As homebrewers, we don't actually make beer. We make wort, then the yeast we pitch makes the beer for us. However, you many not know that the yeast don't actually want to make beer, they mainly want to grow. During that growth cycle the yeast produces three things: metabolic building blocks, catabolic waste, and daughter cells. The metabolic building blocks (esters, aldehydes, and fatty acids) are produced in great numbers, usually more than needed, and are the key flavors in beer. The waste products are alcohols and carbon dioxide. All of which combine to create the finished product.

At Texas Brewing, we want you to make great homebrew. We want you to succeed with every brew. Two of the biggest keys to your success are pitching the right amount of yeast and providing them a good environment to make beer for us. So how much do you need and how much yeast is in a smack pack, vial, sachet, etc? Wyeast and White Labs are both packaged with 100 Billion yeast cells. The dry yeasts are packaged a little differently though. Through research I’ve learned that the dry yeasts have 20 Billion cells per gram, + or - a Billion cells. So this means that Fermentis sachets have roughly 230 Billion cells, Mangrove Jack have roughy 210 Billion, and Danstar have roughly 220 Billion.

Now that we know the approximate amount of cells with which we are starting. How many cells do we need to make a beer? What are the pros and cons of pitching the right amount of yeast? Afterall, pitching the right amount of yeast helps ensure less off-flavors and a more complete fermentation. So how much is enough? The most common rule of thumb is to pitch 1 Million yeast cells per ml of wort per °Plato or an easy calculation is to pitch 4 Billion cells per gravity point in Specific Gravity. For example, Stubby's IPA has an OG of 1.065 and would need approximately 260 Billion cells (65 x 4 = 260), These are the general pitching amount rules.

So, now that we know the rules, let's get a little more specific about amounts based on style. Ales that are known for their yeast character, English ales, and Belgian sours, should be pitched on the lower end. This usually equates to .375 - .5 Million cells per ml of wort per °Plato. While balanced ales, like English Brown, Stouts, and ESB, should be pitched mid-range at .5-.75 Million cells. Yet for clean, crisp ales like American Pale and Blonde ales, pitch on the high end at .75-1 Million cells. Meanwhile, Lagers typically need double the amount of yeast. In fact, most clean lagers will have a rate of 1.25-1.5 Million cells. Cleaner, crisper lagers like Helles and Pilsner, require a high pitch rate at 1.5-1.75 Million cells. Yet, certain ale styles like higher gravity beers like Barleywine and Russian Imperial Stout should be pitched at high rates just like a lager. This helps ensure a complete fermentation of such a big beer.

So how big of a starter do you need? Small yeast starters do not generate much yeast growth due to the lack of available nutrients. So, pitching a single liquid yeast pack into a 1L starter will only result in roughly 1.7x growth, a 2L starter will result in 2.3x growth, and a 4L starter will generate 3x growth. Basically, the bigger the starter, the more growth you will have. So that fresh pack of Wyeast (100 Billion cells) can be increased to roughly 170 Billion in a 1L, 230 Billion in a 2L, or 300 Billion in a 4L. Which means Yoda was wrong, size does matter. 

These are just a few things to keep in mind when formulating a recipe and pitch amount. In my next blog I will go into more specifics on making a yeast starter and what you might need to add to your arsenal of home beer brewing equipment.

--MikeyB

Mikey has been brewing since 1997 and moved onto all grain in 2012. He has worked at Texas Brewing for 4 years now. You can usually find him there on some Fridays and most Saturdays. He's also available by email at mikey@texasbrewinginc.com.