Whether you are an experienced brewer or a beginner, yeast and fermentation should never be ignored if you want to brew great beer. Even with that perfect recipe or the most advanced equipment, just pitching a pack of yeast could be the deciding factor between an amazing beer and just another homebrew.
Which of the four ingredients in beer is actually the most important? Water certainly makes up the biggest part of any beer, malt second, third hops. What can 11g of dry yeast do compared to all those liters and kilos? Bottom line, yeast is by far the most important flavor creator in beer. This being said, do not ignore the water profile nor the malt bill, but remember that the perfect water profile and malt bill will never be delicious if you take for granted your lovely, hard working micro-friends. Here are the top four things to think about to ensure your yeast are working for you not against you
Pitch the correct amount of yeast.
One of the biggest issues with homebrewing is pitch rate, especially when it comes to liquid yeast. Way too many homebrewers pitch too little yeast. And it is not a nerdy thing to calculate how much yeast you need for each batch, it is actually quite easy to do. Following the example below, 10 liters of a 5ish percent ABV beer calls for 101 billion yeast cells, about a half pack of dry yeast or a whole, fresh pack of liquid yeast (dry yeast packs have from 200-300 billion cells, a liquid pack about 100 billion cells). One liquid pack would not be suffice for 20 liters of the same beer. A dry yeast pack, however, would be perfect. Be aware, if you sprinkle dry yeast into wort, chances are half to two thirds of the population will actually stay alive. Always bloom your dry yeast in clean, room temperature water before pitching! Below are the general pitch rates for beer yeast. For an online yeast pitch rate calculator, visit http://www.mrmalty.com/pitching.php.
Ale => 0,75 million X ml of wort X °Plato*
Lager => 1,5 million X ml of wort X °Plato*
1,055 OG = 13,5 °Plato
Pitch Rate = 0,75 million X ml of wort X °Plato
Pitch Rate = 750,000 X 10,000ml X 13,5
Pitch Rate = 101,250,000,000 or 101 billion cells
* Degrees Plato is another way of measuring the sugar content of wort, the relationship between original gravity and Plato is not linear, but to make it easy just divide the O.G. by 4 to get degrees Plato, or say that 1 degree Plato is equal to 1,004 of gravity
Be sure you know your fermentation temperature.
Fermentation temperature is one of the top three most important things to consider when brewing. The temperature during fermentation will very much decide flavor, the first three to four days being the most critical days. The first hours of fermentation is known as the lag phase. Basically, the yeast are waking up, getting used to their environment and soaking up proteins and minerals. After lag phase comes growth phase. During this phase, the yeast population grows exponentially while sugars are being eaten and flavor compounds are produced. That is why controlling temperature is so critical during those first four days of fermentation. Higher temperatures combined with low pitch rate will make for stressed yeast and fruity, estery flavors. It’s hard to fight through those flavors even if you dry hop with 12g per liter.
Most often, the temperatures at the lower end of what is suggested on the package will give the best results. It is very important to remember that during fermentation the temperature can be up to 4 degrees warmer in the bucket. If you have found that spot at home that stays at 22°C all day long, chances are you are actually fermenting at 25°C. Without controlling your fermentation temperature using technical equipment, an ambient temperature of 15 – 17°C is optimal for most American and English ale yeasts.
Give your yeast oxygen.
Yeast need oxygen to grow. Yes, they can grow without oxygen, but that might be like asking a human to do their daily work without eating. When you cook wort, the oxygen that was dissolved in the water is removed. Introducing yeast to wort that has been cooked and not aerated will only make the yeast throw those unwanted ester flavors, and the yeast may not even finish the job. Without introducing elaborate equipment, simply transferring the wort from the kettle to the bucket vigorously is a huge help. Shaking the bucket until your arms get tired is also better than doing nothing. Just remember, adding oxygen in this manner does bring with it the risk of introducing unwanted microorganisms and wort spoilers. Getting technical, you want about 10ppm of oxygen dissolved in the wort for a healthy fermentation..
Keep your yeast healthy, especially with strong beers.
Healthy yeast will always be happier workers. For the most part, both liquid and dry yeast are healthy enough to do the job well. You do not need add excessive yeast nutrients to a yeast starter nor to your wort before fermentation. The only exception is when brewing strong beers or with a lot of extra added sugars. Beers above 8% could use a booster to help the yeast finish up the job. Boosting a beer with a large percentage of sugar is also a good idea. Regular sugars do not come with the added benefit of minerals that sugars from the mash come with. Finally, keep your liquid and dry yeast packages cold and away from direct light.