Short one for today. I would like to share some information about the sugar composition of wort since I had to take this into consideration for an upcoming project I am preparing for publishing here soon (yes, its yeast related). Lets talk sugars today!
I am not sure how many homebrewers thought about the actual sugar composition of their wort before. And I am not speaking about fermentable and non-fermentable ones. The real composition like sucrose, maltose, glucose etc. The question now is why one might think about that problem in the first place. For example, if you are interested to know if a non-Saccharoymces yeast (capable of fermenting glucose only) can ferment something in a wort, you might need to know if glucose is even present in the first place (and this example is pretty close to the question I asked myself to eventually investigate the composition of sugars in wort).
The composition of sugars in wort has been addressed a couple of years ago and published in various papers. Like “Determination of the sugar composition of wort and beer by gas liquid chromatography” by Otter et al published in 1967 [get me to the paper]. I will not go into the scientific details as well as experimental setup of this paper but would like to discuss the results.
Fig 1: Paper header
Otter et al determined the concentrations of six sugars (fructose, glucose, sucrose, maltose, maltotriose and maltotetraose) in 15 different worts with various OGs (ranging from 1.027 up to 1.093). I averaged the sugar compositions of the 15 samples as amount of sugar X relative to the total amount of sugar present in wort. Just to give me a rough idea. So don’t read too much into the numbers here. It’s about the ratio or more like sugar X is highly abundant or not. And yes, I thought about effects of grain bill composition, mash schedules, mash pH, you name it on the sugar composition. Getting a rough idea here.
Fig 2:Sugar composition w[%] of total sugar as average of 15 different worts
About half of the sugars present in wort is maltose (Fig 2). Followed by maltotriose and glucose. And some smaller amounts of fructose, sucrose and maltotetraose. Maltotetraose by the way is a dextrin and can be counted as non-fermentable. Standard Saccharomyces cerevisiae strains are capable of fermenting all the present sugars except maltotetraose. Which might explain why S. cerevisiae is the working horse of brewers. In summary, maltose makes up about half of the total sugars followed by glucose and maltotriose. And some minor amounts of fructose, sucrose and maltotetraose. I am actually surprised about the amount of glucose present in wort. I did not expect that at all.
So there you go. I will address the initial problem about a specific sugar metabolism of a non-Saccharomyces yeast in a future post including some empirical data. Stay tuned!
Eureka Brewing 
Well you have my attention…..
Cheers, thanks for reading. Follow up posts will get posted in the next two months (planning to let my homebrew club evaluate the beers I brewed in March).
Nice summary of wort sugars. Seems like a good starting place to understand the microbial community changes when you have multispecies fermentations Sacc, Brett, Pedio, Lacto, plus??, etc…
Indeed, plus figuring out if a certain yeast can even make a difference in a malt based wort prior to a Sacc pitch or a single fermentation.
Do you have information on the relationship between sugar composition of wort and the typical attenuation figures given for saccharomyces yeasts? How much of this variation on attenuation can be explained by wort composition, how much by other factors?
I don’t have any information about attenuation and sugar composition. I suppose sugar composition is one key determinant for attenuation levels but the genetics of the yeast strains will have an influence as well.
This is really interesting, does the sugar composition change if you add a load of corn or rice to the beer? I know that corn and rice beers are typically drier, but is that a function of the mash temp? or are corn/rice starches generally more prone to being converted to glucose by alpha amylase?
> This is really interesting, does the sugar composition change if you add a load of corn or rice to the beer?
The sugar composition for sure changes in case you use different malts, add corn/rice or any other adjunct. And the mash schedule makes a lot of difference as well.
> I know that corn and rice beers are typically drier, but is that a function of the mash temp? or are corn/rice starches generally more prone to being converted to glucose by alpha amylase?
No idea. I think the second is true (more prone for amylase). But I don’t have any scientific evidence to back this up.
This is great, I am also gathering data on sugar make-up of different fruit for a little experiment i’m trying. Knowing stuff likes this allows us to, theoretically, get really, really precise with our yeast to grist selections. different yeast will produce different esters during the breakdown of each sugar, so by accounting for the ratios you could control which esters and how much are made. this is all part of the next evolution of beer! It’s a shame we’re not in the same country!
Tamir
Hi Tamir, my intentions to look at wort sugars don’t go as deep as you mention. And I see the potential you describe. Sure one could try to dial in the yeasts perfectly in terms of formed molecules. I was simply interested to see a rough distribution to introduce some non-Saccharomyces yeasts to wort to do their thing. And since some of them are limited to a couple of sugars in terms of fermentation, I had to figure out if the sugars are even present in wort. I go the other way round. I know the yeasts and their doing (including some of the unique chemistry) and simply need to see if they can eat something in wort. If they can, the chances are good the unique flavors turn up in the final beer.
I think there is no need to be in the same country. The 21sth century gave us enough technology to circumvent problems like that, right? Just drop me a line if you want to talk. Cheers, Sam
That’s interesting! I’m surprised there isn’t more dextrin. Malt extract is typically 20% higher saccharides.