What do brewers mean by attenuation and how does alcohol tolerance come into play?

[An Ankoù]

Honestly, thinking about it a little bit more there are so many factors (especially the percentage of non-fermentable sugars in honey).

Honey contains mainly fructose and glucose, but also varying amounts of maltose and sucrose. Saccharomyces Cerevisiae, will ferment all of these and you'll end up with a dry mead.There are some other yeasts, S. Ludwigii for example (but very low alcohol tolerance, too) which won't ferment the maltose content. This might be useful if you want a sweeter mead, but it also depends on the amount of maltose in the honey. When I make mead I let it ferment out and then "drip feed" the mead with more honey until the yeast's alcohol tolerance limit is reached. I then add more honey to sweeten the wine.
It's odd. I hate sweet beers, but I love the taste of unfermented honey in my mead.
I bought a half a kilo of dried rosehips to make a rosehip beer and I might very well use them to make a melomel over the weekend. Or a braggot.
There are one or two mead forums around, too, but I don't know how useful they might be.

 

[Yuri]

Honey contains mainly fructose and glucose, but also varying amounts of maltose and sucrose. Saccharomyces Cerevisiae, will ferment all of these and you'll end up with a dry mead.There are some other yeasts, S. Ludwigii for example (but very low alcohol tolerance, too) which won't ferment the maltose content. This might be useful if you want a sweeter mead, but it also depends on the amount of maltose in the honey. When I make mead I let it ferment out and then "drip feed" the mead with more honey until the yeast's alcohol tolerance limit is reached. I then add more honey to sweeten the wine.
It's odd. I hate sweet beers, but I love the taste of unfermented honey in my mead.
I bought a half a kilo of dried rosehips to make a rosehip beer and I might very well use them to make a melomel over the weekend. Or a braggot.
There are one or two mead forums around, too, but I don't know how useful they might be.

"Honey will be fermented completely because it is almost entirely fructose and glucose". I hear so many brewers say this but from my personal scouring of the internet I seem to find that isn't entirely correct. In Lane et al. 2019 it is stated that 25% of the sugars in honey are oligosaccharides, I'll admit a high number compared to a study by Pascual-Maté 2018 where they find this to be 8.5% di- and trisaccharides (excluding tetrasaccharides), but still a substantial amount especially if you have a yeast strain unable to hydrolyse sucrose. In Wang 2011 they found that of the 80% total weight that are sugars in honey, a little under 10% consists of these higher sugars.

I know brewers talk about an EG of 1.000 as "completely dry", but with the sheer amount of honey that we are adding to the fermenter, I kind of reject the statement that honey ferments completely dry. 10% of 1500 grams of honey is still 150 grams of sugar. Albeit these sugars are in relatively small amounts and not as sweet as fructose but still. Anyway, that is a discussion for another time.

So you are saying you have used S. Ludwigii for a fermentation before? That is pretty interesting, where did you buy such a species? Have you tried any different strains within ludwigii?

 

[An Ankoù]

"Honey will be fermented completely because it is almost entirely fructose and glucose". I hear so many brewers say this but from my personal scouring of the internet I seem to find that isn't entirely correct. In Lane et al. 2019 it is stated that 25% of the sugars in honey are oligosaccharides, I'll admit a high number compared to a study by Pascual-Maté 2018 where they find this to be 8.5% di- and trisaccharides (excluding tetrasaccharides), but still a substantial amount especially if you have a yeast strain unable to hydrolyse sucrose. In Wang 2011 they found that of the 80% total weight that are sugars in honey, a little under 10% consists of these higher sugars.

I know brewers talk about an EG of 1.000 as "completely dry", but with the sheer amount of honey that we are adding to the fermenter, I kind of reject the statement that honey ferments completely dry. 10% of 1500 grams of honey is still 150 grams of sugar. Albeit these sugars are in relatively small amounts and not as sweet as fructose but still. Anyway, that is a discussion for another time.

So you are saying you have used S. Ludwigii for a fermentation before? That is pretty interesting, where did you buy such a species? Have you tried any different strains within ludwigii?

Honey may be fermented to near completion depending on the yeast used. many varieties used for beer will routinely hydrolise and ferment maltotriose, for example, while some wine yeasts my struggle with disaccharides. Since we routinely use "brewer's yeast" it may well seem that compete fermentation is taking place. If you do as I do and add fresh honey towards the end of fermentation then there's a likelihood of introducing "willd" yeasts which may belong to the S. Diastaticus group. So while it's wrong to suppose that honey only contains simple sugars, it;s not necessarily wrong to claim complete fermentation in some cases.
I've never used S. Ludwigii and I only mentioned it as an example. I recalled that it had been mentioned in a post somewhere about making low alcohol beers. You can get it from Whitelabs.

As for making mead, have you had a go yet. If not you really should. Brewing is like learning to drive or fly a plane, you can read up and master all the theory but you can't drive until you spent some hours behind the wheel.

 

[Northern_Brewer]

You would basically have to run a GC-MS or something and know exactly the sugars you are targeting for an internal control. Perhaps I will send some samples to a lab to have a GOPOD done or something similar, although an assay for higher sugars of course.

What is my motivation? Honestly I just want to make good meads reliably, using some of my knowledge about biochemistry in the process.

At this stage I think you're overthinking it - as others have said I think you just need to do it and make some mead first.

HPLC works for sugars but you usually have to use something like HILIC, for just total sugar then wet chemistry is probably good enough?

If I can help others with that by spreading some of what I have found for myself that would be ideal. I was thinking of running different yeast strains through my software to find out things like what esters or glycerols/polysaccharides they produce under what conditions (if they are inducible etc), but manufacturers are naturally quite secretive about their yeast so I doubt their sequencing data will be publically available.

White Labs have sequenced most/all of their beer yeasts (but blinded them, but a lot of the blinding have been figured out), for Wyeast and Fermentis/Lallemand you're relying on whether they're in some of the public sequencing efforts from 1002 Genomes etc, which aren't always reliably labelled. And then of course the attribution of commercial strains to original sources varies between iffy and sheer fantasy....

But Gallone et al 2016 is a good place to start, they did some phenotyping as well :
https://www.cell.com/cell/fulltext/S0092-8674(16)31071-6

And this and other sequencing efforts are discussed more over on HBT, there's more science types over there than here :
https://www.homebrewtalk.com/threads/from-the-lab-family-tree-of-white-labs-yeast.642831/

 

[dmtaylor]

A bone-dry mead will finish at 0.992 specific gravity pretty consistently, rarely any lower than that. You might only see this with a hydromel (low gravity mead) or when using a champagne style yeast that is capable of fermenting maximum sugars compared to any other mead yeast.

For mead, you will usually need to ignore "attenuation" as defined by brewers, as this term (actually "apparent attenuation") is applicable really only to brewing of beer, not mead. For mead, the alcohol tolerance usually comes more into play, especially at standard strengths above ~9% ABV. For hydromel, you can expect a final gravity between around 0.992 to 0.997 using pretty much any yeast.