Monday, April 25, 2011

Ambient-Spontaneous Yeast Starters

Fermenting beer with truly wild microbes (that is to say not ones found in a tube, pack, or bottle) has recently started in earnest among American sour beer producers. Russian River, Allagash, Jolly Pumpkin, Midnight Sun, and Jester King have all tried their hands at spontaneous/ambient fermentations. Despite this recent surge in interest, allowing the yeast and bacteria present in the environment to ferment wort is nothing new; spontaneous fermentation was the way beer was originally made before brewers learned to repitch yeast from one batch to the next. This method has been brought to its highest form by Belgian lambic brewers, who produce beers with a balance of acidity and complexity that is unrivaled.

There is nothing special about the wild microbes floating around Belgium; the main sour beer fermenters: Saccharomyces, Lactobacillus, Pediococcus, and Brettanomyces are found all over the world. It is the selective pressure lambic brewers have placed on these microbes (as well as the masterful post-fermentation blending) that allows them to produce such remarkable beers. For decades these brewers and blenders have been reusing the barrels that make good beer, and getting rid of the ones that do not (burning them for fuel in the case of Cantillon). First use barrels are sometimes inoculated with microbe laden beer from an “established” barrel to give it the best chance to produce high-quality beer. All of this effort on the part of the brewer/blender reduces the role luck plays by providing each batch with proven microbes (in addition to the ones that randomly land in the cooling beer).

Many American brewers mimic this process by racking their "spontaneous" beer into barrels that have previously held successful sour beers (which often used commercial bugs). For example Russian River Beatification is allowed to start fermenting in the mash tun before it is moved to barrels that have already been used multiple times for other sour beers, ensuring they are already saturated with microbes and lacking oak character. Vinnie Cilurzo, the head brewer at Russian River, cleans his barrels aggressively with hot water between each batch, allowing only the strong microbes to survive.

Wider is better because it gives more surface area for microbes to land.
Ambient temperature is supposed to be the key indicator for determining when the best time to capture wild microbes is. Wild Brews report that during the hot summer lactic acid bacteria is too prevalent for successful spontaneous fermentations (other people say Acetobacter is the issue). Hot temperatures also slow natural cooling, which allow thermophilic (heat loving) bacteria more time to thrive before the wort cools enough for yeast to ferment. Whatever the reason, most lambic producers take the summer off from brewing, so I decided to follow their lead for my first attempt. At the other end of the mercury, if the outside temperature is below freezing there may not be enough wild microbes to ensure a quick start to fermentation. Allagash only brews their "Coolship Series" beers in the fall and spring skipping the winter since it gets much colder in Maine than it does in the Senne Valley.

Most homebrewer who attempt spontaneous fermentations seem to report poor results from leaving the wort open during natural cooling for inoculation. With this method you are relying 100% on the microbes that happen to fall into your beer. To help reduce the risk of major off-flavors I decided to capture microbes in starters that I could propagate before pitching them into the wort. I made four pints of low gravity (1.030) wort from malt extract, 1/2 oz aged hops, and a pinch of yeast nutrient. I divided the hot wort into three metal pots, each covered with a layer of cheesecloth secured with a rubber-band (to prevent insects from crawling/flying/dropping into the wort as it cooled). I placed these starters to cool in my backyard (40-45 F), upstairs (60-65 F), and barrel room (55-60 F).

The barrel room starter, ready to catch some microbes.I was hoping that the aged hops included in the starter wort would prevent Lactobacillus from lowering the pH before the yeast was able to start fermenting. At this stage of the process aged hops are not strictly required because any bitterness fresh hops impart would be diluted before it reaches the main fermentation. With that being said, I still wanted to see what sort of character the lambic hops (3 year old Willamettes) that I purchased from Freshops last fall would contribute.

The following morning, with the wort cooled and hopefully teaming with life, I moved the three starters into bottles/growlers and left them at ~62 F. I did not give the wort additional aeration except for what it received during funneling. I also attached airlocks to reduce the chance that aerobic microbes would gain a foothold. I was torn by this decision because yeast cells need oxygen to reproduce effectively.

After a couple of days I observed the first signs of activity in all three of the starters (small krausens and a few bubbles through the airlocks). I left them alone for three weeks, enough time for the yeast and lactic acid bacteria to make enough alcohol and lactic acid to kill any enteric bacteria (like E. coli). I would skip tasting the starters at this stage, while no known pathogens can live in fermented beer that isn’t the case for unfermented wort.

The stepped up ambient starters, hard at work.
After three weeks, the "upstairs" starter had grown black mold on the surface of the wort and smelled rather foul (dumper). The “outside” starter had some white mold and smelled a bit spicy (keeper). The “barrel room” starter had no mold and smelled like over-ripe fruit (keeper). I took the two keepers and doubled their volume with fresh unhopped starter wort, and moved them to (sanitized) clear one gallon fermenters so I could see what was going on. Instead of an airlock I capped each jug with a piece of aluminum foil and I shook the fermenters every time I walked by to get oxygen into solution. Both started fermenting quickly and smelled pretty clean. The outside starter fermented a bit more rapidly and produced a mildly sulfury aroma, while the barrel room starter took its time and produced more fruity/funky aromatics. When fermentation slowed down I reattached the airlocks to prevent mold from reappearing.  After two more weeks both starters had developed a light lemony tartness.

Yesterday I brewed five gallons of a turbid mashed lambic, once it was chilled to 70 F I pitching about one quart of each of the starters (but more on that next week). It is going to be tough to wait more than a year to see how this one turns out.

35 comments:

Felipe said...

Hi Michael,
I have a oak barrel (120 liters) that was made from bigger barrels and then burnt to expose the tannins in the oak. I've tried to lager two beers in this barrel but after a few days (4 to 10) the beer already had a very strong oak character. Now the barrel is filled with water, but it is very painful to change the water every week in order to avoid the formation of undesirable bacteria in the barrel.
Do you have experience with 'new' barrels? I have a very good Lambic (7 months old) that I want to lager in the barrel, but I'm afraid that after a few weeks my Lambic will have a very strong oak character.
Cheers!
Felipe

The Mad Fermentationist (Mike) said...

I've never dealt with a new barrel for exactly the reasons you are describing. The classic combination of keeping a barrel microbe free is citric acid and metabisulfite, that way you can let the solution pull out tannins without having to change the water frequently. Here are some suggestions on amounts for different sized barrels: http://www.bluestemwine.com/documents/BarrelSterilization.pdf

You might also try filling it with hot (~140 F) water which would pull the tannins out faster. Hope that helps, good luck.

J Wynia said...

When you stepped up your "keepers", what did you do about/with the mold?

The Mad Fermentationist (Mike) said...

I attempted to leave the mold behind, but I'm sure a small amount made it into the bigger starter.  If you used a vessel with a wider mouth you could attempt to skim it off.  I've also heard people suggest using a turkey baster (or wine thief) to suck up yeast from under the mold.  Here is a massive thread with lots of other experiences on capturing wild yeast.

WallyG3 said...

Mike, I've been reading your blog for about 9 months and this post was by far the most educational and interesting. Cool stuff, thanks!

JC Tetreault said...

The decision to affix an airlock fairly early after initial inoculation is critical to success in achieving spontaneous fermentation. You simply need to create an environment that creates selective pressures for the facultative anaerobes over the aerobic microbes, and this is precisely what the successful spontaneous fermenters do (realizing they have barrels loaded with the good bugs). I think at this scale, you may have even gotten away with shorter inoculation times, as you weren't using that time to cool the starter wort, and plenty of CFUs dropped in in a matter of maybe 20 minutes? it would be useful to put out some plates, so you could count. nonetheless, it sounds like you have some early signs of some nice indigenous bugs. lets hope that your claim that there's 'nothing special' about the Senne Valley holds true!

The Mad Fermentationist (Mike) said...

Glad you enjoyed the post Wally, I' try to do more of these instructional posts that focus on a single topic.

Thanks JC, any new updates on the starters you got going from the grapes? A friend of mine did a spontaneous fermentation in an apple orchard and it had a distinct cidery character (I got a similar character in Sam Adam’s spontaneous fermented orchard beer).

JC Tetreault said...

just the first taste from the first stepped up starter/beers.
http://trilliumbrewing.blogspot.com/2011/02/yeast-hunting-1st-taste.html

so, 1 of 4 has now moved on to another stepped up culture and the long wait of the fermented first batch (single infusion, with a fair share of caramunich/crystal so not quite as much long chain sugars and starches to wait on as would be in a turbid mash wort).

Jim Lemire said...

I attempted to capture my own yeast following a similar technique about a week and half ago. I have some whitish stuff on the top of the wort/beer, but not much of anything I would call a krausen. Are those photos of the two gallon jugs from your initial wild harvest? How long did it take to get clear evidence that you had something? I haven't seen any airlock activity yet either (I know that's not a true sign of anything, but I thought I would get something).

The Mad Fermentationist (Mike) said...

The picture is of the starters soon after they were stepped up. It took a few days to start seeing activity in the initial starters, but it was never much activity. Surprised you haven't seen any CO2 production, maybe you missed it? Try stepping them up to see if there is something worthwhile growing in there.

Good luck!

Jim Lemire said...

thanks for the tip. I added some fresh wort yesterday, took the airlock off, and have been shaking it every so often. There's definitely something there - good white foam/krausen. Smells pretty nice too - yeasty, a bit fruity. Might have a keeper. Now I just have to figure out what to brew with it!

ryanb said...

Mike - Just made 3 starters and placed them in an orchard in upstate NY while I was visiting for the weekend. Placed under 3 apple varieties, then mixed all three the next day and put a airlock on. That was Sunday night into Monday morning...already have loads of activity. I'll keep you updated. thanks for the tips in this department.

The Mad Fermentationist (Mike) said...

Good luck! I talked to Jason Perkins at Allagash this morning for an article I'm writing on spontaneous fermentation for BYO. He wanted to be clear that this can be dangerous when the beer is young, smell rather than taste to see how it is progressing. Interesting to hear how it goes.

ryanb said...

smells like lemon & pepper, crashing it and adding new wort right now. I feel like it would taste great with a light saison & I just happened to have come across the wyeast 3726 Farmhouse strain..I'll keep you updated as things progress

Paul Illa said...

I know this is an old thread... But I have become a real fan of your stylings. I am going to attempt this overnight. Its been rather cool here and I have a nice apple tree I can place this under. I was also going to put one in my basement and see what happens.

Ryan said...

Greetings! One question...

I think I'm going to do this probably on Saturday afternoon into Sunday where the temperature range is 70F to 40F. I want to put one out in the woods near a persimmon tree, another out in a field under pear trees, and another a few miles away behind my grandparents house in the old orchard between the house and the barn. At least...thats the plan. :)

I'm curious about what IBU's did you target to prevent Lacto from taking hold yet not hindering other bacterias that might be desired? Would 10ibu's be enough or is that too much?

The Mad Fermentationist (Mike) said...

With aged hops it is so difficult to talk about IBUs. The advantage of using well-oxidized hops is that they retain most of their anti-microbial properties, while losing much of their bitterness. If you are using "fresh" hops I'd say 15 IBUs would be a good target to avoid above-threshold bitterness while preventing Lacto from dropping the pH too quickly.

Jeremy said...

I tried a wild capture using your method on 11/18. About a qt of 1.030 15 ibu wort cooled overnight in my backyard. Within 4 days a thick krausen had formed, and it fell within 2 more. I checked the gravity and it hadn't moved. There was definite activity, and there was a layer of what yeast normally looks like at the bottom.

I felt a little discouraged, but is decided to just let it ride. Fast forward to 12/2 and activity started again. The krausen didn't get as thick this time, but it also hasn't fallen completely yet either. I'm gonna let it ride longer and see if the krausen completely falls before testing gravity again. Very exciting and interesting things going on.

The Mad Fermentationist (Mike) said...

There are waves of microbes involved, you may of had a homofermentative lactic acid bacteria at first that didn't produce CO2 (although a krausen usually indicates gas is being produced, which would lower the pH).

Jeremy said...

So I decanted it and refreshed it with more very lightly hopped 1.030 wort. It krausened like any other brew I've seen. Looked done after a couple weeks. I let it sit 3 , it measured 1.004, and a week later the same. I've washed it and have a mason jar of it sitting in the fridge. it smelled fairly fruity, slightly funky, and tasted pretty much the same. I'm really looking forward to brewing a truly local saison with it next week.

The Mad Fermentationist (Mike) said...

Excellent! Keep us in the loop on how the beers tastes. If it works out well, consider sending a sample over to Jeff at Bootleg Biology for his Local Yeast Project.

james hilden said...

Hello! I just tried you method on 1/5 when it was in the 40/50s here one night in Texas. I placed one tray out front and one out back near my citrus trees before moving them to the fermenters about 4am. I've done quite a bit of research before I tried it including your website and Jeff Sparrows Wild Brews, and I've been home brewing for about a year. One seems to have no activity and the other had a small krausen (a few mm) that is dying off after only a day and has a funky tart smell. I'm trying to decide if I should throw in some safale dry yeast just to get the get the complete fermentation (I haven't taken FG readings yet.) going to prevent any pathogens from gaining hold, as I've read they die after about 2%abv. Does that sound like a good idea?

The Mad Fermentationist (Mike) said...

The issue with the unwanted microbes is that they can leave behind biogenic amines, which a small percentage of people are allergic to. If they were going to do anything it's already done. A pH below 4.5 also inhibits entric bacteria from growing.

Unlike a pure brewer's yeast, a mixed fermentation should have waves of activity. While whatever microbes took over initially are slowing down, other microbes better suited to the current environment will take over. By Pitching US-05 now you may be out competing some of the other organisms in there.

To be safe, step the wild ferments up before tasting. That way the desired microbes will have a quicker start than this time.

Best of luck!

james hilden said...

Thanks man. Yeah. I'm not sure it's going to work. Smells pretty rancid. Haha.

Jeremy said...

I've had a ton of fun home brewing up to this point, but I can't explain how ecstatic I am with my recent experiment.

On 1/14 I brewed up 1 gal of Jamil's extract saison and pitched a couple tablespoons of slurry from my ambient capture. Today, not 10 days later, I'm getting a SG of 1.010 and a crazily fruity/"Belgian" ester tasting sample. I'm blown away by what truly locally captured yeast may produce. I'm going to let it ride until I'm sure the gravity is stable and then bottle. Looking forward to updating again.

Jeremy said...

I guess taking a sample introduced some oxygen because now a pellicle is forming. Who knows where it's going from here but I'll keep updating.

The Mad Fermentationist (Mike) said...

Glad to hear it is going well! Just be careful, it'll likely continue to dry out and change as other microbes take over (as the pellicle shows).

Jeremy said...

What I thought was a pellicle forming wasn't. I think I was just over zealous watching it and reported premature activity. I bottled it on 2/4 with the gravity still at 1.010, but the sample had lost nearly all the esters I was tasting last time. I opened one a week or so ago and it tasted pretty good, slightly peppery with some funk in the background. I brought some to my homebrew meeting tonight and it was very well received. I saved the yeast slurry from it and I am going to brew another 1 gal batch, then use that to pitch a big batch from.

Thanks a lot for the info found on here to start and for encouraging throughout!

Erin said...

Hey Mike!

I recently did this in Texas on a cool spring night. I put 4 small dixie cups filled with ~1.020 wort out around my backyard: 1 under the awning on porch, one between some flowerpots, one under a tree, and one out in the middle of the open. Brought them in the next morning and by the next day all had signs of life. After a few days 3 had a little blue mold on them that I scooped out. The wide open one smelled kinda gross and had a thick layer of clear slime on top, so I dumped it. The other three smelled different but all reasonably pleasant. Two are still in the dixie cup, but I stepped the porch one up in a 1500 mL 1.040 starter on a stir plate and let it go for three days while I left town. Before I stepped it up it smelled somewhat floral and bready, with a thin white krausen on top. After cold crashing the starter prior to pitching it in a test batch I'm in the process of brewing, I decanted off half the wort. I tasted it and to my surprise it has a really nice lactic sourness, no vinegar. Is that surprising given the copious oxygenation? Does that mean I have mostly lactobacillus in my culture? The test batch I'm brewing with half the culture is about 25 IBU, so I assume that will inhibt the bacteria and bring out the yeast. I'm wondering though should I use this wild capture for something like a Berliner Weiss if it had such a nice clean tartness that quickly?

I've been brewing about 18 months but new to the wild microbe scene :)

Thanks for all the great info

The Mad Fermentationist (Mike) said...

Sounds delicious (and not too surprising given Jester King's success)! If it is mostly Lactobacillus then that would be a good explanation of why oxygen didn't turn it acetic (Acetobacter and Brettanomyces are the two primary microbes capable of that). Would probably be good in a low bitterness-Berliner-type recipe. However, it's always tough to know what flavors will/won't appear as the mixed-culture ages. Good luck!

Erin said...

Well after brewing my 1 gallon test batch with just pilsen DME and 25 IBU worth of Super Galena, took a hydro sample today as my airlock had calmed down. OG was 1.042, down to 1.011 with great floculant yeast cake at the bottom of the jug. Will be interesting to see how much the gravity changes with time if there is any Brett in there. Not much tartness in this beer (likely the hops I guess, still plan to try the Berliner). Has an apple/pear ester aroma/flavor with a peppery finish that reminds me of Saison. Pretty happy so far! I roused the yeast and will give it some more time.

wmjaeger said...

I left out a hydrometer cylinder for testing the next day (I didn't have the hydrometer yet!) and found a beautiful 1/2 inch krausen on top. So I put a loose cork on it (equiv of a piece of foil) and it did it's thing for a day. Then I took the yeast at the bottom (not much) and mixed with some leftover wort and put in a jug with an airlock. It bubbled for 2 days and more yeast formed.
So...the question (if this is the right thread)...it this just random nonsense? Is the yeast growing there bound to be awful? The look of it, the lack of mold, and the timing of bubbling etc. all seemed right on for a good yeast.
Next step??
Thanks...a total newbie here, but totally fascinated!

The Mad Fermentationist (Mike) said...

Give it a smell! Just because a culture has good fermentation properties, doesn't mean it'll produce something worth drinking. If it passes there, test the ABV and pH. If it is over 2% ABV and under a pH of 4.5, you should be safe to try a sip.

From there you'll have to imagine what sorts of malt/hops it would go well with. Might be worth doing a starter with a slightly higher gravity to check the alcohol tolerance as well.

Good luck!

Stuart Fox said...

Sorry, I know this is an old thread, but I have a quick question. A lot of you guys are reporting krausen after a day or so, but some of the other reports I've seen say that saccharomyces doesn't show up until after about 2 weeks.

Has anyone compared a starter from 2 days of capture vs. a starter from 2 weeks of capture in the same place? Just curious to see if the time makes any difference in final gravity or flavor.

Thanks to everyone who contributed to this. Cheers.

The Mad Fermentationist (Mike) said...

It isn't that Saccharomyces doesn't arrive in the wort until two weeks, it just doesn't become dominant until that point (according to some studies of lambic fermentation). Saccharomyces isn't the only microbe capable of creating a krausen either.

Extended exposure to the atmosphere will favor aerobic microbes, which may not produce the best beer!

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