• Posted by Shane Welch on December 10th, 2008, 4:26 PM

    Photos by Michael Harlan Turkell

    When Califia first approached me about writing for Spooning, I thought she would ask me to write about my company, Sixpoint Craft Ales, and the art and science of fermenting craft beer.  But, in subsequent conversations, we guided the intention towards a more general discussion of the phenomenon of fermentation itself, through the eyes of someone who works with it on both a craft and industrial level.

    Of course, beer is not the only food product that is created by fermentation. Staples like bread, cheese, cured meats, pickled vegetables, miso, and countless other comestibles require fermentation. Each branch has its own techniques and nuances, but what I find interesting are the universal features of fermentation among all crafts. However, since beer is my primary discipline, I believe it merits special attention, so let us examine the art of fermenting beer under a microscope…

    When I first started experimenting with fermentation as a home brewer in college, I noticed that the flavor of beer has the remarkable ability to change significantly in a relatively short period of time. For example, a beer that is one or two days old tastes a world apart from a beer that is five to seven days old. A beer that is five to seven days old tastes remarkably different from a beer that is 21 days old.  But this is where it gets interesting: A beer that is 21 days old does not necessarily taste that much different than a beer that is two or three months old. This can be mostly explained by a simple fact: Much of beer’s flavor evolution is due to the metabolic activity of yeast. Specifically, yeast consumes the sugar in the beer (primarily in the form of maltose) and produces carbon dioxide and ethyl alcohol. Primary fermentation–when the vast majority of this metabolic activity takes place–occurs over a span of one to five days. Secondary fermentation—when fermentation rapidly winds down and only residual sugar is fermented by the yeast—occurs in the next one to two weeks after primary fermentation. Afterwards, the yeast runs out of sugar, its food supply, and can no longer produce alcohol and carbon dioxide. The yeast goes into dormancy and eventually settles at the bottom of the beer.

    From these observations, we can derive a general rule: When fermenting beer, there is a flurry of activity when a newly introduced microbiological agent colonizes the product. The more microbiological activity there is, the greater the change in flavor. In the brewing process, when primary fermentation begins, the solution is in chaos.  Billions of individual cells are consuming sugar, creating alcohol and reproducing in an orgiastic microscopic bacchanalia. Naturally, when you drink this solution (which brewers refer to as wort) one or two days after you have pitched the yeast, you taste a super-raw, crude, and funky beverage. The solution is undergoing a metamorphosis.  It is no different than a leaf that falls to the forest floor and biodegrades within days as bacteria, wild yeasts, and spores break down and consume all of its organic material.  It is nature’s efficient system of nutrient cycling.

    Clever humans have learned to isolate specific yeast strains (countless strains exist) that produce desirable flavors, ferment the beer quickly, and operate within a desired temperature range. This is a brilliant example of artificial selection in the realm of food production. The yeast strains selected by brewers may not necessarily be the most adapted for survival, but because they create yummy beer they have been chosen by to be our symbiotic buddies on the path to divine intoxication.

    Since metabolic activity virtually comes to a halt after secondary fermentation, one would assume that the flavor of beer stops evolving at this point.  However, those of you who have ever had the luxury of sampling a 10-year-old bottle of barley wine or an aged Belgian Quadrupel know this is not true. How does the flavor evolution continue?

    The answer can be found in the process I call “inorganic fermentation.” What I am referring to here are the pathways by which a beer’s flavor evolves that have absolutely nothing to do with yeast, bacteria, or any other microbiological agent. It is the reason why a six-month-old barley tastes so different from one aged for six years. While most microbiologists would not classify this change as true fermentation, anyone open-minded enough to incorporate the entire scope of the sciences can see that the physical world is still driving the flavor to change–even if this change is not initiated by living agents.

    One of the most common inorganic mechanisms of change in beer after fermentation by yeast is oxidation. When one hears the word “oxidation,” one naturally thinks of oxygen, but chemists use this as a blanket term to describe the process by which elements and compounds take electrons from others. These electron-takers are known as “oxidizers.” Oxygen is one of the most common oxidizers on the planet, mostly because of its ubiquity. On a chemical level, oxygen wants to “take” electrons from other compounds because it only has six electrons in its outer shell. Since elements at this stage have a strong desire to have their outer shell completely filled with eight electrons, oxygen has a propensity to seek out electrons from potential donors.This is significant on a molecular level because it encourages oxygen to bind to compounds with electrons to spare (or, at least, with electrons that are vulnerable to theft!).

    In general, food chemists see oxygen (and other oxidizers) as staling agents. Virtually every food product rapidly becomes stale if it is exposed to oxygen after it has been harvested or cured. That is why food packaged in the absence of oxygen–whether vacuum-sealed or sealed with inert nitrogen–lasts much longer than food exposed to oxygen. The same phenomenon occurs within the cells in your body. Oxygen and other oxidizing “free radicals” bind to your cells, accelerating their “staling” and thus accelerating your aging process. Hence the huge trend in marketing foods with an abundance of “antioxidants” which supposedly retard or offset the aging process.

    As oxidation reactions increase in beer over time, it usually develops a stale flavor and becomes increasingly unpleasant. However, this is not the case for all beers:  styles such as Imperial Stout, barley wine, and Belgian strong ales age wonderfully with the help of oxidation. Anyone who has tasted an aged sample of these styles and perceived a distinct sherry flavor and aroma has detected the effects of the right amount of oxidation. This particular oxidation occurs with a group of malty-flavored organic compounds known as melanoidins. The oxidation of melanoidins produces a myriad of byproducts, but one of the most desired is the almond-like benzaldehyde. Working in symphony with other byproducts, the different compounds are responsible for the flavor of sherry that is sometimes present in beer.

    The more I work with fermentation, the more I realize the importance of time and, even more, timing, to the final product. I equate this to a jazz musician’s understanding of timing, a sense of when to play and when to remain quiet, listening to the cues from others. A nuanced brewer who approaches the craft with finesse understands when to let the yeast work its magic and when to take the beer away from the yeast. Similarly, a cellarman—who handles the product after fermentation, while it is aging—knows exactly when the right amount of oxidation has transformed the beer, creating the perfect amount of sherry notes, without causing the beer to taste stale. At this point, the beer has reached its peak and is ripe for consumption. The great lesson here is that, when working with Mother Nature and the Universe, we must learn when to participate, contribute and do it our way, and when to step aside, leave things alone and let them follow their natural rhythm.

    Shane C. Welch was born and raised in Wisconsin, where he first started homebrewing beer while in college.  Eventually college seemed boring and brewing beer seemed exciting, so he decided to make a career out of making great beer. Sixpoint Craft Ales is the manifestation of those early aspirations.

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