One common mistake that beginner brewers often make is not adding enough yeast to their wort; a measure of which is commonly referred to as the “pitching rate.” The pitching rate is determined by the starting/original gravity (S.G. or O.G.) of the wort and is important for multiple reasons, some of which I will discuss here.
It is important for me to not that this write up is not intended to be the definitive guide to pitching rates. My intention is to give beginners a clear understanding of the concepts surrounding the practice and why it is so important to the quality of a finished beer.
How it Works
Brewers yeast is a one-celled fungus known as “Saccharomyces cerevisiae” (ale yeast) and “Saccharomyces uvarum” (lager yeast). While these aren’t the only yeasts used to ferment, they are the 2 yeasts that a beginner brewer is most likely to encounter and use for their first handful of beers. For clarities sake, I will focus on these two strains for the time being.
Upon entering the wort, the first thing our little friends do is replicate until they have sufficient numbers to be able to properly ferment a batch of wort into our beloved beer. This is why there is a “lag time”, or a period of inactivity between adding yeast and the start of fermentation. It is during this lag time that your wort is the most susceptible to an infection, caused by unwanted bacteria, which could potentially ruin a batch of beer that you’ve worked so hard to produce.
There is really only one fix for this, and this to introduce plenty of yeast into your wort in order to shorten the lag time. Remember, the yeast reproduce to appropriate numbers, before doing anything, so the more yeast you introduce to the wort the more you shorten the lag time.
This is also where Original Gravity comes into play. As touched upon earlier, the gravity is the measurement of fermentable sugars in your wort, which is what our yeast friends feed off of to produce alcohol. Measuring this not only gives us a good idea of what the alcohol content will be when the beer is finished, but also gives us an idea of how much yeast we need to add to properly ferment in a timely manner.
After a quick search of the HBT forum, I’ve found that it takes somewhere in the ball park of 4 billion healthy yeast cells, per OG point, to ferment a 5 gallon batch of ale that starts at 1.048 OG. If we are to take that as gospel that would mean that anything less is going to lengthen your lag time, thus, making your wort more at risk for an infection of some sort. If it helps, dry yeast contains about 20 billion cells per gram, while liquid yeasts have about 100-300 billion cells depending on size.
In the end, if you want to properly protect your beer from getting an infection during the fermentation stage, it is imperative that you:
Chill your wort to proper temperature.
Properly take your O.G. measurement (I do it twice, just to be sure it’s accurate)
Do a quick calculation of how much yeast you need based off of your O.G. There are plenty of sites online that do this for you. is my personal favorite, but there are a handful of others that I know of.
Pitch enough healthy yeast to do the job.
As a whole, our little yeasty friends are very tough. However, they are not indestructible. In order to help our yeast not only make beer, but help protect that beer from outside infection, we need to do a few things to take care of them:
1. Food: That sugary wort is it. Consider making a starter a few days before brewing just to make sure you have healthy viable yeast.
2. Oxygen: This is why we aggressively stir and shake our fermentation vessel, the more oxygen the better. It really is hard to introduce too much oxygen. Shake and stir vigorously!
3. Proper temperature control: You don’t have to have a fancy fermentation chamber to treat yeast right. This simply means pitching at the proper temps (I prefer 58-68 degrees F for ales) and making sure that the temp doesn’t swing too much after fermentation has started.
In short, infections are what nightmares are made of to brewers. Anyone who has ever had one dreads the thought of losing another batch of beer. The good news is that taking proper care of yeast, pitching enough of it, and proper sanitation (a topic for another day) can eliminate 99% of infections that a brewer is likely to get.
Think of all the time and effort you put into your brews: from setup, actual brewing time, clean up, and then the wait for fermentation to stop. Do you want to lose a batch because you didn’t take basic steps to ensure your yeasts success? Take care of your yeast, use enough of it, and then enjoy the fruits of your labor.