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Yeast Mash experiments

Posted: Thu Nov 10, 2016 9:23 pm
by Bilsch
In another thread I posited an idea of using yeast to scavenge oxygen in the mash in place of sulfites. The reason for wanting an alternative to nameta is for ale brewing since most of the yeasts do not tolerate sulfites well during fermentation. One big problem with this idea is that yeast die at typical mash temperatures and cannot continue to do their DO removal job all the way through to mashout. However if one doughed in at typical acid rest temperatures and held long enough for the yeast to scavenge the oxygen, you could then move as quickly as possible up to beta rest temperatures and at least limit HSA damage to the wort.

Today I had time to throw together a simple test to look at the basic process and I have posted all the results below. Based on the numbers generated by the second test, I feel confident that yeast can at least keep up with the diffusion of oxygen caused by mechanically mixing grain with water. It is doubtful a mash cap and gentle handling alone could be enough to stave off all oxidation while transitioning from 35c to 70c and mash out and therefore this method probably is not suitable for brewing lagers. However for ales the probable small amount of HSA from this procedure might be tolerable or even desirable. It definitely deserves more testing in a full batch of beer and I intend to add this to my ever lengthening 'to brew' list.

Run #1
Water RO 500ml Temp: 35c
Profile: Ca 30, Mg 4, Na 6.2, SO4 16, Cl 55
Yeast, dry: 0.22 gm (Lessafre bread type) Dextrose: 0.22 gm
Grain, 2 row 86 grams

Time - DO mg/l
0 - 7.5
6 - 7.03
20 - 1.69
41 - 0.31
1:04 - 0.32
1: 05 - add grain
1:07 - 0.70
1:12 - 0.55
1:18 - 2.82 (average, reading unstable)
1:25 - 2.49 (average, reading unstable)
1:57 - 0.34 (average, reading unstable)

At the 1:18 mark I started to get quite unstable DO readings from my meter. Re-calibrating it had no effect and then I also noticed quite a few bubbles in the electrolyte under the membrane. I had a new one and so decided to change the bonded cap membrane and electrolyte on the meter and start the whole test over again.

Run #2
Water RO 500ml Temp: 35c
Profile: Ca 30, Mg 4, Na 6.2, SO4 16, Cl 55
Yeast, dry: 0.22 gm (Lessafre bread type) Dextrose: 0.22 gm
Grain, 2 row 86 grams

Time - DO mg/l
0 - 6.34
10 - 4.75
20 - 1.95
40 - 0.25
58 - 0.31
1:00 - add grain
1:03 - 0.30
1:08 - 0.25
1:13 - 0.41
1:20 - 0.44
1:28 - 0.44
1:38 - 0.33
1:39 - Raise temperature to 65c

It took roughly 11 minutes to increase the temperature to 65c where I held for another hour. The sample jar was kept uncovered during the whole process and as typical in low oxygen mashes it was very difficult to smell. After conversion I sampled the wort and found it to be quite pleasing with usual lodo fresh malt flavors.

Note: These were mini type mashes done in mason jars and heated by water bath.

Re: Yeast Mash experiments

Posted: Fri Nov 11, 2016 2:58 pm
by TheHairyHop
very interesting. I was thinking of doing qualitative experiments with this method, as I don't have a DO meter. At the very least, it could be used to minimize the amount of necessary SMB. Thank you for going through the steps and posting the results.

Re: Yeast Mash experiments

Posted: Sat Nov 12, 2016 6:35 am
by bjanat
Thanks for doing this. I was going to comment on one thing, if you use yeast with high temperature tolerance you might do the dough-in at 50C. Norwegian farmhouse yeast (kveik) ferments ideally at 40C, and although I don't know the exact tolerance, it could be interesting to try. I have some at home, and might do it next time. In the US it's available from The Yeast Bay ... voss-kveik

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Re: Yeast Mash experiments

Posted: Sat Nov 12, 2016 5:14 pm
by Bilsch
Your both welcome.

Another thing that these tests were useful for was confirming the time needed for yeast to reduce DO to a minimum level in brewing water and that seems to be about 40 minutes only.

Standard baking yeast is active up to at least 48c so not too far apart from the farmhouse yeast. I did also read that at temperatures of below 37c glutathione leaks out of the yeast cell walls. Interestingly enough this chemical is an antioxidant. Baking yeast strains are apparently selected for their higher glutathione content as it has positive conditioning effects on dough.
Here is interesting article on antioxidants in baking which also mentions bisulfite use. ... 7REDUC.PDF

Re: Yeast Mash experiments

Posted: Sun Nov 13, 2016 9:05 pm
by TheHairyHop
I noticed that the DO jumped 100% on your first run after adding the grain, but the content barely changed on your second. did something happen in the first experiment while adding grain that didn't happen in the second, or do you think it comes down to the faulty meter?

Re: Yeast Mash experiments

Posted: Mon Nov 14, 2016 12:45 am
by Bilsch
That's a good question..
Both runs were done exactly the same so I feel confident the odd numbers in 1 were meter related. There were a lot of bubbles in the electrolyte so I'm amazed I got any coherent numbers from the first run at all. Granted it is strange though it acted up when it did. While not to the same extreme both runs did indicate that the DO levels started to rise about 8-10 min after dough in. I found that interesting as one wouldent really expect a delay.