Run this before every batch goes into bottles. The reading is
the one thing standing between a recipe and a safe shelf-stable product.
Before you measure
Meter calibrated today, two point, at 4.0 and 7.0, with fresh
buffer. Write the calibration down.
Product equilibrated. Wait the time your scheduled process
specifies from when the acid went in. A thick sauce takes longer than a thin one.
Sample at the specified temperature, usually around 20C. A hot
sample reads lower than the same product cooled.
More than one sample, from different parts of the batch.
What your reading means
At or below your process target
Proceed. Record the value, the time and the meter.
Your scheduled process target, not 4.6. Most sit at or under 4.0
because the line is a limit rather than a goal.
Above target, below 4.6
Do not bottle. Correct and re-measure after full equilibration.
Inside the legal threshold and outside your filed process, which
means this batch was not made to the process you registered.
At or above 4.6
Stop. This is not a shelf-stable product.
Below roughly 4.6 the botulism organism cannot grow. At or above it
the control is absent, and nothing about the taste or appearance will tell you.
Readings differ across the batch
Do not average them. Blend thoroughly, equilibrate again, re-measure.
A pocket above the line is exactly the failure the rules are written
around, and an average hides it.
If it is too high
Add acid and re-equilibrate, then measure again. Do not bottle on the expectation
that it will fall further.
If a correction takes the batch outside the formulation in your filing, that is a
process question rather than a recipe adjustment. Record what happened either way;
a corrected batch with a record is defensible and a corrected batch without one is
not.
References
21 CFR Part 114,
Acidified Foods. Low-acid foods to which acid is added, water activity above 0.85, finished equilibrium pH 4.6 or lower reached within the time designated in the scheduled process. 114.3 excludes carbonated beverages, jams, jellies and preserves, foods stored, distributed and retailed under refrigeration, and acid foods including condiment sauces containing small amounts of low-acid food whose finished equilibrium pH does not significantly differ from the predominant acid.
ecfr.govUS Food and Drug Administration.
Draft Guidance for Industry, Chapter 16: Acidified Foods.
fda.gov 