Next time you grab a six pack with friends, you should consider the microorganisms that made your beverage.

There is no better way to get introduced to the complex process than to head over to one of Tucson’s hip new craft breweries and talk with L.J. Combs, brewer at Pueblo Vida Brewing Company, a brewing company in downtown Tucson that just celebrated its one-year anniversary on Nov. 14.

“Everything starts over here, this is called the brewhouse,” said Combs, pointing out different pieces of shiny steel brewing equipment. “Basically everything starts off by making this giant vat of oatmeal. So you fill this with crushed grains … and then you steep it at like 150 degrees and that converts the starches into sugars that the yeast can then consume later in the process.”

After a series of boiling and cooling, the resulting mixture is transferred to a fermenter with yeast.

“It’s in [the fermenter] for like two weeks or a month and a half depending on what kind of beer it is,” Combs said. “Then it goes into the bright tank, which is where it’s carbonated, and then into kegs and then people’s mouths.”

The process of brewing is a chain of events in which each step needs to be done exactly right and in order for the next one to work out. Subtle variations at different stages are responsible for the wide range of flavors seen in different types of beer. The first step in the process of brewing is malting the grains.

After the grain is harvested, it is steeped in water and allowed to germinate for four to six days. The enzymes produced by the grains during germination, such as alpha-amylase, are essential for later parts of the brewing process. Then the grain is kilned to stop the germination. Depending on which flavors are desired, the length of time the grain is kilned can vary.

“The longer it’s kilned the more bitter it is and the more chocolatey dark flavors attach,” Combs said “Stouts use a lot of those.”

The next step in the process is to mill the grain, which is cracking off the husk so water can access the starches. Then the grain is mashed. At this stage the two most important enzymes are alpha-amylase and beta-amylase.

“They function best at different temperatures,” Combs said. “One functions best at 140 degrees to 149 degrees, the other one is 150 degrees to 167 degrees, so most people will mash at like 150 degrees — a good compromise between the two enzymes.”

These enzymes break down the starches in the grain and produce the sugars maltose and sucrose. During fermentation the yeast consumes those sugars and converts them to alcohol and carbon dioxide.

Given how many steps there are in this process there are many ways to mess up, which could ruin the taste of the resulting beer.

“Throughout the process there’s like 12 different off flavors that can be created if you do things wrong,” Combs said. “If you ferment a couple degrees higher than you wanted to, then you create these buttery flavors and things that people don’t want to drink.”

The fermentation process is very important for creating the variety of different flavors found in beer. Esters and fusels are flavor compounds produced during fermentation that depend upon the type of yeast used. They result in a variety of flavors like banana, clove, apple and cherry among many others.

“If you ferment at a higher temperature you release more esters and more fusels so you can get more fruity flavors,” Combs said.

The amount of yeast pitched, or added to the fermenter, is another factor that influences fermentation. Over-pitching the yeast leads to leftover sugar in the beer and poor fermentation. Under-pitching the yeast stresses the yeast and creates sulfurous flavors.

Hops are also an important aroma compound in beer that offer a range of flavors like grassy, fruity, or piney flavors. If hops are not kept at the right temperature or are not fresh enough they can also result in off flavors like cheese or wet socks.

The flavor of the beer is not only influenced during the brewing process. Many factors can influence the taste of beer when its being stored and served. If beer is not kept at a consistent temperature it can ruin the carbonation and the flavor. Bottled beer in clear or green bottles can get skunked since light can cause reactions that lead to off-flavors. Also tap lines that are not frequently cleaned will develop protein build-up, which causes a buttery flavor called diacetyl.

“If you go to a dive bar and you get Coors Light that’s been there and the lines haven’t been cleaned for, you know, 60 years it tastes super buttery and really gross,” Combs said.

How does someone get involved in brewing?

Combs got his start home brewing in college and then apprenticed at Pueblo Vida for three months before getting hired — a standard process for those looking to becoming brewers.

If you are intrigued by the science of brewing, there are ways to get involved in home brewing through student clubs, such as the Arizona Home Brew Club.

“It’s kind of a club for anyone who is interested in making their own alcoholic beverage,” Aidan Blum, a chemical engineering senior and the president of the Arizona Home Brew Club, said. “We also do cider and wine and we actually just did a club mead fermentation … Our big thing though is obviously the beer as the brewing name suggests.”

The club’s general meetings include discussing the science behind home brewing including the alpha-amylase binding sites on different starches and the types of cereal crops that can be used.

“Brewing is probably actually the most complicated out of all the fermented products that we deal with,” Blum said. “What you have to do though is take the starches that are located in the endosperm of most cereals and turn that starch into sugar which is what your body does — it’s what your saliva does actually … the enzyme alpha-amylase is actually in your saliva.”

Given how challenging brewing can be, what is the best part of being a brewer?

“My favorite part is smelling and tasting the finished beer and looking for off flavors,” Combs said. “There are so many different off flavors you can have and once you know what they are you find them in a lot more things than you would expect.”

Follow Genevieve Patterson on Twitter.