This has been bothering me and I've never gotten a good answer. considering the fact that I don't do anything to kill off the yeast and I don't brew beers that get past the yeast's alcohol tolerance, I would expect them to ferment out all the sugar in the beer, but generally there's some sweetness, and the final gravity proves that.
What is the main determinant of residual sugar?
- Thread starter hector219
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Shred
Former Microbrewery Founder & Pro Brewer
Could be a few things causing it. Are you using a specialty grain that leaves residual sweetness (i.e. caramel/crystal)? Are you doing all-grain or extract? There's more room for variation in all-grain. Extract should finish pretty close (if not dead on) to the estimated FG unless something else is preventing it. Are your pitching rates appropriate? Fermentation temps?
WoodlandBrew
Well-Known Member
My blog has a few posts on that subject. My book discusses it to greater length. The short answer is: some long chain sugars can taste sweet but are not converted by yeast.
Yeah, if you are doing extract with specialty grains, those grains contain unfermentable sugars (as well as the extract to an extent). If you are heavy on those grains you will have residual sweetness.
If you are all grain, it could be that same thing or that you are mashing too high. High mash temps allow certain enzymes to work that create unfermentable sugars.
Also I suppose could be yeast amount/health, but that usually produces other noticeable off flavors.
Moral: go easier on specialty grains (especially crystals), mash at lower temps, and make big healthy yeast starters.
If you are all grain, it could be that same thing or that you are mashing too high. High mash temps allow certain enzymes to work that create unfermentable sugars.
Also I suppose could be yeast amount/health, but that usually produces other noticeable off flavors.
Moral: go easier on specialty grains (especially crystals), mash at lower temps, and make big healthy yeast starters.
