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.
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.
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!