Wednesday, April 24, 2013

On Failure (3/26/13)

When you write about your own projects, there's always a temptation to emphasize your successes and avoid talking about the mishaps. However, I think that we experimentalists have an obligation to document failures as well as successes.

One of the most spectacular failures of my brewing career occurred with this last attempt at a Berliner Weisse. I performed the same souring technique that I used in my previous, highly successful, batch of Berliner Weisse: Mash and boil normally, then leave the beer at 95F—after adding lactobacillus but before adding yeast—for a few days. I knew something was wrong within 24 hours of souring. Instead of the cabbagey aroma of dimethyl sulfide that I expected, the beer smelled like parmesan cheese. After three days, I tasted very little acidity, so I let it go for another 24 hours. At this point it had some acidity, but it was a back-of-the-throat, acetic acidity, not the clean lactic acid I was hoping for.

The next surprise came when I measured the gravity after souring: 1.005. The beer had already fermented! The lactobacillus should have produced enough acid to deter any other fermentative organisms, but apparently did not. Nevertheless, I boiled the beer for 60 minutes and added a packet of yeast. The beer still smelled strongly of cheese after boiling and fermenting. Not even close to drinkable. I dumped the entire batch and threw out the bucket I fermented it in. This marks the first time I've dumped a batch before bottling.

My theory is that the lactobacillus culture I bought was not viable and hence did not produce enough acidity to protect the wort from the trace amounts of wild yeast and bacteria that managed to infiltrate the covering of plastic wrap and tape that I placed over the kettle during souring. In the future I will make a starter with the lactobacillus to hasten souring and ensure that the bacteria is alive before adding it to a full batch of beer.

Update: Thanks to Greg Noonan's excellent, though technical, book, New Brewing Lager Beer, I now believe that my main problem in this batch was a Gram-negative bacteria known as Clostridium butyricum, which produces butyric acid—a major component of the aroma of Parmesan cheese. In order to protect against these bacteria in the future, I will sour my beers at a higher temperature—say 115 - 120F—because clostridium bacteria are inactive above 112F, while lactobacillus delbruckii is active up to 131F.


Gravity before souring: 1.032
Gravity after souring: 1.005

Mash adjustments: 5.5 grams Calcium Chloride
Sparge adjustments: 1 drop 88% lactic acid
Mash in: 153F
Mash length: 60
Efficiency: 63%

Yeast: US05
Bacteria: Lactobacillus delbruckii (White Labs)
Pitching temp: 65F

Malts Mashed Amount % Max Pts.
2 row 6.5 90% 36.00
Barley (flaked) 0.75 10% 32.00
Hops/Additions Amount Time AA%
Magnum 0.25 60 14.0%

3/29/13: More cheesy than cabbagey aroma during souring this time. Souring has progressed more slowly, although identical inoculation rates and souring temperatures were used. The lack of pilsner malt would explain the lower levels of DMS this time.

3/30/13: 96 hours in. No krausen has formed this time, however, the beer seems to have fermented.  Boiled and pitched US05.

Even after a 60 minute boil and a few weeks of fermentation with yeast, the beer retained a strong parmesan cheese aroma which is quite unpleasant.

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