Low-temperature pasteurization
Updated
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The numbers, and why the band is narrow
The published window is 180 to 185F, held for 30 minutes, and both ends of it matter.
- Below 180F may not destroy the organisms the process exists to destroy.
- Above 185F and you lose the crispness that was the entire reason to do it this way.
That is a five degree band held for half an hour, which is why this is a thermometer process rather than a watch-the-pot one. Guessing inside a five degree window is not a thing anybody can do.
What it buys
Texture. A boiling water process is hotter and costs crispness, and for a product whose appeal is the snap, that cost is the product. This is the one place in the craft where a more demanding process is rewarded directly in the jar.
What it demands
Attention for the full thirty minutes, and a thermometer you trust. It does not scale the way a boiling water canner does, because holding a band is harder than holding a boil and gets harder as the vessel gets bigger. Makers who move to volume often move away from this for exactly that reason, and lose a little texture doing it.
As with everything else on this section, the commercial version of this decision belongs to your filed process. It is not a substitution to make on your own authority once you are selling.
Calibrate the thermometer, not just the process
A five degree band is narrower than the error on an uncalibrated dial thermometer, which means the instrument has to be checked rather than trusted. Boiling water at your altitude is a free calibration point and it takes a minute. A process held confidently at what the dial calls 182F and is actually 176F has the form of a safe process and not the substance of one, and nothing about the jar will tell you afterwards.