Hey, gang! Today’s Vocabrewlary lesson closes the loop on the main ingredients in beer (yes, I didn’t do one on water but I also don’t feel like I could do it justice in this format.) When people drink a lot of “mainstream” beers, yeast might be the last thing they think of. Can they taste the malts? You betcha! So much chocolate and caramel! Are those hops coming through? Oh, man, soooo hawpy! What about that yeast? *crickets*
It’s easy to forget about what yeast does for beer because most popular beer styles use yeast as a workhorse, not a flavor enhancer. Without yeast, beer would not be beer. If that sentence didn’t clue you in, yeast is like, super important you guys. The thing is, there are SO many types of yeasts that impart SO many different flavors and have such varying characteristics that they’d be nearly impossible to list here. That’s why, as usual, I’m going to keep it simple and talk about the role of yeast in the brewing process, the three big types of yeast and some of the flavors these organisms provide to your favorite beverage.
As always, my typical disclaimer about the fact that this is a general overview of the topic mentioned above and not an in-depth science lesson applies.
What Yeast Does
When it comes to making beer, yeast swoops in at the end of the brewing process to make your brew alcoholic. If you don’t have yeast, all you have is a sugary liquid (called “wort”) that may taste sweet and delicious but wouldn’t get you drunk if you drank a dozen pints. As we’ve discussed in prior Vocabrewlary Lessons, mixing hot water with your malts makes wort. This wort is what you add the yeast to in order to make beer. The science behind this can be fairly complex but the gist of it is that yeast eats sugar and turns it into ethanol (alcohol) and CO2.
The hard part of the brewing process with yeast is that yeast doesn’t just like being happy, yeast needs to be happy. Stressed yeast cells cause off-flavors in beers and can straight up stop doing their job if they’re pissed off enough. Certain yeasts prefer certain temperatures and can also require different fermentation times depending on the strain. It’s not as easy as just pouring in a package of yeast and walking away. Fermentation control is one of the biggest causes of bad tasting beer by home brewers.
Types of Yeast
There are 3 main types of yeast being used right now in brewing. The biggest categories of yeast is brewer’s yeast and wild yeast. While technically Brettanomyces (referenced again soon below) is a wild yeast, the fact that it’s now a commercially available strain makes it on the fence of both brewer’s yeast and wild.
Lager Yeast (saccharomyces pastorianus)
We touched on this quite a bit in the lager Vocabrewlary Lesson so I’ll keep this one short. Lager yeast is a “clean” yeast, imparting minimal flavors to beer. It prefers cooler temperatures and therefore needs to ferment longer because they work slower.
Ale Yeast (saccharomyces cerevisiae)
This is a HUGE category of yeast and much too broad for me to break down individually. However, I will touch of a few of these strains that are prominent in craft beer.
American Ale – These are going to be mostly “clean” in flavor and aroma, allowing the malts and hops to shine.
English Ale – Slightly more fruity than their American counterparts, the English Ale yeast doesn’t fully attenuate (the process of eating the sugars in wort) as the American Ale yeast so the beers can be slightly sweeter and also have character that is not found or acceptable in American beers (like diacetyl).
Weissbier (Hefeweizen) – Imparts flavors and aromas of banana and clove. If you have an authentic weissbier, these two flavors/aromas are unmistakable and unavoidable. These beers also are unfiltered so the yeast will settle at the bottom of your bottle. It’s up to you as to whether you want to pour it into your beer or not. If you do, though, you’ll want to leave an ounce or so of beer in the bottle, swirl it all around to make sure the yeast gets picked up and then dump that slurry into your glass.
Belgian Strains – These can be spicy (white pepper/black pepper), fruity and leave the beer with a dry finish. They can even have hints of bubble gum.
Breweries that use wild yeast have a few ways of obtaining them. They can get their yeast from through “open air fermentation” which is just seeing what yeast fall into their wort (this is how traditional lambics from Belgium are made). The second way is that brewers can collect a sample of yeast from something (even a brewmaster’s beard) and multiply the yeast and use it for fermenting their beer. Or they can order the “wild yeast” from a supplier because those folks can provide some strains now as well. In all three cases, Brettanomyces (commonly referred to as “brett”) is the most common wild yeast used in brewing. This is the yeast that aside from being found in those Lambic styles mentioned above, is now found in a lot of American craft beers. Brett is found naturally on the skins of fruits and is considered an infection to a beer that wasn’t brewed to specifically include it. The flavors imparted by brett are horse blanket, barnyard and cherry pie. Some brewers do 100% brett fermentations and others prefer to introduce brett at the end of their ale yeast fermentation (this is known as “mixed-fermentation”). Brewers also have the choice of using brett without any souring agents or including bacteria such as lactobacillus to the beer because it plays well with the Brett flavors.
That’s the quick rundown of yeast as it’s used in beer. There are details I’ve left out but if you want to know more, Google is a vast resource of knowledge. Also, just as someone literally wrote the book on hops as I mentioned last Vocabrewlary Lesson, someone has also written the book on yeast. If you’re really hardcore, that’s going on your birthday wish list.
Do you have a beer term that you’d like to know more about? Email me at firstname.lastname@example.org or comment below with something you’d like to see explained in a future Vocabrewlary Lesson.