Where Local and Global Appetites Collide

Cooking Science: Our Friend Fermentation

With Fathers’ Day just a couple of days away, I thought I’d do my inaugural cooking science post on something near and dear to many fathers’ hearts: beer.

Beer – it does a body good.  No, wrong liquid.

Beer – it’s what’s for dinner.  Well, maybe for some.

Beer – the other white meat.  See above.

Ok, enough goofing around – this is serious science here.

So what is beer?  We’ve all seen the commercials: pure mountain spring water, malted barley, American-grown Cascade hops… but what are those things, what do they contribute to the final product, and why does it make you feel the way it does?

Alcohol Production

Let’s start with yeast.  Yeast is the one thing they don’t mention in the commercials, but it’s what gives beer its intoxicating properties.  Yeast is a microorganism (a fungus, actually, but I don’t want to gross you out) that can thrive in environments with very little oxygen.  Most energy-producing metabolic processes (converting glucose into energy) in oxygen-rich surroundings produce only energy and two end products: carbon dioxide (CO2) and water (H2O).

Without the oxygen, though, the glucose is broken down into: energy + CO2 + alcohol (2CH3CH2OH).  This process of energy production in a cell in anaerobic conditions (w/o oxygen) is the very definition of fermentation.

Physiological Effects

We all know it’s the alcohol from the fermentation process that produces the physical/mental effects of beer, but why and how does it do that?

Essentially, alcohol molecules have a chemical nature that allows them to easily penetrate cell membranes.  The alcohol molecules have hydrocarbon groups similar to fats, and a very water-like -OH group on one end.  This makes it possible for alcohols to mix easily with both water (like the contents of your cells) and fats (like a cell membrane).

When alcohol enters your cells, it causes disruptions to the normal functioning of those cells.  Disruptions to the cells of our central nervous system bring on our feelings of intoxication.


Up there, I said that fermentation requires a source of glucose (a monosaccharide, or simple sugar).  In winemaking, that’s easy* – grapes are naturally full of glucose.

Beer, though, is brewed from grains that contain starches instead of glucose.  The good news (in this case) is that starches can be broken down into simple sugars through a process called malting.  In this two-step process, the grains (usually barley, but sometimes wheat, rice, millet, etc) are soaked in water until they sprout (usually a few days), and then heated and dried.

The sprouting grains produce enzymes (molecules that speed up reactions) that will break the starches down into their component sugars.  The heating stops the growth process so that you’re left with lots of simple sugars to feed the yeast.  The dried end product (barley malt) is often ground and can be stored for long periods of time.

Flavoring & Preservation

The beers of 1000+ years ago were basically just water, malted grain, and yeast, and they were consumed soon after brewing because they would spoil.  Flavoring agents that doubled as preservatives were first added to beers about that time.  Some of the first were rosemary & coriander, followed not too long afterwards by hops.

Hops are little cone-shaped flowers of the vine Humulus lupulus that have aromatic compounds in their sap and in little oil glands at the bases of their leaves.  The sap compounds (humulone & lupulone) provide a bitterness to the brew, and those from the glands (mostly terpene myrcene) provide aroma.  These same compounds also delay spoilage.


Now that we’ve run through some of the theory, we’ll take a quick look at how that all comes together in the process of making beer:

Mashing: the dried barley malt is soaked in water, getting the starch-breaking enzymes fired up and doing their job.  The end result of the mashing process is a sweet brown syrup called wort.

Boiling: hops are added to the wort and they’re boiled. This pulls the flavoring compounds out of the hops, stops the enzymatic activity of the mashing, kills any bacteria, and concentrates the wort.

Fermentation: yeast goes into the cooled wort and fermentation begins.

Conditioning: getting rid of the spent yeast and other impurities.

Time for a cold one

Obviously, this is a very complicated subject that I’ve given only the most cursory overview of (and even that ended up being twice as long as I expected).  There are lots of other things we could have gone into, but I’m hopeful that this is enough background for now.

So the next time you pop open a can of Pabst Blue Ribbon, or a bottle of Racer 5 (my own fave at the moment), you can think about all of the history and chemistry and microbiology that went into that brew.  And don’t forget to regale your husband or dad (or wife or mom, for that matter) with the story of their favorite beer – I’m sure they’ll be highly impressed!

*I realize that there’s really nothing ‘easy’ about winemaking and it takes a huge degree of skill and artistry.  It’s just that the fermentation step is easier to get going.

Tucson Food Dude
Tucson Food Dude

  1. Love your humorous, playful side — a nice balance to the meticulous detail which I find fascinating. But I have a question. This sounds awfully complicated. Did primitive peoples just stumble upon the process one step at a time?

  2. I’ve just got to find a way to work “penetrating my cell membranes” into the conversation this weekend!

    It does make you wonder, figuring beer (like so many things we take for granted today) being a happy accident, who was the first one to taste some of the water left in a pot of grains too long and say ‘Hm, this tastes kinda interesting’?

  3. Hi Mary – Thank you for the compliments. Your question is a tough one to answer because the process goes back so far. There are written recipes on Babylonian clay tablets for beer dating back to 4300BC. I did a little research on the question, and most historians attribute it to the ‘happy accident’ category, with wild yeasts getting into seeds or grains that were being left to germinate in water or got wet due to rainfall. Belgian lambic beers still use a version of that process, where the wort is cooled in a large, shallow open tank. That allows wild yeasts and other microorganisms to get in and add different flavors to each brew. I hope that helps!

  4. Jennifer, you’ll have to let me know if you’re able to work that in and how you do it!

    I’ll go a little beyond your question, and ask who actually kept drinking it long enough to say, ‘Hm, this tastes kinda interesting, and it’s making me feel all groovy’.

  5. I can only imagine what beer commercials would be like if they advertised the “all important” yeast ingredient. 🙂

    Very interesting information, Food Dude. Thanks for all your knowledge!

  6. Hi, Kristine – Yes, “…pure mountain spring water and only the highest-quality, tastiest fungi” might not be the best marketing strategy.

    Thanks for taking the time to comment, and I’m glad you enjoyed it!

  7. Wonder about the variations (of the above process) employed at our different local breweries that make for various creative tastes? Will you be doing a post on our brewers?

  8. Hi Monica – I like the way you think. We do have some great breweries in town, and it might be interesting to see some of the local variations. I just might work on that!

  9. Hey TFD, loved the post and on Thursday when we’re all celebrating my newest professional adventure at Barrio Brewery, we’ll toast to the lovely yeastie beasties!

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