German Brewing

So I wanted to do a small pilot experiment investigating whether it would be possible to eliminate the preboil step and just rely on sulfites alone to remove the oxygen from the strike water.

Because my DO meter is only rated to 122 degrees F, I heated 2 liters of water to slightly below that temperature in a saucepan.

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Then, I measured the initial DO content to be 8.13 ppm.

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Next I measured out 130 mg/l of SMB, or 260 milligrams

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As soon as I added the sulfite I gave it a quick stir to distribute it uniformly, and then set a timer going. I measured the DO once every minute.

1 minute in

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2 minutes in

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3 minutes in

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I missed the measurement at 4 minutes because I was taking my lunch out of the oven. Anyway, here's 5 minutes:

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6 minutes

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7 minutes

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8 minutes

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9 minutes

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10 minutes

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Okay, so after 10 minutes we got down to 1.15. I decided next to see what would happen if I splashed the water a little. So I poured it from a height of about 5 inches into another pot, then measured the DO

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So how long is it gonna take us to get under 1 ppm? I waited another 10 minutes after this point (20 minutes total) and took another measurement

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Hmm. Why is it so high? I wonder if we've already used up a lot of our sulfites, so let's measure that

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Wow, down to less than 50 ppm. We started with 130 * .76 = 98.8 ppm, so we just used up more than half of it. At a little over 1 ppm DO left and with the reduced sulfite concentration, it doesn't look like it can reduce oxygen faster than it's diffusing in at this point. It's possible that we would have gotten below 1 ppm if I hadn't poured the water, so that may need some further investigation.

So obviously this a little pilot experiment and it isn't a full scale mash. However, I think it suggests something very important:

SULFITE IS NOT A CURE-ALL MAGIC BULLET!

You can't just add some fairy dust to your water and expect it to keep your mash and boil under 0.5 ppm DO for 3 hours straight. Henry's law is a bitch, and the lower your DO levels become the faster more oxygen diffuses in. You need to win the battle on EVERY FRONT and your system is only as good as the weakest link in the chain. For me, this means preboil, high sulfite dose, NO splashing or leaky hoses, no copper/iron/manganese etc in the water and some sort of inset lid or mash cap with as little headspace for air as possible.

Nice experiment. I've often wondered if a larger dose would enable us to skip the preboil.

Well ain't that just a PITA....

Also suggests to me that you need to get the SMB into the water very shortly after boiling and limit the headspace in the HLT with a tight fitting cover.

This is fascinating stuff!