OnTap Magazine

So here are some easy steps you can take to ensure that your yeast (and maybe other things you care about, come to think about it) is happy and will make you some really good beer. Keeping yeast happy will help you make way better beer. So don’t believe in magic. Believe in your fungal friends and you won’t go wrong. Now go brew. Ensuring the happiness of your yeast starts well before you pitch the stuff into cooled wort. When we create wort, we produce the precursor nutrients that yeast cells need in order to ferment beer. Yeast needs a few things to live healthy lives: Sugar, oxygen, minerals and the right temperature. In making good wort, we’re helping with the sugar and mineral components of that equation. Ensuring that you’ve converted the malt’s starch into sugar is the first step. Use the iodine test if you’re not sure. Measure your pre-boil gravity to check if you’ve hit the recipe’s specified number. If not, you need to lengthen your mash time and (perhaps) add some dried malt extract to supplement the sugars in your wort. Minerals important to yeast health occur naturally in malts, so are normally not needed in additional quantities. The exception is when you brew high-gravity beers like double IPAs, imperial stouts, barley wines and the like. Then, adding a teaspoon of yeast nutrient (which most homebrew stores stock) into the boil can give yeast some additional help down the line when the high percentage of alcohol produced in fermentation threatens to kill your fungal friends. Sad, but true. Yeast produces alcohol as part of its metabolism but alcohol also poisons yeast to death (dramatic stuff!). FEED THEM S T E P 01 If you’re using dried yeast, make sure to rehydrate the yeast in some sterilised water (at room temperature, i.e. 20-25°C) about 30 minutes before pitching. If you’re using liquid yeast (good choice, by the way), make a yeast starter by brewing a “small beer” without hops, using some dried malt extract (100 grams) and about 1.2 litres of water. Boil this wort for about 15-20 minutes, chill to pitching temperature (20-25°C) and pitch the liquid yeast in a suitable container (I’ve used a 2-litre, sanitised water bottle with the cap cracked open just a bit with very good results). Leave your starter for 24 hours before your brew day and pitch the resultant slurry into the chilled wort as normal. On the topic of pitching: make sure that the temperature of your wort is, at most, 5°C higher than the yeast’s temperature. This will avoid yeast shock, which is the microbiological version of diving into a very cold swimming pool. It kind of makes your heart stop for a while. So, if your yeast is at 22°C, make sure your wort is somewhere between 22 and 27°C. Generally speaking, yeast should not be pitched into wort that is warmer than 30°C or cooler than 15°C. The final thing you can do to give your yeast a head start is to oxygenate your wort. Depending on the size of the brew and its gravity, this may be as simple as splashing your wort into the fermenter and shaking it around a bit (small volume or low-gravity beers) or as complex as actually introducing oxygen into the wort using food- grade oxygen and something called an aeration stone (large volume or high- gravity beers). Once yeast is busy fermenting your wort, your job is not done. Primary fermentation is a pretty violent affair, and to ensure that yeast does what it’s supposed to (i.e. ferment the right amount of sugars, produce nice flavors and not nasty ones), you’ve got to ensure that it has the best possible conditions to do so. For one, make sure that your fermentation vessel is not exposed to UV light. More importantly, ensure a steady, healthy fermentation temperature. For most ales, that range is between 18 and 22°C. For lagers, it can be as low as 5-15°C. Generally, higher-than-ideal fermentation temperatures lead to more fruity and sometimes-unpleasant flavours. Really high temperature can also result in fusel alcohol formation, which will give your beer a boozy, heavy character and your beer drinkers much the same feeling, only in the form of a bad hangover. Overly cold temperatures can cause yeast to go into suspended animation, sci- fi style, and that means that your wort will not ferment to completion. This is called a stuck fermentation, or as it is known among brewers the world over, hell itself. There are other causes of stuck fermentations (such as not having enough fermentable sugars in your wort--see above), but low temperature is definitely one of them. One additional measure you can consider is to tap off your yeast from the fermenting beer after the first week or so of fermentation. Having a conical fermenter helps considerably for this. Tapping off yeast has two functions: (1) it avoids exhausted or dying yeast from producing off-flavours in your beer and (2) it allows you to re-use that yeast for future brews. S T E P 02 GIVE THEM A GOOD START S T E P 03 SUPPORT THEM IN LATER LIFE 54 | Winter 2018 | ontapmag.co.za