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Pitch Yeast

 

Lag Time

 

Fermentation

 

Flocculation

 

 

 

After cooling the wort below 80 F, it’s time to innoculate it with your beer yeast. This act is called pitching. Comes from days of old when they would actually walk along the open fermenters and pitch the yeast like sowing seeds.

It is important to control the temperature during fermentation as it is an exothermic process and produces heat. Run away fermentations produce all kinds of nasty flavor compounds and a hot solventy beer. We don’t want that ! Also, higher order alcohols can be produced at temps above 80 and these will give you a nasty headache or hangover.  Keep the fermenting beer as cool as reasonable for the yeast and style you are making. For ales this means just at or below room temps ( ideally mid 60s ) while for lagers we want a cold fermentation of 40-58 F.

 

Keep in mind that yeast are alive and like all living things they will start to acclimate to their new environment after pitching. Depending on the strain, their health, the amount of active yeast and the medium they are being introduced to will all determine just how they behave.

During the early stages the yeast will usually undergo a lag time. This is the period after pitching that they are multiplying (respiration) and taking up sterols in the wort to get ready for fermentation.

It can range from a couple hours to 24. The longer the lag, the more potential for other rogue yeast or bacteria to get going in the wort and ruin the beer. A short lag is prefered.  It indicates things are fine and the little buggers are ready to go.

After the lag, the yeast start consuming the sugars. This is fermentation. They start with the simple sugars first, the easy ones to pass through their cell walls and digest producing CO2 and alcohol as waste along with many other compounds that are important to the finished beer. Depending on beer style, amount of yeast, temps, etc will determine how long this may take. As a rule of thumb let’s assume a standard brown ale. Dry yeast usually ferments a beer in 12 to 32 hours for an ale and if using a pitchable liquid yeast pack can take a few days. Lagers take longer because they ferment at a much colder temperature and is the reason why lagers taste crisp, clean and without any fruitiness ( esters )  that may be imparted in a ale. It is not unusual for lagers to take a week or more to ferment.

At the end of fermentation, when most the sugars that can be consumed have been, the yeast will clump together and start falling to the bottom. This is called flocculation. This trait is noted with most yeast strains so as to pick an appropriate one to match the beer being made. High flocculation means the yeast tend to clear well and sometimes early while low flocculation means they tend the hang around in the beer. Such an example would be hefeweizen which is cloudy due to the strains of yeast used.

 

 

 

 

 

 

Fermentation