“In addition to the lack of nutrients, wort with a high percentage of refined sugar (about 30%) may cause the yeast to lose the ability to secrete the enzymes that allow them to ferment maltose, resulting in a stuck fermentation.” (Palmer, p. 86)
He does use the qualifier “may.”
Hey, that’s my thing! If anyone has any questions about it, I’d be happy to answer them. That thread got really long and cumbersome. At the end of those trials, I came up with something I’d consider as good or better than D2. Flavor-wise it was really close to D2, but the color wasn’t quite there. Beer I’ve made with it were more like La Trappe than St. Bernardus, in color and flavor.
The next thing on my list is to make a syrup that tastes like whatever they put in St. Bernardus that makes it so chocolatey.
I don’t have a page number for you, but it’s come up on Brew Strong a couple of times. I think he says they lose the ability to ferment polysaccharides if they acclimatize to a monosaccharide environment. Whether this is actually the case, I do not know.
I just don’t believe it at all. In that batch, maybe they’ll stop fermenting it because of a combination of factors with the trigger being a high percentage of glucose to start, but maybe not. If John is right though, wouldn’t every kit-and-kilo batch that Aussie brewers made be ridiculously sweet? Those are more than 30% glucose, and while I haven’t heard much good about those types of brews, I’ve never heard that they were cloying.
I grow yeast on glucose all of the time and this has never, ever happened to me. I’ll have to talk to John about it and see where he’s getting his info and what the parameters of the experiments are. It may be that when the source says “polysaccharide” they are referring specifically to more than two sugar molecules, since a two sugar chain is typically just called a disaccharide and not included in the polysaccharide term.
See 12.5.8 Regulation of sugar metabolism in Brewing: Science and Practice by Briggs, Boulton, Brookes, Stevens.
Ok - are you saying read it because it supports what I’m saying, or contradicts? Because to me it agrees with what I said.
Have you investigated this further?
I can’t find any mention that yeast lose the ability to ferment maltose either, only temporary inhibition.
I don’t think it would make sense to talk about polysaccharides since the limit most strains of saccharomyces can ferment is maltotriose.
I haven’t, because I haven’t found any credible source that says they actually lose the ability to ferment maltose. Yes, in the presence of glucose they will not ferment maltose - it’s called catabolite repression. They preferentially ferment the glucose because it is easier. Once the glucose is consumed they ferment the disaccharides - it’s not a hard switch, just a general trend.
Perhaps it is a misunderstanding that they will lose their ability to ferment maltose.
We just had a presentation at my club about yeast and he mentioned this preferencial fermentation thing. The theory he put forth is that once the yeast is done with the simple sugars, if there were enough of them to start with, the ethanol concentration is high enough to interfere with the yeast’s ability to continue fermenting the maltose. but there would have to be ALOT of sugar for that to happen I would think.
Any appreciable decrease in the ability to ferment maltose would show up in the attenuation of the wort. It’s probably not a go/no-go thing, but more a sliding scale thing.
Here’s info from one of the major “candi sugar” suppliers for beer in Belgium:
http://www.castlemalting.com/CastleMaltingSugar.asp?Language=English
I’m pretty sure D2 is the Candimic dark 78%