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Apr 24, 2014

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A yeast primer

By Gregg Smith

Fermentation, where would a brewer be without it? Certainly beer wouldn't be the same. Without yeast doing its job beer would be a very sweet cup of tea indeed. Of course you usually don't give it a second thought, just add a pack of yeast and let those little guys go to town right? Sure, and not quite.

Let's take some time to cover what can be done with the yeast to make your homebrew more like the commercial beers you enjoy. First, what's your favorite type of beer? Homebrew shops usually start new brewers off with ale kits, and there's a very good reason. Ale yeast is a unique strain (consider a strain the same as a purebred) which has a natural characteristic of working best in warm temperature ranges of approximately 60-75 degrees fahrenheit. Lacking sophisticated temperature control required for the fussier lager beers, ale is a logical place for most brewers to begin.

Perhaps you've continued to buy kit beers. That's okay because the suggestions made here can be instituted without changing anything else about the kit. Should you continue to use the packet of yeast under the can's plastic lid it's understandable; that packet is very convenient and frankly it's a no-brainer. Problem is you don't really know what conditions that yeast has seen. Yeast is very susceptible to temperature extremes and if it was stored in a hot warehouse it may have caused irreparable damage to the tiny yeast cells inside.

Luck may be with you, but the probability is high for kit yeast to result in a sluggish fermentation, or worse, one which never starts. Instead of using the packet you get with the can see if your homebrew shop carries refrigerated packs of quality dry yeast. (There's also liquid yeast for more advanced styles and brewing) When arriving home treat it just as you would hops; place it in a zip plastic bag and store it in the 'fridge.

So you've switched to a high grade, known yeast variety, what's next? If you have been opening the packets and simply sprinkling the dry yeast into the fermenter you're overdue to make a little change. Before pitching (adding) the yeast allow it to acclimate first. You wouldn't go from couch potato to overnight marathon running would you? Don't expect this of your yeast either. Give it a chance to get in shape. At the start of your brewing day take the yeast out of the fridge and let it warm to room temperature. There, now that was an easy step.

The next step takes place about fifteen minutes before the end of your boil. Get a sanitized bowl and fill it half way with tepid (about 90 degree) water. Open the yeast, pour it in, stir gently,and let it sit. This process is called "rehydrating the yeast", It can be thought of as some warm up stretching in the morning. When the wort is cooled to around 70o degrees add the yeast. The other thing needed is oxygen so when you first pour water into your primary fermenter slosh it around a bit, but be careful not to slosh it after the yeast is pitched.

Once you've pitched the yeast treat it like an invited guest. Don't place it in the hottest room in the house. Pretend you're running a fine hotel and supply your boarder with a steady temperature range of 60 to 75 degrees. Over the next day or so you can check the fermenter for signs of activity; it should look like it's churning and bubbling. Ferment comes from the Latin word fervere "to boil" so the activity is normal and routinely begins within a day to a day and a half. The best overall advice is don't fret. Mother nature and the yeast will take care of everything over a week's time.

As you brew more you'll start to hear of liquid yeasts. These are yet another improvement. Liquid brands are a more pure strain sealed in an inner pack which is surrounded by an outer packet of sterile wort. Keep it in the 'fridge and remove the pack a day before you plan brewing. Allow it warm to room temperature and follow the directions which call for puncturing the "inner" pack while the outer package remains sealed. Over the next day you'll notice the pack begin to swell. Don't panic, although it might resemble a zeppelin it's normal. This is the yeast getting a head start and in fact is called "a starter". After brewing and cooling the wort you only need open the liquid pack and add it to your primary. Advantages of the liquid yeast are low levels of off flavors and aromas. The reason for this is because liquid yeasts are very pure and because the "head start" leaves little room for wild microbes to establish themselves in your beer. Liquid yeasts cost a bit more but experienced brewers swear by the results.

One other fermentation hint; place the fermenter on a table. This will make life a lot easier when it comes time for racking (transferring it to a secondary fermenter or bottling bucket).

Secondary fermenter? Quite simply it's a method of letting your beer age a bit while removing it from contact with all the trub and other gunk in the bottom of your fermenter. After active fermentation appears complete (a couple of days after it quits churning and bubbling through the airlock) sanitize a hose and carefully siphon the beer into another fermenter called a secondary. When siphoning don't slosh the beer and be sure to siphon from a level just above the layer of gunk at the bottom of your "primary" fermenter. Now you just let it sit there for 5 to 10 days 'till you're ready to bottle. The effort will yield a more mature beer with a thinner layer of sediment in the bottom of your bottles.

So the simple steps toward better yeast care are: buy a wellknown quality yeast, store it in the refrigerator, rehydrate the yeast, maintain fermentation temperatures in the correct range, and rack to a secondary fermenter. Next time we'll discuss priming, bottling and storing. Until then I've got a date with a cold home brew.

One last temperature factor can ruin all the efforts you have taken so far. The best temperature for ale yeast to do its work is about 60 to 70oF. Once you start fermenting above 75o you enter the range where fusel oils can be produced. Fusel oils add a solvent like aroma to your beer, a very undesirable character.

In warm weather locations it's very common to be above 70o for much of the year. What's a poor amateur brewer to do? First, try putting the fermenter in the north east corner of a basement. Don't have a basement? Place it near your air conditioner (and cover it from light). Still a bit too warm in either the basement or near an air conditioner? No problem, wrap a towel around the primary fermenter and place it in a pan of shallow cool water. The towel will wick up the water and natural evaporation will give you and additional 2-4o of cooling. Need a little more cooling? The breeze of a small fan can buy you a couple more degrees. If it's still too warm you may need to invest in a second-hand refrigerator and modify it with a thermostat kit.

Gregg Smith

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