Yeast Shepherding Part 1: Why we search for yeast

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How many beer styles are there? Well, the Beer Judge Certification Program (BJCP), which is widely considered to be the authority on beer style guidelines, lists around 114 subcategories for beer styles. To a neophyte craft beer enthusiast, this may seem like a lot to learn, but to any one of the 4000+ breweries in this country, such a small number of styles means that any single beer style can be expected to exist in a mind-boggling number of iterations. To give an example, a search for “IPA” on Beer Advocate gives nearly 16,000 results. Even searching for one of the more esoteric styles, “sahti” yields 20 commercial examples. If the thousands of craft breweries want to try something new, we’ll have to be very creative.

Certainly, chemically reconstructing ancient recipes from archaeological sites is one option–and an exciting way to reintroduce beers that were previously lost to history. Of course, this process is limited to what has already been done in human history and regardless, could never keep pace with the current rapid growth in breweries and beer demand. The recent increase in overall market share of craft beer indicates that the American public has, on average, become more discerning and sophisticated in its beer consumption. Increasingly, folks at bars are demanding new beers. They want something they haven’t tried before.

Obviously, there are many beers that cannot be narrowly defined by traditional style guidelines and indeed, these are some of the most exciting beers out there right now. However, given the composition of beer, we find only a few dimensions over which to vary our recipes. Hops have been a popular choice, giving way to the myriad IPA recipes mentioned above. In turn, several new hop varieties are being bred and added to our lexicon each year. Malted grain is another avenue of exploration, and the recent explosion of “ancient grains” as well as enthusiasm surrounding heritage grains provides us further means of expanding our craft brewing color palette.  If that doesn’t excite you, there are numerous breakfast cereals that can be made into beer. Although water chemistry is another possible variable, brewing water itself has not yet ignited a fervid passion among beer drinkers (with some notable exceptions). That said, varying water chemistry is a more subtle way to explore flavor profiles. For those who disdain subtlety, there is always the option of adjunct ingredients–adding something beyond the holy Four. This has also been done extensively, with ingredients that run the gamut from hot chili peppers to lobster. So what’s left?

Disciples of the Reinheitsgebot (at least the ronn-blogpost_yeastmatingmodern version), will note that I haven’t mentioned yeast yet. Well, that’s what I’ve been leading up to, I suppose. Those who claim to know their beer will often divide known beers into two categories: ales and lagers. The distinction relates to genetic differences between the yeasts that are used to ferment these beers. Ales are the product of fermentation by Saccharomyces cerevisiae, whereas lagers are fermented by S. pastorianus, now widely considered to be a hybrid product of fusion that occurred between S. cerevisiae and S. eubayanus, perhaps in the 15th century. Lagers are thus the half-sisters of ales. Until fairly recently, this was pretty much it in terms of brewer’s yeast biodiversity. Some breweries have begun carrying out primary fermentations with strains of Brettanomyces, a strain typically associated with contamination or secondary fermentation of sour beers. The use of new species in beer fermentation has opened doors to a world of new flavors.

In traditional lambics and Flanders reds, fermentation is carried out spontaneously. This means there is likely a large population of microorganisms that work in concert to ferment these beers. This population is undefined and can vary substantially from batch to batch. Because this is largely controlled by what organisms happen to inhabit the brewery (walls, ceilings, dust), it is unpredictable and difficult to tease apart. Some work has been done to study the ecological succession in these wild ales, but thoroughly controlling flavor in each batch is still a difficult task. When we look at the actual ronn-blogpost_koelschip-smorganisms present in some American wild beers, we see not only S. cerevisiae, but members of Pichia, Candida, Dekkera (Brettanomyces), as well as lactic acid bacteria, Leuconostoc spp. and Streptococci. Whoa. So who’s doing what? And how do we replicate it reproducibly? What other species can make beer? What unknown flavors are hiding out there right before our eyes? Also, whence can we harvest even more flavors and aromas?

Perhaps, rather than thinking along species lines, we can think about tastes and aromas themselves. Flavors produced during fermentation are metabolic byproducts, often in rather low concentrations. Because the taste thresholds for these are also low, we detect them easily and note the flavors. One such example is 4-vinylguaiacol–a compound that can be detected in beer at concentrations as low as 200 parts per billion and gives hefeweizens their notable clove-like flavor. This is produced only by specific yeast strains that have the so-called POF gene. This gene codes for an enzyme that can convert ferulic acid, found in malt, into 4-vinylguaiacol. The example of the POF gene is a particularly interesting one, because it shows us not only the connection between genetics and beer flavor, but the complex relationship between flavor, context and perception. If you were wondering what “POF” stood for, the gene was named for “phenolic off-flavor”. That’s because in the wrong context, a clove flavor is considered a beer defect or off-flavor. But in the context of a hefeweizen, it is not only acceptable, it is required (see BJCP guidelines, above).

One can imagine how and why the phenolic flavors imparted by certain Brettanomyces strains, often described as “band-aid”, “barnyard”, “smoky” or “mousey”, could be construed as defects. For these reasons, brewers have historically done all they could to keep this species away from their beer. But given the right context, the aroma of a horse blanket could provide a welcomed complexity to an otherwise “clean-tasting” (read: boring) beer. Aromas, given their connection to the reptilian brain, are strong evokers of memory. So instead of that beer being a simple thirst-slaker, perhaps a more interesting choice of yeast would trigger vivid memories of those halcyon caballero days, lazily trotting around the ranch on your increasingly sweaty horse in the hot New Mexican sun. Or, that time you had a hay ride at your niece’s birthday party. Either way, there is a complexity here that elevates the drinking experience to something more than a drinking experience, and it’s all due to some nano-sized molecular differences among micro-sized organisms.


Getting back to the role of context, there are certainly some beer recipes that are well suited for the phenolic flavors, yet even these require a suitable cultural context. The growth of the craft beer movement in the US has led to greater interest in complex beer flavors. It is this gradual enlightenment of the beer-drinking community that has enabled a wider acceptance of beers with unusual flavors, thereby giving the economic impetus and support to brewers who pursue these avenues of creativity. It is this pattern that has led to the proliferation of göses, American wild ales and yes, sahtis.

Here, I am actually understating the role of the drinking community, since it is the drinkers’ demands that determine which brewers succeed and fail. Given the increasing demand for new beers, craft brewers not only have a newfound ability to experiment with nontraditional flavors and organisms, they should feel an imperative to do so. This brings us back to the discussion of how to push the boundaries of new beer flavors. At Aeronaut, we built a laboratory that allows us to isolate and examine new species of yeast (and what the hell, bacteria too). We can not only capture never-before-brewed-with strains, but we can characterize them and identify them in-house. Yeast are everywhere, and every one of them is filled with numerous genes that produce flavors and aromas. Because these flavor-active compounds are all produced in different amounts and ratios, we cannot yet predict how each of these organisms will fare at making beer, nor can we anticipate what strange new flavors we will find (or, for that matter, their public acceptance). Our thesis is that these strains, purified and well characterized (and perhaps selectively bred), will create not only a rich variety of new beer flavors but will behave in a reproducible manner. In this way, we will contribute completely novel beers to the craft brewing world.

So, we have set out on a journey to collect these strains and begin taming them for brewing purposes. More on our first results in a follow-up post…

-Ronn Friedlander

Thanks to Becka Schuelke for the awesome sketches!

Aeronaut lets its beaker flag fly

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Those of you who frequent the Aeronaut establishment will astutely notice (it is assumed that Aeronaut customers are both astute and highly sophisticated) the dynamic nature of the space–from the art on the walls that changes monthly, to the ever-changing beer menu. You’ve probably also noticed that we put up a new fermenter every few months. Perhaps you’ve come in one week to find a shuffleboard court, and then come back a few months later to find a 9-course tasting restaurant in its place. Well, Aeronaut has another new addition that you may have noticed if you’ve strolled our halls in the past two months–a new laboratory!

Now, to be fair, we’ve had a yeast lab all along, since day one. But it was out of sight, tucked away in the far corner of the brew space, behind the pallet storage. The only way one of our guests would have seen it is if they were on a VIP tour. The setup back there was a bit cramped, so on the rare occasion when we took a tour to the lab, it was single-file. Despite its diminutive size, this lab enabled us to grow a diverse variety of yeast, experiment with bioreactors and begin to isolate wild yeast strains to be used in brewing. But as we grew the lab’s functions, it began to outgrow that corner space. So we decided to move it to the far end of the building, in the Foods Hub near Tasting Counter. This space is much bigger, isolated from the grain dust of the brewing area, and more visible. We are very proud of our lab and what we do in it, so why not give it some more prominence?

Since all of the Aeronaut founders are scientists, and two-thirds of them have worked in biology labs, it’s been a big priority of ours from the beginning to have a large, capable and sophisticated lab [see post on yeast strains]. Getting the right equipment without breaking the bank has been a long process. Even though we haven’t had the room until now, we’ve been accumulating awesome lab gear, like shaking incubators, a spectrophotometer, a laminar flow hood, gel boxes and a PCR machine, to name a few. While we’ve been waiting to expand the lab into its own space, we’ve kept all of the gear in storage.

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With our new space, we were able to pull this equipment out of hiding and start putting it to use. The lab team has grown to 3 scientists, so there’s a lot going on. Broadly speaking, the lab now performs three unique functions. The first is to maintain, grow, monitor and propagate a large variety of yeast (and bacteria) for our production beer. This has been the lab’s bread and butter since day one. The second main function is experimentation. This is pretty far-reaching, and includes testing yeast growth techniques, brewing nano-size batches of beer and purifying and testing wild yeast strains to bring into the brewery. The third function is quality control. This is a very important part of the lab’s functions and includes microbiological checks and measurements of color and bitterness in beer. We’re also developing tools for sensory analysis. As diverse as they are, all of these functions really serve a single purpose: to continuously make our beer better, more consistent and more unique.

We’ve already got our benchtop bioreactor running and are actively testing new growth conditions for our yeast. We’re not only isolating and purifying wild yeast, but we are running test fermentations and selecting the best specimens for genetic analysis as well (we can do that too now!). We’ve developed a system for rapid prototyping of beers so that the brew team has more information to work with when designing recipes for production. Stay tuned, because we’ll be following up with more posts about each of these exciting ongoing projects in Aeronaut labs.

“Bites Beats Beamers & BENEFIT” (with Room To Read)

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“imagine Dr. Seuss” – LIVE POSTING from “Bites, Beats, Beamers & Benefit 001″

Hello folks – Ben here reporting from the happy trenches of AERONAUT on a Friday night. As we test a new series of Friday events, “Bites Beats & Beamers” {featuring multimedia collaborations between light and audio artists filling the walls and airspace of AERONAUT). I’m live blogging tonight, joined by special guests, the awesome group, Room to Read – adding a fourth B onto our series: Benefit!

Adding “BBB & Benefit”, AERONAUT is opening up the taproom to connect our community with local charities doing amazing work at home and abroad. There’s no group that we’d rather have on board for the launch of this initiative than R2R.

What’s Room to Read? They’re a non-profit that works with communities around the world from Africa to Asia, raising money for literacy with a special focus on making direct investments in the tools – including schools, materials, and education – that allow local authors and teachers to produce learning materials that work for children in their home communities.

Visiting with Deepti Kanneganti & Barbara Heffner from Room to Read, she explains to me the concept:

“Imagine Dr. Seuss. You could translate Dr. Seuss into Nepalese, however at Room to Read, we would instead seek out and invest in a local author who could write a work in the cultural context of that country, or village”

In Somerville and abroad, AERONAUT stands with those who stand for the preservation of cultural identity. This is a personal mission in addition to a corporate one. As once-travellers & teachers abroad (before the brewery gobbled us up), founders Ronn, Dan & I have had the fortunate opportunity to visit Nepal, India, and Vietnam amongst many other beautiful places that Room to Read invests in. In sketchpads and schools, we’ve experienced firsthand the joy of learning and the power of communication.

So Friday we’re hosting a free benefit event including a Bites, Beats, and Beamers DJ / VJ team for a live juke boxing where you can pay $1 to either request a song or to enter a raffle full of beer-tastic prizes. Each dollar buys one book for girls in third world countries, to further their education and promote gender equality and literacy in education in the developing world.

One Dollar, One Song, One Book.

Thank you Deepti, Barbara, and our awesome DJs – Aidan and Darren, plus Marissa who’s made it happen on the AERONAUT side. And Readers – if you have any charities that you’d like to suggest for BBBB, please let me know!

Ben //

Fermentation Fest 2015 Part 2: Fear and loathing at the fermentation festival

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A panoply of smells, at once full, fragrant and fetid filled the air. There was a general churning as attendees slipped to and fro past one another. It started off with the demonstrators setting up in the early Sunday morning hours and rather swiftly built to a climax at mid-day with thousands of individuals acting in concert to dish out, consume and metabolize all that was on offer. Put an airlock on this one: the 2015 Fermentation Festival was in full swing.

These days, palates are growing more sophisticated and there is a growing demand for knowledge that will fuel better, more unique and more reproducible fermented products. That demand, plus the timeless allure of free samples drew vast numbers of people to the Boston Public Market on Sunday. The fanfare was split between the Boston Public Market and the adjacent sidewalk along Surface Road. Despite semi-frigid temperatures, numerous attendees eagerly plunged their hands into towering piles of shredded cabbage in order to take part in the so-called “kraut mob”: a not-for-human-consumption demonstration of sauerkraut-making techniques.

Most of the outdoor space was populated by vendors of lacto-fermented foods. At times, I found myself wondering inwardly whether society could sustain such a large number of saurkraut purveyors. Setting those concerns aside, I ambled down Surface Road, sampling krauts of all colors and flavors. My favorite was one spiced with juniper and caraway. The krautmachers informed me that these spices gave it an “old-world” flair. I took that to mean that my personal taste is not so much outmoded as it is retro. Another booth attendant offered patrons samples of pickles that best matched the color of their sweatshirts. Despite the fact that my own sweatshirt was neon yellow and pink, there were plenty of choices available to suit me. Yum.

An avid fermentationist, I attended not only as a voyeur but as a demonstrator in the “Science Corner” as well. There, we set up a table alongside Ben Wolfe from Tufts, who was demonstrating the microbes found on various fermented foods and describing the work of his lab, which studies food microbiology. Further down the line, there were reps from Gingko Bioworks, showing off their bioengineered yeast that could generate fine fragrances, and AOBiome, which recently rebranded as Mother Dirt–a company that attempts to reintroduce ammonia oxidizing bacteria to the human skin microbiome. At Aeronaut’s booth, we demonstrated cultures of lactic acid bacteria and yeast, giving people a chance to see these microbes on petri dishes and under the microscope. We also discussed the science of brewing and both lactic acid and ethanol fermentation. I was astonished at how many people who attended our demo turned out to be microbiologists or bioengineers. While we were not allowed to serve beer at our table, we did have samples of lactic-fermented wort, which was sour but not alcoholic. The final product was only sampled in the legal and licensed surrounds of Hopsters Alley.

A day of tasting, learning, exploring and for some, competing in a pickle contest, eventually tapered off and everyone had to either go home or stay behind and enjoy copious amounts of apple cider donuts at the Public Market. Yes, the 2015 Boston Fermentation Festival came and went, but not without leaving everyone involved memories to savor until next year. And sauerkraut.

Fermentation Fest 2015 Part 1: The appeal of the fermented

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For those of you who aren’t in “the know”, the Third Annual Boston Fermentation Festival is happening this Sunday, October 4 (and it’s free!). Aeronaut will be there pouring beer samples, demonstrating sour beers and fermentation science in the “Science Corner”, and sharing knowledge at the “Fermentation Help Desk”. We are also excited to be hosting the official After Party right in the Aeronaut Tap Room. We’ll be serving our beer, giving fermentation-focused tours, and Tasting Counter will be sharing some fermentation-focused foods, like miso-cured duck with pickled veggies. As we gear up for this exciting Sunday, those of us who make a living out of feeding microbes take some time to reflect on the power and appeal of fermented foods.


Shit where you eat. Please.

As most Fermentation Fest attendees will attest, the best foods are those that have already been partially digested. Farm-fresh plants are appealing to humans and microbes alike. When yeast and bacteria gain access to fresh foods like cucumbers, barley or juice they immediately go to work eating whatever sugars they can get at. If this is set up correctly, what they will create is a soup of their own waste products blended with undigested bits of food. In the case of pickled vegetables, this usually takes the form of a sour, more limp and pungent version of the starting material. With wines and beers, we get a mix of undigested complex sugars and alcohol. In all of these cases, the microbes typically only cease their feeding frenzy when they are either out of food, or when they are literally drowning in their own waste. Acids and alcohols are toxic for these microbes, even at middling concentrations. Fortunately for us, this results in some balanced, highly palatable foods and it’s in large part because the microbes, complex as they are, have still not figured out how to avoid shitting where they eat.

And it’s not just acids and alcohols that infuse these fermented products. In fact, microbes also generate other more sparse chemicals like phenols and sulfur compounds that contribute complex aromas and flavors. Beyond giving these foods sourness or intoxicating qualities, they provide character. Sometimes this takes the form of a bubblegum smell. Other times, it’s like rotting flesh. Achieving the right balance and ratio of these compounds takes knowledge and years of experience. Practitioners of fermentation strive to know how to choose the right starting products in right amounts, and how to keep them under the right conditions for the right amount of time. This is the art of fermentation.

Our place in fermentation history

On the most superficial level, humans have an aversion to the smells of fermentation, at least at first. It’s likely that this has a basis in natural selection, since in uncontrolled settings, fermentation usually accompanies putrefaction and the generation of toxins. Eating spoiled foods is not generally good for you. It’s historically been safer to just avoid things that have certain “off” smells. But over time, as humans are apt to do, we’ve engineered the risk out of this situation. Generations of beer- and cheese-makers have figured out how to let microbes get involved in the process without putting the consumers at risk. We know, for example, that the blue mold on a ripe Roquefort is not only harmless, but adds a delicious spiciness to the cheese. We’ve known for centuries that the vigorous bubbling produced by the yeast cultures transferred from batch to batch of beer, is a sign that alcohol is being produced, which prevents harmful bacteria from growing. Generations of trial and error have given humanity the recipes for fermented products that are tasty and safe.

Viewed from a microbiological standpoint, what we’ve learned is how to empirically set up culture conditions that select for specific microbes. Salty brine is the perfect environment for the exotically named Leuconostoc mesenteroides, which kicks off the pickling process for cabbage and cucumbers. Roquefort’s blue mold, Penicillium roqueforti, needs a bit of oxygen but not too much, in order to grow. So cheese-makers have learned to poke holes in the pressed curd prior to aging. Lactobacilli do well in warm temperatures and then produce acid, which blocks the growth of other microbes. Thus, our yogurt makers keep milk warm to help with the process.

Though humanity owes many of its achievements to trial-and-error, tradition and empiricism, as we mature we demand to know the underlying truth. Over time, we’ve started putting the pieces together and now know the identities of many of the individual microbes involved, as well as the metabolic pathways of the relevant processes. This has had some unintended effects. In the beer world, the works of Pasteur that led to the isolation of individualSaccharomyces colonies resulted in highly reproducible and very “clean” fermentations. This made brewing possible at immense scales. The resultant 20th century dominance of macro-breweries left us (particularly here in the USA) with a rather boring and flavorless understanding of beer. In time, as we grew more worldly and some of us sampled the lambics of Belgium and the Stock Ales of England, we became aware that something was missing. There was a complexity that was seriously lacking in our beers, due to the absence of other microbes, thought of as contaminants during the age of classical microbiology. It has only been in the last decade or two that non-Saccharomyces microbes have made a significant comeback in our beers. The story of cheeses in this country is surprisingly similar.

There’s a common theme here. Industrialization increased the reproducibility and uniformity of our products and our belongings. Importantly, this increased access to these products, but as we’ve grown used to these things and become more sophisticated in matters of aesthetics and flavors, we’ve increasingly yearned for strangeness and heterogeneity. This story is eloquently told in the book “Salt: a world history”, by Mark Kurlansky. He writes of the advent of table salt by Morton’s, which was celebrated for its uniformity and purity. This salt was so uniform that it could be poured. While this product is still on everyone’s dinner table today, there is a growing market for Himalayan pink salt and fluer de sel, which are distinctly different and non-uniform. Today, more and more people demand foods with character–foods that aren’t “clean”.

Something smells rotten

The first time someone put a bowl of kimchi in front of you, I would wager that you were not immediately salivating at the smell. “Garbage” or “barnyard” were not in your then-juvenile lexicon of things epicurean. But for many of you, your curiosity outweighed your reluctance and you tried a bite. At that moment, you were greeted by a strange mix of flavors–sour, spicy, salty…and you reserved judgement. This was too odd to dismiss or accept just yet. Over time, more opportunities presented themselves and you found yourself wanting to try more. Somehow, the odd smell of decay and the accompanying feeling of uncertainty gave the whole experience a depth wholly absent from your daily meals. Those hours spent alone at McDonald’s, wolfing down Big Macs and fries now seemed even emptier. You found yourself craving fermented cabbages. This feeling didn’t end there, though. It spread to items like washed-rind cheeses and sour ales. Fermented foods elevated your eating experience to something almost spiritual.

A mix of disgust and desire now attend you as you devour these foods. Consuming these not-quite spoiled foods is an act of hedonism with curious parallels to the erotic. Indeed, spankings, hair-pulling and the smell of sweat were probably not things you thought you’d ever enjoy when you were young, but here we are. And it’s not just you: there is a growing public consensus that fermented foods are desirable. Now, we are entering a time when our love of fish sauce (which, incidentally, is derived from barrels of pressed dead anchovies) can be declared as boldly as our love of nipple clamps. We’ll see you at the Fermentation Fest.

We’ll be reporting back after the festival for part 2 of this article. Stay tuned…

Autumn tidings from winter squash

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Is it just me, or was today shorter than yesterday? The first hints of an autumn zephyr are in the air. The leaves of the deciduous trees can no longer deny reality: their chlorophyll reserves are running low. Soon, we will be greeted with the smells and flavors of Fall–an old friend that can be counted on to return every September. Fall is full of traditions, like apple picking and carving jack-o-lanterns. These annual rituals reflect the goings-on of the natural world, with our own touches added in. Perhaps the reason we humans find comfort in traditions is that the Earth had its own traditions long before humanity was in its infancy. We find comfort in the cyclic. These traditions are a reminder that there is a predictability to the world, despite its seeming chaos. We have no idea what will happen tomorrow, but we can always count on cinnamon-doused baked goods in the Fall. The annual transition from Summer to Fall is a bittersweet one, but our wonderful rituals that vaguely involve earth tones, gourds and hay rides somehow tip the balance in favor of sweetness.

It may seem odd that Aeronaut, of all institutions, is publishing a blog discussing Tradition. After all, we are only in our second year. However, as I began to write about our smoked butternut squash beer, Lagerfeuer, I found myself trying to avoid repetition of last year’s publication about the very same beer. What occurs to me now is that we find ourselves at a special moment in the history of Aeronaut, wherein we get to establish new traditions to repeat each year. The tremendous amount of work that goes into our smoked butternut squash beer is fast becoming a ritual that heightens the anticipation and appreciation of this unique lager.

Like last year, Lagerfeuer began its life at the farm. This time, I wanted to get a little closer to the source of our squash. We found an excellent local source of butternut squash this year, out at Plainville Farm in Hadley, MA. I drove the pickup truck out there last week and this time, I got to walk the fields and get up close and personal with the squash in their native environment.

There, I encountered an endless expanse of butternut squash, each one filled with enough seeds to plant yet another field of squash. We loaded the truck with around 800 pounds of it, which somehow didn’t even seem like that much after looking over the vast fields.

Obviously, there was much peeling and seeding to be done. We threw a squash prepping bee at Aeronaut a few days later. Nine intrepid volunteers joined us to peel squash after squash, separate the seeds, and slice them up into neat strips so that they would smoke evenly. Butternut squash are unique in having very distinct shapes and personalities, varying remarkably from one to another. Some were very long and thin, others were wide and straight, and still others tilted to the side. Everyone had their own technique for peeling and cutting the squash, which was fun to observe. Some folks tried to peel the squash in one continuous strip. Others debated the merits of halving them vertically or horizontally. Regardless of the method, once they were peeled and cut, they all endedup as uniform orange chunks.

The next day, I drove nine bins full of squash chunks over to our old friends at Blue Ribbon BBQ for a thorough smoking. This year, we gave them all a pre-roast to increase the permeability and soften them up. It took all day to smoke the whole batch. When they were done, the squash pieces shrunk down to about half of their original size, which made it easier to carry them back to Aeronaut.

For this year’s brew, we decided to skip the pureeing process. Last year, we pureed all of the smoked squash to make sure they extracted thoroughly and to make sure they passed through our pump from the mash tun to the lauter tun. While we did achieve those goals, the thick squash puree caused the mash to stick quite intensely, which made the runoff of wort extremely slow and cleanup a total mess. So this year, we made sure the squash chunks were small, and deposited them directly into the lauter tun. Having tested this method last winter, we knew we’d get excellent flavor, sugar and color extraction from the squash. The richness of red and white oak smoke filled the brewery during this year’s Lagerfeuer brew, and the wort ran off without a hitch.

Now, we just have to let the yeast do their work eating all those sugars. We eagerly anticipate this year’s release of Lagerfeuer, which is fast becoming as welcome and familiar as pumpkins, apple cider and those odd, but ubiquitous cornucopias. Look for it in late October!

Sumac’s Back

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The ‘nautiest among you will recall last year’s sumac beer, which featured freshly harvested sumac from the fields surrounding Four Star Farms. The beer, dubbed “Field Day”, turned out delightfully tart and refreshing. It has since become a subject of discussion among taproom patrons who often ask when we’ll have it again. As August draws to a close, we are happy to say that more Field Day is now on tap!

As with any experimental, ingredient-driven beer, we brew, learn and repeat. Last year, we were thrilled that a handful of volunteers showed up with sleeves rolled, ready to drive out to Northfield with us and harvest sumac. It took several hours and the help of some long, telescopic loppers to gather enough sumac for a full brewery-scale batch. We drove back with the haul, which another eager team of volunteers helped us break apart into its constituent furry berries.

To get the sumac flavor out of the berries, we did a hot steep and mash, and then ran off the concentrated tea right into the kettle during the boil of its host pale ale. Once the beer was fermented, we tasted it and were left wanting even more sumac flavor. So, we ended up making another few gallons of sumac tea from another harvest, boiling it to pasteurize, and adding it to the batch. This topped off the flavor to our liking. The next obstacle we faced was removing the cloudiness. Apparently, the presence of many proteins extracted from the sumac created a haze in the beer. We tried several methods to reduce this haze, but were minimally successful. So, we just served the beer au naturel. It was a hit! Something totally unique and delicious. We resolved to do it again when the sumac season next rolled around.

This year, we asked ourselves how to improve the beer. Obviously, we wanted even more sumac flavor, since we had to top it off last time. One way to achieve that is to gather more sumac. However, we also noted that sumac from earlier in the season would be fresher and stronger in flavor and acidity. So we moved our picking time up by a full month, from early September. This year, we resolved to pick the sumac in early August after a dry period. We scouted out the plants in advance, noting the differences between male, which would never fruit, and female, which would provide us large clusters of the berries we wanted. We also anticipated how difficult it would be to harvest from taller plants, so we located a cache of sumac plants on the opposite side of Four Star Farms.

Another big difference was the number of people we brought out to Four Star this year. August 8th was our first ever Field Day: a festival celebrating farm and brewery and food collaboration. Over the course of the day, we entertained around 500 people who enjoyed the farm, toured the hop yards, drank Aeronaut ales, and enjoyed the sounds of some 27 bands. During this festival, I took two teams of willing participants out into the fields to help harvest some staghorn sumac for this year’s Field Day beer. In total, over the course of a few hours, about 20 helpers collected a total of 27% more sumac than last year. Between that and the improved quality of the early harvest, we were on track for success!

Brew day: the sumac was staged, and me, Dan and Sean were all prepping the sumac berries while Mark was finishing the mash for the brew. We stuck with our hand-mashed berry method this time, but we elected to make an additional improvement. We wanted to reduce extraction of tannins and excess proteins from the sumac, so we reduced the temperature of the steeping liquid to room temperature. This still allowed us to extract a ton of water-soluble elements from the sumac with the help of vigorous agitation, but reduced tannin extraction. We also figured this would reduce the amount of haze in the final beer.

Another change we made was to extract the sumac tea prior to adding it to the boil. This way, we could add it more rapidly and have a more precise boil time. We measured the pH of the sumac tea concentrate and it reached 2.8! Considering it was the same volume of liquid as last year’s sumac tea, we were thrilled to see it lower than last year’s pH of 3.0. Now remember, we are working on a logarithmic scale here, so this difference represents more than a 50% increase in acidity. Needless to say, we were excited. Of course, this concentrated sumac tea was all diluted in the beer, so the pH of the beer was nowhere near this low, so you’re safe…for now.

After a quick and vigorous fermentation, the beer was ready. This time, the sumac flavor came through loud and clear from the beginning. The beer also turned out less cloudy than last time. One other difference was that this year, less of the red color was extracted. So the beer doesn’t have the same hue as last year’s. Perhaps next year we’ll do a blend of hot and cold steeps. Or a CO2 extraction.

All in all, this beer was very labor-intensive, but since it’s a labor of love, the beer is full of love. Peace, love and sumac beer!