Chapter 10 - What is Different for Brewing Lager Beer?
What makes lager beer different from ale beer, you ask?
Well, the main difference is temperature. Make that temperature and time. No, there's three: Temperature, Time and Yeast. Let's start with yeast.
As discussed in Chapter 6 - Yeast, lager yeasts like lower fermentation temperatures. Lager yeast produce less fruity esters than ale yeasts but can produce more sulfur compounds during primary fermentation. Many first time lager brewers are astonished by the rotten egg smell coming from their fermentors, sometimes letting it convince them that the batch is infected and causing them to dump it. Don't do it! Fortunately, these compounds continue to vent during the conditioning (lagering) phase and the chemical precursors of other odious compounds are gradually eaten up by the yeast. A previously rank smelling beer that is properly lagered will be sulfur-free and delicious at bottling time. Speaking of Time...