Phenols and Brett - The Fruity and The Funky
The science underpinning brewing can be a fascinating subject. However, rather than focusing on practical applications, academic brewing experiments are often stripped down (e.g., an isolated enzyme applied to a specific substrate molecule). This can yield interesting results and demonstrate specific cause and effect relationships, but may not provide a definitive answer on what occurs in real-brewery conditions. While lacking the process control and analytic tools of a laboratory, homebrewers have managed to produce some very interesting experiments (e.g., Brulosophy, BBR&BYO).
One of the topics covered during my NHC presentation, and the accompanying Zymurgy article, was the effect of phenols in the wort on funky-phenolics produced by Brett. I haven't seen or read evidence that "stress" or additional sugars cause Brett to produce more of its signature funky character. Additional fermentation of wort sugars results in more esters, which explains why 100% Brett beers tend to be fruitier compared to funkier mixed-fermentations. When I was asked to give a presentation at the Mid-Atlantic MBAA meeting November 7th, I decided to brew an experiment to serve to confirm(?) that phenols in the base beer are one difference (along with strain selection and pressure).
I brewed two nearly-identical worts with the same malts, and saccharification rest temperatures. The two deviations I made were starting one of the mashes with a ferulic acid rest (15 minutes at 113F) and changing from phosphoric to lactic acid for pH adjustment. The addition of lactic acid will allow the production of fruity ethyl lactate. There has been debate over the effectiveness of the ferulic acid rest, a traditional start to a hefeweizen mash, but in Brewing with Wheat Stan cites a study that found adding a rest for 10-15 minutes doubles the perception of clove (4 vinyl-guaiacol) in the finished hefeweizen. This would only be the case when fermentation is carried out by a brewer's yeast that is capable of this conversion (aka POF+). So I pitched the high-ferulic-acid wort with Belgian Ale (WLP550). To really highlight the difference, I fermented the single-infusion wort with English Ale (WLP002) to minimize phenol production.
Tasting both batches after primary fermentation revealed the pre-conditions of the test had been met; the batch fermented with Belgian yeast smelled distinctly of cloves, while the English ale lacked any spice. Surprisingly the two batches hit the same pre-Brett final gravity as well. Into each batch I pitched half of a starter of Brettanomyces bruxellensis (WLP650). Now I'm waiting for the science to happen, the conversion of 4VG to funky 4 ethyl-guiacol by the Brett!
Tasting notes for both batches at 4 months.
Post-script (4/13/2015): I sat down to do an updated tasting, only to find that the beers hadn't changed much. The Funky beer still was more Belgian-y than funky, and the fruity beer was still more clove-y than anything else. They'd rounded out, but the changes were subtle enough that they didn't warrant writing up full tasting notes again.
Influence of the Mash (Fruity)
Recipe Specifics
----------------
Batch Size (Gal): 5.25
Total Grain (Lbs): 11.00
Anticipated OG: 1.055
Anticipated SRM: 3.7
Anticipated IBU: 37.4
Brewhouse Efficiency: 73 %
Wort Boil Time: 60 Minutes
Grain
-------
90.9% - 10.00 lbs. American Pale Malt
9.1% - 1.00 lbs. Flaked Soft White Wheat
Hops
------
1.00 oz. Horizon (Pellet, 10.50% AA) @ 45 min.
Extras
-------
0.50 Whirlfloc @ 15 min.
0.50 tsp Yeast Nutrient @ 15 min.
Yeast
------
White Labs WLP002 English Ale
Water Profile
----------------
Profile: Washington, DC
Mash Schedule
-----------------
Sacch Rest - 75 min @ 148F
Notes
-------
Brewed 7/6/14 by myself
Add 1/4 tsp of 88% lactic acid to mash along with 2 g of CaCl.
Acidified batch sparge with 1/4 tsp of lactic acid.
Chilled to 85F, racked leave most of the break behind. Left at 65F to chill before pitching. Slow, smooth fermentation.
7/20/14 Down to 1.012. Racked to secondary with 200 ml of Brett brux (WLP650). Left at 65 F to ferment.
9/28/14 Kegged with 3.25 oz of table sugar. Purged head space, left at ambient temp to carbonate for about a month.
Influence of the Mash (Funky)
Recipe Specifics
----------------
Batch Size (Gal): 5.25
Total Grain (Lbs): 11.00
Anticipated OG: 1.055
Anticipated SRM: 3.7
Anticipated IBU: 37.4
Brewhouse Efficiency: 73 %
Wort Boil Time: 60 Minutes
Grain
-------
90.9% - 10.00 lbs. American Pale Malt
9.1% - 1.00 lbs. Flaked Soft White Wheat
Hops
------
1.00 oz. Horizon (Pellet, 10.50% AA) @ 45 min.
Extras
-------
0.50 Whirlfloc @ 15 min.
0.50 tsp Yeast Nutrient @ 15 min.
Yeast
------
White Labs WLP550 Belgian Ale
Water Profile
----------------
Profile: Washington, DC
Mash Schedule
-----------------
Ferulic Acid - 15 min @ 113F
Sacch Rest - 60 min @ 148F
Notes
-------
Brewed 7/6/14 by myself
No water adjustments for ferulic acid rest (works better at slightly elevated pH).
Added 3/4 tsp of 10% phosphoric acid and 2 g of CaCl to the mash at start of saccharification.
Added 3/4 tsp of 10% phosphoric acid to batch sparge water.
Collected 6.75 gallons of 1.042 runnings.
Chilled to 80 F. Racked to a carboy, leave much of the trub behind. Left at 65F to chill before pitching yeast. Explosive fermentation within a day.
7/20/14 racked to secondary with 200 ml of active Brett B (White Labs) starter. Down to 1.012. Left at 65F to ferment.
9/28/14 Kegged with 3.25 oz of table sugar. Purged head space, left at ambient temp to carbonate for about a month.
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7 comments:
Interesting read. Precursors fascinate me, and this post illustrates that I should also contemplate brewing salts and acids when aiming for something specific. Not only the actual pH but also the acid used to achieve it, in other words.
Thanks a lot!
I also had similar theory that isoamyl acetate might lead to more funkiness.
I added Brett Bruxellis to a beer fermented with Wyeast 1214 which had a lot of banana character, but after secondary that had been completely replaced by classic brett funk.
Thoughts?
This post has inspired me to see what Brett Bruxellis into a hefeweizen might lead to flavour wise.
I can't think of a scientific explanation for why isoamyl acetate in the young beer would produce a funkier result after the Brett was finished. Brett is capable of hydrolyzing the banana ester, but that would simply result in a reduction in that flavor (which sounds like what you observed). Jolly Pumpkin Weizen Bam is a great example of what funk can do for a hefeweizen!
Hey Mike, that was a really interesting read. I've been trying to make a lot of funky beers lately and this will really help.
One question though, will using Acidulated malt instead of lactic acid to adjust PH achieve the same result?
I'm really excited for the results of this experiment. I'm thinking of doing something similar but with butyric acid included in one batch - I made some rather pukey butyric berliner weisses early in the summer, pitched some Brett into each and they're now extremely fruity - peach, banana, apricot, and so on.
Does this mean you could potentially make a quicker funky beer by pitching saccharomyces mid-way through an all-brett fermentation?
It depends on the strain and the relative attenuation profiles. Oxbow does some great beers pitching a highly attenuative ale strain to finish up fermentation when the Brett slows down. If your goal is funk though, I think the earlier you get the brewers yeast into the beer the better.
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