Dexrin and Fermentability?

[PeeBee]

This one's for "geeks" to answer, or even to have the stamina to read!

I thought I had all this yeast fermentability (and therefore "attenuation") business stitched up. But recently I've been getting references that make it all muddy again.

I started by believing: Dextrin seems to be defined as polysaccharides with about 20 glucose molecules bonded together, starting with "maltotriose" which has three. How well yeast can handle this dextrin determines "attenuation". A fairly poor attenuating yeast will barely be able to ferment the simplest dextrin (e.g. "maltotriose"); they'll have attenuation figures in the 65-70% range. A high attenuating yeast will ferment longer chain dextrin and have attenuation figures covering the 80%+ range. Some dextrin is simply unfermentable (too "branched", perhaps "cyclic" - ring structures - or terminating in enzyme incompatible structures).

Some "inconsistences" could be ignored as bo11ocks, like "dextrin is unfermentable" and dextrin is an "oligosaccharide" (some definitions of "oligosaccharides" suggest 10 glucose elements which is clearly not compatible with "20" to define "dextrin", but other definitions would place "10" in a "short-chain" definition).

These assumptions have done me well for the last few years, manipulating mash schedules and yeast choices to get the final results I want. In particular high temperature mashes and specific (what I've termed "maltotriose adverse") yeasts to get high finish gravity beers (especially for "historic" beer emulations).

BUT! Recently I've been exploring the very high attenuating yeast "S. cerevisiae var. diastaticus" (attenuating 85-90%+) considered by some to be an "infection" and by others to be an important quality (e.g. dry saison brewers). There's the usual bo11ocks about dextrin being unfermentable and then there's:

THE MYSTERIES OF DIASTATIC BREWING YEAST

Okay, not a "real" research paper, but difficult to ignore all the same.

It appears to be using "maltotriose" to test the performance of diastatic yeasts ("I decided to look at the maltotriose use ability of all the STA1+ ‘Beer 2’ strains"). Sort of knocks my assumptions on the head.

So what is correct?

[PeeBee]

Here's two articles (not academic) from the same site that give some background to "dextrin". They come dangerously close to contradicting themselves; in this case limited fermentability of dextrin wins out, but it's not always the case elsewhere.

https://beerandbrewing.com/dictionary/7ymtLJGtZT/

https://beerandbrewing.com/dictionary/PrbJ3jJxdi/

[PhilB]

Hi PeeBee

This one's for "geeks" to answer ...

... don't know if I'm "geek" enough, but I'll give it a go

So what is correct?

... erm, BOTH! ... just like you've said in the pre-amble to your question ...

Dextrin seems to be defined as polysaccharides with about 20 glucose molecules bonded together, starting with "maltotriose" which has three. How well yeast can handle this dextrin determines "attenuation". A fairly poor attenuating yeast will barely be able to ferment the simplest dextrin (e.g. "maltotriose"); they'll have attenuation figures in the 65-70% range. A high attenuating yeast will ferment longer chain dextrin and have attenuation figures covering the 80%+ range ... I've been exploring the very high attenuating yeast "S. cerevisiae var. diastaticus" (attenuating 85-90%+)

... there are low attenuating yeast, higher attenuating yeast and really high attenuating yeast ... what differentiates them is what proportions of higher order sugars (dextrins) they are able to ferment, and (as is explained in the (first) paper you linked to) what makes really high attenuating yeasts able to attenuate so many higher order sugars is their ability to produce glucoamylase enzymes* ... because those really high attenuating yeast don't just ferment those higher order sugars, they produce enzymes to "mash" them, and then they ferment the simpler sugars those enzymes produce ... it looks to me like all the "answers" are contained in your question, so I'm not sure what it is you don't understand

Unless, I've not understood your misunderstanding
Cheers, PhilB

* that paper then goes on to identify that amongst the really high attenuating yeasts (with the STA1 gene) there are really high attenuating yeast (STA1, with "a large 1162 bp deletion in the promoter of STA1" e.g. WLP570) and really-really high attenuating yeast (STA1, without "a large 1162 bp deletion in the promoter of STA1", e.g. WY3711)

[PeeBee]

This is what I need! If I can continue to believe different (non-diastaticus) yeasts have a variable ability to deal with dextrin, and that paper is solely concentrating on a quite separate, but perhaps related, mechanism for fermenting dextrin. If this is right then I can skip along happy I'm not spouting cobblers.

("McMullan" would disagree, but it appears the "Norwegian Troll" isn't interested in returning to this forum?).

I can also keep saying that these sites that say "dextrin is unfermentable" (all dextrin that is) are talking bo11ocks.

Thanks.

[Jocky]

Once again with the personal insults I see.

[MashBag]

PeeBee. Sorry mate, that is stirring or bating and you know it's unnecessary. Go on, take it out.

Have you been drinking beer again

[PeeBee]

"Personal insults"? "Stirring and baiting"? If it's referring to my "Norwegian Troll" jibe, that's a term of endearment! And I remembered McMullan (he's still active on other forums, but not this one it seems) following my "not spouting cobblers" remark - I wouldn't have been allowed to get away with that! He had the important role of not allowing me to descend into an abusive foul-mouthed git.

So *!$%&* to you lot, and will you now answer my £*!&!* question instead of playing PC Plod. I'm in the middle of my weekly alcohol abstention spell, so, no, I've not been drinking beer again, and I'm none too happy about it.

*(&%!£$* do-gooding, flippin' hippies.

[PhilB]

Hi PeeBee

This is what I need! If I can continue to believe different (non-diastaticus) yeasts have a variable ability to deal with dextrin ...

... yep, although it's not quite so straightforward as (simply) yeast selection, as in one yeast vs. another (it never is, is it? ) ... as White and Zainasheff put it, in "Yeast: The Practical Guide to Beer Fermentation" (p22-23 in my copy, with my underlining for emphasis) ...

Because yeast utilize some sugars more easily than others, they take up sugar in a specific order, with simpler sugars first: glucose, fructose, sucrose, maltose, and then maltotriose. Most of the sugar in a typical all-malt wort is maltose, with lesser amounts of glucose and maltotriose. Yeast take glucose into the cell through facilitated diffusion, without expending any metabolic energy. It is so easy for yeast to utilize glucose that the presence of glucose actually suppresses the yeast's ability to utilize maltose and maltotriose. All brewers yeast can utilize maltose, but not all of them can utilize maltotriose to the same extent. The ability to utilize different sugars, the relative proportions of the sugars in the wort, and the nutrients present in the wort determine the yeast's metabolism. The yeast's metabolism in turn determines the rate of fermentation and the degree of attenuation.

If this is right then I can skip along happy I'm not spouting cobblers.

... feel free to skip right on through

Cheers, PhilB

[MashBag]

So *!$%&* to you lot, and will you now answer my £*!&!* question instead of playing PC Plod. I'm in the middle of my weekly alcohol abstention spell, so, no, I've not been drinking beer again, and I'm none too happy about it.

*(&%!£$* do-gooding, flippin' hippies.

Lmao.