Automating HACCP temperature logs without losing the evidence

Every UK food business must have a food safety management system based on HACCP principles, and temperature control is the critical control point that shows up on almost every inspection. In practice that means recording fridge and freezer temperatures, acting when they drift, and being able to show both when an Environmental Health Officer visits.

What the record has to show

The Food Standards Agency's guidance (the Safer Food, Better Business pack for small businesses, and the full HACCP approach for larger ones) does not prescribe a logging interval, but it does expect three things:

1. Evidence that checks happened. Chilled food should be kept at 8 °C or below by law in England, Wales and Northern Ireland; most businesses target 1–5 °C. Frozen food is normally held at −18 °C or colder.
2. Evidence of what you did when something went wrong. A reading out of range is not a failure; failing to notice or act on it is. The record should show the deviation, who saw it, and the corrective action.
3. A record you can produce. Daily or weekly sheets, kept for an agreed period, that an inspector can read in minutes.

Where paper falls short

Paper logs are usually completed twice a day. Between the morning and the evening check a fridge can fail, recover and fail again with nothing on the sheet. Entries are easy to backfill from memory. And a lost clipboard is a lost year of evidence.

Where stand-alone loggers fall short

USB and Wi-Fi loggers close the gap in frequency but open another one: someone has to collect the files, and the record stops when the Wi-Fi does. Alerts, if any, go to one phone. There is rarely a trail of who acknowledged what.

What an automated record should do

• Log often enough to catch a real failure — every ten to twenty minutes is plenty — and keep the record somewhere nobody can edit it.
• Separate a defrost cycle from an excursion. A rule that fires on the first warm reading will fire on every defrost. Requiring the condition to persist for a set number of minutes, and clearing it only once the temperature is back inside the band by a margin, removes the noise without hiding the real events.
• Escalate until somebody acts. Email, then SMS, then a phone call, with the acknowledgement recorded.
• Capture the corrective action at the moment of acknowledgement, because that is when it is known.
• Survive the internet going down. LoRaWAN gateways do not buffer readings, so the sensors should. The probe sensors Tempa deploys store thousands of timestamped readings and resend the ones the network missed once it returns; the gap is filled at the right time, not papered over.
• Produce the report in three clicks, with the readings at a stated interval, the deviations and actions, a sign-off line, and a fingerprint (a SHA-256 hash) that proves the file has not been altered.

That is the design brief Tempa's Sense pack was built to. The daily and weekly HACCP records, the monthly compliance summary and the deviation log are generated from an append-only database, and every PDF carries its hash.

This article is general information, not legal advice. Check the current FSA guidance for your business type and nation.