Sour Mash in Aluminum Kettle?

[cygnus2048]

I'm about to brew a Berliner Weisse using a sour mash for the first time and since I brew with BIAB I plan to leave the souring mash in the kettle for up to three days. My kettle is aluminum and I'm concerned about the sour mash reacting with the Al. I'm not worried with Al dissolving in normal brewing but with a Sour Mash pH approaching 2.5-3 I am concerned. I've tried searching for anything talking about this but most results have to do with people using Al foil to cover the sour mash. I know the foil has an oxidized protective layer but nowhere near as robust as what *should* be on a used boil kettle.

Anyone have any thoughts in this area?

Thanks.

 

[insanim8er]

From palmer's book:

Aluminum pots usually won't cause metallic flavors unless the brewing water is alkaline with a pH level greater than 9.

 

[chask31]

Cygnus, I know this is an old post. I am planning to try this and was wondering how your results were. Thanks!

 

[mabrungard]

Sour mashing is not an ideal way to sour. You are FAR better off with mashing normally and then souring the resulting wort. It is very important to keep oxygen from the wort during the souring step to avoid enabling other spoiling organisms an opportunity create too much funk. It is more difficult to keep a kettle air-tight.

I just soured a batch of wort in a corny keg with a heating pad wrapped around it and a blanket to help insulate it. Lacto is not a large CO2 producer and I just vented the keg every day. It worked very well.

 

[ArcLight]

Sour mashing is not an ideal way to sour. You are FAR better off with mashing normally and then souring the resulting wort. It is very important to keep oxygen from the wort during the souring step to avoid enabling other spoiling organisms an opportunity create too much funk. It is more difficult to keep a kettle air-tight.

I just soured a batch of wort in a corny keg with a heating pad wrapped around it and a blanket to help insulate it. Lacto is not a large CO2 producer and I just vented the keg every day. It worked very well.

I concur, and you get much more control.

Just to expand on what Martin is saying - Acetobacter (vinegar) likes Oxygen, while Lactobacilus doesn't particularly care for it. For Berliner Weiss you definitely don't want vinegar flavor.

What you can also do is: grind (or crush very tightly) a pound of grain and place it in a glass jug. Fill it with warm water (around 99 degrees F), and keep it as close to that temperature as you can for a few days, in the dark. Then taste it. If its ok, perform your normal mash and add it in at the end (or beginning if your water is hard), and perform your normal boil.

 

[CorporateHippie]

Sour mashing is not an ideal way to sour. You are FAR better off with mashing normally and then souring the resulting wort. It is very important to keep oxygen from the wort during the souring step to avoid enabling other spoiling organisms an opportunity create too much funk. It is more difficult to keep a kettle air-tight.

I just soured a batch of wort in a corny keg with a heating pad wrapped around it and a blanket to help insulate it. Lacto is not a large CO2 producer and I just vented the keg every day. It worked very well.

I have sour mashed several times with good results but I am curious on your process.... How long did you leave it in the corny before you took it out? Did you pitch a handful of grains, a lacto starter, or nothing? Also did you purge the oxygen with CO2?

 

[cygnus2048]

I've had fantastic results with my sour mashing. I've made my Berliner Weisse twice and both times it's been great. I'm still not sure if I'm dissolving lots of Al during the sour mash but my kettle is well oxidized and I never scrub it so I think it's all fine.

Regarding the sour mash approach I use... I've done a massive amount of research into it and here are some key points from my research and eperience.

1) I always do a sour-mash starter. ~500mL wort with 3 tablespoons of uncrushed 2-row.

2) While cooling the wort down to ~115F I take samples and adjust the pH down to 5.0 with small additions of Lactic Acid. (The reason for this is that the nasty, unwanted bacteria are less likely to reproduce at the reduced pH.)

3) I then add the uncrushed 2-row and flood the head-space of the flask with CO2 and cover with Al foil. (Again, the CO2 helps minimize unwanted bacteria, such as Acetobacter from taking hold)

3) I then hold at 115F for 24hrs. (Like the other steps, this temperature is chosen to favor Lacto but inhibit the other nasties)

4) After 24hrs I swirl the flask and smell for any bad odors. If OK I hold at 115F for another 24hrs. I do this three times.

5) If after the 3rd day smell is still OK I give it a taste. It should have a very prominent sourness but be "clean", i.e., no funk or cheese. If happy with it, I proceed with the mash.

6) With the main mash I again cool it to 115F, add the lacto starter, flood head-space of my kettle with CO2 and cover.

7) I then sample the taste of the sour mash every 12 hours until the desired sourness has been obtained. Once there, it's time to boil!

One final thing that I do is when creating a yeast starter i do a two-stage propagation and I use the wort from the souring mash for the starter. I just draw some off, boil for 10min, cool, then add the yeast. The reason I use the souring mash is to try to acclimate the yeast to the increased acidic environment, much more than they are used to, in an effort to try to achieve full attenuation. (I'm not sure if this is required or not but I've achieved very good results and will continue to do it)

Hope you find some of this useful and your results are as positive as mine!

 

[mabrungard]

How long did you leave it in the corny before you took it out? Did you pitch a handful of grains, a lacto starter, or nothing? Also did you purge the oxygen with CO2?

The last batch was in the corny for 4 days and the pH was 3.1. As echoed by Cygnus, I did use the handful of grain for souring a 1.5L starter.

Since the raw wort was runoff directly from the mash tun into the corny, its temperature largely precludes oxygen uptake. In addition, the keg was completely full with very little headspace. Oxygen doesn't appear to be a significant concern in this case.

By the way, I like that minor acidification step that Cygnus did to help overwhelm unwanted bacteria in the starter. I didn't do that, but it is a reasonable and easy step to take. Next time!

 

[ArcLight]

I've had fantastic results with my sour mashing. I've made my Berliner Weisse twice and both times it's been great. I'm still not sure if I'm dissolving lots of Al during the sour mash but my kettle is well oxidized and I never scrub it so I think it's all fine.

Regarding the sour mash approach I use... I've done a massive amount of research into it and here are some key points from my research and eperience.

...snip... (see above for the full post)

Hope you find some of this useful and your results are as positive as mine!

1. You mention wort for your starter. Do you:
A - mash, then cool down to 115F,
or
B - Do you heat the water to 115F and add the grain (or heat the grain and water to 115).

In fact - the wort has oxygen in it, which makes me think its best to mash, on the stove top, boil it to drive off the O2, then cool it.


2. How do you maintain the starter flask at 115F? Are you using a stir plate? (based on #4 it seems no)

3. Since you want to keep Oxygen out, it seems like it's a good idea to use a stopper and airlock. And fill the beaker to minimize head space. Does Lacto produce any krausen, so I need a little head space?


4. The temperature you listed (115 F or 46C) seems a bit hot. I thought Lacto preferred 30-40F.
Is it a case of Lacto is uncomfortable at 115, but other bacteria are even less comfortable?
Acetobacter is also acid tolerant, but prefers a range of 25-30C, so I see why 40C (104F) would be a good temperature. Or is that too low? (Enteric bacteria like 35F)

5. Could you post some links to good articles. I love to look through research and data.

 

[cygnus2048]

1. You mention wort for your starter. Do you:
A - mash, then cool down to 115F,
or
B - Do you heat the water to 115F and add the grain (or heat the grain and water to 115).

For the Sour starter I use DME and for the yeast starter I draw off some sour mash liquid from the kettle. In either case I just boil for 10min before adding the grain for sour starter or yeast for yeast starter.

2. How do you maintain the starter flask at 115F? Are you using a stir plate? (based on #4 it seems no)

I do not use a stir plate for the sour starter (I do for the yeast starter). The reason to swirl before the smell is, in essence, to increase the surface area of the liquid by coating the walls of the flask. This allows more volatilization of the liquid and makes it easier to detect any nasties. To maintain temperature I just place it in my oven along with a small space heater and temperature control unit.

3. Since you want to keep Oxygen out, it seems like it's a good idea to use a stopper and airlock. And fill the beaker to minimize head space. Does Lacto produce any krausen, so I need a little head space?

Most of the Lacto strains you will be working with are homofermentative, meaning they produce only lactic acid from glucose so you will not get any off-gassing at all and no krausen. Also, remember that CO2 is heavier than air so as long as nothing is disturbing the environment (such as a stir-plate) and it's fairly well sealed (foil) the amount of O2 that will reach the starter is very minimal over the relatively short duration that we are talking about.

4. The temperature you listed (115 F or 46C) seems a bit hot. I thought Lacto preferred 30-40F.
Is it a case of Lacto is uncomfortable at 115, but other bacteria are even less comfortable?
Acetobacter is also acid tolerant, but prefers a range of 25-30C, so I see why 40C (104F) would be a good temperature. Or is that too low? (Enteric bacteria like 35F)

It is on the high-side for Lacto and the optimal for most strains are around 40C as you mentioned. However, by increasing to 46C you are slightly less than optimal for lacto but much less optimal for the bad bacteria. If I had a pure strain of lacto, such as one purchased, I too would use the optimal temp around 40C. However, when just using malt to inoculate the starter it's a bit of a roll of the dice and I'm trying to do anything I can to push the odds in my favor.

I'm sorry but all I have are notes from my research and did not save the sources so I cannot provide any. I can tell you that I found it all from many days on google.

Good luck!

 

[dannymars]

Yeah, but what about the aluminum kettle?