Saturday, April 14, 2007

"Forbidden Fruit" fermentations

As I alluded to in the last posting, I'm going to review the fermentations of our first two Belgian-style ales, Saison du Pelican and Grand Cru de Pelican. Both were fermented with the Wyeast strain 3463 "Forbidden Fruit," which is from the Hoegaarden brewery.
To make our Saison, we first did some trials in house with wort from our Kiwanda Cream Ale. We took an "Activator" packet of 3463 and pitched it into some Kiwanda wort siphoned from our knockout loop. The cooled wort was about 66 degrees and oxygenated to about 15 ppm of dissolved oxygen. We allowed the yeast to ferment at ambient temperatures, which was about 66 degrees on average.
Because it was December, the temperature in the brewery often dropped to the low sixties and even high fifties, so we periodically gave the whole Corny can an immersion in 100 degree water to warm it up and keep the yeast going. Even so, it did not attenuate to the same degree as our house ale yeast, Wyeast 1056. We figured this was simply due to insufficient temperature management with our primitive "pilot" fermenter, and didn't worry about the discrepancy in apparent degree of fermentation.
For the first few days of fermentation, we noticed little difference between the two worts as they fermented. The 3463 trial batch had a similar sensory profile initially, with a little slower fermentation overall and a bit more residual extract at every point that we tested along the way. For instance, on day five of the parallel fermentations, the main batch of Kiwanda Cream Ale had attenuated from 12.2 degrees Plato to 2.3 degrees Plato, while the "Forbidden Kiwanda" (as we began calling it) had attenuated from 12.2 degrees Plato to 3.3 degrees. The main batch of Kiwanda was already fully attenuated, and actually 1 day into the diacetyl rest, while the Forbidden Kiwanda did not fully attenuate until day nine. It never did reach the same finishing extract as the main batch of Kiwanda Cream Ale, ending at a measured apparent extract of 2.8 degrees Plato. Again, pitching rate and temperature management probably played a big role in this discrepancy.
From a sensory standpoint, however, we really started to notice some significant differences along about day six of the fermentation. Whereas the Kiwanda Cream Ale showed a floral and clean light fruity aroma with some diacetyl and hydrogen sulfide yet to dissipate, the Forbidden Kiwanda began developing more of an overtly fruity and tart aroma, with some mild phenol and spicy character. By day nine, the main batch of Kiwanda was clean on our diacetyl forcing tests, and there was only a slight amount of hydrogen sulfide left in the beer. The Forbidden Kiwanda on the other hand did not finish its fermentation until day 8 or 9, but threw a very large amount of hydrogen sulfide during the initial fermentaion which dissipated very quickly. The diacetyl was still evident upon forcing on day nine, but rather than worry about it, we re-primed the Kiwanda with some sterile sugar water and let it ferment one more time. It was not the most stylistically authentic way to go, but it had the benefit of naturally carbonating the beer and forcing the yeast to take up all of the diacetyl.
In the end, we were really pleased with the flavor development of the Forbidden Kiwanda, and decided to go ahead with 3463 for our Saison and Grand Cru beers.
We ordered a 2 liter starter for our first batch, which was the Saison du Pelican. Timing the yeast starter with our brew schedule, we pulled about 1.5 bbl of Kiwanda Cream Ale wort from a batch in process, and gave that 3 days to propagate. The Wyeast slurry density specification is 1.2 billion cells per milliliter, so when you multiply that by 2 liters, I calculate that we started with 2.4 trillion total cells. After a 3 day propagation and knocking out the main Saison wort, the measured cell count was 7.9 million cells per milliliter, and the total wort volume was 1960 liters, for a total cell count of 15.5 trillion cells, nearly three doublings of our initial yeast population. It was enough yeast to get a healthy start to our first generation fermentation.
The Saison was knocked out at 70 degrees F at 13.6 degrees Plato. Our plan was to allow the yeast to ferment uninhibited by temperature control and let it free rise as high as it would go. The following day it was up to 74 degrees and extract had dropped to 9.6 degrees Plato. The day after that it was at 80 degrees and extract was down to 6 degrees Plato. By day three, the temperature had peaked at 82 degrees and extract had fallen to 3 Plato. The attenuation limit for this beer was reached on day 5 at 1.9 degrees Plato. We gave the beer a 3 day diacetyl rest, forcing it clean two days in a row before gradually lowering the temperature in 10 degree increments starting on day 8. At this point our sensory notes from the fermentation report were "fruity, phenol, dry & snappy," just the kind of character we were looking for in the finished beer. By day 13 we had completely chilled the beer to 32 degrees and harvested a yeast crop to our next Belgian style Ale, the Grand Cru de Pelican.
The Grand Cru de Pelican was a big beer, with a starting extract of 21.8 degrees Plato. We intentionally pitched this beer heavy to make sure it would ferment properly, with a pitch rate of 26.7 million cells per milliliter. Yeast viability measured very high, at 98.5% viable, but the beer did not start any visible fermentation overnight. A cell count the following day showed that significant growth had occurred overnight; we measured nearly 40 million cells per milliliter. So we hooked up a sterilized tee assembly and oxygenated the tank for 35 minutes at 15 cubic feet per hour. Shortly thereafter, the yeast took off and began fermenting vigorously. The temperature rose from 72 degrees to 85 degrees and finally peaked at 94 degrees on day 3 of fermentation! It took a leap of faith to go to this extreme, but it seemed to work pretty well up to this point. By day 4 the temperature was dropping off, and fermentation had largely ceased. The beer was only 74% attenuated at this point, so this was quite a problem. We tried rousing the yeast and waiting patiently, but to no avail. 5 days went by without any change in measured extract, so we harvested some fresh 1056 yeast from a Doryman's Dark Ale fermentation and pitched that into the Grand Cru. Slowly, the 1056 began fermenting the last bit of fermentable extract from the Grand Cru, and over the next 6 days, the beer attenuated to 4.4 degrees Plato, or about 80%. this was a little short of the target we had set for attenuating this beer, but at this point we were very happy to have the beer finish at all.
Luckily, the flavor complexity that developed in the Grand Cru was really worth all the fussing around. Our tasting notes even at this early point in the process were "spicy, caramel, phenol, alcoholic, smooth, soft finish." Again, really hitting the flavor and aroma targets we had set for this beer.
So that's all for now on the first two fermentations. Yesterday we started the 3726 "Farmhouse" yeast and after some initial worry it appears to be propagating up very well today. We are on schedule to brew the first batch of "Heiferweizen" tomorrow. In my next posting I'll outline our propagation procedure and then the brewing of Heiferweizen.
Thanks for reading!
Brews To You!


1 comment:

matt dinges said...

Hey Darren,

This just got pointed out to me...I've got a split batch going...think something like Christoffel Blonde as the base half with Bohemian lager yeast, the other half with Forbidden Fruit. The FF threw a lot of sulphide for me in the first couple of days...really stank up my cellar! I had it pretty low in temp too...66*F I think.

Anyway, I'll be in Oregon from May 17-23...any chance I might be able to taste these beers at the pub?