Better attenuation from a multi-rest mash?

Just mash lower if you want better attenuation.

 

The better attenuation is likely from breaking down beta-glucans during the acid rest. Mashing lower will do at least as well though.

 

The published attenuation ranges for yeast strains are sometimes next to useless. There are many factors which affect attenuation. They are all related to the yeast (strain/count/health) or the wort (fermentability). From a practical standpoint, the most important ones (in no particular order) seem to be...
- Yeast strain
- Grain Bill
- Mash Temp(s)
- Mash Time
- Other fermentables/non-fermentables added

I suspect your acid rest and protein rest didn't affect attenuation very much. Those temp ranges are not ones where the amylases are very active. The acid rest would have affected pH, which can have a small effect (either good or bad) on fermentability. The protein rest may have affected mash efficiency (as opposed to fermentability per se) by breaking down Beta Glucans and keeping starches from getting locked up in gummy bricks. But this is not a big issue with malted barley.

 

Maybe not. Two experimenters have found that, at least under their lab conditions, that lower temp doesn't necessarily mean more attenuation. With single infusion mashes, Greg Doss found peak fermentability at 153F. Kai Troester found peak fermentability at 152F.

I can't explain why they got different results than the conventional wisdom. I speculate that the regional styles that were historically brewed with lower mash temps may have got higher attenuation for reasons other than mash temp (e.g. highly attenuative yeast strains, very attenuable grains, longer mash times).

 

With modern malts, the maltster has done a lot of work that the brewer had to do in the past. It seems like most modern malt , even German pils malt, is so highly modified that it's hard to reduce fermentability mashing just base malts, no matter how the mash is handled.

 

In the case of decoctions (4VG rest at 108F, main mash sacch rest at 148, mash out at 168, decoction sacch rests at 157, double decocts typically), my hefeweizens typically finish 4-5 pts lower than the non-decocted versions rested solely at 148 F (4VG rest done as well).

 

How long did it take you to get from your protein rest temp to your sach. rest temp? Maybe extended time in the extreme low end of the sach. rest temp range can account for increased fermentability?

 

Supposedly you can have conversion occur as low as the 130's, so I was well below that when I rested at 108 F. Its about 45-60 minutes to pull a decoction, bring up to sacch rest, hold for 10 minutes, bring up to boil, boil for 10-15 minutes then add back to the main mash.

One thing you do have me thinking about now is the length of time at 148F, which most likely wasn't constant between non-decocted and double decocted. For my single decoctions, its the same rest time at 148 F as non decocted, so given the increased attenuation from my single decoctions relative to non-decocted, and similar attenuation between double and single decoctions, my guess is that the increased fermentability is due to the rest at 157F during the decoction sacch rests.

 

Boiling the decoction ruptures cell walls and results in more complete conversion; total time available to convert is usually higher with a decoction mash too.

 

When I plug your recipe into Brewcipher (V2.0), and force the OG to 1.050, I get an FG prediction of 1.0096, less than 2 points away from 1.008. That's with my own system's power attenuation factor (0.984, i.e. the cosmological constant that works best for me).

 

Exactly. As an extreme example, I have gotten 87% apparent attenuation from WY1728 (advertised at 69-73%) with no adjuncts, just fermenting a little warm (not that warm, ~70F, the pale ale was fine).

edit: this was a low gravity beer, 1.032 OG, so that makes a big difference too.

 

I'd just adjust my crystal malt for starters; if this requires an unreasonable addition, wheat might be helpful, since it's slightly less fermentable. Trying a different type/brand of base malt might get you there too - they aren't identical, even within the pils, pale, etc. classification.

 

I have a little experience with an accidental multi-step mash when I doughed in and for whatever reason only had 148° in the tun. I pulled out a bit and threw it on the burner to heat to boiling (took about 15 minutes), and got it up to my intended 156°. That batch finished lower than intended (by about .005 points), and definitely lower than when I hit the target mash-in temperature on a previous batch of the same recipe the year before.

 

I sometimes will dry out a beer by doughing in cold and raising the temp slowly, stirring, to a typical beta-sacc rest temp. My quads (all > 1.090) finish quite dry (< 1.005).

 

You could only reach this conclusion if you knew more facts about this person's brewing technique.

The acid rest can play a huge factor in the beer if it is setting the ph of the mash into the correct range, which will improve conversion, and in turn setting pre-fermentation to the correct ph which will help encourage healthy fermentation. The protein rest will also help break down proteins in the oats, wheat and rye and convert them into more easier converted sugars, which will give the yeast a greater amount of sugars to consume than what one would typically get from a single infusion mash on those grains. Better fermentation conditions and more fermentable sugars greatly increases the probability of improved attenuation.

However, we don't know if the ph of the mash was checked or whether the brewer normally makes appropriate adjustments for ph. We also don't know pitching rate, oxygenation, water profile, or other factors that would affect attenuation.

 

I did mention that it may have influenced mash pH, which could have had a small effect on fermentability. Fermentability is not the same thing as efficiency, which is where pH would potentially have a more significant impact. pH impact on fermentability was shown by Kai to be small, within the bounds of reasonable pH ranges. Now if you're talking about going from some horrible pH to a good one, okay, but I don't think mattbk has those kinds of problems.

Proteins in the mash are not converted to sugars, 'easier converted' or otherwise.