German Brewing

I wanted to look at how much sulfite carries through from the HLT to the fermenter, as well as test whether goat completely boils off or if we need to be specific and conservative with our dosing. Our normal dose is ~75 mg/L in both the MT and HLT. Since the test strips measure 10-1000 mg/ml, I was concerned about being confined to the lower end of the range, so I ran the experiment using 100 mg/L in both the HLT and MT. Here we go:

Test Strips:

Test Strips.jpg (204 KiB) Viewed 9655 times

Instructions.jpg (304.47 KiB) Viewed 9655 times

Titrating to pH (6-9):

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Control test strips (mg/l of goat)

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Controls 100 and 1000 mg per liter.jpg (198.32 KiB) Viewed 9654 times

I pre-boiled the mash water and let it cool without agitating it. I then put the goat on the bottom of the MT and transferred enough water from the HLT through the port underneath the false bottom to cover the bottom of the kettle. Once the salts were dissolved, I put in the grains and transferred the remaining water. As soon as the water broke through the grain bed, I took the first sample. From that point, I took a sample every 30 minutes.

Dough-in

MT @ Dough-In.jpg (234.22 KiB) Viewed 9654 times

30 minutes into the mash

MT @ 30 min.jpg (282.86 KiB) Viewed 9654 times

60 minutes into the mash

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90 minutes into the mash

MT @ 90 min.jpg (196.03 KiB) Viewed 9655 times

120 minutes into the mash

MT @ 120 min.jpg (197.86 KiB) Viewed 9655 times

Using 100 mg/l dosed sparge water, I began lautering and took a measurement of the final mash runnings.

MT @ Final Runnings .jpg (201.23 KiB) Viewed 9655 times

Once the boil kettle was full, I took a measurement of the now combined mash and sparge runnings.

BK - Post Lautering.jpg (200.17 KiB) Viewed 9655 times

I took a reading once the wort got up to a boil (about 20 minutes after lautering) and then every 30 minutes afterwards.

BK @ 0 min.jpg (198.14 KiB) Viewed 9655 times

30 minutes into the boil

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60 minutes into the boil

BK @ 60 min.jpg (160.91 KiB) Viewed 9655 times

90 minutes into the boil

BK @ 90 min.jpg (171.08 KiB) Viewed 9655 times

120 minutes into the boil

BK @ 120 min.jpg (200.72 KiB) Viewed 9655 times

I chilled the wort and took another reading, which represents the sulfite content going into the fermenter

BK - Post Chilling.jpg (177.02 KiB) Viewed 9655 times

Here are all of the strips laid out (and rehydrated with RO to eliminate dry/wet appearance differences).

All Strips.jpg (161.69 KiB) Viewed 9655 times

Furthermore, I had just brewed a helles before learning of goat, so I brewed the exact same recipe using goat as a comparison. The second helles was dosed 75 mg/L in the mash and sparge water, but no hog was used. The no-goat beer was about 3 weeks out of primary fermentation and the goat beer was about 1 week out of primary fermentation. I took a sulfite reading from each.

Goat vs No Goat Scale.jpg (183.04 KiB) Viewed 9655 times

Goat vs No Goat Strips.jpg (186.37 KiB) Viewed 9655 times

I appears to me that goat is initially consumed during dough-in, but does not change much after that. Comparing the 100 mg/l goat control and MT dough-in strips, it appears that 25-50 mg/l of sulfites were consumed during dough-in.

The final runnings contained sulfite concentrations nearly identical to the sparge water, indicating not much was consumed during lautering. As well, the wort sulfite concentrations went up after lautering, so the sparge water likely does not need to be dosed.

Additionally, goat does not completely boil off, so only the amount needed to control oxygen infusion during the mash is warranted.

It appears that a cold fermentation (7C pitch, free rise to 9C, hold) and transferring to a keg at 2% remaining extract (4-4.5% total) to spunded results in approximately 10ppm of yeast derived sulfites. A goat dose may not be necessary unless another transfer (e.g., umdrucken) or bottling is required, or possibly if a warm fermentation doesn't retain the same sulfite levels as a cold fermentation.

Sorry to be a newb, but what is "goat" ? Is this a reference to SMB ? From your experiment/findings, I'm assuming so. From your findings, it seems a minimum dose to up to 50 mg/L for mashing in. I wonder how low one could get that starting dose with through purging of the grain bed + mash tun with CO2/nitrogen.