Fermentation for hobby brewers

Two weeks ago you could read here how to get yeast for brewing as a hobby brewer. Whether dry yeast, liquid yeast or harvested yeast – having yeast alone is not enough. What to do with the yeast then and what to watch out for, that’s what we’re going to talk about this week.

One thing we have to say up front: proper yeast management is an art in itself. Not for nothing it is said "the brewer makes the wort, the yeast makes the beer". A short research in the German and English Internet will show you: Yeast is partly a hobby within a hobby for hobby brewers and the optimization possibilities are endless. Therefore, we recommend beginners to simply use dry yeast. You can rehydrate it according to our recommendations and simply add it after the wort has cooled down. Then you put the beer in a constant temperature place and wait. It works and is complicated enough at the beginning, if we are honest. If you still want to learn more and maybe find out something new, you are welcome to read on, because you can still improve a lot from there.

Storage of the yeast

Gabs in the last post before, sorry, but fits here also well in: in a plastic box in the refrigerator can be stored dry yeast super. Keeps the yeast clean and cold while keeping the WAF high…

A point that was somewhat neglected in the last article: the storage of the yeast. Liquid and harvested yeast needs to be stored at 4 °C and this constantly. Even the shortest shipping time or unrefrigerated pickup from a buddy will do damage to the yeast. Therefore: chill the yeast as soon as you get it, and if you pick up harvested yeast, always chill it in the cooler (not frozen)!) keep. Dry yeast is somewhat more forgiving: Fermentis gives z.B. for its dry yeast Safale US-05: "The product can be stored and transported at room temperature for up to 3 months without any losses. Store at the destination below 10 °C."Dry yeast is therefore much less stressful to store. I always pack mine in a tupperware box in the fridge, as shown in the last article.

The difference between bottom and top fermentation

Maybe in this context it is interesting to explain what is the difference between bottom and top fermenting. Quite quickly said: top-fermenting yeast, Saccharomyces cerevisiae, ferment at warmer temperatures (between 16 and 22 °C, depending on the strain), bottom-fermenting yeast, Saccharomyces pastorianus, ferments at lower temperatures (Ca. between 8 and 12 °C). However, the temperature always depends on the yeast strain and is specified by the manufacturer. Which exactly is suitable you can take from your recipe or search in the hobby brewers forum. As a guideline, I would always choose something in the lower third of the specified range as the fermentation temperature. Keeping the correct fermentation temperature constant is important so that the yeasts can properly develop their flavor. A warm fermented lager tastes just awful. The two types of yeast behave differently, however, because the name is program. Top-fermenting yeast rises to the top after fermentation begins and forms what is called krausen. This is a carpet of foam and yeast on the fermenting beer. You can see it also in the post picture. The top fermenting yeast stays there ("top") until fermentation is complete and all extract or sugar is fermented. Bottom-fermenting yeast also forms a krausen, but quickly sinks to the bottom and then continues to ferment there, so it ferments below. Due to the warmer temperatures in top fermentation, this is also over more quickly than bottom fermentation. In simplified terms, bottom-fermented beers need about 2-6 weeks to complete fermentation, top-fermented beers more like 4-14 days. Of course, this is not a guarantee and must be checked in each individual case, but it is about right. Top fermented beers are for example Pale Ales or wheat beers, bottom fermented beers are lagers like Pils, Helles or Bock beers.

Here is a simplified illustration of the difference between bottom-fermenting yeast and top-fermenting yeast. When yeast is added to the fermenter, the krausen forms in both fermentations. During bottom fermentation, however, it decomposes quickly and the yeast sinks to the bottom. The fermentation continues there. The top-fermenting yeast always stays on top until the fermentation is finished. Then also this sinks.

The pitching

Alone already to the yeast gift, the so-called Tempering, could fill more than one blog post. In short, yeast pitching can be summarized like this: You bring the wort to the so-called Setting temperature, This is the temperature at which the yeast is added. This is ideally done with a cooling coil or plate heat exchanger, otherwise overnight chilling works as we have recommended before. When the starting temperature is reached (or. 2 days before, if you work with starter), you have to "prepare" the yeast sufficiently, i.e. rehydrate dry yeast, possibly propagate liquid or harvested yeast in a starter or "beat" the smackpack 1-2 days before. Then you add the yeast to the wort. You should avoid too big temperature differences between yeast and wort to not shock the yeast. The wort should also be aerate. The professional does this with a bubbling stone and pure oxygen from the gas bottle, in the hobby area also the whisk, in order to stir some air under the wort for a few minutes. This is the only point in the brewing process where we want to bring oxygen into the beer. This is done to provide the yeast with oxygen, which it needs at the beginning of fermentation to propagate in the wort. But what happens then?

The fermentation

In the past, brewers typically fermented their beer at a constant temperature. They controlled it through suitably tempered cellars, which they cooled even further with ice as needed. If we are honest, this is the easiest way to ferment beer today (without the ice, of course). Especially if you have a suitably tempered cellar, this is therefore also in the hobby the means of choice. In the case of top fermentation, this is also less problematic, but with bottom fermenting yeasts, fermenting at a constant temperature is not quite ideal. This is due to the fact that hardly anyone has a cellar cold enough for this (the cellar should be below 12 °C) and then it is also due to the fact that such a bottom fermentation at 8 °C lasts quite a long time. While an ale with 13 °P at 20 °C can easily be fermented out in 3-5 days, it can take 4 or even 6 weeks at 8 °C for a comparable Marzen. So you see, you always have to differentiate according to beer type and your own preferences/technical possibilities. A good solution to counteract such problems is to raise the fermentation temperature towards the end of fermentation. In practice, for lager beers, for example, you can make after ca. 50% of the available sugar is fermented simply raise the temperature to 18 or 20 °C. As a result, such a bottom fermentation often lasts only 2 weeks. The undesirable flavors of warm fermentation are usually formed at the beginning of fermentation, and less towards the end. At the increased temperature, the fermentation process is much faster. This way you can brew good lagers in a short time without any problems.

Fast lager fermentation. You can raise the temperature to as low as 20 °C after reaching 50% of the expected fermentation level. This is how you can "finish fermenting" lagers faster. This of course requires a proper control of the fermentation temperature. It is important to adjust the temperature to the degree of fermentation, not to go by time.

The technical prerequisite

The classic 30-L fermentation vat in a refrigerator converted into a fermentation chamber. This is ideal especially in the beginning and is the perfect way to control the fermentation temperature.

Who wants to operate such a fermentation without a suitably tempered cellar, always needs a way to control the temperature of his beer. In the industry and in the ambitious hobby brewing area, this is done with cooled double-jacketed ZKGs. The investment in the cold side is also worthwhile for the not so ambitious hobby brewer. But it does not have to be a 2000 € ZKG. A small "standard size" refrigerator without an icebox is sufficient to accommodate the common 30 l fermentation buckets. Then all you need is a temperature control: set the thermostat of the fridge to "minimum" and control the socket in which the fridge is plugged in by means of an Inkbird temperature controller or even better something like a Brewpi. How to attach which temperature probe you can find in the Hobby Brewers Forum. I have always glued the "beer" probe to the outside wall of the container. This is not ideal, but it works. Keyword for those who want to do it better in the forum search is here "Thermowell". With both systems one can selectively switch on or off the socket into which the refrigerator is plugged and thus control the desired temperature. Also possible: in the cold winter put the fermentation bucket in an insulated box in the cold garden shed. You can build the box yourself out of styrofoam and wood, put a terrarium heater in the box and use it specifically to heat the chamber (at 0 °C outside temperature you have to heat of course and not cool). Please note: Electrical tinkering should only be done by qualified personnel and also the use of heaters in closed insulated rooms is dangerous, for example fire hazard. So you should always inform yourself beforehand if what you are going to do is possible without danger.

Ideal for fermentation control: an electronic controller that measures the beer temperature and switches a refrigerator on and off accordingly. This is indispensable especially for bottom-fermented beers.

I hope we have been able to give you a good overview of the fermentation process in the hobby sector. You will certainly read more about this later, but I guess you have to start somewhere. You can read more about this topic at Brulosophy or at the famous article in brau!magazine on the subject of yeast starter. Also the forum search brings so some to light and of course every beginner’s book on the subject of hobby brewing has some info on the topic. Other interesting books to read are "Abriss der Bierbrauerei" by Ludwig Narziss, Werner Back, Martina Gastl and Martin Zarnkow published by Wiley VCH, "Scientific Principles of Malting and Brewing" by Charles Bamford or as recommended last time the book "Yeast: The practical guide to beer fermentation" by Chris White and Jamil Zainasheff, published in 2010 in the Brewing Elements series by Brewers Publications. All these books are rather tailored to industrial use to varying degrees, but still full of good info. Last but not least, we would like to point out that everything written here is not free of risk. Read our article here before you brew on a hobby scale and take it to heart.

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