It’s very easy to forget the most important component of any painting is not its nuance, direction, color scheme, or even its finished image; the most important aspect of any painting is actually the canvas on which it is painted. Without the canvas, or raw material an artist paints on, there is no painting. It is almost always the things we cannot see, or forget are even there, that are most intimately responsible for how we eventually perceive something. Forgive the overly poetic metaphor, but such is the case of yeast in beer. Though hard to see and rarely glamorized like the ever-popular hop, yeast could be argued to be the most important ingredient in beer.

This is one of two articles meant to provoke thought on one of the four pillars of beer’s creation. This article is designed appeal to the layman and stress the importance of yeast, while the following piece will offer more technical advice and expertise on the subject for those who are or are seeking to become more advanced home-brewers.

Let’s say you want to design a recipe for an IPA. Aside from dreaming up the taste profile and stylistic category you’d like it to fall in, most homebrewers will decide on the the hops they want to add to the beer to make it unique or to emulate another beer’s taste. Once the hops have been decided on, usually the questions of malts will be attended to. Will the beer’s malt bill be simple so the hops shine? Will the malt bill be complex so as to balance the hops? If you’ve decided the beer should be a hop bomb, a simple malt bill seems the way to go. Now, if you reference other recipes to see what type of yeast is typically used for, let’s call it an American IPA, you’ll likely see a generic American ale yeast in use. You might think, “Great! I’ll use that,” and move on to deciding how much water you’ll need to make the size batch you intend. However, there are two questions you should ask yourself first: why am I using that yeast, and how much of it do I need?

The why, when making an American IPA, is likely the fact that the yeast generally creates little to no flavor of its own during fermentation. That characteristic is paramount to the IPA because it will let the hops do the talking in the glass, besides providing the amount of alcohol we desire from the recipe. Say you made the same beer with Belgian ale yeast, there would be a multitude of flavors created by the yeast during fermentation that could run the risk of clashing with those hops you wanted to showcase.

The answer to the question of how much yeast to use is always recipe dependent. This is where the math your teachers always told you would someday come in handy comes in handy. You see, many home-brewers operate under the assumption that one pack, satchel, or vial of yeast is enough yeast to make any batch of beer. This is not the case. For instance, liquid yeast generally only has enough cells to ferment 5 gallons of beer at a 1.050 – 1.060 gravity range on its own. If your American IPA has an original gravity (OG) of 1.080, there is too little yeast in that liquid culture to ferment the beer the way it ought to be fermented. Add just the one pack or vial to that 1.080 batch and it will still ferment, but it won’t be an ideal environment for the yeast. Sometimes an under-pitch will work just fine, even wonderfully, and sometimes it won’t. The same can be said for over-pitching. The negative effects of too little or too much yeast can be stalled fermentations, unhealthy off-flavors, haze, or a whole host of other effects.

My purpose here is to enlighten, not to frighten, so I reiterate that much of the time, an under- or over-pitch will result in a beer that tastes just fine. However, it is important to note that professional breweries invest a great deal of time, effort, money, and personnel into making sure that their yeast is added in the proper quantity, chosen specifically, and cared for immaculately. If you want to make beer at home like a professional, it’s worth your while to think about your yeast. Look forward to a more in-depth discussion about yeast, yeast starters, and yeast resources in the next article.