Barley

Beer has been made quite possibly for as long as people have cultivated cereals—that is, for a very long time. Archaeological evidence of grain processing might indicate that beer or beer-like beverages originated not long after humans figured out that grinding or pounding plant material yielded better tasting, sweeter food—a practice that goes back tens of thousands of years.

This beverage might have originated in an even earlier era, before stone tools, because the chewing of grain (as is still done in making Andean chicha) adds salivary enzymes that convert starches into sugar, ready for fermentation. On this basis, beer could conceivably have been made in some form right back to the point at which our species began behaving in the modern manner, around 100,000 years ago.

Many grains, including rice, millet, corn, and sorghum, are used to make beers in different areas of the world, but the key grain used in brewing western-style beers is barley. This prevalence is not just a matter of historical coincidence: Barley has what you might call an enzymatic toolbox that makes it the perfect brewing ingredient.

Like most grasses, barley has a fairly simple anatomy. For brewers, the spike at the top is the important part of the barley plant, because it is where the seeds sit. The structure of the spike varies significantly among different strains of barley, and those different structures are keenly relevant to brewing beer. Spikes can vary in the number of rows of seeds they bear, in multiples of two: two, four, and six. And although more might intuitively seem better, six is not necessarily the preferred row number. Indeed, European brewers overwhelmingly prefer two-row barley.

The barley seed is layered, a property that is important for understanding why it is the preferred cereal for making beer. And it is the tiny sliver of seed tissue called the aleurone layer that is critical in brewing.

During the normal life cycle of a barley plant, the endosperm of the seed develops a large reserve of starch, destined to power later development when the seed starts to germinate. In its original form this starch is not directly available to the seed for growth, but the aleurone layer contains a reserve of enzymes that are released when germination starts. Those enzymes promptly begin to break down the endosperm boundary, exposing the starch granules inside to other aleurone enzymes that break them down into sugars, primarily maltose.

Although other grains have an aleurone layer in their seeds, none has quite the capacity that barley does to break open the endosperm and turn starch into sugar. Accordingly, a brewer making beer primarily with rice or wheat will usually also add some barley. The process of getting the sugars out of the barley seed by starting germination is known as malting. Maltsters soak and aerate the seeds to stimulate sprouting, then dry them to stop the sprouting process before the resulting sugars are consumed. The dormant sugars can then be exposed to the tender mercies of the yeast whenever required, allowing the maltsters to hijack nature’s system by keeping the barley seeds from germinating until they want to make their malt. At that point, germination is artificially induced.