Keeping o2 out of the brewhouse

[Bryan R]

So I(and others) have been testing keeping o2 out of the brewhouse. I pre-boiled my brewing water, and tried to minimze any splashing or unwanted uptake measuring with my DO meter, when brewing my last beer. My last beer was a Vienna, and the recipe looked like this...

85% Vienna
13% chit malt
2% carahell
FWH magnum
60 min Mittelfrueh

12.7p
20ibu tinseth
~11ebc

Enhanced double decocoction, ala Kai, I think 35 minutes total boil time.

EBC prediction after Decoction/boil ~14

Boiling out all o2 start:


End:


DO reading:


DO mash reading:


Pre-boil:


Post boil, compared to 6srm IPA:


Post boil, comapred to 3.2 srm Pils:


Beer entering lagering:


I think it can be seen that low o2 definitely effects colors (which, I think we knew), but is it the key to it? Is it a polyphenol that is easily oxidized? I have some ideas how to keep o2 even lower, to see if this helps.

[Weizenberg]

pH also affects colour.

[Bryan R]

Mash pH

[Weizenberg]

Looking good!

For an even brighter beer you can adjust the wort pH to 5.1 instead of 5.2, but there is a snag. Technical lactic acid doesn't taste too well. Apart from being expensive, there is an unwanted flavour impact. This is one of the reasons why German breweries work with 'Sauergut' (biological lactic acid - acidulated wort), rather than technical lactic acid.

For the home Brewer the best compromise is to use acidulated malt in the grist, then adjust the wort with technical lactic acid, hoping to have as littler gap as possible to overcome. That's why some people prefer to mash at pH 5.4, the gap will be less once it comes to adjusting the wort pH.

Working with Sauergut instead of technical lactic acid is probably the biggest distinctive factor in German brewing. Hardly anyone outside Germany seems to do it (I yet have to hear about someone doing this).

I think that working with Sauergut will have a far bigger flavour impact than removing oxygen from mash water.

Am quite surprised most texts I read about German brewing delegate this to a side-note, given its considerable impact.

[Bryan R]

Ahh, yes this grist included acidulated malt, then altered with lactic in the boil.

[Weizenberg]

If you want to do it 100% German, then you need to have your own acidulated wort for these purposes.

Boiling water is not a great way of de-oxygenating. It may render the beer rather empty tasting. Maybe I'll write my musings on this up once I've done it for my next batch.

Ths process is equally important for flushing depth filters.

[Techbrau]

Empty tasting because of minerals lost to the precipitation of calcium carbonates? If the water is already low alkalinity, there will be little if any precipitation. Even if this is a concern, you can always start with RO water and add your mineral additions after preboiling and force cooling.

I agree that boiling alone isn't enough to keep oxygen at bay because it diffuses back in during the mash, as you can see from Bryan's DO readings. This would still be a problem even with water deoxygenated via bubbling CO2 up through a column as the German breweries do. In lieu of a closed system in which we can mash under a layer of nitrogen or argon gas (which appears to be common in German breweries) it seems to me that we'd need to resort to chemical antioxidants such as potassium metabisulfite added to the strike water before doughing in.

I've got a batch of helles (96.5% pils, 3.5% carahell) lagering now which was made with deoxygenated mash water. The malt flavor is noticably clearer and fresher than the previous batch I made which didn't use degassed water.

[Weizenberg]

Now that's interesting. Are all the other variables the same? Ie did you brew the same batch with regular liquor?

[Techbrau]

Aside from the water being preboiled in the second batch, the only other difference was the grist, which was 97% pils, 2% carahell, and 1% caramunich 1 for the previous batch. It's not a perfect comparison for that reason.

My next batch will likely be exactly the same as the 96.5/3.5 batch, but using potassium metabisulfite in the brewing water.

[Weizenberg]

1% of Caramunich 1 is quite noticeable in a Helles. Also, the water composition cannot change. For the comparison to be conclusive, only one variable, namely the degassed water, should change.

Its important to avoid false positives, a different malt composition as well as a different water composition makes a comparison difficult.