diving in to ambient fermentation …

[kestrelbrewing]

You know how you can never get that last bit of LME out of the container in time for it to be part of the wort? Well, I started collecting those leftover bits a year or so ago and now I have about 12 lbs of mixed LME along with some random hops from prior brews taking up space in my fridge. I even have some leftover crushed grain I can use as steeping grains. I was considering just mixing up a frankenbeer and use one of my washed yeasts, but I thought if I'm going to make something utterly random, why not go the whole 9 yards and try an ambient fermentation.

I have ordered a 6" deep full sized, stainless steel steam table tray which will comfortably hold 6+ gallons of liquid. My plan is to do a 1 hour boil using 6 lbs of LME (which should yield a guesstimated gravity of around 1.040) and 15 IBU worth of my oldest hops. Then transfer to the steam table tray, cover the whole thing with cheesecloth, and set it in my basement brewery with a fan stuck in the window near the ceiling for airflow.

I have questions for anyone who may have gone down this route:

1. How long should I expect to wait for fermentation to start?
2. Assuming it starts, how long should I let fermentation go on before transferring to a carboy and applying an airlock?
3. Is cheesecloth the right choice here? I want to keep the actual insects out but leave enough of an opening to allow the microscopic bugs to get in.
4. Is the fan really necessary?

Thanks!

 

[OldDogBrewing]

What do you want to do exactly? One thing is air inoculation and another thing is open fermentation and they are not the same

 

[RPh_Guy]

Lag time depends on various factors including how many microbes land in your wort, how aggressive they are, what temperature it is, etc.

A few hours should be adequate for inoculation. You should have it somewhere with air flow; the more the better. You can transfer it to your fermentation vessel any time afterwards.

You don't really need to keep out insects, so cheesecloth is fine.

I suggest you pre-acidify to 4.0-4.5.
If you want it to be sour you should probably reduce the hops to 5-10 IBU.

 

[kestrelbrewing]

What do you want to do exactly? One thing is air inoculation and another thing is open fermentation and they are not the same

Both, actually. It's an experiment …

 

[kestrelbrewing]

Lag time depends on various factors including how many microbes land in your wort, how aggressive they are, what temperature it is, etc.

A few hours should be adequate for inoculation. You should have it somewhere with air flow; the more the better. You can transfer it to your fermentation vessel any time afterwards.

You don't really need to keep out insects, so cheesecloth is fine.

I suggest you pre-acidify to 4.0-4.5.
If you want it to be sour you should probably reduce the hops to 5-10 IBU.

Microbes and aggressiveness is the great unknowable … I do have a raspberry bush, fig tree, tomatoes, and a lemon tree in the yard outside the window where I'm planning to do this and I've had great success with sourdough especially when using spent brewing grain as a starter. Also, this will happen in the basement where I have been brewing mostly Belgian beers, including a half dozen pseudo lambics, for the past 7 years so who knows what's living in the air down there.

Airflow is good. I am in San Diego on the top of a hill so we get reliable sea breezes every day that blow through the house. There is a west (ocean, though we can only barely see the ocean on a very clear day) facing window at one end of the basement and open windows at the other end.

In terms of acidification, is there a recommended method for doing so? I am thinking citric acid which I have lying around from cheesemaking and would end up being flavor neutral. If this works out, my intent is to go with a more lambic-ish all grain bill and I might try using lemon juice (because I'm cheap and I have a lemon tree).

In terms of hops, I have a few ounces of 5.7% AA German Tradition hops that have been sitting in the fridge for like 3 years that I was thinking of using. I was thinking of trying to get to 1.040 and drop a half ounce which would put me at 13 IBU. Again, if this works, I would use something in the 2.2% AA range because (and I think you guessed this already based on your comments) is to go in the direction of an actual lambic.

Unfortunately, I've had a surprise camping trip sprung on me by the wife so this project might have to wait until next week.

 

[OldDogBrewing]

Both, actually. It's an experiment …

Then you need to expose to the air to catch yeast in a well ventilated space or with a fan introducing outside air, so you have more chances.

Regarding the fermentation, you should add an airlock when the fermentation is slowing down but still happening, by fermenting in a shallow container, you should get a bigger ester production

 

[kestrelbrewing]

Then you need to expose to the air to catch yeast in a well ventilated space or with a fan introducing outside air, so you have more chances.

Regarding the fermentation, you should add an airlock when the fermentation is slowing down but still happening, by fermenting in a shallow container, you should get a bigger ester production

That's the plan. I have an older glass 5 gallon fermenter I was given on standby …

 

[RPh_Guy]

In terms of acidification, is there a recommended method for doing so?

I suggest either lactic acid or phoshoric acid.
Citric acid is often not flavor neutral ... AND it's a substrate for the bacteria to produce some unwanted flavors.

Again, if this works, I would use something in the 2.2% AA range because (and I think you guessed this already based on your comments) is to go in the direction of an actual lambic.

You will likely need to pitch Brett if you want it to taste like a lambic.

Personally I would definitely not do open fermentation with a wild culture. The risk of mold, excessive ethyl acetate, and/or acetic acid is unacceptable in my opinion. Mold in particular is a very high risk and will outright ruin the batch.

 

[kestrelbrewing]

I suggest either lactic acid or phoshoric acid.
Citric acid is often not flavor neutral ... AND it's a substrate for the bacteria to produce some unwanted flavors.

You will likely need to pitch Brett if you want it to taste like a lambic.

Personally I would definitely not do open fermentation with a wild culture. The risk of mold, excessive ethyl acetate, and/or acetic acid is unacceptable in my opinion. Mold in particular is a very high risk and will outright ruin the batch.

Good to know on the citric acid. Will pick up some lactic at the home-brew store.

Lambic is the long term goal. The short term is just to see what, if anything, lurks in the basement after 7 years of brewing, including quite a bit of pseudo lambic brewing. I am anticipating this being undrinkable, probably fit only for killing slugs in the garden. It is purely an experiment.

 

[kestrelbrewing]

Update: Brewed a Julebryg (Swedish Xmas beer with quite a bit of rye) and decided to use the second runnings as my ambient fermentation test bed.
• Starting with 5 gal. of second runnings
• 1 hour boil with the same hop bill as the original beer (Tahoma and Bobek) but at half the original amounts
• Ended up with ±4 gallons at 1.050
• Started fermenting after about 36 hours
• Sat in the Koeldinghy for 7 days when the foam blanket started to subside - no signs of mold.
• Transferred 3.5 gallons into a 5 gallon carboy
• Has been sitting in there slowly bubbling away at 1 bubble out of the airlock per second for about 2 weeks now.
• Airlock smells very good

As I don't need this carboy until March, I plan to just let this beer run until then. I will then bottle in 12 oz bottles, let condition for 3 weeks, and open a bottle every other week.

Fun experiment. I recommend it.

 

[kestrelbrewing]

The Koeldinghy, full depth hotel steam table tray with a bottling spigot installed in the bottom (this was testing for leaks).

 

[OldDogBrewing]

The Koeldinghy, full depth hotel steam table tray with a bottling spigot installed in the bottom (this was testing for leaks).
View attachment 701795

Looks great! It gives me some ideas for the day I build my own koelship

 

[kestrelbrewing]

Looks great! It gives me some ideas for the day I build my own koelship

Got the tray at RestaurantDepot.com, it was about $20 new with shipping. The wood is leftover poplar from the deck I built and the bottling spigot was one I accidentally bought when I got a second bottling bucket for lambics/wild beers and thought it wouldn't come with a spigot.
Took about an hour and a half and most of that was figuring out how to put the hole in the tray without buying thing else. Tried a hole saw from a doorknob kit, that didn't work. Dremel was taking forever. In the end, I just punched a bunch of holes with a nail and a piece of scrap wood underneath which let me punch out the hole. Then smoothed out the edges with the Dremel.
One thing to note: the steam tray is like an amplifier. Every nail punch sounds like a gong and when you start with the Dremel … might be a good time for some ear protection.