Reviews, Commentary and Opinions on Midwest Craft Beer and Microbreweries

June 9, 2008

Home Brewin’:

Reusing Yeast

Take control of your home brew?and be a cheap skate?by resurrecting your yeast batch after batch.
by Jug Dunningan

Jug Dunningan is just here for the beer.
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Ever see those commercials where the kids throw out their roll-over phone minutes and the mother freaks out on them? Home brewing can be like that. You go and buy the best two-row barley, premium hops, oxygen absorbent bottle caps and a high quality yeast. You do your magic, and two weeks later you bottle your craftsmanship and clean out the carboys for next time. Now it?s time to make a trip to your favorite home brew supply store and buy more barley, hops, and yeast.

Home brewing is not only fun, it?s economical by nature. As I?m sure you realize, the price of beer is on the rise, mostly due to hop and barley shortages. Some craft beers are as much as $10 for a 4-pack. Of course, some things are worth paying for, and I?d put quality beer in that category, but as a home brewer I have to scratch my head when I see how much craft beer can cost.

Let?s quick do some math. We?ll make a nice summer weizen with a target original gravity of about 1.050 (a fairly medium-bodied brew). We?ll need 6 pounds of wheat malt, 5 pounds of two-row barley (about $11), 2 ounces of Hallertau hops ($4) and a quality yeast ($6 for the Wyeast activator pack, which is all I use). Not counting our time and original equipment cost, we can make 5 gallons (very close to nine six-packs) of quality craft beer for $21. That breaks down to $2.33 per six-pack! Not bad, eh?

This isn?t an article about how to be a cheap skate, but if it pushes you over the edge to start home brewing, all the better. In the above example we spent close to 30 percent of our home brew cost on yeast. Yeast is the most important ingredient in making a craft beer. I get asked all the time if and how I reuse my yeast. The answer is I do, a lot, because it is pretty easy and I?ll tell you how it?s done.

First, I need to give you some basic yeast-handling tips. As I said, yeast is the most important ingredient when home brewing. If you don?t get it right, use a contaminated yeast, or follow an unsanitary process you will ruin your beer. This is reason enough to scare many would-be cultivators away. But take heart, because it?s not a tough process to master.

Basic Yeast Rules
? Only reuse a high quality liquid yeast. If you don?t start with a good strain, it?s not going to get any better.
? Only reuse a yeast that fermented quickly and flocculated properly. Don?t reuse anything that took longer than 24 hours to start, had a stuck or lagged fermentation, or did not reach proper attenuation levels.
? Reuse the yeast in a timely manner. I have reused yeast over 6 months old, but I would recommend using it within 3 months.
? Sanitation, sanitation, sanitation. I can?t stress this enough.
? Don?t reuse yeast for more than 5 generations maximum. I generally only use yeast for 3 generations.

There are many ways to cultivate or reuse your yeast, but these are the two methods I use the most. In the first one I simply reuse the original yeast cake. When I ferment, I rack to a secondary fermenter once the bubbling slows to less than one bubble per minute. This may be a bit sooner than some like to do it, but I don?t like the brew sitting in the sediment and dead yeast cells any longer than possible. When I rack the brew and I know I am going to pitch another batch on top of the yeast cake, I make sure to leave a ?beer barrier? over top of the yeast cake of about half an inch. The beer is hopped, alcoholic and slightly acidic and will form a natural sanitation barrier over the yeast. Simply snap the lid back on your fermenter, complete with an air-lock, and place in a cool (60), dark place. After you brew your next batch, make sure to cool the wort to about 70 and dump it on the yeast cake. That?s all there is too it. Fermentation will start quickly and incredibly vigorously. Congratulations, you just shaved 30 percent off your brewing costs.

If you reuse the same yeast to make different styles of beers (for instance, I reused a London ale yeast after making an IPA to make a brown ale), you should brew the lighter beers first, since the remaining beer in the fermenter can affect the color of the next batch.

I have waited as long as two weeks to reuse the yeast cake and had no problems, but I wouldn?t recommend waiting much longer than that.

When using this method, you will be over-pitching?using way more yeast than needed. This can affect the attenuation rate (and ester production) of your brew, so keep this in mind when planning your beer style. I have had little problems with the final product doing this, though.

Keep in mind that over-pitching yeast can affect attenuation rate and ester production.
The other method reusing yeast is slightly more involved. There are several schools of thought on how to do this, but I?ve had lots of succes with this technique. As I mentioned earlier, I rack to the secondary while the beer is still bubbling about once per minute. This means I still have a good amount of yeast still in suspension. After the secondary fermentation is complete, the yeast drop out of suspension and go dormant on the bottom of the fermenter. At this stage the yeast prepare for dormancy by producing glycogen. This is basically life sustaining food for their time in dormancy, and is an important fuel for them for when they come out of dormancy. It is important to wait until this process has occurred before harvesting the yeast. After you notice the sediment layer form on the fermenter, wait an additional two days after fermentation stops to allow for this.

Now it?s time to bottle. I rack my beer from the secondary into a bottling bucket. Again, while doing this I leave a ?beer barrier? over top of the yeast cake. I sanitize some 12 oz bottles (I usually don?t get more than two bottles? worth from this method) by running them through the heated dry setting in the dishwasher, then soaking them in a bleach water solution along with a small funnel, two bottle-sized rubber stoppers, and two fermentation locks. Now, pour about an inch of the beer barrier into each 12-ounce bottle and discard the rest. Fill the bottle up to about two or three inches from the top with your yeast slurry (you need the extra room for the fermentation lock and in case it begins to ferment again). Stopper the bottles and insert the fermentation locks. Place your bottles in the far back (the coldest part) of your refrigerator?just make sure they don?t freeze?and you?re done!

When it?s time to reuse the yeast, I suggest making a starter, although I often just dump the yeast straight from the bottle into my new wort. To make a starter I sanitize a two-liter soda bottle. I mash one pound of barley in about half a gallon of water (roughly 1.044 wort). Using our sanitized funnel and our bottle-sized rubber stoppers I turn the two-liter bottle into a mini-fermenter. Then I wait until a healthy fermentation begins (usually over night) and pitch it into my new batch. It is that simple.

As I said, everyone does this a little differently. This is the way Jug does it, and it works well. I?ve done this hundreds of times and haven?t had a single bad beer result. Some people claim the yeast from the primary fermentation is better to use, but, if it is, it isn?t by much. And this way you don?t have to deal with the original protein sediment or having to wash the yeast. Plus, we counteract all that a bit by racking to the secondary early.

By reusing our yeast, our beer now only costs us $1.66 a six-pack. Beat that!


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