Temperature control
When did you last check your probe?
Here is an uncomfortable thought. If your thermometer reads two degrees high, every temperature record you have written this year is wrong — and they all look perfectly fine on paper.
The five-minute check
Two reference points, both free:
- An ice slurry — crushed ice with a little water, stirred — should read close to 0 °C
- Boiling water should read close to 100 °C, adjusted for altitude
Let the reading stabilise before you take it. Record what it actually showed, not what it should have shown.
Why this matters more than one reading
A probe is the instrument that measures your critical limits. If it is wrong, every decision made with it was made on bad information — and every record written from it is unreliable.
That is the part people miss. A probe found out of tolerance is not a single non-conformance. It raises a question about every reading taken since the last verified check, and you need to be able to say when that was.
What to do when it fails
Adjust it if it can be adjusted, or replace it. Then record what you found, what you did, and what product or period is affected. A probe quietly swapped for a new one with no record leaves an unexplained gap.
This is also the argument for checking monthly rather than annually. A monthly check means at most a month of readings in doubt. An annual one means a year.
Which instruments count
Anything that measures a critical limit. Probe thermometers obviously, but also fridge and coolroom display readings, data loggers, and any gauge you rely on to make a release decision. Each needs an identifier, a tolerance and a check frequency.
What to do this week
Check every probe you own against an ice slurry. Write down the date, the reading and who did it. If you have never done this, the first round often finds something — which is precisely the point.
The short version
Ice slurry should read about 0 °C, boiling water about 100 °C. A probe out of tolerance puts every reading since the last check in doubt, so check monthly and write down what you found.
This is general information, not advice for your specific business. Check the requirements that apply to you against the current Food Standards Code and your own licence conditions.
The records for this
The free Food Safety Record Pack has fifteen everyday records including temperature, cooling, calibration and cleaning logs — with document control and a worked example on every sheet. No cost.
Read next
60 °C to 21 °C within two hours, then 21 °C to 5 °C within four more. Cool in shallow batches, and record the time at each stage.
Read it ›A record needs a date, a reading and a name. Complete it at the time, not at the end of the shift, and always record what you did about an out-of-limit result.
Read it ›