Raising Yeast Attenuation with Step Mashing?

[mediant]

There's a recipes section at Castle Malting website, many of which are using low-attenuating yeast such as T-58, S-33, which struggle with maltotriose sugar.

I just recently realized that there are quite a few unusual things about these recipes.

Take for instance their Leffe Blond clone recipe.
Apart from unusually high fermentation temperature, apparent attenuation seems to be approaching 90%, which is way higher for an all-grain beer fermented with T-58 than manufacturer's specified 70%. This is pretty much consistent across most of their recipes, so it's not a typo.

The key seems to be the step mashing program they employ, specifically a 80-minute rest at 63C (145F).

My understanding is rest that long at this temperature favors both limit-dextrinase and B-amylase action, which results in wort with less maltotriose content.

Quoting from "Brewing" by Michael J. Lewis, Tom W. Young:

13.5.1 Fermentable sugars
Fermentable sugars dominate the composition of malt wort. The maxi-
mum fermentability of wort that can be produced by malt enzymes in
conventional mashing is 75-78%. This is mostly made up of maltose and
maltotriose which are the result of a- and B-amylase acting together.
Interestingly, if a-amylase action is favored during mashing (e.g. at rela-
tively high mash temperature) maltotriose forms a higher proportion of
the fermentable sugar fraction than if B-amylase action is favored. The
reason is that maltotriose arises from B-amylase action on odd-numbered
linear dextrins. Favoring a-amylase action produces more such dextrins
for B-amylase action. This is important if a brewer’s yeast has some diffi-
culty handling maltotriose.

So the question is - can long step mash rests at low temperatures really have such dramatic effect on yeast attenuation? Is it really possible to raise the yeast attenuation by almost 20% above the specification, or is it just a misunderstanding?

 

[RPh_Guy]

Sounds like you've answered your own questions already

The listed attenuations by yeast producers are on a reference wort, so that we can compare strains "apples to apples" so to speak.

You can throw these listed attenuation values out the window if you make a highly fermentable wort or a less fermentable wort.

Hope this helps

 

[divrack]

yes, basically. the key is a long rest at beta (I always mix them up) 144ish and hot ferment will give you a very much higher attenuation. adding nutrients and o2 obviously helps also.
I don't think any of the other 'steps' are actually necessary though and I imagine you could have a shorter mash too.
Belgian yeasts can be funny, stalling out early if not happy, but eating and eating if treated right, specifically ramping up the temperature towards the end.

 

[brewbama]

Yes, attenuation is affected by the mash schedule. For example according to Kai Troester, in the Hochkurz mash schedule “the maltose rest should be held at or around 63C (145F) and it’s length is used to control the fermentability of the wort (aka potential yeast attenuation). A good starting point for its duration is 30 min. Longer for more fermentable wort and shorter for less fermentable wort. If even higher fermentability is desired an intermediate rest at 65C (150F) can be added. The lower the temperature (within a given range of course) the longer the beta-amylase will be able to work and produce maltose.

The dextrinization rest at 70-72C (158-162F) needs to be held until the mash is iodine negative but may be extended to 45-60 min. Many authors contribute head retention and mouthfeel benefits to extending this rest.

Finally the mash may be raised to mash out temp and subsequently lautered.”

http://braukaiser.com/wiki/index.php/Infusion_Mashing

However, this is a double edge sword: it depends on whether you are aiming for a style appropriate dryer crisp beer or not. A malty beer might use 45 min at the maltose rest and 15 min (or longer) at dextrinization to create more ‘mouthfeel’. Yeast choice can affect ‘mouthfeel’ as well: English strains tend to quit sooner leaving a more full beer (and they don’t process maltotriose well). And higher attention could mean lowering SG by diluting or using less fermentables if you want to hit a certain ABV.

http://www.********************/wp-content/uploads/2017/04/pkjdf.pdf

http://www.********************/wp-content/uploads/2017/04/pddvxvf.pdf

http://braukaiser.com/wiki/index.php/Braukaiser.com

 

[thehaze]

T-58, although Fermentis states 70% attenuation, I never got under 75% attenuation with this yeast. Highest attenuation was around 81%, I think. All recipes brewed with T-58 were mashed low and long and I always had sugar in the boil.

S-33 is stubborn. I never got over 68% attenuation.

Regarding mashing low and long: it will yield a more fermentable wort. I recommend at least 90 minutes at 145-147F.

 

[mediant]

Big thanks to everyone for their replies.

I think I wasn't focused enough with my question. It goes without saying that there are many ways to influence yeast attenuation in general via mashing programs, which usually affects fermentability via wort dextrin content.

The specific aspect that interested me was the possibility to raise the attenuation of yeasts that do not digest maltotriose well in all-malt wort, without the need to resort to adding simple sugars or adjuncts. T-58, wine yeast maybe and whatnot.

 

[couchsending]

Adding sugar can actually hurt fermentability if certain yeasts struggle with Maltotriose.

 

[Kent88]

Haven't really explored what yeasts can handle, but a link in my signature does discuss mashing , the length of time it takes, and the impact on fermentability.

 

[RPh_Guy]

the possibility to raise the attenuation of yeasts that do not digest maltotriose well in all-malt wort

Manipulating variables to increase the "fermentability" of wort does so by reducing the maltotriose (and dextrins), and instead increasing more digestible sugars like glucose and maltose.
Reduce the combined dextrin & maltotriose percentage of extract to ~10% and voila -- 90% attenuation.
If my understanding is correct, keeping the yeast happy helps them chew through more maltotriose as well.

Someone help if I'm off base please. I'm no expert on this topic.

 

[Lefou]

Your grain choices can also make a difference.
A base malt grist with more diastatic potential (Pilsner, Vienna, white wheat) can provide more enzymes to produce a potentially drier beer than would a pale ale malt mixed with a lightly-kilned Munich or crystal. The mash method and temps further enhance the wort properties, so it's important to match your grain and yeast combination for the style you'd like to have.

 

[couchsending]

Your grain choices can also make a difference.
A base malt grist with more diastatic potential (Pilsner, Vienna, white wheat) can provide more enzymes to produce a potentially drier beer than would a pale ale malt mixed with a lightly-kilned Munich or crystal. The mash method and temps further enhance the wort properties, so it's important to match your grain and yeast combination for the style you'd like to have.

And then there’s American 2 row which might have twice the DP of European Pilsner malt.

 

[brewbama]

...
If my understanding is correct, keeping the yeast happy helps them chew through more maltotriose as well.

Someone help if I'm off base please. I'm no expert on this topic.

I agree taking care of yeast as the most important employee of the brewery is very important. And I agree producing a more fermentable wort with less dextrose is key to higher attenuation.

However, I don’t agree that taking care of them in a certain way allows them to consume maltotriose. Some yeast are capable of consuming maltotriose and some are not. For example a Saison yeast can, which results in a dry beer. Some English yeasts won’t leaving residual sugars resulting in a ‘full’ body. In each case you want the reaction to maltotriose so your beer ends up true to style.

Picking the yeast strain is important to produce the intended beer.