Aside from perhaps yeast, grains are arguably the most important aspect of beer. They provide the sugar for fermentation, a great deal of the flavor, enzymes to help the yeast break down difficult-to-digest sugars, and almost solely are responsible for the texture of a beer. In short, grains are to beer as grapes are to wine (suck it, Jim Koch).
The sugars in harvested grains are not readily useable by yeast. They start as starches, which are long strings of sugar molecules in a chain. Yeast can’t work it’s magic on these so they must first be broken up. Fortunately, this can be done by a process called “malting”. Basically, to malt a grain, you let it start to grow (germinate, for the botany-inclined) by soaking it in water. The germination process releases enzymes that break down the starches into sugars. It is then, in a controlled fashion, heated (kilned) to stop the germination. The amount of kilning affects the grain’s flavor and color.
The most common grain used in beer (and the only one allowed in Germany while still called ‘beer’) is barley. Barley used in brewing comes in various strains, each of which are processed in any number of ways, allowing for a wide range of options for ways to change your beer. In a general sense, most barley grains fall into two categories: Two-row and Six-row. Two-row is the traditional barley strain used in most European beers. Six-row is more common in American beers and has been bred to have higher enzyme content that will help break down more complex sugars in adjuncts added to the beer.
Wheat is used often in certain styles of beers (the over-arching category would be aptly named ‘wheat beers’). Germany and Belgium are most known for their various styles of beers featuring wheat. Wheat malts can not be used as 100% of your grain bill as they lack enough of the enzymes needed, and therefore should be used in conjunction with barley. Wheat also adds a noticeable haze to beer.
Other grains, such as oats, rye, even potatoes can be used to add fermentable sugars, too, but are more rare. We’ll try to do a beer and post about these on an individual basis.