Is clarifying while fermenting a problem?

Question

The all-grain saga continues. I boosted the SG to 1.070 from the OG of 1.030 with cane sugar. 10 days later, the fermentation seems to have stopped and the gravity is 1.040. As mentioned before, the collected wort was very cloudy and I wonder if the specific gravity of the original wort was effected by the suspended solids so that my actual sugar extraction during the mashing process was not as great as indicated by the hydrometer. So, I am considering clarifying the mix and starting over with the fermentation. Will probably have to adjust the pH to get back to a yeast friendly wort.

Will clarifying at this point remove fermentable sugars? My understanding is that clarifying removes suspended solids and not dissolved sugars. Is this true? Will this give me a more accurate gravity measurement/max abv calculation? Should I just clarify and bottle this as a sweet light beer at this point (abv estimated @ 4%) instead of going for the higher abv desired at the start of this batch?

Answer 1

Clarification will not remove dissolved sugars. It's the same reason why in order to remove the proteins that cause chill haze, you have to chill the beer first to get the proteins to precipitate out of solution into solids.

When the sugar dissolves, it interacts with the water on a molecular level, producing no overall charge. Yet, all finings work by electrostatic attraction (opposite charges attract), and so the fining cannot remove the combined sugar and water since it has no charge.

I don't know the full history of this brew, but if you just want to get an accurate gravity reading, you of course don't need to clarify the whole brew - just take a sample and leave that to settle or add a small amount of finings to accelerate clearing. Also, I doubt clarifying will help your stuck ferment. Instead, just rouse the yeast a little and also raise the temperature 5 degrees if it's on the cold side for your yeast - the increased metabolic rate will help them get started again.

If that doesn't work, you can try a forced ferment test. The forced ferment tells you what the actual FG is for this brew. From your figures, there should be at least 10 points left of 100% fermentable succrose left, plus whatever fermentables came from your mash, so you'd expect the FG to be 1.020 or less, assuming 70%+ attenuation.

Racking off and starting the ferment again seems like a lot of effort. I would try these few simple things first.

Answer 2

Suspended solids will not effect the hydrometer readings. Clarifying will not remove the dissolved sugars.

Your high FG is because you had more simple sugar than maltose present by adding 40 additional points of gravity with sugar. Your yeast feasted on the simple sugar and wore itself out before attacking the maltose.

I am not a fan of trying to save these types of failures, but your best bet is to make a 1 gallon starter of fresh yeast and pitch it at high krausen.

If it tastes OK then you can bottle it but that might be dangerous with the high gravity reading.