A strong, healthy fermentation is the key to
good beer (assuming the rest of the process went smoothly).
Commercial brewers aim for a pitching rate of at least 200
billion yeast cells for every 5 gallons of wort. By contrast,
the pitchable liquid yeast used by homebrewers provides roughly
30-60 billion yeast cells. Homebrewers who regularly prepare
yeast starters swear by them as being the key to better beer. At
some point in your brewing career, you will need or want to
create a yeast starter. Yeast starters are acceptable for any
batch of beer, but they are especially recommended for certain
situations:
- When brewing beers with an original gravity over 1.070,
yeast starters are a must. High gravity beers really put
yeast to the test, so preparing a yeast starter will ensure
a strong start and a healthy, vigorous fermentation. While
the standard yeast starter size is 1 quart, up to 2 quarts
is acceptable for a high gravity ale.
- Yeast starters are highly recommended for lagers as
well. Lagers ferment at lower temperatures than ales, so
fermentation activity will be a little slower. Again,
pitching a large yeast starter is a good way to ensure a
strong, healthy fermentation at such temperatures. Like high
gravity beers, a 2- to 3-quart starter can be used for
lagers.
- Finally, yeast starters are recommended when the yeast
is past its "best before" date. Using the freshest yeast
possible is always highly recommended, but if the yeast
you're using is a little old, a yeast starter will help the
yeast along its way to a healthy fermentation.
Preparing a yeast starter is relatively easy,
but sanitation is of the utmost importance. Unless
you are very careful to make sure everything is sterilized
properly, bacteria and wild yeast will infect your starter and
ruin the entire process. Here's how it's done:
- The first step is preparing the yeast for the starter.
If you're using liquid yeast, allow your yeast to reach room
temperature before proceeding. If you're using a "smack
pack," you'll need to break the inner pouch. If you're using
a vial of liquid yeast, this is not necessary - simply bring
the yeast up to room temperature and proceed. If you're
using dry yeast, boil 1 cup of water for 5 minutes, then let
it cool to approximately 100º F. Stir in 2 packets of the
dry yeast and cover it with plastic wrap. (If you want to
see whether your dry yeast is still viable, simply boil 1
teaspoon of sugar or dried malt extract in a small amount of
water and add it to your yeast-warm water mixture. After 30
minutes, the yeast should be churning as it devours the
sugar. No churning means dead yeast, so it's a good idea to
have a back-up plan if you use dry yeast.)
- Once your yeast is ready, create a starter wort by
adding 1 cup of dried malt extract for every 1 quart of
water. Consider the size of your yeast starter vessel. There
must be room for headspace, so if you're using a 1-quart
container, you'll want to use less water and, therefore,
less DME.
- Boil the starter wort gently for at least 15 minutes,
then cool it in an ice bath to the recommended fermentation
temperature for your yeast. The recommended vessel for
making a yeast starter is a Pyrex flask since you can boil
the wort directly in the flask, but you can use any glass
bottle you want as long as it can be sterilized and fitted
with a stopper and airlock.
- Once the starter wort is cooled to the proper
temperature, pour it into a sanitized Pyrex flask or a glass
bottle. This is the point in the process at which sanitation
is paramount. Sanitize everything that will come in
contact with the yeast - the flask or bottle, the stopper,
the airlock, the outside of the yeast package and the
scissors that open the smack pack (if applicable, of
course...).
- Pitch the yeast into the flask or bottle, seal it with a
rubber stopper and an airlock and shake it vigorously to
aerate the wort.
- During the yeast starter fermentation, make sure to
maintain the desired beer fermentation temperature.
Fermentation within the starter should occur within 12 hours
of pitching, but it may not necessarily be evident given the
starter wort volume. The best indication of fermentation
taking place is a layer of sediment on the bottom of the
flask or bottle.
- The best time to pitch the yeast starter to your main
wort is during active fermentation or immediately
thereafter, which should be in approximately 3 days. If you
wait a few days between the end of the yeast starter
fermentation and pitching to your main wort, revive the
starter with more boiled, cooled wort before pitching.
- When pitching the starter to your main wort, you can
either swirl the flask or bottle to bring the layer of yeast
at the bottom into suspension or you can decant the starter
wort and pitch only the slurry. If you plan to decant the
starter beer and pitch only the slurry, it is recommended
that you refrigerate the starter overnight to flocculate the
yeast.
- To achieve a larger yeast starter for high gravity beers
or lagers, additional quarts of wort can be added to the
starter one quart at a time to build the yeast population
even higher. Needless to say, this process will take longer
and a larger bottle will be necessary for starters of this
size. Like 1-quart starters, larger yeast starters can be
added right into the main wort or decanted and only the
yeast slurry pitched. However, keep in mind that a large
starter may add more volume to your main wort than you would
like, so you may only want to pitch the slurry.
