Oxalates and beerstone

[trentm]

I hardly know enough to ask the question. If I understand correctly, we want to precipitate oxalates in the mash and an appropriate amount of calcium does this. If not precipitated, oxalates can cause haze in finished product and beerstone build-up in the fermenter and down the line.

Questions:

1) What is an appropriate level of Ca to ensure precipitation of oxalates ?

2) If oxalates are precipitated in the mash, would you expect beerstone to build up in the mash tun?

3) Are there other concerns regarding oxalates in brewing and beerstone formation?

 

[ajdelange]

1) What is an appropriate level of Ca to ensure precipitation of oxalates ?

I generally run perhaps 25 mg/L Ca++ and have never experienced beerstone in the mash tun, decoction kettle or kettle.

2) If oxalates are precipitated in the mash, would you expect beerstone to build up in the mash tun?

Based on my experience the places you will find beer stone are in fermenters and kegs.

3) Are there other concerns regarding oxalates in brewing and beerstone formation?

If you think calcium oxalate as beerstone is a pain in the nether regions you will find calcium oxalate as kidney stones much worse. The main reason I keep calcium as high as I do (recognizing that most people will thing I am running it too low) is to avoid kidney stones.

Note: my kegs and fermenters get occasional cleanings with a mixture of nitric and phosphoric acids to prevent beer stone formation. Once formed it is very hard to get off.

 

[mabrungard]

Based on entirely empirical observations from brewers that have reported beerstone problems in their brewery, I concluded that the minimum calcium level MAY be about 40 ppm to avoid beerstone. Based on AJ's comment above, my recommendation may be conservative.

When AJ and I were helping with the Water book, I raised the question on oxalate content of grain and the stoichiometric need for calcium to precipitate oxalate. John Palmer found that the minimum Ca content needed to be about 3 times the oxalate content and he also said he found other books that said Ca needed to be 4.5 to 5 times the oxalate content. The story I got was that oxalate content in grain is variable...I also didn't get any information on what the typical range of oxalate in malt is! So, I couldn't assess what a desirable calcium content for oxalate removal was. If someone could find that sort of data, I would appreciate it.

 

[ajdelange]

I think the key word, as used by Martin, when it comes to oxalates is MAY. There is, naturally, much interest in the mechanisms of calcium oxalate precipitation in vivo where things are much more complex than in vitro so, naturally, a bunch of in vitro studies have been done as a stepping off point for the more significant in vivo work. The in vitro studies are amazingly diverse in their methods and results. Anyone can look up the solubility product for calcium oxalate and draw conclusions about where the metastable boundary is but apparently where precipitation actually occurs once that boundary is crossed is a complicated subject. I seem to recall seeing something about the causes of precipitation being 25% (don't quote me on these numbers)predictable from the thermo dynamics (solubility calculation), 25% from ionic strength considerations (which is part of the thermo as far as I am concerned) and the rest unknown.

Narziß apparently found oxalate concentrations of 5.6 - 22.8 mg/100g in barley malt and 22.1 - 50.3 in wheat malt. I stumbled across a patent for beerstone reduction that said that the amount in finished beer must be lowered to 15 ppm to prevent gushing. The patent proposes the use of oxalate decarboxylase.

That's about all I know.

 

[trentm]

Thanks for the information. Seems to be poorly understood. Now that, with the help of this forum, I have dialed in my desired water profiles, I have less of an issue with beerstone formation (typically my Ca is ~50 ppm). However, it does still form (at a lower level) on my boil kettle and fermenter. Perhaps that's good as Oxalates need to be precipitated for the beers sake (and kidneys?). Before learning how to adjust my water profile, I had a terrible problem with beerstone. For canned wort, it was nearly impossible to remove from my canning jars. I really have no idea what was going on to cause such issues.

Thanks again Brew Science!

 

[mabrungard]

Before learning how to adjust my water profile, I had a terrible problem with beerstone. For canned wort, it was nearly impossible to remove from my canning jars. I really have no idea what was going on to cause such issues.

Interesting! What was your unadjusted water like? Low calcium???

 

[trentm]

Interesting! What was your unadjusted water like? Low calcium???

Thanks for asking. Unfortunately, I don't know. Before I found brew science I just used dechlorinated tap water and adjusted mash pH with lactic acid. I live in CA where, I understand, we get water from many different sources. It may come from; snow melt, wells, or CO river (wildly variable).

While I wish I could help you guys who understand water/brewing chemistry with this complex subject, as a water neophyte, I am grateful to have the advice of experts. It has done wonders for my beers.

 

[Borisfa]

Narziß apparently found oxalate concentrations of 5.6 - 22.8 mg/100g in barley malt and 22.1 - 50.3 in wheat malt. I stumbled across a patent for beerstone reduction that said that the amount in finished beer must be lowered to 15 ppm to prevent gushing. The patent proposes the use of oxalate decarboxylase.That's about all I know.

So, imagine a batch with 60 L of finished beer, the we have about 35 L of mash water plus 45 L of sparge water, and about 12 kg of barley malt.

If all oxalate will precipitate as calcium oxalate, so I will need, only to precipitate the oxalate, 234 ppm of Calcium (see below). It is?

- Oxalate present: 22,8 mg/100 g * 12000 g of malt = 2736 mg in 35 L ~ 78 ppm of oxalate in solution (considering all oxalate soluble). If I need 3 times Calcium to precipitate, so I will need 234 ppm in mash water.

Calcium is also needed as a enzimatic co-factor to flaculation in fermentation, so, how much Calcium should I add to this?

And more, some people tell that barley malt has 1% mass of phosphate that is also precipitate by Calcium during mash (Calcium consuption). The amount recommended for Calcium in water is between 50-150 ppm, so, the balace does not close. Where is the mistake?

Best Regards,

Fabiano da Mata

 

[ajdelange]

i think you are trying to over engineer this. As noted in the rest of the thread precipitation of calcium oxalate is very difficult to predict. While the stoichimietry makes it clear that you would need 12*228/90 = 30.4 mmol of calcium or about 1.2 grams to remove all the oxalate from 12 kg of malt using Narziß worst case number it is not at all clear that it will all precipitate nor that you might not be closer to Narziß best case number in which case you would only need 0.3 grams. Spread over 60 L beer those minimum and maxium amounts translate to 4 - 20 mg/L if you wanted to add enough calcium to the water to account for the oxalate. But don't forget that the malt itself contains a fair amount of calcium which makes it entirely possible to brew with out accounting for the oxalate. As I mentioned above I brew most of my beers with calcium levels below the recommended 50 ppm Ca in the water but I don't brew with Ca as low as 10 or 20 either with the extra, to my way of thinking, being a little extra insurance. As visible oxalate crystals in my beer are few and far between I am comfortable with this and haven't been to see the lithotrypter in over 7 years (or more - time goes fast). Nor do my beers gush.