How does beer fermentation work in the beer brewing process?
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Fermentation is the metabolic process of yeast. During the course of fermentation, they reproduce and build up stores of food for the next generation and they build up reserves. All that happens during fermentation. And the by-product of fermentation is actually the alcohol and carbon dioxide that we are actually looking for. In making wort, what you’re really trying to do is make the best home for yeast you possibly can so then they will give you the best beer you can possibly get but it’s not the interest of the yeast to make sure that your beer is the best because what you’re really looking for is their by-product, the c02 and alcohol. That’s why higher alcohol fermentation is more difficult because some new yeast don’t like to live in their own waste, very high concentrations. A beer will ferment usually 3 or 4 days.
[How Long Fermentation Should Take: Allow the primary fermentation stage to wind down. This will be 2-6 days (4-10 days for lagers)]
At the end of 3 - 4 days, probably 3 days, we will have future pitches and then we will cold crash. That involves the rapid decreasing in fermentation temperature from our target beer temperature during fermentation which is 68 down to 38. The goal being to drop the yeast load, the number of yeast cells that wants expansion drop them down to a very low level of let’s say, 1 to 2 million cells per millimeter. So then we can rack the beer of transfer into kegs. That process takes two days. Sometimes we leave it until 3, depending on production cycle. Beer typically isn’t in the tank for more than 7 days.
When it comes to fermentation, the ideal one is cool your beer quick, put a lot of yeast in and 2 weeks later you got a beer. That’s the best scenario. If you over-pitch or you under-pitch, you’re gonna get a different effect in the beer. Under pitching, it stresses the yeast because they got this big sugar environment, they’re creating alcohol, their population is low so you get different by-products that they squeeze out from the stress. You over-pitch, they’re gonna eat it all up and may not catch those esters that you’re hoping to get. If you get fermentation but you’re not clean, one of your vessels didn’t get cleaned, it can get crazy. It can bubble up and spill all over the place and get sour. It can taste like dirty dishwater itself. There’s a number of things that can go wrong if you don’t start clean and that’s in any point too. The yeast metabolize like we metabolize. They can only metabolize within their range. There’s residual sugars that they can’t break down that long chain of sugar but you get your wild yeast, they can get those.They’ll start eating those and that’s where you get your over carbonation and those off flavors and dirty flavors. And there’s those breweries that they do sours and then they know how to manipulate the yeast and get the good sour flavor and not the dirty ones.
