Tips for getting high gravity worts to completion and restarting/repitching stalled fermentations ?

[brewman !]

I do a lot of reiterative mashes for high gravity brews. 1.080 to 1.120. I always have trouble getting them to ferment dry - less than 1.020. What are the secrets to getting high gravity worts to ferment dry ?

I've tried repitching stalled worts to get them drier, never with any success. How does one repitch a fermentation to get it to finish ?

Thanks

 

[RM-MN]

Lets start with the yeast you might use. Some are more attenuative than others. Choose one that is the most attenuative.

Now think about the job they have ahead of them. More workers mean each one needs to work less hard. Pitch a large amount.

Wort contains a mixture of sugars. Make it so more of the sugars are fermentable. That means a mash that is slow to denature the beta enzyme. Keep it cool, like 145 to 148F.

Make your yeast happy, start them with a little lower OG, then after a couple to 4 days, feed them simple sugars. That way they will have attenuated the most possible with the lower OG wort and will have a very easy time digesting the simple sugar at a time when they might be struggling with alcohol poisoning.

 

[InspectorJon]

Adding amylase enzyme to the beer can help convert unfermentable sugars in a beer that finishes too high. Google "amylase enzyme stuck fermentation". I used it once on an imperial stout that finished around 1.040. A teaspoon of enzyme got it to drop another 10 points over a week or so. If you use it, be sure to let it work for some time. Amylase works much slower at fermentation temperature than in the mash. This is a method for fixing a problem and I am not sure it is entirely predictable. Better to do the things RH-MN said above and avoid the problem to begin with.

It is pretty normal for high gravity wort to finish high. Trying to get them below 1.020 may be an unrealistic expectation. A lot if commercial imperial stouts finish north of 1.040. @bracconiere has some experience using enzyme to get higher gravity wort to finish dry. I think he uses it in the mash.

 

[brewman !]

Thanks for the tips. Very interesting about the amylase. I happen to have some on hand. I'll add it to my currently stuck fermentation and see what happens.

I often ferment will a less attenutive yeast for its flavor profile, hoping to pitch a second yeast later on to get it dry. This rarely works. Why ?

 

[bracconiere]

i pitch "gluco" amylase into the fermenter for low calories beer....

but if you're starting with 1.120 wort, a FG of 1.020, is around 13% ABV...about the most much yeast can handle...i'd say get a pack of super duper turbo yeast...harvest the yeast, to get rid of the crappy tasting nutrients..and it WILL go to 16% ABV...or from 1.120, to 1.002.....

edit: but that would require gluco added to the fermenter....

 

[couchsending]

Why do you want to get below 1.020?

 

[Bobby_M]

Why do you want to get below 1.020?

Rocket fuel perhaps? You'd either want to mash in the upper 140's (147-149F) for 90 minutes or better yet, step mash it. If not, add simple sugars like dextrose for a portion of the gravity.

 

[marc1]

If you want it really dry, as @bracconiere says, use glucoamylase in the fermenter. It will take it down close to 1.000 if the yeast can handle it.

White Labs has a Super High Gravity Ale yeast that can supposedly go up to 25%, so that may work. I've never tried it, most of my beer is <5%

 

[TestTickle]

I often ferment will a less attenutive yeast for its flavor profile, hoping to pitch a second yeast later on to get it dry. This rarely works. Why ?

In my experience, it's probably because you are pitching yeast into a hostile environment. Higher levels of alcohol and the lower pH caused by fermentation can both be rough for most yeast. You might try re-pitching with a more alcohol tolerant strain to see if it budges.

Out of curiosity, what types of beer are we talking about?

 

[AlexKay]

Wait. High-gravity beers can take longer — sometimes much longer — before they’re done. I’ve had even real workhorse yeasts like US-05 take a few weeks to get to final gravity. This assumes you had a good size pitch to begin with. If you did, I recommend waiting rather than fiddling with things.

 

[Kickass]

I often ferment will a less attenutive yeast

I wouldn’t say a 75%+ attenuation is low. What yeast strains are you using?

 

[duncan_disorderly]

Lallemand states that Belle Saison can be used to re-start fermentations and I have had success with this on the couple of occasions I've tried it. It's not the ideal solution, with it being a diastaticus strain, but it may be better than an unstuck fermentation. I didn't pick up much if any saison character in the beers, the most recent of which stopped at 1010 from a start around 1062. The Belle saison was pitched at 1024.

 

[Beermeister32]

I did a lighter beer once with Gluco (Beano) and it really took it down. I’ve also used amylase enzyme in the fermenter, it works but not as radically as Beano.

Add more yeast at the end of your fermentation cycle. Your flavor profile more or less is done at this point, so you can use a different yeast that might be more attenuative without screwing things up.

I had a batch that I was playing around with once and added some hungry Hornindal kviek slurry I had. It took right off again for a few more points. Worked great!

 

[Dr_Jeff]

I've had good sucess with big beers, by starting with a healthy amount of yeast, after two to three days when the yeast profile has been set, add in some WLP-099 High gravity yeast, ideally it has been on a stir plate and at high krausen.

It has worked numerous times for me.

 

[Northern_Brewer]

I do a lot of reiterative mashes for high gravity brews. 1.080 to 1.120. I always have trouble getting them to ferment dry - less than 1.020. What are the secrets to getting high gravity worts to ferment dry ?

This presentation has useful tips for high-gravity fermentations - they're a stressful environment for any yeast, you just need to keep your yeast super-happy.
https://quaff.org/wp-content/uploads/2012/11/HighGravityFermentation-1.ppt
But I don't think you're doing too badly - 1.120 to 1.020 is over 83% attenuation so your only option to go much beyond that is either enzymes or a diastatic yeast like the saisons that have been mentioned. I wouldn't consider 1.020 "stalled" or "unfinished" in this context.

So I wouldn't get too hung up on the absolute values of FG - it's what it tastes like that matters, and the perception of sweetness gets skewed when you've got that much alcohol kicking around in any case.