr. Free-Ride: — like wine, is that the water in the wine and the alcohol in the wine boil at different temperatures. The alcohol doesn’t need to be quite as hot to turn into vapor, so it goes up into the tube to condense and be collected before the water really gets boiling.

Younger offspring: And then you get more alcohol?

Dr. Free-Ride’s better half: Nope, it’s the same amount of alcohol you started with before you distilled it. You’ve just separated it from a lot of the water.

Elder offspring: And other muddy, yucky stuff.

Dr. Free-Ride: I will thank you not to refer to wine as muddy, yucky stuff.

Younger offspring: So yeast make alcohol.

Elder offspring: And distillation can separate alcohol from other stuff.

Dr. Free-Ride: And you children make really scary dead-yeast faces.

Comments

  1. #1 ctenotrish
    February 13, 2009

    Ah, my friday is complete. That was as satisfying as a big Cab Sav! :)

  2. #2 jj
    February 13, 2009

    Wow, already understand the idea of fermentation and distilling. I didn’t really know (or care so much)the process until I was almost in college – and I only learned because it was easier to make beer than buy at 18! (now I make beer for the fun and love of it)

    Great post, one of my favorite parts of Friday!

  3. #3 Larry Ayers
    February 13, 2009

    Janet, do you take notes during these exchanges with your sprogs? Or do you reconstruct them entirely from memory?

    I’m just curious, as I also try to transcribe conversations, just for the fun of it. I don’t take notes, though!

    I’ve said it before, but I’ll repeat myself: these Friday Sprog Blogging posts should appear in book form some day!

  4. #4 jj
    February 13, 2009

    That’s right. And in conditions with plenty of oxygen, the yeast will get a lot of energy out of the sugar and give off carbon dioxide as a waste product. But when they’re deprived of oxygen, they can still get energy out of the sugar — not quite as much, but they manage. And then, they give off alcohol as a waste product. Here, let me show you

    I’d say that’s only partly true (or at leased form what I pull from that) – Oxygen is required for yeast reproduction. C02 is also part of the anaerobic process of fermentation. And this is very important to brewers, as we allow all CO2 to escape during almost the entire process. Once fermentation has ceased due to lack of sugars, we add an exact amount of sugar (depending on volume) to re-energize the yeast. Then we seal it off and allow that last little added bit of sugar to ferment out and create the fizz we love in beer.

    This is also why it is important to seal (we use an air lock, allow CO2 to leave fermenter, but nothing to come in, like a 1 way valve) – if oxygen get’s into your unfermented beer (wort), it allows for more reproduction of yeast and you need control over what strain of yeast lives in your brew or else you get nasty phenols and esters. The porccess goes – boil to sterilize, cool, aerate, pitch yeast, and seal.

    And that’s my little rant, as you can tell I have a love for brewing and beer (Brew Organic!)

  5. #5 J-Dog
    February 13, 2009

    Larry is correct! Book! Book! Boook!

  6. #6 Super Sally
    February 13, 2009

    So when and how did YO become such and expert on brandy???

    This conversation will certainly give a different nuance to my glass of wine this evening (TGIF).

    [It just occurred to me that if might also give a different nuance to Duke's NA beer.]

  7. #7 Tim Eisele
    February 13, 2009

    Following up on JJ’s comment, just splitting the glucose into three ethanols doesn’t balance. I believe the actual fermentation reaction is:

    C6H12O6 ==> 2C2H5OH + 2CO2

    So we only get 2 ethanols per glucose, not three, and the yeast gain energy from fully-oxidizing 1/3 of the carbon present (not just from splitting up the glucose molecule).

    Still, this doesn’t really change the thrust of the discussion, and your “better half” did a pretty respectable job for an off-the-cuff explanation.

  8. #8 JJ
    February 13, 2009

    Way to be on the stoichiometry Tim!
    One other note, I do believe that yeast can and does ferment starches other than glucose – In brewing, once again, we heat our grain (at lease 30% barley) through a heating scheme to activate α Amylase and β Amylase, to break down the complex starches into fermentables. Depending on your heating profile, you will end up with a mix of different sugars (this is because α and β amylase activate and deactivate at different temps, and α cleaves starches in the middle of the chain, were β cleaves at the ends, creating a possibility for multiple lengths [or is that backwards?]). Different fermentables have a differing level of fermentability – the less complex the starch the more fermentable. Things like Dextrose (cane sugar) are highly fermentible, where maltodextrin is only about 12% fermentible. Lactose is considered to be completely unfermentable.

    I ♥ yeast! Be my valentine saccharomyces cerevisiae

  9. #9 Abel Pharmboy
    February 13, 2009

    Tim Eisele got here first to make the clarification that explains why my 1995 batch of fermenting barleywine exploded with such force that I came home from lab to see glass shards embedded in my kitchen ceiling (and a gooey, hoppy mess covering larger shards of glass all across the kitchen floor).

    Anyway, it’s not that I’m lazy – well, yes, I am – but I had to link to you guys for today’s Friday Fermentable. Well done around: kids and parents.

  10. #10 Clare
    February 13, 2009

    The really interesting thing about distillation chemistry is that you can’t make a solution of greater than 96% ethanol in water by distillation. I can’t remember the exact chemistry because it was quite some time ago I did that subject, but alcohol is more soluble in a solution of 97% ethanol, so it won’t distill off anymore.

    To get 100% ethanol they have to add benzene, which is why you whould never drink 100% ethanol broken back to a lower %, only 96% ethanol broken back.

  11. #11 clare
    February 13, 2009

    Ah, I found a link that explains it.

  12. #12 Isis the Scientist
    February 13, 2009

    Can I please send Little Isis to play with the Sprogs? He has so much to learn!!!

  13. #13 Danimal
    February 14, 2009

    I need a drink. Do not care beer or wine all is fine.

  14. #14 ScienceSealedDelivered
    February 14, 2009

    Now do coffee!

  15. #15 Carrie
    February 17, 2009

    And I wish I liked organic chemistry more — just so I’d remember things like the composition of sugar and alcohal….

  16. #16 Bob the builder
    October 26, 2009

    So… Why is there cold water around a fermenter?