2 x 20L brew BOTH stopped at 1.020?!

[time01]

ill start shaking tomorrow and see how it goes, thanks for the tips guys, hope I can rescue it!

 

[time01]

it has come down to 1026, but very little air lock activity still.

gave it a swirl and took 200ml out for forced ferment test, should I add yeast to it?

a lot of chunks at the bottom.

 

[carniebrew]

No, not until you know if it will ferment out. Shake the 200ml often over the next couple of days then check the gravity. If it ferments out to near your expected FG, then so should your main brew...eventually....

 

[treefiddy]

Hi, mega-noob here, haven't even completed a first brew but have a pretty strong science background

Im pretty sure I remember reading in the last week or so about brews stopping ferment at 1020 being that sometimes brewing yeasts can lose the ability to break dual and triple bond sugars like Maltose if there is too much glucose or dextrose in the mix. (Being that they're single bond sugars and far easier than breaking the bonds of a maltose)

Could that be the reason?

Think of simple sugars (monosaccharides) like glucose as circles.
More complex sugars are not double or triple bonded, but more like two or more circles joined together (disaccharides and polysaccharides).

Yeast usually need to break the circles apart from one another before those circles can be converted into alcohols.
It seems reasonable that yeast would like to break down the single circles into alcohol before they begin begin the hard work of breaking down larger sugars.

If the yeast was in poor health to begin with (old, sitting on a warm shelf) and there are no nutrients to help them along, then they could easily stall half way through K&K brew (because half the sugars are simple).