Homebrewing with Yeast Starters: How and Why

Yeast is one of THE most important components in our beer.  It decides the overall balance of the finished beer, which qualities will be enhanced and suppressed, and easily accounts for 80% of the overall flavor profile of your beer.  The question is, why wouldn’t we want to make sure that these guys are being pampered?! This week, we will talk about what’s happening in your yeast starter, how to properly calculate cells like the pros, go over how easy this extra step is, and how much it adds to each of your beers!

What Is This Really Doing for My Beer?

All you’re really doing when you make a starter is making a small amount of hop free session beer so your yeast can grow and prepare for the beer that you’re really going to put them in.  When you pitch the right amount of healthy yeast, your yeast will stress less, produce less off flavors, ensure proper attenuation (how much of the sugar the yeast actually eat) and give you a cleaner finished beer. 

Yeast starters are one of the the easiest ways to take your beer to the next level with minimal effort.  For the cost of a stir plate, some dry malt extract and a package of yeast, you can make every batch jump up an entire shelf in quality!  This is one of the first steps that every brewer should take when they pick up this wonderful fermentation habit!

Aerobic vs Anaerobic

You’ve heard these terms since your freshman science class.  Simply put, aerobic means with oxygen, and anaerobic means without oxygen, and with yeast, oxygen makes all of the difference!  These little guys need oxygen to work their magic, whether you are making a starter or just fermenting your latest libation.

The real difference is what they’re doing during each phase.  During the anaerobic phase, the yeast are actively fermenting and creating ethanol, which is the overall goal with all of this!  We lovingly refer to this phase as the fermentation phase, for obvious reasons. Although your wort needs to have oxygen when you pitch your yeast initially to help them get the juices flowing and ensure a healthy fermentation, for actual fermentation to work, it needs to be anaerobic overall to force the yeast to actually ferment and create alcohol.

When we make a yeast starter, what we are doing is creating an aerobic environment with low sugar concentration.  When yeast are in this phase, they aren’t even producing ethanol! When the gravity is low, and there is plenty of oxygen to support regular cellular respiration, the cells can replicate easily, and stay in this replication phase.  The beauty of this is that, in theory and with proper scientific process, you could reasonably keep a specific yeast strain going indefinitely. Your yeast cells will not advance in generation or mutate as long as you do this part right, and basically don’t stress them too much.  More on this process in a minute!

This aerobic part of the process is why a magnetic stir plate is so important.  When you put your starter on the stir plate, you are ensuring plenty of oxygen is constantly in solution and available for the cells to use, which in turn keeps them in that replicative state.  This being said, even if you don’t have a stir plate, making a starter will always be better than not making a starter if your cell count is too low for the beer you’re brewing, even if your oxygenation method is swirling your flask (or even a growler) every time you walk by.

When your yeast starter is on the stir plate, just remember that you don’t have to have a crazy vortex spinning down the middle like it’s tornado on the plains.  Just as long as the magnetic stir bar is spinning, your speed controls are moderate, and you are actively keeping the yeast off of the bottom of the erlenmeyer flask and in your starter wort, even lazily, then you are doing it right.

How Do I Know If It’s Right To Make A Starter?

Whether or not you make a yeast starter depends on a three common variables different to just about every beer:

• What is your projected original gravity (OG)?
• How many gallons are you putting into your fermenter?
• How many cells are you starting with?

Your beer recipes will generally have an OG that you are shooting for, and if you’re not using a recipe, you can easily calculate your projected gravity using the amount of base malt or malt extract going into your recipe and, if brewing all-grain, what your average efficiency is.

Once you know what kind of gravity you’ll be shooting for, you’ll need to know how much wort that you actually plan to put into the fermenter.  For example, if you’re making a 5 gallon batch, you’re trying to make 5 gallons of FINISHED BEER, which means you’ll have to account for fermentation losses.  All of our Beer Ingredient Kit gravities are calculated with 5.5 gallons of wort being fermented, so you’ll always want to pursue propagation with that in mind!

Starting cells can depend on a few factors, most of which is type of yeast, the manufacturer and the manufacture date.  It seems that most liquid yeast purveyors make home brew ready yeast packs in either 100 billion cells pitches (White Labs or Wyeast) or 200 billion cell pitches (Imperial Organic Yeast or Gigayeast), although there are some purveyors that vary cell counts quite a bit more from strain to strain.

There are many online yeast viability calculators that can help you determine how many viable cells you have in your yeast pack before you get started.  Although I find these calculators to be very aggressive in determining actual viable cells (seems like they always severely underestimate actual viability - full disclosure, I haven’t done actual lab testing on this...YET!), the only other way would be to perform a cell count yourself, which is quite a bit of work.

The process of determining whether or not you need a starter is easy once you have determined the basics!  Rule of thumb for most ales is 1 million yeast cells per milliliter of wort per degree plato, which is about 1.004 specific gravity, and for lagers is more like 2 million per milliliter per degree plato.  For higher gravity beers, and especially high gravity lagers, it’s not uncommon to pitch as many as 3-4 million per mL per degree plato. It’s fairly simply math if you want to do it long hand, but we generally refer to one of the available online calculators and let them do it.  Less math means more brewing, after all!

Let’s take it step by step.  Say you are making a Cream Ale at 1.052 OG.  For this normal ale, you will want to pitch about 6 to 10 million yeast cells per milliliter of wort.  According to YeastCalculator.com, one of my favorite and most used pitching calculators, the sweet spot is 9.6 million cells per milliliter, making the total cells you need 200 billion cells.  Do you need a starter? If you are using Imperial Yeast, then no! They already start with 200 billion! If you are using White Labs or Wyeast, then you’ll either need about a 1 liter starter, or you’ll need to pitch two packs!

How about a higher gravity beer?  Let’s say you are brewing Andromeda, one of the tastiest NE Style Double IPA’s ever.  OG is at 1.081, with 5.5 gallons going into the fermentor.  Our online calculator says that 14.6 million cells per milliliter is just about right, and we’ll need a total of 305 billion cells to get a clean fermentation.  Do you need a starter? The answer is a resounding yes! Starting with 100 billion cells, you will need to put a liter and half on the stir plate to get to your target pitch!

There are, of course, exceptions to these rules.  Some strains, such as the cool kveik strains, work better under pressure, and are genetically geared towards NOT producing the off flavors that we associate with under-pitched and poorly fermented beers, flavors like hot alcohol (higher production of acetone and higher alcohols - the ones that become the ‘heads’ were you distilling) and acetaldehyde, our favorite green apple nastiness.  This is also the case with some yeast driven beer styles, such as Belgians, because by stressing the yeast just a little, they produce more of the delicious ester characteristics that we love so much.

The Importance of Yeast Nutrients

A big part of building a healthy yeast pitch for brew day is making sure that, once this culture is built, there are enough solid nutrients to maintain it.  When yeast replicate, they use nutrients for cell respiration, and one the best things that you can do is make sure that they have enough nutrients to continue replication and move seamlessly into fermentation without creating any undue stress.  While there are tons of great products on the market, we always try to stay away from anything that is generally labelled, things simply called ‘yeast nutrient’ or ‘yeast energizer’ and doesn’t really have an explanation or list of nutrients or ingredients.  These are usually just a shot of Diammonium Phosphate, and sometimes a mix of yeast hulls.  These products are by no means bad, and are definitely better than nothing at all, but lack the complexity of some of the more complex nutrients that are just as readily available, such as Fermaid K and Fermaid O. 

First and foremost, all yeast use nitrogen to help fuel protein synthesis and maintain cellular growth.  Since we’re actively growing yeast, this seems like the most important part, and is why using more generically named nutrients is better than nothing.  DAP is basically a shot of nitrogen for the yeast! The rest of the vitamins, cell wall fractions for absorbing toxic fatty acids, and sterols that the Fermaid line of products provides is what really sets these products above the basic stuff.

When adding additions, we keep a very general dosing rate, which is about half a gram per liter of starter.  Admittedly, this may be a little overkill, but not by much. This dose rate seems to help ensure not only a healthy starter, but that our yeast pitches go into fermentation with some nutrients in reserve.  From there, our standard nutrient regime for beer is by the book. Both of these Fermaid products recommend a gram to a gram and a half per gallon at 33% sugar depletion, and for us, that translates into a day two of fermentation addition on just about every beer.

The Actual How-To Part

The actual process of making a starter is SO easy, and can be done in several different ways.  There are all kinds of cool and innovative ways that homebrewers have developed to cut down the required time and energy to make this happen!

One of the easiest ways that most people make a starter, which you can watch in our How To Make A Yeast Starter video on BrewChatter TV on YouTube (you can watch it below!), is to simply add the right amount of DME to an erlenmeyer flask (use one of the online calculators to calculate your necessary volume of starter and how much dry malt extract to use), boil the whole concoction for 15 minutes to ensure sterility and to make sure the chlorine in city water gets boiled off, chill the whole thing down, and pitch your yeast.  This is easy, and may be one of the most common ways to make a starter.

If you want to save time, you can also plan ahead!  Many people will make starter wort ahead of time, and it’s easy to do with the brewing equipment that you already have!  Instead of making just a single starter for brew day, what if you were to make a gallon of 1.076 - 1.080 wort? It doesn’t take a whole lot of DME to do, about 1.8 pounds per gallon, and you can put it into quart mason jars, which are 32 oz or about a liter, and seal and sterilize your jars by boiling them in your brew pot for 10 or 15 minutes!  When you’re ready to do a starter, all you have to do is pop a jar, pour it into your flask, and pour an equal amount of clean, filtered water in with it, pitch your yeast and turn on the stir plate! For an extra 30 minutes of preparation, you’re ready to do your next four starters at a moment’s notice with almost zero effort! You can even do this on brew day while you’re waiting for water to boil or wort to cool!  This is not a new idea, but it’s so simple that I wanted to make sure that we mentioned it.

One of my other favorite methods, especially if you’re brewing often and heavily, has always been to do a mini brew day with some American 2 Row or Dry Malt Extract and make 5 full gallons of wort at 1.040.  You can mash or mix as necessary, boil for 15 minutes just like with a small starter, then cool it down and throw it in a keg. Put enough pressure on the keg to make sure that it’s sealed and safe, then throw it in the kegerator.  This way, once it’s time to do a starter, you can just plug in a picnic faucet and pour your desired starter size into your flask and pitch immediately!

What I like about this method is that it gives me another opportunity to brew, but it does have a couple of downsides.  First and foremost, you have to be VERY clean, and you have to make sure that you sanitize your flask and picnic line, since you won’t be boiling it,  and clean your picnic line immediately after use, otherwise you will grow some cool stuff that you probably don’t want growing on your equipment. The other caveat is planning.  Since you’re pitching cold yeast into cold wort, it takes almost a full extra day to get started and moving, just as if you were to cool your flask in the fridge overnight instead of using an ice bath and pitching immediately.  It’s still extremely convenient, and if you have the extra fridge and keg space, even if you have a 1.5 or 2.5 gallon keg, it can save you hours in the long run!

Once your starter is actually made, it’s very simple!  Now that you have your yeast in solution, it’s ideal to put it on a stir plate and allow it to spin, at room temperature, for 48 hours.  You can keep it on the starter for a week or so if you have to, but 48 hours is usually the sweet spot.

Another thing to remember is that even if you are doing a starter with a lager yeast, you don’t need to do your starter at fermentation temperature, just like you wouldn’t do a starter for a Belgian style yeast strain at 75° F.  Room temp is kind of the standard across the board, and works perfectly for just about any strain that you would start.

Decanting Vs. Direct Pitching

The two methods for pitching your yeast once your starter is ready are simple.  You can either pour the whole thing in your fermenter, or you can crash chill it overnight to get the yeast out of suspension and to the bottom of the flask, then pour off the excess starter wort and add just the slurry into your fermenter.  Both of these methods work perfectly, and it honestly comes down to personal preference and time constraints. The excess starter wort is not enough to impact the flavor or color of your beer, and won’t add anything but extra volume to your finished product.

We usually use this method because it’s easy, and there’s not much in the way of benefits to decanting other than your own personal preference.  We’ll usually account for the extra volume in our brew day water measurements and call it a wash.

Keeping a Yeast Library Without Getting Crazy

Keeping a yeast library is super fun, and can help you save money per batch, as well as save cool strains that are only available seasonally.  For us, keeping a small yeast library is a must, since we try to do multiple trials with new yeast strains so that we can better describe and understand them. 

One of the best ways we’ve found to propagate and maintain a strain is to overbuild your starter.  This keeps your initial strain as close to what came from the lab as possible, and gives you a starting culture to use for your next starter.  Rule of thumb is that you get about 100 billion cells from a half liter of starter, so by overbuilding by just a little every time you do a starter, then storing that little bit extra in a sanitized mason jar in the fridge, you can have access to your own fresh yeast any time!

We try not to let these overbuilt starters stay in the fridge for more than three months without throwing them on a starter again, but it doesn’t always happen that way, which means that sometimes, a multiple step starter is necessary.

To plan a multiple step starter, it’s good to use a more advanced yeast calculator like the one available from BrewUnited.  This will help you stay inside healthy growth factors and ensure a healthy culture.  We also like to use this calculator when building up wild yeast or yeast from a bottle conditioned beer because of the versatility.

Thank you all for reading!  Hopefully this article and our Yeast Starter video has shown you how easy and beneficial yeast starters are!!  Just like with everything in this hobby, you can be super casual and make better beer, or you can start a full on lab in your basement, mad scientist style, and still make better beer!  Going full geek is never a bad thing!

Don’t forget to check out our other videos on BrewChatter TV for more fun and informative topics!  Connect with us on Facebook, Instagram and Twitter to stay up to date with what’s going on now and what’s coming next!  Brew On!