The second most common I get about home brewing is: “How do you make beer?” What follows is a brief explanation of how beer is made. This is not a “how to”, but rather what physicists would call a cartoon picture; a sort of summary of what’s happening. The most important thing to understand about beer is fermentation; the conversion of sugars to alcohol and CO2. Fermentation is carried out by yeast. So the basic recipe is, make a sugar solution, add yeast, wait, and then you have beer. Of course the actual implementation is more complicated, but this is why apple juice bottles swell up if left in the fridge too long.
Beer starts with grains such as barley, wheat, and rye. The grains are wetted, left to sprout, then quickly dried; a process known as malting. When the grain is sprouted it creates an enzyme that will convert starch to sugar. This is what gives the sprout energy to get started. By drying the grain immediately the enzyme is locked in, waiting for later use. The resulting grain is called malt.
The malt can be used as is, or can be kilned or roasted. Further heating of the malted grain results in caramelization, in which simple sugars are converted to more complex sugars. These complex sugars are no longer fermentable (too big for yeast to eat), but they can contribute flavor, color, and body to the beer. The uncooked malts are known as “base” malts, and the cooked malts are “specialty grains”.
Base malts are fairly universal, with slight variations depending on where they are grown and how they are malted. Generally base malts are classified by country of origin: American, British, Continental, Belgian, etc. Specialty grains are the source of most of beer’s character. Some malt is lightly roasted like cereal, lending nuance to pale ales. A more medium roast starts to look like bread crust, the source of malty goodness in a red ale. Dark roasted malts take on the look and aroma of coffee, ideal for stouts and porters.
The brewing process begins with mashing. The base malts and specialty grains are put into hot water; 150-155 F for about an hour. The hot water reactivates the enzymes in the base malt. Once activated, the enzymes begin to convert starch in the base malt into sugar. The hot water also steeps the caramelized sugars out of the specialty grains. The spent grain is then removed and the sugary liquid is called the mash.
The mash contains a variety of fermentable and unfermentable sugars; this is the sugary solution that is fed to the yeast. Brewing is actually something like keeping fish in an aquarium; you have to create the right environment for them to thrive. But instead of water we use malt juice and instead of fish we use yeast. Aquariums rarely provided such a delicious product.
Following the mash, the solution is brought to a boil and hops are added. “Hops” refers to the female flower of the hop plant. These flowers have tangy flavors and aromas which are most commonly piney, citrusy, earthy, fruity, or spicy. Hops have high concentrations of bitter oils. Bittering is essential for beer, to counter the sweetness of all the malt sugars.
Hops also have preservative properties. There is actually a whole world to hops and how/when they should be added to beer. I think I will leave that for another piece. For now it will suffice to say that boiling is necessary to sterilize the solution and also to increase the absorption of bittering oils from the hops.
The boil is typically 60 or 90 minutes. The result is a very hot solution, with lots of fermentable sugars, and a fairly bitter taste. This solution is called wort (pronounced wert). The wort is almost ready for fermentation at this point, but must be cooled before the yeast is added. I have already written about yeast and what they do to the beer. In summary, temperature is critical. The wort must be cooled to the proper temperature before the yeast is added, or ‘pitched’. For ales this temperature is typically 64-68 degrees.
There are a variety of ways to make hot things cold and virtually any of them will work with beer. Most home brewers build an immersion chiller. A length of copper tube is shaped into a coil and fitted so that it can be connected to a faucet. Cold water is then flowed through the coil and the whole thing drops directly into the beer.
When the wort is chilled, it must go into a fermentor. At this point, the precious fluid is at its most vulnerable. Wandering bacteria and yeast would just love to get their mouths around a 5 gallon jug of unfermented malt sugars. You have to protect it. The wort goes into a sterilized jug, usually glass. The top of the jug is fitted with an airlock, an ingenius contraption that lets fermentation gases escape without letting air in. A crude version is a tube with one end fitting perfectly into the mouth of the jug and the other end stuck in a bucket of water. Finally, one of the key steps of brewing, you wait.
The yeast goes through its 3 phases of life: propagation, fermentation, sedimentation. The whole process typically takes 3 weeks. Once complete the wort is officially beer and ready for bottling.