HELP: WLP540 Abbey IV Attenuation

On 09/05, I brewed a Rochefort 8 - mashed at 149F, with an OG 1.087, aerated with O2, pitched with a 3L starter of WLP540 Abbey IV, and fermented at 71-72F. Beersmith estimated this to land somewhere near 1.010.

Exactly a month later, it is at 1.023 despite rousing the yeast, bumping to 74F, and adding leftover yeast from the 3L starter.

Beersmith calculates 1.087 > 1.023 as 71.9% apparent attenuation. White labs states 74-82% attenuation.

At this point, it is a bit too sweet, and I don’t know what else to do to bring it down.

Should I perhaps bring it up a few more degrees and rouse the yeast again? If yes, how high should I go at this point? Ambient house temperature is approximately 78 F.

Yeah, I would. No major worries with the temp now  - the first several days would’ve determined the flavor profile. Give it a gentle rouse and warm up near 80F for several more days. I hope it helps. Let us know !

EDIT  -  Also, did you use a hydrometer or refractometer to measure FG ?  Using a refractometer for FG requires a correction to account for the alcohol present. Just wondering, in case you got a bad reading.

I use a Thermapen thermometer for the mash and testing with two hydrometers. Both read exactly the same.

Did you provide the wort with proper aeration when pitching your yeast?  Was your grain bill heavy on specialty malts that might reduce attenuation?

Aerated with 02 for about a minute. Specialty malts were low, primarily 2-row. I did use 2 # of Candi Syrup’s D180 at the end of the boil.

I have since re-roused the yeast and moved the thermostat to 78F.

I would be ecstatic if it dropped another 10 points.

Given your recipe and process I would think it’ll drop some more points. I’ll be curious to see how you come out. Good luck !

How’s this going?

I have a Holtrop-ish Rochefort 8 on the go too, 21 liters OG 1.079, with the WLP 540 (700ml stepped to 3.5L starter) which is at 1.016 after 2.5 weeks, sat at 76F (pitched at 63) having been roused several times.  It looks to be going no lower, so about 80%AA.  My adaptations led to 15% sugar in total and the mash was 2.5hrs at 147, with a brief mash out to follow.

Going by Stan Hieronymous’ figures for OG and attenuation, it looks like the real thing finishes around 1.008/9.  I wish I could get it down there.  Tastes great, but a 1.016 body with 3.5vols plus of CO2 will be a pretty full mouth feel.  I guess I’ve just got to mash even lower next time.

with 15% sugar and a 147 mash temp you should be able to get 1.079 down to 1.008 without a problem.

starter size sounds sufficient too. If you mash too much lower you’ll drop out the bottom of the alpha range and won’t get as fermentable a wort because the alpha amylase won’t be breaking the longer chain sugars to allow the beta amylase to nip off the ends.

+1 to Jonathan’s comments. I wouldn’t mash lower than that. Are you measuring your FG by hydrometer or refractometer? If hydrometer, is it reading accurately ? If refractometer, did you do a correction for the abv present ? I agree that if you roused and it’s been @ 76F that it’s probably done.

If Beersmith is telling you that 1.087 to 1.023 is 71.9% apparent attenuation, then there is a bug in Brad’s software.

AA = (O.G. - F.G.) / (O.G. - 1) x 100 (multiplying by 100 yields AA as a percentage value instead of as a fraction)

AA = (1.087 - 1.023) / (1.087 - 1) x 100 = 73.6%  (which is the lower end of the given range for the strain)

Here’s a clear cut example of why it is important for all brewers to learn basic brewing mathematics before using brewing software.

In limited experience, I’ve also seen “underattenuation” (at least in terms of what Rochefort gets) with the first generation of this yeast.  Doing a 6 → 8 → 10 clone series repitching from one to the next resulted in much better attenuation.

Was it a single-step or a two-step starter? What was your starter gravity?

A lot of brewers make the mistake of brewing a big beer with yeast grown in 1.040 gravity wort.  Pitching a culture grown in 1.040 wort into 1.087 wort seriously stresses the yeast cells.  A better approach is to pitch the vial into 1L of 1.030 gravity wort, wait twelve to eighteen hours, chill and decant the supernatant (a.k.a the clear liquid that lies above the slurry), and then pitch the slurry into 3 liters of 1.060 wort.  Using this process, we are also increasing osmotic pressure with each step.

This makes sense.  With WLP 530, I’ve had tripels drop as far as 1.085 to 1.009 with 13% sugar (I’ve never harvested and repitched yet) and a 150F mash.  Looking around, 540 seems like a very different animal.

Not sure if it’s a consideration for the OP too, but I’m considering krausening-in some US-05.

There are no hard and fast rules, but I would say that in most cases the mistake is making a high gravity starter.

The starter was well within the ratio of growth (4X at most). The gravity was low, the way every yeast lab propagates yeast.  The idea is that you can pitch the correct number of cells, grown in ideal conditions (LOW GRAVITY WORT).

Whether or not this is always true is another deal.  540 is one of the few where I’ve had any problem at all with starter grown yeast.  However, I would never encourage someone to make high gravity starters.  But obviously certain yeasts benefit more than others from growing in brewing conditions.

I always wait to pitch my candy sugar until at least high krausen for this reason.  Not based on science at all, just based on general observation…don’t give the yeast the dessert until they pretty much are finished with dinner.  I may have just been a lucky SOB, but I get almost all Belgians to finish well into the upper range attenuation stated for the yeast.

1.087 is not that big, in my estimation.  There is no reason this shouldn’t attenuate further.

I’d go with a decent sized starter pitched when the yeast is active.

From the Alcohol and Attenuation Tool in BS 2.1.

I’m not disagreeing, as my own experience with pitching slurries from 1.060ish beers has been quite successful, but I am curious what the biology is behind this. Is there a mechanism that the yeast has to acclimate to higher osmotic pressures?

I think the key here is the recommendation to pitch at 12-18 hours, and not after the starter has fermented to completion. I think the alcohol content in the starter is probably the biggest detriment to yeast health. By pitching earlier in the process you will avoid some of that alcohol.

Kai ran an experiment a few years ago comparing yeast growth (per gram of extract) vs starter gravity. He saw virtually no difference between a 5,7 or 10 Plato starter wort on yeast growth, and they were all at nearly 100% viability. A 20 Plato wort did see a 33% lower growth rate and was about 90% viable. He attributed the lower viability to the alcohol content. It’s unclear where the break point is between 10 and 20 Plato where yeast growth and viability start to tail off in a starter, but even at 20 Plato the results weren’t disastrous. It stands to reason that a 1.060 starter isn’t going to be horrendously detrimental to yeast health.

http://braukaiser.com/blog/blog/2013/05/28/starter-wort-gravity-and-yeast-growth/

Is this advice to try to get the FG down a bit? I’m going to do the same later today with my own, ‘stuck’ at 1.016.  Guessing I will have to stick to a 1L starter (using US-05) to keep to the general rule of keeping it below 5% of the 21L batch, seeing it won’t be decanted.  Not sure whether to use 1 sachet or two, though will assume I should stick to 1.040 wort.

I must have been lucky with 540/WY1762. It’s my go to strain for dubbel and quad and I’ve used it many times, finishing 1.010ish (occasionally below) on first pitch. But I mash low, usually 149F for dubbel and 148F for quad, 15%+ sugar/syrup, plenty of yeast, nutrient, and oxygenation.

EDIT  -  I will add though that I’ve only used WY1762, never WLP540. So I don’t know if there are any subtle differences in performance associated there.