Keeping o2 out of the brewhouse

[Weizenberg]

Ok, I now have it from good authority that indeed the brewing liquor is de-oxygenated, particularly the under letting water in the sparge tun (to fill the empty space under the mesh) and the sparge water itself. This is also the case for the water used in the filter phase.

In commercial breweries the CO2 is dosed according to some calculations (no idea how to do these) and then bubbled through the liquor once it reached the desired temperature.

The consensus is that it is beneficial to the taste.

Good find!

[Techbrau]

I kegged my latest helles today after about a week of lagering in the primary vessel. The taste is extremely clean and clear, and tastes "fresher" than I've ever had a batch before. The malt flavor is predominantly graham cracker-esque and not so much "fresh field of grain" like we're going for, but I think it's a positive step. I assume my mash was sitting around 2ppm O2 like Bryan's, so we can probably do much better than that using k-meta.

I'm getting more and more convinced that this is one of the last remaining secrets to getting the elusive flavor of "it"

[wobdee]

Great news! I have a Czech Dark I'll be kegging tonight that was deoxygenated with a preboil, looking forward to a taste.

[Bryan R]

[Weizenberg]

I am not sure I'd wat to boil the o2 off, since this alters the water profile. I guess one should be able to do it like the breweries, using kegs and CO2. I might give it a go soon....

[wobdee]

[Bryan R]

I think for your test of this you should just use RO. But I am pretty sure you water is under the threshold of anything precipitating. If you look at Munich and Munich boiled in brunwater you will see what I mean. You would think boiling removes everything , but it doesn't as you have the minimums.

[Techbrau]

Boiling alone is not enough. German breweries can get away with degassing their water and then mashing under nitrogen in a closed system. Because we can't do that, oxygen will continue to diffuse back into the mash. When Bryan pre boiled his mash water, it was down to a fraction of a ppm of oxygen, but then began to absorb oxygen and sat at around 2 ppm for the duration of his mash. While going from the 6 ppm you would have with non-degassed water to 2 ppm is an improvement, I think we need to get it lower.

The easiest way that I can think to do this right now is adding potassium metabisulfite to chemically buffer out any oxygen which diffuses into the mash. Using 1/3 of a tablet per gallon of water (approximately 208 mg of potassium metabisulfite) should add about 22 ppm of sulfites to the mash, which should be enough to take care of oxygen without adding to many extra minerals. It will change the water profile, but it's hard to know by how much since some of the sulfites escape as SO2 during the boil and others end up forming SO4 and staying in the wort. My best estimate would be to figure that using this method will give you an extra 10 ppm of SO4 than was originally in your water, along with a couple ppm of potassium. Boiling the wort should destroy or drive off everything added by the k-meta except the aforementioned potassium and SO4.

I still think pre-boiling is a good idea, because you know that the oxygen content is 0 immediately after boiling. Otherwise, you'd have to try and guess how much extra k-meta to add in order to scavenge all of the initial dissolved oxygen and still have enough sulfites left over in solution to capture any that diffuses in. Just remember to add your potassium metabisulfite after pre boiling.

[Weizenberg]

It's tricky. Arguably the decoctions will remove some of the O2. I found it interesting that the professional systems only de-oxygenate the water once it reached the desired temperature for dough-in. That happens with CO2. I know that an award-winning home brewer in Munich always treats the water with slaked lime, then titrates the m- and p- value in order to determine the RA, then adjusts the water with lactic acid and CaCl2 until the RA is below or at -2dH.

His sparge tun has empty space that is filled with water before the grain goes in. This water is de-oxygenated with CO2.

I *might* try de-oxygenating the dough-in water just before it's used. I am not sure about boiling it due to the time and energy cost, as well as the potential uncertainty about the actual liquor composition. My attitude may change though

[wobdee]

https://www.morebeer.com/articles/oxidation_in_beer