Wyeast 3787 High Attenuation

[gERgMan]

I just racked my Rochefort 8 clone to a secondary this weekend. It had been in the primary for 2 weeks. The OG was 1.072, which is a little inaccurate since I forgot to measure the OG before I pitched a 2L starter of the Wyeast 3787 that had been growing for two days (OG of starter was 1.080 in order to match the OG of the batch, so there was some alcohol added to the 5 gal. batch of beer). Upon racking to the secondary, I measured the SG at 73F and it was a 1.004!! This is the lowest I have ever seen an SG, and my attentuation would be 94%!

I know Wyeast 3787 has a higher attenuation than most ale yeast, and the fermentation temp was 75F for most of the time in the primary. Has anybody seen an attenuation this high with belgian style ales? I am planning on repitching yeast later this week and then bottling this weekend as I see no more fermentation happening.

 

[cweston]

Was there a lot of candi sugar (or similar sugar) in the recipe?

That sugar will attenuate virtually 100%. This is one reason many Belgian recipe have a very high ABV--high OG plus very high attenuation.

 

[Bugeaterbrewing]

I will echo the above about the sugar being the likely culprit. I am a little concerned about the high fermentation temperature. In a beer with such a high OG, your wort temperature will be as high as 8-10° above the ambient temperature. Many belgian yeasts and beers will come out great with fermentation that high IF fermentation starts out cool (65-68&#176 and the wort temperature is allowed to gradually rise to the higher temps after the most active part of fermentation is done (first 48 hours). If you started out with the wort at 75° and did not control the fermentation temps, the wort could have quickly jumped to as high as 85° and stayed there for a couple days. This type of rapid rise is conducive to creating massive amounts of fusel alcohols. These tend to cause equally massive headaches.

If you check out the brewing techniques outlined in Wild Brews or in Brew Like a Monk you will see that cool starts and gradual temperature rises are the norm for most belgian brews. This extremely active fermentation will also contribute to the extremely low FG as would a low mash temperature (148-150) and/or extended mash (90 minutes or more).

Wayne
Bugeater Brewing Company

 

[gERgMan]

So, yes there was about 1.5 lbs of Candi sugar in this batch. So that may explain the highly fermentable sugars present, and thus the low FG. Thanks for the thoughts on this.

In terms of the fermentation temp, I am a little concerned now. I hope I didn't affect the flavor that much by doing this fermentation at such a high temp. Does it matter if the temperature I quoted was the temp off of the pail thermometer (you know, those sticker-like thermometers that adhere to the pail) and not the room/ambient temp? According to that, it was at 72-75F. After a couple of days, I wrapped a blanket around it when I noticed the pail thermometer dipping to 68F. I stuck a real thermometer between the pail and the blanket and watched that temperature everyday. It seemed to hold around 72-72F, just like the pail thermometer.

I do know that the fermentation temp started out higher than what you were describing in terms of starting low and creeping up. It was a big starter and fermentation was real active, real quick. I imagine this helped with the low FG as well.

How much do fusel alcohols contribute to off-taste? I am not worried about the headaches from drinking this brew if there are a lot of fusel alcohols since this is a big, special brew, beer that I won't be hammering a bunch of in a single sitting. I sure hope this tastes good.....

 

[cweston]

I think it'll be fine--72-75 wort temp during active fermentation is really not egregiously high for the style. Obviously this beer is going to be a little more watery than you'd like, but I think the taste will be fine.

 

[gERgMan]

I am not sure how accurate those pail thermometers are, I imagine the temp in the center of the fermenting wort is higher than what the sticky pail thermometer is reading. I hope that it is not too much higher. I tasted it after transferring and it had a very good taste. It was a little "watery", but I actually liked it that way a little since some of these "big" brews can get to be a bit too thick and viscous. I suppose that is how they are suppose to be though.

So let me ask this question. Most big beers recommend adding another dose of yeast a few days before bottling to ensure complete fermentation and to improve bottle conditioning. Given that I have a near-complete fermentation, does this seem like a thing I should forgo? Will this brew still carbonate appropriately if I don't repitch some yeast?

 

[cweston]

So let me ask this question. Most big beers recommend adding another dose of yeast a few days before bottling to ensure complete fermentation and to improve bottle conditioning. Given that I have a near-complete fermentation, does this seem like a thing I should forgo? Will this brew still carbonate appropriately if I don't repitch some yeast?

Dunno. I don't think having a complete fermentation is really the issue--the issue is whether or not there are enough living yeast cells in suspension after a long bulk aging to ensure good carbonation. It's particularly an issue with Belgian styles becuase they are typically well-carbonated. I have a tripel that's been in secondary for about 4 weeks. I'm not sure when I'll bottle it, and I haven't decided whether I'll add any yeast or not.