Hello again, everybody. I'm Brad with Northern Brewer. Another question that we do often get
quite a bit is about the whole process and topic of kettle souring. So, we are going to
put together a little video here to demonstrate the process and a lot of tips in order to
to help you out along the way. To do this we are going to be using our Duck Duck Gose kit
which by movie magic I already have in front of me.
So, let's get to it! Kettle souring is basically using lactobacillus to make your work sour before
it's boiled. What this helps to do is it keeps the lactobacillus out of the rest of your brew house
so you don't have to worry about contaminating batches down the line. Before we really get into
depth on all the the different steps involved we'll just give you a short overview of the
process. It's as easy as creating your wort how you normally would, whether you're using malt
extract or by all-grain methods. Collect the wort into your boil kettle. Bring it to a boil and
that just makes sure it's sanitary. Chill it back down. Add some lactobacillus. Wait for it to sour.
Then you're going to boil it again, add some hops and whatever other ingredients might be in
your boil. And then you proceed as normal with a standard fermentation and packaging methods.
Before we go in depth on our whole brew day here, let's talk a little bit about lactobacillus. What
is it? Well, lactobacillus is a strain of bacteria that actually produces lactic acid,
and that's what we perceive as sour on our palate. It's been used for centuries and centuries
to make sour beers. This is just one method you can use to make a real quick-turn sour
beer without having to invest a lot of time and a lot of space in your fermentation area.
Much like standard brewing yeast, whether it's an ale or a lager, you will find that lactobacillus
does come in a few different flavors. They do have certain benefits. Some will sour at lower
temperatures, some will create a more intense sour. In the case of the beer in this video we are
using the Omega Yeast Labs Lactobacillus Blend. It is a blend of two different lactobacillus
strains that produce a rapid sourness and they work wonderful at kettle souring temperatures.
If you're as excited as us to get back in the brew cave and see more full-length brewing videos,
let us know down below what you'd like to see -- whether it's a technique, a recipe,
any sort of beer style. And, be sure to subscribe so you know when those videos drop.
Alright, let's hit the brewhouse and see how it's done!
Just as with any brew day you're going to start by creating your wort, whether it's by malt extract
or all-grain methods. This particular recipe, the Duck Duck Gose, is really heavy on wheat,
both malted and unmalted. It does have a handful of Pilsner malt and Munich malt in it as well.
Because of the very high proportion of wheat we definitely recommend using some rice hulls;
that will keep your mash from sticking up.
Otherwise just proceed along with your malt extract recipe as you normally would.
One technique I often employ when making lower gravity beers is to actually use a bit
of a thinner mash. What this does is help so you don't accidentally end up over-sparging your mash.
By over-sparging you can accidentally leech tannins and silicates and other
astringent tasting compounds. Here we've chosen a match temperature of 152 degrees,
and as you can see here we've set the mash up in a recirculating manner that keeps everything
moving along helps with extract efficiency and can also help with timing and clarity of your wort.
During the beginning portion of the mash we also did take a pH measurement just to be sure we're
on the right track. As you can see we hit a pH of 5.3, which is perfect for most beer styles.
So, after the mash was converted -- it took a little under an hour -- we did start to run
off into the kettle. As an aside, I have been asked about this in the past: why the false
bottom in the boil kettle? Well, you will see later that is awesome at keeping the hops (and
in this case coriander) out of the fermenter. It's just another little trick that I use to
make sure the wort is nice and clear going into fermentation.
Just like any other recipe, if you are doing this in an all-grain manner,
just run off in your kettle and sparge as you normally would generally, about an hour.
Once you have collected your full boil volume of wort,
here is where I actually acidified the wort down to a pH of 4.5 before we got any further in the
process. One reason to acidify your work down to 4.5 is to ensure that there is a
extra level of protection against antimicrobial infection and also it gives the lactobacillus a
bit of a head start getting down into the pH range where you're going to notice a nice tartness.
To acidify the work we use lactic acid, and in this roughly 13 gallons of pre-boil
wort it took roughly a little over 20 milliliters to get down to the pH of 4.5. We do recommend
using a pH meter if you're going to try this more advanced technique. Otherwise, if you don't,
you can use pH paper; just understand they're not quite as accurate. So, don't worry about nailing
an exact pH; just acidify down so you're somewhere between 4.0 and 5.0, you'll be close enough.
Now that we've acidified our work down to 4.5, the next step is to bring it to a boil.
We only need to do this for a few minutes because it's only intended function is just to make sure
the word is as clean and sanitary as possible. Once you've boiled your wort for a few minutes, go
ahead and chill it back down to roughly 80 to 90 degrees. This is where you add your lactobacillus.
Once you've added the lactobacillus it is best practice to get any oxygen you
can out of the headspace in the kettle. An excess of oxygen can lead to things like
acetobacter being grown in there, which you're going to get a vinegar taste.
So, it is best practice to purge that with CO2 to get rid of any oxygen.
As you see here I simply remove the disconnect off my CO2 cylinder for my kegging setup
and blew CO2 under there at roughly 10 psi for about a minute, and close the lid quickly.
Anything you can do to seal the lid against the kettle is going to keep yet more oxygen out.
This is probably not ideal but I just wrapped it in saran wrap here and it seemed to do the trick.
So, now that lactobacillus has been added it just becomes a game of time and temperature.
At that point please understand this will take one to three days to properly sour your kettle
so do plan your brew day accordingly. As you can see here I used a heat wrap and a
digital fermentation temperature controller to keep the kettle warm -- then just let it sit.
If you do not have the luxury of having a heat wrap and a digital fermentation controller
you can use a heating pad from the pharmacy, you can use a heated blanket,
you could even use a water bath with a sous-vide cooker in it and to try to keep that temp warm.
Or any other innovative method you can imagine.
Here at Northern Brewer we have a couple of those people who just can't keep their mitts
off of things, so I do recommend a note to let people know you are doing kettle souring process.
Now it's a waiting game and you've got to understand that lacto doesn't really have a
very set schedule, so you've got to wait for it to do its thing. The best way of monitoring how
that is going is by taking pH readings, hopefully every day would be ideal. In this case it did take
us three full days, mostly because my heat wrap fell off night number one. But, after that was
rectified we let it go and a total of three days later we hit a pH of 3.6, which is pretty perfect.
Generally when doing kettle sours you're gonna see people call out a range of about 3.2 to 3.7
and we ended a little bit higher. I would have liked to have gotten down to about 3.5, but
the tartness is certainly there, so it did definitely work.
Without a pH meter, all you really have to do is taste the work,
and if it tastes nice and pleasantly tart to you you're done, and you can go ahead and proceed.
Oh yeah, there's a little bit of sourness in there, pH of 3.6, that's
pretty perfect. It's real nice with a clean malt base in the background. You can really taste that
wheat. Obviously there's no hops in here yet but we're going to bitter this to about 13 IBU or so.
Ideally probably try to hit about 3.4 or 3.5 but the tartness is certainly there, and according
to BJCP it's supposed to be a mild tartness, so i think we nailed it. Here's to hoping!
Once we do hit our final pH it is time to proceed with the rest of the batch
just as you normally would. We did conduct a 60-minute boil here. We added our hops at the
very beginning; we were targeting roughly 15 IBU. Towards the end of the boil we did add coriander.
In this case I used whole coriander, but just to make sure you get the flavor impact you
really desire from it, go ahead and put it in a clean coffee grinder or a spice
grinder (or a mortar or pestle) and crush it up. You don't need to pulverize it into a powder,
just break those seeds open so the wort can get in there and get all those nice oils out.
Now that the boil is over and the wort is cooled down, what we have is a soured wort that still
needs to be fermented in order to turn it into a beer. For that we have chosen Omega Yeast Labs
German Ale yeast, pretty traditional stuff. Best practice with this ale strain is to keep it a
little bit on the cool side; it'll result in a really clean fermentation with just a very small
ester profile. This particular batch took about a week to fully ferment out, and then we put it
in the fridge to cold crash it for a few days just to allow any residual yeast to settle out.
Then it's time to move on to packaging. The packaging step is where we're going to be
adding our salt, a traditional ingredient in a gose. To do this I took about 150 milliliters
worth of water, brought it to a very brief boil in the microwave, stir the salt in to dissolve.
Because of the high temperatures you can be ensure that this is a sanitary environment.
And then, what you can do is if you're kegging you can add your salt solution directly to the
keg like I've done here. If you're bottling, add it to your bottling bucket before you go ahead
and get the beer into the bottling bucket. Then fill your bottles or seal your keg and carbonate.
Here we have our finished gose and I gotta tell you, it turned out pretty darn good.
It has a really nice soft wheat malt character; it's almost slightly bready with a little bit of a
little bit of graham cracker almost. The coriander really comes through with some nice lemon, citrus
notes. And, you can actually almost smell the tartness of it too. When this beer was still warm
(after it had been fermented, before it was cooled down and carbonated) I was a little concerned that
the tartness wasn't going to be there. But, now that it is cold with some carbonation, it gets you
right about here. It is, in my book, the perfect level of tartness. And the salt, while it's there,
it is certainly not overpowering. It's almost like sitting next to an ocean enjoying a beer.
We certainly had a good time making this video and getting a little bit more in
depth on the process of making a kettle sour. If you enjoyed watching this as much as we
enjoyed making the video, go ahead and hit that like button,
subscribe if you're not already. And more importantly, let us know down
below if there's any other processes, recipes, techniques, or anything else you'd like to see.
Once again - cheers!
you