Equilibrium pH, and why 4.6

One number decides whether your product is a shelf-stable food you can make in a modest facility or a low-acid canned food requiring equipment you do not have.

The number the whole category turns on

4.6. An acidified food must achieve a finished equilibrium pH of 4.6 or lower.

Below that, Clostridium botulinum cannot produce toxin, which is why the threshold exists and why it is not negotiable. Above it, you are making a low-acid canned food, which is a different regulatory category with retort processing requirements.

Producers often target meaningfully below 4.6 rather than at it, because 4.6 is the limit rather than the goal and there is no credit for being close to a cliff.

Equilibrium is the operative word

Not the pH of the sauce when you bottle it. The pH after everything in the jar has come to equilibrium, which for a product containing solid pieces can take considerably longer than people expect.

A sauce measuring 4.2 at filling can drift upward as acid is absorbed into pepper or vegetable pieces and the interior of those pieces gives up its own higher pH to the mixture.

Which is why the scheduled process specifies a time within which equilibrium pH must be achieved, and why measuring at the wrong moment tells you nothing useful.

How long you have

Whatever your scheduled process designates. It is one of the critical factors the process authority sets, and it depends on your formulation, your particle size and your container.

Hold product for that period and measure then. Measuring immediately and shipping is the commonest way a compliant-looking product turns out not to be.

What happens above it

The regulation is explicit. If the equilibrium pH of finished product is higher than 4.6, the processor must fully reprocess that portion, thermally process it as a low-acid food, or set it aside for further evaluation.

Those are the three options. Shipping it is not among them, and neither is adding acid to the bottles.

References