Stalled Fermentation on an Alt

I have an "Alt" that has an OG of 1.050 and fermented really nice for about 48 hours and then slowed way down. We let it go for another 5 days and the ferm lock was bubbling about once in 40 seconds. We assumed it was done and put the carboys in the fridge to cold crash them for a couple of days. We just went to keg them and we end up with a FG of only 1.020. It tastes pretty good but is no where near the 5%+ we were expecting. We are going to leave one keg and then take the other and try to do a secondary fermentation with out adding yeast or sugars. Is this a mistake and what else could we have done?

My brew-mistress is guessing that we did not have the right Mash temps. Any and all thoughts are really appreciated.

Am I understanding correctly that you cold crashed it after a total of 7 days and while there were still signs of active fermentation (the airlock was still bubbling every 40 seconds)?

If this is true, you cold crashed too early, stopping the fermentation before it was done. You needed to let the fermentation run until it was done, before cold crashing or kegging or bottling. 3 weeks would not be unusual. If you're not sure if fermentation is done, you can test it with a hydrometer - compare readings taken three days apart, if they are the same, then fermentation is done. If the airlock is bubbling then the yeast is still working.

If I misinterpreted your post, then yes, you might look at the mash temps - if your temps were higher than you wanted, you would end up with more non-fermentables in your wort, leaving you with a higher final gravity.

Thanks Jim,
You are correct in your understanding. We were just working under the principals of folks like Papazzian that indicate after your yeast settles to the bottom and the activity has slowed considerably you are better off to pull the beer off the yeast bed and be done with it. We were taught that a 6 day fermentation is about it. I don't know if that is now old school and new theories have prevailed. Got any recommendations on updated books that are more current? Thanks again for the help!

So basically you stuck your OWN fermentation?

Warm it back up and give it a gently swirl. And the yeast hopefully will wake back up.

Yeah I guess... if that really was the problem. I guess I am confused by my previous understanding about fermentation time and what may be a new theory. None of the books I have (really old I guess) talk about a fermentation going more than a week or so. When activity slows way down and the Kreusen drops you are done. Is this completely a wrong theory now?

AlchemyBrewing said:

Yeah I guess... if that really was the problem. I guess I am confused by my previous understanding about fermentation time and what may be a new theory. None of the books I have (really old I guess) talk about a fermentation going more than a week or so. When activity slows way down and the Kreusen drops you are done. Is this completely a wrong theory now?

Click to expand...

You really only know your fermentation is done, or anything else really with a hydrometer. Or by giving the beer plenty of time on the yeast.

Fermentation is just the tip of the iceburgh of what the yeast do, they are very fastiduous creatures and if given time, will clean up the byproducts of their fermentation, the stuff that leads to off flavors.

Krausems, calendars and airlock bubbling are very inaacurate guides to what a beer is doing. The only diagnostic tool is a hydro reading.

I've had krausen fall and the beer still not near terminal gravity (verified by a hydrometer) as well as having a krausen staying up for over three weeks despite fermentation being done (as verified by a hydrometer.)

Papazian's book is over 30 years old, and very little has been revised in subsequent editions. Palmers is getting near 10 years old and even there he as revised stuff from the online edition.

Information does change. Now most of us leave our beer in primary for 3-4 weeks to give the yeast plenty of time NOT to get stuck, and to clean up after itself.

THIS is where the most state of the art info is....and most of it has been discussed and repeated over and over so it's not hard to find.

You can read about it here https://www.homebrewtalk.com/f163/s...mil-zainasheff-weigh-176837/?highlight=palmer

Bottom line, patience in brewing is the "new black."

Thanks man. Do you just use a wine thief to get the sample for the hydro? I really appreciate this.

You can but I prefer a turkey baster and a hydrometer test jar.

I am using a 6.5gal glass carboy and don't think a turkey baster will get down far enough to pull a sample. What are you fermenting in?

AlchemyBrewing said:

I am using a 6.5gal glass carboy and don't think a turkey baster will get down far enough to pull a sample. What are you fermenting in?

Click to expand...

Mine works with buckets and carboys.

Ok... I just listened to the BrewStrong Pod cast and the thing I don't understand is that while I was seeing some of the activity in the fermlock all the yeast had fallen off the top. They indicated that was a good indication that fermentation is done. Is that not valid?

AlchemyBrewing said:

Ok... I just listened to the BrewStrong Pod cast and the thing I don't understand is that while I was seeing some of the activity in the fermlock all the yeast had fallen off the top. They indicated that was a good indication that fermentation is done. Is that not valid?

Click to expand...

Eh, not really. Always confirm with a hydrometer reading. Just because there is not a big frothy krausen on top doesn't necessarily mean that the yeast have stopped doing their thing.

The difference is between making an assumption, and knowing. I've been surprised by the yeasties, AND airlocks on numerous occasions to ever assume anything about what is happening in my fermenter based on either of those things. On the other hand, if I take a gravity reading I know exactly where my beer is at at any given time.

It takes about thirty seconds and I have my answer.

*shrug*

Thanks for your patience with me. You have to understand that this is like learning something all over again. I will give it a try next batch and see how it goes.

AlchemyBrewing said:

Any and all thoughts are really appreciated.

Click to expand...

What yeast? Many of the German ale yeasts are known for being slow to ferment. As others have mentioned, you likely cold-crashed before it was done fermenting.

WLP029 German Kolsch/Alt Yeast

AlchemyBrewing said:

Thanks Jim,
You are correct in your understanding. We were just working under the principals of folks like Papazzian that indicate after your yeast settles to the bottom and the activity has slowed considerably you are better off to pull the beer off the yeast bed and be done with it. We were taught that a 6 day fermentation is about it. I don't know if that is now old school and new theories have prevailed. Got any recommendations on updated books that are more current? Thanks again for the help!

Click to expand...

When the yeast are working, they are eating sugars and releasing alcohol and CO2. The CO2 is why your airlock was bubbling. If your airlock is bubbling, its an almost foolproof sign that the yeast is still working and way to early to do anything, no need to take hydrometer readings yet, just let it sit.

You and the Brew Mistress might check out basicbrewing.com and get one or two of their videos - it might be helpful to you to see the process.

Cheers!