How are commercial beers carbonated?

Factual Questions
21

There are certainly complicated methods to do it, and they are discussed in length on the internet. The easiest way, is to make a weak wort (1C DME in 1Qt water), cool, aerate well, and pitch some ( a few Tbs) of the yeast from the trub into it. (standard sanitation processes apply) After it’s consumed the sugars there, pour off most of the liquid, leaving the new yeast cake, and feed again with more weak wort. This will end up being a starter for your next batch. The brewing board I frequent recommends that you don’t do this more than 4 or 5 times in a row.

You can preserve the yeast, and get into washing and slanting if you want to get advanced, but I’ve never bothered. It will get you past the 4/5 uses idea though. New yeast is about $7 on a batch of beer, and I often pitch on the last batch’s cake, so I get 2 batches of beer out of some yeasts. Most of the time, my “next batch” isn’t compatable with the “last batch’s” yeast profie anyway, so I tend to use new yeast every time. The $7 won’t break my budget.

August West, what is the benefit to spending extra effort to get below the .1ml/355ml O2 insertion level? Is it to just slam every possible moment of shelf life into the package? How much difference does it make in terms of time/effects?

22

Oxygen is packaged beer’s biggest enemy, outside of beer-spoiling bacteria and wild yeasts. Oxidized beer tastes horrible, so we want to have as close to zero as we can get. The effect of oxygen on beer depends on a lot of variables. If the beer is kept cold, it happens much more slowly. Some yeasts create a fair amount of sulfur, which acts as an antioxidant.

It’s just an aspect of overall quality that we monitor, it can also tell us about problems up the line, such as leaky hoses leading to the filter or such.