In John Palmer’s How To Brew, he recommends pitching around 400 billion yeast cells for a 5-gallon batch of high-gravity beer. (He does not, thankfully, recommend counting them out one by one.) On a per-bottle basis, that means more than 7 billion yeast helped make that 12-ounce bottle of imperial stout—equivalent to the world’s human population.

VIVA LA RESISTANCE?

Unlike their wild counterparts, many cultured strains evolved to have redundant sets of chromosomes. While more resistant to genetic mutation, the tradeoff is that they now reproduce asexually instead of the more fun way.

LONGEVITY

In 1995, Dr. Raul Cano of California Polytechnic State University reportedly extracted and revived dormant yeast cells from a 45-million-year-old piece of Burmese amber, knocking the laboratory-grade socks off the scientific community. Today, this ancient yeast is used to create beers in the Fossil Fuels Brewing Company lineup, currently brewed by Kelley Bros. Brewing in Manteca, CA.

TEAM BUILDING

Though typically only a few micrometers across, yeast in actively fermenting beers can generate a thick foam upwards of a foot high. While this might not seem particularly Herculean, it’s the scale equivalent of seeing an anthill a hundred stories tall.

SELF-SACRIFICE

There comes a certain point when one needs to throw in the microscopic towel. After a yeast cell dies, it will often go through a process called autolysis during which it releases enzymes that break down its cellular structures: dispersing nutrients and minerals and, in turn, helping to feed its neighbors.

Granted, it’s hard to be sexy when you’re only a few micrometers across.

But while there have been countless developments improving the science and art of brewing over the past few hundred years—a significantly expanded variety of hops, vast improvements to malt kilning, the invention of numerous technological doohickeys to improve quality control, etc.—the identification, isolation, and selective breeding of yeast has likely been the most formative.

Carbonation can be traced back through the centuries. There is evidence that the ancient Sumerians had foam in their beer, which would indicate the existence of carbonation. It would be a few more centuries before airtight commercial bottles allowed drinkers to have stronger carbonation one pop at a time and then a few years more before advances in molecular sciences allowed brewers to force carbonation into the beer itself.

To just think of carbonation as merely bubbles in a glass is to dismiss the science, passion and countless hours brewers and researchers have put into making sure the effervescence is all it should be.

More Than Bubbles

Carbonation occurs after carbon dioxide (CO₂) is dissolved inside a liquid. In beer natural carbonation first occurs during the fermentation process when yeast absorbs the sugar in the wort creating both alcohol and carbon dioxide. Some brewers will also add additional sugars to unpasteurized bottles of beer, allowing yeast to feast a second time, thus allowing additional CO₂ into the beer.

It’s the weakest link theory. Do one thing wrong and it doesn’t matter that you got the other 99 right. A near-invisible film on the carboys, and you get pickle juice where that beautiful pale ale should be, no matter how much thriving, pedigreed yeast you pitched. It can be frustrating until that last piece of the puzzle snaps into place, and then all of a sudden, your beers become much better.

Most of the homebrew I get to taste is pretty wonderful, but among the ones that are not, certain problems are fairly common. I present a few of them here. Of course, at whatever level you brew, there are always improvements you can make. Double check these before you move on.

You can’t sanitize dirty stuff.

Even professional brewers wrestle with this, but you absolutely have to get a handle on it. If not, the rest of your efforts can be a big waste of time, and no great recipe, hand-cultured yeast, or cool label can make your beer drinkable.

Vessels and tools on the “hot side” of brewing, that is, before the wort is chilled and inoculated, need to be as clean as your food cooking equipment.

But in your fermenter, every batch of beer deposits a fresh coating onto the sides and bottom regardless of what material it’s made of. This protein film can be nearly invisible but it can harbor bacteria, which may turn your beer unpleasantly sour. Eventually, the film will build up enough to be noticed, but by this point you’re in deep trouble.

Scouring with a carboy brush will not remove this film and neither will bleach. Breweries use specialized cleaning chemicals, and you should, too. Caustic soda (lye) was long the cleaner of choice for breweries. Cheap and powerful, it does have drawbacks. It is extremely corrosive to copper, brass and aluminum, as well as organic materials like skin and eyes. For obvious reasons, protective gloves and eyewear are mandatory. It also must be used with very hot water. The other downside to caustic—and this is why I stopped using it—is that with hard water, it throws a chalky deposit that requires an acid to rinse away. It’s also getting harder to find. I don’t recommend it.

Oxygenated cleaners like Five Star PBW® (Powdered Brewery Wash) work extremely well even in cold water, are safe, and are available through homebrew supply channels. Just mix according to directions and watch the gunk come off. I swear that the first time I deep-cleaned my carboys, it looked like there were little bats flying around in there. Don’t forget your racking hoses, bottling wand, and anything else than comes in contact with your beer. Once it’s clean, then you can sanitize it.

Avoid stale liquid extract.

The ratio of water to solids in liquid extracts is perfect for a set of chemical reactions called “Maillard” or “non-enzymatic” browning. Proteins or their subcomponents combine with various sugars to create caramel and other flavors. It sounds good, and it’s the same type of reactions that occur in malt kilning and wort boiling, but the transformation in malt extract doesn’t add anything good. It tends to morph into something stale, harsh and cardboardy.

The watchword here is to buy a brand of liquid extract that sells well, or use dry extract, which is more shelf stable.