Monday, November 4, 2013

Sour Experiment #1 - Two Week Sour

Lacto starters souring on top of the HLT to stay warm.One of the most annoying (and intimidating) aspects of brewing sour beers is how long they take to ferment. Sure there are shortcuts, like sour mashing, but rarely do the results approach the nuances of long-aged mixed-fermentation beers. One of the last things I did while I was at Modern Times in August was to taste the four versions of a beer I brewed with an experimental souring technique two weeks earlier.

Souring a beer before the alcoholic fermentation is a good idea, but a sour mash presents three major issues:

1. After souring the mash, it can be difficult to separate the wort from the spent grain.

2. Exposure to air during souring can lead to the growth of unwanted aerobic microbes that produce off-flavors.

3. Allowing the pH to drop too low can cause fermentation issues for most ale yeasts.

Wort souring in their water baths.To remedy problem #1, I dipped into my bag of tricks and pulled out the sour worting technique I used a few years ago. After a single-infusion mash, I collected the reddish wort and heated it in the kettle to near boiling to ensure any microbes from the grain were dead. With this method the wort is drained with a standard temperature and pH, so there are no issues lautering as usual.

To address problem #2, I ran the wort through the plate chiller (aiming for 115F), and into four plastic carboys, each of which had been flushed with carbon dioxide (back at home I miss the plumbed CO2 lines at the brewery). Flushed kegs would work equally well.

To achieve the acidity, I pitched one carboy each with a starter of Wyeast Lactobacillus, a starter made from the microbes living on pale malt, a starter from the microbes living on acid malt, and a small hop-sock of crushed acid malt. For the grain starters I followed a similar protocol to the one used for that previous sour worting batch. My goal was to determine which of these microbial sources produced the best results.

Transferring the soured wort off the grain bag.To maintain the temperature in Lactobacillus’s ideal range, I placed each carboy in one of the pilot system’s vessels, filled with 120F water. At the start and end of each day for three days I removed the carboys, reheated the water, and replaced them. I also insulated the rig with blankets to help maintain temperature. Usually they'd be down to about 100F by the time I reheated. I didn’t have room for the fourth (pale malt starter) so I left it under the blanket.

The results were surprising. After three days, the least sour of the bunch was the Wyeast Lacto, clean and pleasantly tart. The two grain-starters were next (despite the temperature difference), they were still clean, but a bit more lactic. The grain bag was the most acidic, but also had a slightly stranger aroma that was more in line with what I expect from a sour mash but luckily not as cheesy or intense. With acid production complete (pH 3.4-3.5), I boiled each in turn with a small dose of hops and yeast nutrient. During each boil I cleaned and sanitized the fermentor, refilling it with 68F wort post-boil.

Heating the soured wort.To resolve problem #3, rather than fermenting with pH sensitive Saccharomyces, I opted for a 100% Brett fermentation with the BSI Brett Drie we had on hand for production brews of Neverwhere, Roraima, and Southern Lands. Brett works quickly at a pH as low as 3, and produces interesting flavors too.

The four versions, the color difference is all the microbes and fermentation.My last day working in San Diego I racked each of them to a Corny keg, and shook in carbonation. The pale malt starter and the steeped acid malt were my favorites. Each had a nice acidity with a pleasant Brett character. I had skipped boiling the Wyeast Lacto portion and the result was a subtle raw graininess similar to what I taste in my no-boil Berliner weisses. The acid malt starter had an unpleasant aroma not present before the Brett fermentation, just sort of rough. With that interesting range of characters, we decided to blend the three we liked to make 15 gallons of beer to serve at the Tasting Room Grand Opening.

Reviews were mostly positive on Untappd, "I'm not one for sour beets, but this is fantastic! Tickles the taste buds in the back of your mouth in just the right way." - Stephanie P. "Had it 3 times so far might get another" - Heather H. Both included pictures of the finished beer as well, something I never got to see for myself!

I had a beer at GABF from TRiNiTY Brewing (7 Day Sour) that used a similar technique, but fermented with a mixture of Brett strains post-kettle-souring. The result was terrifically funky, and brightly acidic. I think I’ll have to try something similar, integrating a strain like Brett Drie/Trois which ferments quickly, with others that produce more classic Brett aromatics.


Unknown said...

Was looking forward to this! Thanks for the write-up. Out of curiosity, you mentioned that the steeped acid grains provided the most amount of tartness, how confident are you that it was the overall process and not the variable amount of bugs on those specific acid grains used? It sounds like this could provide wildly different results every time, all based on how potent the individual grains used are. Also, do you think the acidified grains played a significant part, or could anyone happen to just switch out acid grains for something else?

likehumansdo said...

Wow, cool! How did you extract/cultivate the bugs from the pale and acid malts?

Anonymous said...

Maybe its because I just tried it out, but I see this technique everywhere now. I'm glad to see its gaining traction, as its an easy way for homebrewers to play around with a very interesting set of styles without fear of contaminating their equipment.

I posted a write-up of my first experience with the sour mashing technique over at my Life Fermented blog recently:

The Mad Fermentationist (Mike) said...

Variability is certainly the biggest disadvantage of using wild microbes from grain, with or without a starter. Any grain should work as the pale and acid malts did similar in the starters. Not sure if when the lactic acid is sprayed onto the malt whether or not any lice Lacto come along for the ride.

To make the starters I used a process very similar to the one I employed for my Quick Oud Bruin.

Sour mashes have been around for years, I think this technique (souring the wort) is much better.

D. W. McClain said...

I soured a wort a few months ago for a sour imperial porter. I used Papazian's method, which is, I think, a hybrid of souring the mash and souring the wort. Basically, since I was doing a partial, I mashed, soured that wort, and then added DME on boil day. But I think I'd prefer your approach of a sour starter. Theoretically, you could keep a sour starter on hand... no?

D. W. McClain said...

So, just to be clear, you preferred the grain sock directly added to the wort, to the starter made from acid malt?

D-Form said...

I've been reading your blog for too long. I just sour worted a batch of Berliner Weiss but had a slightly different procedure. Mine was inspired by the sous vide cooking method. I put all of the wort and a handful of grain in a big ziploc like bag, purged with CO2 and then squeezed all the air out. Put the bag in a water bath that stayed between 107 and 115 for three days.

It was very sour and had a super clean aroma with no off aromas.

It's fermenting right now with Safale 05. I also added a handful of acid malt at the end of the mash.

I do BIAB for my test batches and sour mashing would be easy with this method. Just dump the bag into your kettle lined with your BIAB and you're good to go.

The Mad Fermentationist (Mike) said...

I actually liked the cleaner character of the starter, although it wasn't quite as sour as I would have liked (thus the blending).

D-Form, sounds like an interesting technique unless you happen to get a heterofermentative strain of Lacto that produces CO2, then it sounds like a big mess!

D-Form said...

I've completed a few more sour worts since my last comment and finally had one that was heterofermentative. Luckily a mess wasn't created but I had to empty the bag of CO2 twice a day. It was 2.5 gallons of wort in a 10 gallon bag.

Working on a new one now and going to try pitching a Brett strain after a short boil. Did you just ferment like a regular ale (with Brett) then keg without any extra aging?

The Mad Fermentationist (Mike) said...

100% Brett beers tend to take a little longer than ales to ferment out and clear. Just make sure you are pitching enough Brett (lager-sized starter is safest).

Mr Gadget said...

Very interesting and informative article Mike. Thanks for posting. I have a quick question regarding sour worting that I cannot find the answer to. I want to brew a sour with an OG of around 59. How much will the Lacto lower the OG when souring? Thanks for your time Bryan. Cheers from the UK

PS. Your American Sour Ale book is fantastic! Great work!

The Mad Fermentationist (Mike) said...

Pure Lacto shouldn't lower the gravity by more than a few points. This is something I got wrong in American Sour Beers, check out this study. The issue is that there is a history of lab cultures containing some yeast...

Unknown said...

I'm trying to come close to a flander's red sour by using a quick kettle sour technique. After letting the lacto work, boiling, and transferring to the primary fermenter, I have an ale yeast (S-05) or a Brett Lambicus (WLP653) to use. I like the profile of Brett L, but read it takes several months to acheive the full flavor (kind of defeats the purpose of the quick kettle sour). I'm torn between using an ale to attenuate down to my FG in a week or so, or add some complexity with the Brett. Do you think the Brett will be able to do its thing in less than 1 month? Also, should I keep my temps @ 85 F during primary fermentation. I saw WLP653 lists this as the optimum temp. Sidenote: I'm going to attempt this quick one to have for now, and then make a batch the traditional way and let it age for a year or so.

The Mad Fermentationist (Mike) said...

If you make a big starter of Brett lambicus, you should be able to get the beer to terminal by 3-5 weeks. Never done primary fermentation with WLP653, but I would be reluctant to push any Brett strain that warm the first time. 70F and then warming into the mid-70s could certainly be a safer option. Best of luck!

Unknown said...

I thought 85 seemed high, but everything I read about WLP653 lists that as its optimum temp. It's been fermenting for five days, and the activity in the carboy seems to have halted. I took a gravity reading and it has only reached 1040 (OG was 1060). It doesn't quite have that cherry pie aroma/flavor that the starter had. I'm assuming it's because it's still very early in the fermentation. Even though the fermentation appears to have stopped (not much bubbling through the airlock, low floc inside fermenter), do you think its possible for this pitch to still get the OG down towards 1010?

The Mad Fermentationist (Mike) said...

Chad Yakobson only achieved ~50% apparent attenuation with WLP653 in his master's dissertation, so you might not get as low as you are hoping. Keep it warm and hopefully it continues to work!