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In my last two articles I have introduced you to my curiosity in the science of perception and flavor, and expanded upon that idea with, hopefully, a fun shot-and-beer pairing (tequila shots and sour beers? Yes!). This time around, I’d like to get a little bit nerdier about a portion of this concept by exploring the mystery of fermentation. Throughout beer’s history, fermentation had been the one component that had always eluded our comprehension, but I think it can be argued that it is the most important process in the crafting of beer. Not only is alcohol and carbonation created, but also an array of other flavor and aroma compounds. Fermentation is where artistry is juxtaposed with science.

We talk so much of brewers and their craft, we neglect the involvement of the millions of microscopic organisms that do most of the “heavy lifting” in the making of beer. Of the major four ingredients in beer (malt, hops, water and yeast) yeast was the one that wasn’t included in the original Reinheitsgebot German purity law of 1516. At the time, they didn’t know what caused this sugar-rich barley water to become beer. The brewer crafted their barley tea and hoped, if all was “right”, that it would soon bubble and foam with activity. As a matter of fact, monk brewers in Europe referred to this foam as “Godisgood”, because it was believed to be a result of divine intervention. A lack of understanding in what yeast was, and what was needed for it to perform consistently and efficiently, required more education on the part of the brewer.


It wasn’t until advances in the knowledge and understanding of yeast were made that beer started its direction toward what we enjoy today. Yeast is a eukaryotic organism in the scientific genus of Saccharomyces (“sugar fungus”) whose main purpose is to reproduce. In the process of reproduction, our beloved yeast metabolizes (“eats”) sugars and produces many byproducts as a result, most notable being ethyl alcohol and carbon dioxide.

(WARNING: A bit of beer-nerd science coming up but well worth reading to understand why you like the types of beers you do!)
There are somewhere in the neighborhood of seventy strains of brewing yeasts commercially available, most of which are strains of two species in the genus Sacchromyces, either S. cerevisiae or S. pastorianus. These two strains present the first division in the category of beer: ales and lagers. The ONLY difference between ales and lagers is fermentation. Both can be light or dark, strong, bitter, sweet, full or thin. Each has its own family of yeasts that operate best in a specific temperature range in differing amounts of time. Ales (cerevisiae), which compose the majority of craft beer, are fermented at warmer (55-65°F) temperatures for shorter (usually less than one week) periods of time. Lagers (pastorianus) differ with a colder (40-50°F) fermentation temperature and longer (one month+) time. However, both convert sugars to alcohol and CO2.

As the two major byproducts of fermentation, one should assume that both alcohol and CO2. have an impact on your perception of the beer in your glass. But, just how much is surprising. I didn’t know that alcohol content impacts which aromatic compounds are made volatile (airborne) and when. There are two families of aromatic compounds worth mentioning, those that are hydrophilic (water-soluable) and those that are hydrophobic (alcohol-soluable). The way I found it best explained is in the difference between grape juice and wine. Apart from sugar content and fermentation flavor differences, most wines don’t have a pronounced “grape” flavor. Additionally, aromatic compounds vary in density, and the alcohol content, alongside with this density, dictates which compounds are made volatile and when. This suggests there may be something to the thirst we can have for big, high-alcohol content beers.

Carbonation also has more of an impact than just providing pleasant bubbles. First, those bubbles help to carry the aromatic compounds to the surface of the beer and when they pop, those that are volatile are released and travel to your nose. For anyone that’s had a chance to have a beer served on cask, or even the “Nitro” style, alongside the regular carbonated version, you will certainly notice the cask/Nitro style is lacking in comparison. CO2, in water, also creates a small amount of carbonic acid. Combined with the prickle of the bubbles on your tongue, this light acidity can lead to a desired “sharp” quality in many styles. Carbonation also leads to a more pronounced perception of dryness, as well as bitterness. (Even more reason to stop putting IPAs on cask…)

Now, there has been a good amount of talk about aromatic compounds and how they are impacted by some of the by-products of fermentation, but they are themselves the most often overlooked fermentation by-product. For the purposes of this article, we will talk about the two most desirable and pronounced families of aromatic compounds: esters (fruit) and phenols (spice). All fermentations result in various amounts of these compounds. Lager yeast, being more efficient at their lower fermentation temperatures, produce fewer of either of these, adding to their clean flavor. Ale yeast, however, is the “quick and dirty” fermentation that results in an encyclopedia of flavors you and I wouldn’t normally associate with malted barley and dried hop flowers. For example, when you have a German Hefeweizen, that classic banana and clove characteristic is all yeast-derived. All of these aromatic compounds make what we know as a beer we prefer taste like…a beer we prefer.

We will touch, briefly, on the idea of fermentation with non-traditional yeasts and other organisms. Wild ales and sours, like IPAs before them,  have gained a very vocal following, albeit a very vocal minority. These beers are much more challenging, because of their flavors not usually associated with beer. If we’re just talking standard fermentation with a non-traditional (“wild”) yeast, like Brettanomyces (“Brett”), these flavors can be described in a number of ways. I associate the influence of Brett with an earthy, mushroomy character in most cases. It’s funky, weird and oh, so enjoyable. That’s oversimplifying things, because like brewer’s yeast there are several different strains of Brett that reveal themselves in different ways, but it’s a good enough approximation for me and my love of what it does.

Sours can be made through a couple of different fermentation approaches. Recently we have seen an explosion in “Kettle Sours”, that are soured pre-boil with lactic acid bacteria (Lactobacillus). This creates everything from a nice tartness to a sharp acidity, but little else. Beers can be fermented with a “mixed culture” of brewer’s yeast, wild yeast and souring bacteria. This culture can be added to the liquid in stainless steel fermenters like in a regular fermentation, added to wooden barrels, or obtained “spontaneously”. However the culture is introduced, each critter involved contributes its own list of flavors, making these beers some of the most complex, but challenging, beers.

All of this assumes that the yeast, or other critters, are what the brewery intended to have fermenting their beer. If this were not the case, the result would be an infection. Infection sounds quite a bit more menacing than things usually are. Menacing or not, the result is not what the brewer intended and could be justifiably called “bad”. That’s not to say it has to taste bad, there have been many happy accidents in beer, but “bad” speaks to flaw. Now, “bad” will speak to bad if a souring or spoilage bacteria gets into a beer where it doesn’t belong. First, these guys can chew up all kinds of things brewer’s yeast can’t, leading to an elevated level of carbonation. This extra pressure can cause your bottle or can to overflow immediately upon opening. Worse, this can cause bottles and cans to explode when the pressure gets too great. Add to that a long list of flavors I’m not interested in boring you with, and you will understand the power that understanding fermentation and its causes has on the beer you and I enjoy.

So that is an expanded look at fermentation, or my understanding of it. Brewers have a daily challenge on their hands in wrangling yeast into a successful and appropriate fermentation. It is both art and science, juxtaposed, that help in this endeavor. And for all of their hard work, all we have to do is drink and be thankful…so, here’s some beers to check out, with fermentation in mind…


Fancy Lawnmower
Kolsch (4.9% ABV) | Saint Arnold Brewing Company (Houston, TX)
A Houston staple, Fancy Lawnmower is a light, crisp and easy German-style beer that straddles the line between Ale and Lager fermentation. Kolsch is just as much a style of beer as it is a style of fermentation. The beer is initially fermented at warmer-than-lager temperatures, but not quite warm enough for ale. The end result is a flavorful crowd pleaser, capable of satisfying a fan of domestics, imports or craft brews.

Hefeweizen (4.9% ABV) | Saint Arnold Brewing Company (Houston, TX)
Years ago, Saint Arnold put a spotlight on fermentation, and the impact both it and yeast have on the beers we enjoy. The series was called “Moveable Yeast” and Weedwacker was born there. Here is a perfect showcase of how different a beer is based on fermentation alone. Weedwacker IS Lawnmower, fermented with a German Hefeweizen yeast. Rather than the crisp, clean qualities of a Kolsch, here you find that banana & clove flavor typical of Hefeweizen.

The Salty Lady
Gose (5.0% ABV) | Martin House Brewing Company (Fort Worth, TX)
One of the most popular “kettle sour” beers at the Smith Street location right now, what with Lisa putting it in
everyone’s hands and guests coming back to get more. As mentioned in the body of the article, souring in this way creates acidity and not much else, so Martin House adds coriander and salt (traditional for a German-style Gose) to the mix.

Petite Golden Sour
American Wild Ale (3.5% ABV) | The Collective Brewing Project (Fort Worth, TX)
This is a “barrel-soured” treat that we just started seeing on an irregular basis at the Smith Street location, as well as a few other stores in Houston. Despite its low alcohol, PGS combines a very pronounced, sharp acidity with the flavors of mixed culture fermentation. More challenging, and rewarding, than Salty Lady, PGS is a Texas specialty worth seeking out.

Urban Funkhouse
Saison (7.2% ABV) | The Collective Brewing Project (Fort Worth, TX)
This is where all of the fireworks go off for me. If you have been in store anytime in the last month, I have dragged you by ear or nose to the end of the Texas aisle where I have/had the Collective beers stacked. Many of you know Saison is my favorite style. After reading this article, I hope that you know that I enjoy funky, wild ales. So, it should come as no surprise that Urban Funkhouse is going to successfully put me in the poor house. So beautiful and challenging, it’s funky, hoppy, tart and complex. I can’t say enough about this beer, but with limited and occasional supply, I may stop talking altogether and save it for myself.


Owned and operated by the same Houston family since 1962, Spec’s is a true destination shopping experience. We now operate over 150 stores all over the great state of Texas and offer a large selection of wines, spirits and finer foods.

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