I'd like to add some constructive advice to this old thread: one can adjust the initial pH of a brine to minimize any botulism risk.
I view the risk as small, but botulism can kill, so it's hard to find the patience for a FlyerTalk "of course I can leave my smart phone on while we land!"
debate. In both cases I'm willing to take risks, but I'm not willing to impose those risks on others. Dismissing another user's expertise is not the same thing as dismissing the risk; true wisdom is knowing what one doesn't know.
The bacteria that causes botulism does not grow at a pH below 4.6, although the toxin then persists below this pH. The pH of finished sauerkraut is between 3.0 and 4.0. Vinegar has a pH in the range 2.4 to 2.7. This is a logarithmic scale, so getting the initial pH of a brine below 4.6 leaves plenty of headroom for one's fermentation to complete. Though fermentation takes place in stages, and a lower initial pH may affect this progression. A balance is in order here.
I've been making hot sauce annually for about a decade, fermenting in a beer-making carboy using kimchi juice as starter. (This year I'm switching to a crock, which lead me to this forum.) I've been using a pH meter and small amounts of white vinegar to adjust the initial pH to the range 4.2 to 4.4.
Wikipedia's Acetic acid
entry states that a 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4. Using this, one can use an online pH calculator
to determine the pH of various dilutions.
An acetic acid concentration of 0.00006 M yields a pH of 4.6, while a concentration of 0.006 M yields a pH of 3.5. This is a factor of 100. However, the situation is more complicated that calculating salinity: pH concerns the active
hydrogen ions, and what encourages a hydrogen ion to go active is above my pay grade. In particular, this process is well understood in water, but my chiles could be having a buffer effect. So nothing beats a well-calibrated pH meter for seeing what's actually going on.
Nevertheless, one can use these pH calculators to make an educated guess how much vinegar to add to a brine, to reduce pH below 4.6 without unnecessarily affecting the initial stages of fermentation. We're talking a few tablespoons, to provide a large margin of error.
For what it's worth, I find that my pH meter tells me to add more vinegar than these calculators suggest, indicating that my chiles are indeed having a buffer effect.