Beer Byte – October

Yeast: Operation Fermentation

Fermentation may have been a better invention than fire

David Wallace

So we’ve already talked about hops and malt, but we’re still missing a key ingredient in the beer making recipe. Yeast is the third main component of beer and it’s extra important since it gives beer it’s booze! Making beer is one big science experiment and that’s most evident in the fermentation process. Things can get a little technical here, but we’re gonna try to simplify it for everyone!

Yeast is one of the last ingredients added in the beer making process (aside from final flavoring hops). We’re gonna dig into this a bit more in another post, but briefly the beer making process starts with adding hot water to malt which yields a sugary liquid called wort. Then the wort is boiled and hops may be added at this stage. At this point, there is no alcohol yet in the beer! That’s where the yeast comes in. The mixture is transferred to the fermenter and brewer’s yeast is added. The yeast then feeds on the sugars from the malt, resulting in alcohol and CO2. Still with me? Cool.

So what exactly is yeast? Yeast is a microscopic, single-celled organism that’s part of the fungus kingdom. Feeling thirsty yet? Yeast cells feed on carbohydrates (which are made of sugars) and convert them to alcohol and carbon dioxide. This process is called fermentation.

Is there yeast in other alcohols too? Of course! Since fermentation occurs with yeast, it’s a primary ingredient in all alcohol. In wine, the yeast feeds on fruit sugars and in clear spirits, it feeds on starches like potatoes. And remember that whiskey also uses grains! Fermentation isn’t just in the drink world either. Lots of foods are made using this process, including bread, soy sauce, vinegar and more!

What a minute, why isn’t bread alcoholic then? Well actually it is! Yeast used in brewing and baking undergoes the same process of converting sugars into ethanol and carbon dioxide. The CO2 is what causes bread to rise! But when bread bakes, the alcohol cooks off. But bread does in fact have traces of alcohol even after baking. You’d get stuffed long before getting tipsy from bread though!

Are there different types of brewer’s yeast? – Definitely and it completely depends on what you’re making. Some yeast strains have specifically been cultivated for certain flavors. Generally, there are two types of yeast in brewing: top-fermenting and bottom-fermenting. Top-fermenting yeasts react best in warm water and are generally used to make ales. Bottom-fermenting yeasts do better in cold temperatures and are used to make lagers. But within these two categories, there are thousands of strains of yeast to choose from. Definitely gives me a new appreciation for some of my favorite beers. 

My dad’s homebrew ready for fermentation.

How long does fermentation take? Like most things with beermaking, it depends. Lagers take much longer to ferment than ales. Also a high alcohol beer will need a longer conditioning (also called secondary fermentation) time. And the darker the beer, the longer the fermentation process. Brewers really need to know their stuff to make sure their product has had adequate time to bubble.

So there you have it! Hops, malt, yeast and water, what more could you need??