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Beer Science: Sour and Funky Beers

Sour beer isn’t a new idea; actually, the earliest beers have been in all probability all sour by right now’s requirements. That is largely because of the wild yeasts and micro organism that might infiltrate old-world open-container brewing techniques and add their own distinctive flavors to the brew. Ultimately, these wild flavors and bitter notes have been phased out as brewers improved their sanitation methods and began using closed containers and chrome steel. Maintaining wild yeasts and micro organism out allowed brewers to decide on particular yeast and micro organism strains, which meant the flavor and alcohol content material of their beer can be more predictable.

As a basic rule, having a predicable recipe is an effective factor, however shouldn’t we have the ability to have our cake and eat it too? Over the centuries, brewmasters have labored to isolate the precise strains of micro organism and yeast that made those historic beers so good, and omit all the ones that made them so dangerous. Once upon a time, sour beers have been manufactured by just a few specialized breweries in Belgium and Germany, however in recent times, small breweries everywhere in the world have begun experimenting with sour beers. And where good beer goes (haha, Gose?) individuals will comply with. In the end, sour beers have earned a small however thirsty following in America, and I’m proud to be amongst them.

Beer pouringI was inspired to write down about sour beers a couple of weeks in the past after attending a sour beer tasting occasion, referred to as Sour Beer Takeover, at the Historic Sixth & I Synagogue in Washington, DC. Actually, once I began writing, I couldn’t stop–which suggests I’ll be doling out the bitter beer love in two installments. The first installment, under, is concerning the science of sour beer (and regular beer too). It’s an excellent primer for the beer nerd in all of us. The second installment, to be posted next week, will spotlight a few of the superb local brews I tasted on the event. It’ll come complete with my evaluations and rankings, as well as some fun tidbits from the occasion. However for now, let’s get right down to the science and uncover how a humble grain of barley becomes a refreshing sour beer. (Protip: you may need to pour your self a chilly one earlier than reading on.)

Beer Science

All beer starts with grain. Normally, that’s both solely barley, or a mixture of grains (like barley, wheat or corn). Grains are made up of principally starch, which is the beginning materials for beer. Starches are principally long chains of sugar molecules, and these sugars are what are needed for fermentation (and alcohol production) to happen. The trick of turning grain into beer is breaking those starches down into small, easy fermentable sugars, like glucose. The primary several steps in brewing are geared toward separating as lots of those small, simple sugars as attainable.

Malted grain sm


Malting is step one in turning grain into beer. The raw grain is dampened with warm water and allowed to sprout (germinate). Malt is outlined as germinated grain. Germination triggers the production of an enzyme, referred to as amylase, which instantly begins changing starch into usable sugars. Beneath totally different circumstances, the young plant may use these sugars to help it develop, however since this little sprout is intended for brewing, those sugars are going to go towards a nobler cause–beer. Once the sprouts have grown to roughly three-quarters of an inch, the malt is drained and roasted in a kiln, which stops the work of the amylase enzyme. Malt could also be roasted until it’s mild, dark, or black. The roast degree of the malt is what determines the color and malt taste of the final beer. One other wrinkle that sometimes comes into play at this stage is smoke. As an alternative of roasting in a kiln, some malts are dried over smoking woodchips. Smoked malt is what provides Rauchbiers (smoked beers) their smoky flavor. Smoked beers are comparatively uncommon, but some sours, including a two of the native brews I’ll mention in my second installment, are smoked to add warmth and character.

Brewing science: Starches are transformed to fermentable sugars by way of enzymes and heat.
Taste results: Malting itself modifications the flavour of the ultimate beer, as is evidenced by the slightly totally different flavor of unmalted beers. The stability of barley to other grains as well as the extent to which the malt is roasted or smoked determines the color and last maltiness of the beer.


As soon as the malt is absolutely roasted, it’s ground right into a mash and added to a tank referred to as a mash tun. Right here, it’s churned with water and heated, further breaking down starches into fermentable sugars. Longer mash time often means extra fermentable sugars. Shorter mash time means extra unfermentable starches and other compounds, which give beer extra body. The cooked mash is then transferred to a brand new vessel, the place the solids are allowed to settle to the bottom.

Brewing science: Starches are converted to fermentable sugars by way of heat and agitation.
Taste results: Brews that spend extra time within the mash tun tend to end up with extra flavors from alcohol and other fermentation products, however have a lighter body than people who spend much less time there.

Hop sm


The liquid portion of the mash, referred to as the wort is drained off and moved to a kettle. Flavorful hops (and some other botanicals) are added right now, and the wort is boiled. This kills any pre-existing microorganisms, reminiscent of yeasts, bacteria, and molds which may spoil the beer or introduce undesirable flavors. Boiling additionally helps break down a few of the remaining unfermentable compounds and develops the malt and hop flavors. Once the wort is sterilized, it’s strained, cooled, and transferred to a fermentation vat. Strained wort is principally unfermented beer.

Brewing science: Wild microorganisms are boiled off. Hops even have some anti-microbial results that assist sterilize the beer. A couple of more starches are converted to sugar by way of warmth and agitation.
Taste results: Hops add their waxy, bitter, resinous, citrusy notes to the brew, along with some other botanicals (e.g. orange peel or coriander). This technique of flavor infusion is just like steeping tea. Sterilization of the wort prevents off flavors from creating during fermentation.

Wort w Hops WM sm

Principal Fermentation

This is where the magic occurs! The steps up till this level have centered on maximizing the amount of sugar we will draw out of our grain. Sugars are essential because they drive fermentation. Fermentation microbes need sugar to be able to produce alcohol, carbon dioxide (CO2), and delicious taste and aroma compounds. Up till this stage, the method of creating sour beer has been largely interchangeable with making common beer, however fermentation modifications every part. The difference between bitter and common beers has the whole lot to do with which strains of bacteria and yeast are chosen for fermentation. Listed here are the microbial MVP’s you’ll see most often in bitter beers:

  • Lactobacillus (aka “Lacto”) – A micro organism which produces lactic acid, the most typical supply of sourness in bitter beer. There are two Lacto sub-types essential to bitter beer:
    • homofermentative, which solely produce lactic acid, and
    • heterofermentative, which produce lactic acid, acetic acid (vinegary), alcohol, CO2, and other flavor and aroma compounds.
  • Brettanomyces (aka “Brett”) – A yeast which produces alcohol, CO2, and variety of unusual and funky taste and aroma compounds. Those compounds will range based mostly on the precise pressure of Brett used, and what the temperature and different environmental circumstances are throughout fermentation. Examples of some sought-after Brett flavors and aromas embrace fruit, citrus, barnyard, vinous (wine-like), musk, and butter. Brett might typically produce some sourness as nicely, however to not the extent of Lacto.
  • Prime-fermenting Saccharomyces cerevisiae (aka “ale yeast”) – The yeast used to make regular ales. It imparts no sourness, solely alcohol, CO2, and regular ale-like taste and aroma compounds.
  • Backside-fermenting Saccharomyces cerevisiae (aka “lager yeast” or “beer yeast”) – The yeast used to make common lagers. It imparts no sourness, solely alcohol, CO2, and common lager-like taste and aroma compounds.

As you may think, regular beer is brewed using only ale yeast or lager yeast. Actually, the fascinating character imparted by Brett is taken into account an off-flavor in regular beer. I mention them here as MVP’s for sour beer because most sour beer brewers choose to use a blend of fermentation microbes, including the common tasting ones, to realize the right stability of flavors. Principal fermentation can progress in any variety of methods. Sour beers are sometimes separated into totally different batches or fermentation levels as a result of each microbe requires its own special circumstances to thrive.

Yeast and Lacto Fermentation (anaerobic) vert WM sm

If the brewer decides to use multiple of those fermenting microbes, he’s possible to choose one of many following two fermentation procedures: (1) separate the sterile wort between several small vats and inoculate every one with a unique microbe; or (2) put all of the sterile wort into one huge vat and add the varied microbes separately, sterilizing between each change.

BrettAnna Y. Myces 4 smIf the brewer chooses choice 1 (separate vats), one vat would get Lacto; another would get Brett and so on. Every beer can be fermented separately, and then blended again together on the end. This feature is good as a result of it doesn’t require any mid-fermentation sterilization. Every batch is allowed to ferment in peace; nevertheless, it requires more room and gear than many small breweries are capable of spare for a single beer.

If the brewer chooses choice 2 (single vat with one microbe at a time), he would transfer all of his sterile wort into one massive fermentation vat and inoculate it together with his first microbe–typically a homofermentative Lacto. The bacteria would eat sugar and produce lactic acid until the beer reached the brewer’s desired acidity degree. Lacto fermentation would then be halted by boiling off the micro organism. The newly sterilized, partially-fermented (now bitter) beer would then be inoculated with a yeast to finish off the remaining sugars within the beer. For a simple, clean-tasting bitter beer, the brewer may choose an ale or lager yeast. For funky fruity sour beer, he would probably select Brett.

The CO2 produced during fermentation is collected and saved to be added again into the beer at a later stage.

Brewing science: Microbes ferment nearly all of sugars into alcohol, CO2, acids, flavors, and aromas. Sour beer fermentation MVP’s are Lacto bacteria, Brett yeast, and (to a lesser extent) ale and lager yeasts.
Taste effects: More Lacto means extra sourness, extra Brett means more funky fruitiness, extra ale or lager yeast means more “clean” beer flavor. Brewers can control the stability of those points by either brewing separate small batches of single-strain beer and blending them at the end, or they will ferment their beer in levels, sterilizing the beer in between inoculations.

Second Fermentation and Lagering (Resting)

After the principal fermentation, a lot of the heavy lifting is completed, and the younger bitter beer can now be allowed to rest in a storage tank. The beer is cooled drastically to sluggish the activity of fermentation microbes and encourage giant particulates to settle out of answer. As sediment gathers on the bottom of the tank, the beer becomes much less cloudy. It’s allowed to rest at this cool temperature for a number of weeks, months, or years depending on the beer. Throughout this resting interval, often known as lagering, a sluggish second fermentation happens, further enhancing the flavor of the beer and including carbonation. In certain forms of beers, resembling framboise, further fruit (or one other sugar supply) is added earlier than second fermentation to provide fermentation microbes a recent batch of sugar to work on.

Brewing science: Lingering sugars are fermented slowly at low temperatures. Cloudiness is decreased resulting from sedimentation. Flavor mellows and modifications over time, and fermentation microbes need to work more durable to seek out meals.
Flavor effects: Ageing allows the flavor of the beer to mellow and improve. Newly shaped CO2 is trapped, enhancing the beer’s effervescence. Off-putting particulates settle out of answer.

Sour Beer Bottle sm

Carbonation, Packaging and Pasteurization

Now the beer is ready for the ending touches. It might be filtered or centrifuged to improve its clarity, and CO2 (which was collected throughout principal fermentation) is now pumped again in. The beer is then packaged into kegs, cans, or bottles. Although only a few sugars stay in the beer, there remains the danger that fermentation may continue during storage, probably inflicting a buildup of CO2 inside the packaging. This isn’t a problem for beer packaged in kegs, as kegs can stand up to astonishingly high quantities of strain (about 300 psi—for context, automotive tires are often inflated to about 32 psi). Nevertheless, cans and bottles aren’t as robust, in order that they’re pasteurized after packaging to kill off any remaining fermentation microbes. Pasteurization improves the steadiness and shelf lifetime of canned and bottled beers, however slightly alters their flavor. Some beers packaged in cans or bottles might stay unpasteurized if the brewery employs sterile filtration as an alternative. Sterile filtration bodily filters out yeast and another dwelling microbes as an alternative of killing them. This pasteurization work-around is how some brewers are allowed to explain their canned or bottled beer as “draft beer”.

Brewing science: Remaining measures are taken to make clear the beer and add CO2 back in. Beer is packaged and sterilized (besides keg beer) to stop further fermentation.
Flavor effects: Filtration removes any particulates which can detract from the looks or taste of the beer. Further CO2 modifications the physique and lightness of the beer, while growing “carbonated” style (barely tangy). Pasteurization of canned and bottled beers requires heat, which slightly modifications their flavor and halts fermentation.

Now let’s all crack open a pleasant cold Bud Mild to have fun our new-found information of bitter beers! Simply kidding. Listed here are a couple of sours I’ve found in my local beer stores which have contributed to my appreciation of bitter beers. It’s under no circumstances an entire record, however give any (or all!) of these a attempt and increase your beer palate. When you’ve got a favorite bitter beer, tell me within the feedback; I’d love to listen to your suggestions!

Festina Pêche – Dogfish Head Brewery
The Kimmie, The Yink & The Holy Gose – Anderson Valley Brewing Company
Rodenbach – Brouwerij Rodenbach N.V.
Monk’s Café Flemish Sour Ale – Brouwerij Van Steenberge N.V.
Petrus Aged Pale – De Brabandere
Petrus Oud Bruin – De Brabandere
Petrus Aged Pink – De Brabandere


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2. O’Brien, C., Engert, G., Zeender, N. & Roy, M. Sour Beer Takeover. (2014). at

3. Bennion, M. The science of meals. (Harper & Row, 1980).

four. Nummer, B. A. Brewing With Lactic Acid Bacteria. Extra Beer (2012). at

5. Wyeast Laboratories. What’s Yeast? Yeast Fundamentals at