The Hamilton VisiTrace DO probes are reported to sense 0 to 2 ppm DO at temps up to 85C. That would suffice for mash use. I was lusting after them at last year's CBC but the $2k price tag was too much for me.
Thanks Martin for taking the time to write.
I would love to see the validation tests this company has run.
I am a bit suspicious because many researchers have indicated that measuring DO in the mash is not directly possible, and none of the published data uses a DO meter.
In the Stability of Beer chapter of the Handbook of Brewing, 2012, August Gresser writes: It is known that oxygen at higher temperatures reacts with polyphenols, anthocyanes and tannoids. Brighter beers that are richer in polyphenols are more sensitive to oxygen in comparison with medium - colored beer and, especially, darker beers. For this reason, the brewer should carefully monitor the presence of oxygen with instruments during wort filtration and also during mashing, wort boiling or in general in the field of higher temperatures. Oxygen cannot be determined during the mashing process – one can take values from empirical procedures...
In Enzymic and Non-Enzymic Oxidation in the Brewhouse, 1999, Bamforth states:
An additional complication concerns the assessment of oxygen consumption at this stage in the process. Direct measurement of oxygen in mash is fraught with difficulty and most people have reverted to redox measurements (using redox probes or colorimetric techniques) to gain an indication of the extent of oxidative damage. The interpretation and relevance of such measurements is by no means straightforward.