I truly believe if you take care of your yeast, your yeast will take care of your beer. It has been said that a healthy fermentation will ensure a good, well attenuated beer. Yeast have a tendency to slow down or even stop the fermentation process when they feel stressed or any extreme environmental changes occur, EX. huge temperature changes, huge PH changes and under pitching yeast.
Underpitching is defined by not adding enough viable or healthy yeast to an unfermented batch of beer. Which is why you should use a yeast starter. If you are a veteran brewer than this is a process you are probably aware of. If you haven’t you are either:
- Underpitching you yeast numbers if you are using fresh liquid cultures.
- Using Dry Yeast: which requires no wort starter. Just rehydration.
In other words, you should never pitch a strain of yeast directly out of the package. If you don’t add enough healthy yeast, the fermentation process may not start at all, or more than likely not ferment to completion, leaving your batch of beer cloyingly sweet with a funny-unbalanced taste. If you were to enter this type of beer into a beer competition, it would be considered a major flaw. Yeast starters both act a wake up for your yeast, it will also trigger yeast budding (reproduction) , and encourage better overall health for the yeast strain being used. http://www.mrmalty.com/calc/calc.html is the most famous yeast pitching calculator.
If you are making a “high gravity” beer, (a beer with a high Alcohol by volume), a yeast starter is of the highest importance. When brewing one of these types of beers, the stress on the yeast becomes higher. You must consider that yeast expels alcohol as basically a waste product. Alcohol is also toxic to the yeast in high volumes. When this style of beer nears the yeast’s threshold of ABV tolerance the yeast may start to “conk” out. Keep in mind that all yeast strains have a different tolerance to alcohol. Being that this style of beer creates a high stress environment, you still want to make sure that your viable yeast count is higher than normal to ferment such a big beer.
If you are thinking of making a lager, a starter is also something that is considered by most brewers as a necessity. Consider the fact that lagers ferment at lower temperatures than ales, a bigger starter can help kick-start your batch of beer that much more quickly. The idea behind this is to lower the lag time of your beer, to allow your intended yeast strain to “take hold” of the beer. Your lag time should be no more than 24 hrs if possible. In other words, you beer should start the fermentation process as quickly as possible.