The Chemistry in the Beer Making Process

The chemical process in the first step of beer making entails proteins and enzymes in the barley grains. When the barley is soaked in water, it triggers the sprouting process, which facilitates the production of those enzymes. The brewer has to remove them from the water at the proper point (exactly when depends on the barley, the brewer and the type of beer being brewed) and then dry them in a kiln. That preserves the enzymes for the next stage in the process. Once they barley is dried, the brewer soaks it again, this time in warm water ranging between 145 and 160 degrees F. Not only does that further activate the barley's enzymes, but it transforms the starch into sugar, which plays a key role later during the fermentation.

Because all of those good sugars and proteins are now in the water, the brewer needs to retain it. He heats the water and drains it from the barley, then sets it aside while he rinses the barley with a fresh batch of hot water, which he then adds to the original water. The resulting mixture is called wort--the base root of beer, which contains all of the flavorful enzymes extracted from the barley. The brewer then brings it to a boil, killing off any harmful bacteria and getting rid of some excess water in the process. Hops are added to the wort to give it more flavor during the boiling process.

The next stage in the process is the most well-known: the beer needs to ferment. Yeast facilitates the fermentation by absorbing the sugars in the wort and transforming it into alcohol. The yeast also creates a certain amount of carbon dioxide in the process, which needs to be removed from the mixture. The wort is placed into a fermenter, which contains an airlock to release the CO2. When the yeast is added, it can then ferment for as long as it needs to until the chemical process is complete and the sugar has been turned into alcohol. Fermentation can take anywhere from a few days to a few weeks.

Many large brewing companies pasteurize their beer, which uses a brief flash of heat to kill any existing fermenting bacteria. (Beer can also be cold-filtered to remove such bacteria or bottle-conditioned to allow the beer to age.) Pasteurization allows beer to be transported without fermenting and spoiling the taste, but can lead to a "cooked" feeling which beer experts tend to dislike.

The last step is carbonation. Once the beer has fermented for an appropriate length of time (i.e., the CO2 is no longer bubbling out of the airlock, a sign that the yeast is running out of sugar to consume), the brewer adds a small amount of sugar back into the mix. That creates a sort of "short-term" fermentation, as the yeasts absorb it and produce carbon dioxide bubbles. Large brewing companies will often carbonate their beer while it is still fermenting, which saves time. The pasteurization process ensures that the yeasts are dead, allowing them to carbonate their beer in this manner.