Alternate methods for oxygen scavenging mash water

[Bryan R]

Nice work.

[Owenbräu]

Looks great, Bilsch. Are you going to follow up with an SMB hefe and compare?

[Brody]

[Owenbräu]

Post 33 says no SMB at any point. Is this maybe a different beer?

[Bilsch]

I didn't use any SMB in this weisse because I wanted to see what the yeast (for de-oxygenating strike water) could do on it's own. Maybe Brody did use it in his test?

These past few months I've have been having a little problem with ferments finishing at as low gravity as I want them even while using yeast strains at temperatures very familiar to me. Oddly this batch is the first since switching to LoDO that finished at the gravity where I expected it to. So I will be making this same batch again using both the yeast oxygen scavenge technique and about 20 mg/l SMB. I want to see what effect the sulfites have, if any, on the fermentation. This all might be completely unrelated but I have to test it out.

As the members here have mentioned many times.. so many levers to pull.

[Brody]

[Bilsch]

Further yeast oxygen scavenging testing.
I have made three batches of beer so far using the YOS method of deoxygenating feed water and all has been working quite well. The first one was a hefeweizen where I used no additional Nameta. The second was a brown ale with 17mg/l additional SMB and lastly a Kolsch using the YOS procedure followed by 20mg/l SMB. Granted these styles are not testing the system like a helles would but that complex a beer is not appropriate this early in this project. Time and lagering will tell the full story but am as pleased as can be with the results so far. Also the reduced heatload while brewing this hot summer is a plus.
Simple tests have shown that yeast much prefer dextrose to drymalt extract as an energy source while scavenging oxygen and will do their job in half the time and with half the carbohydrate. Since 1/2 as much dextrose is required compared to DME, the amount in 7 gallons of mash water is only about 6 grams. But looking at the overall system it will probably have less effect on the final beer flavor in the system when using a completely fermentable clean sugar vs malt extract. More accurate numbers to follow.
On the topic of residuals from this process in the brewing water.. I found an old 5 micron filter bag in my lab from some long ago experiments and thought that might work well to corral the yeast while they work their DO magic on the water while afterword allowing for their easy removal. I tested the filter in a tub of water with dry yeast inside to see what would happen. The bag was only able to strain out about 1/2 the yeast cells, which would be expected due to their slightly smaller size. Duda sells 0.5 and 1 micron ones of similar construction and so those were ordered for further testing, which I will report.
Coincidentally these #4 sock type filters with molded plastic top ring will fit nicely inside my 10 gal corny. The plan is to fill the keg with 8 gal of water, I typically use 7 on a brew day, and suspend the bag from the cap of the keg, keeping the opening of the filter above the water level. Then before sealing it up, load the yeast cells into the bag. Next close and purge the keg a few times with carbon dioxide, leaving a few pounds of positive pressure. Lastly affix a spunding valve with gauge to be able to track pressure build if any, however I expect little. This deoxygenating reactor, as it were, should nicely clean up all the O2 in the keg including the headspace if given some time. I expect the yeast to be able to come close to zero DO especially given there is no contact to atmospheric oxygen possible. The reaction should be stable and could be prepared days in advance of brewing. When the DO water is required it would be forced out of the keg through the standpipe by positive CO2 pressure never touching the atmosphere. The water leaving the bottom the keg will uncover the filter bag as the level falls, slowly straining out the yeast cells. Also if the filter gets clogged and does not flow well, it won’t matter with the extra 1 gallon of water in the keg.
The next logical step would seem be to use a gas permeable membrane to sequester both the yeast cells and their carbohydrate fuel. In theory this would remove any negative effect the products and by products of this system on the brewing water. However I suspect that keeping the yeast and sugar together on one side of the membrane might cause them, once they have used up the easy oxygen, to shift to anaerobic fermentation. That would then eliminate the usefulness of a membrane type system.
However there might be some merit to designing a counterflow setup similar to the gas stripping devices employing a O2 and CO2 permeable membrane with feed water on one side and stripping gasses on the other. One might use instead a liquid liquid setup and recirculate an active yeast slurry counter to the feed water. The savings being not having to use low oxygen stripping gasses but instead free labor from microorganisms. All this would depend on a suitably large surface area of contact which I’m not sure is possible with a liquid to liquid system. If it was.. another wild idea would be to counterflow cooled wort from the brewery with incoming feed water and exchange the DO between the two streams. If it could be done though the Germans probably would already doing it.

[Brody]

Very cool, I think I'll try the dextrose next time. Did you take up a lot of oxygen mashing in the Hef without the SMS?

[Bilsch]

These are the readings I took.
DO at mash in was 0.29 mg/l
5 min 0.61 mg/l
15 min 0.72 mg/l
29 min 0.62 mg/l
55 min 1.26 mg/l
65 min 0.74 mg/l
120 min 1.20 mg/l
Measurements were taken in a rush in between brewing duties and obviously all the readings aren't accurate but do give a clue to what was happening as time went by in the mash unprotected by the sulfites. Did it effect the beer, almost certainly but it did turn out quite tasty. So maybe there is room in a hefeweizen for a little oxidation character, or more specifically.. room for them to hide.

[Brody]

Interesting, very cool stuff