HACCP — Hazard Analysis and Critical Control Points, codified by Codex Alimentarius and required in practice by every major food audit scheme (BRCGS, IFS, FSSC 22000, SQF) — is a food safety system, not a quality control method. Its seven principles are about identifying hazards, deciding where they must be controlled, setting limits at those points, monitoring them, correcting deviations, verifying the system and keeping records.
SPC is not mentioned. SPC is, however, the natural way to satisfy principles 4 (monitoring), 5 (corrective action) and 6 (verification) — and the way most plants satisfy them instead is a clipboard.
The distinction that everything hinges on
| Critical limit (HACCP) | Control limit (SPC) | |
|---|---|---|
| Where it comes from | Science, legislation, validated process authority | The process's own behaviour |
| What it means | Cross it and the product is potentially unsafe | Cross it and something has changed |
| Chosen or computed | Chosen | Computed |
| Consequence | Deviation, hold, corrective action, records | Investigation |
| On a chart | A separate reference line, if shown at all | The limits themselves |
A pasteuriser with a critical limit of 72 °C for 15 seconds does not become unsafe at 71.9 °C because of anything statistical. And a pasteuriser drifting from 74.5 °C to 72.6 °C over four hours has told you, loudly, that something is wrong — while every single reading passed the CCP check.
That gap is the entire contribution SPC makes to food safety. The checksheet records a series of passes right up to the failure. The chart shows the drift on the second or third reading, when it is a maintenance job rather than a product hold.
The corollary is just as important: never treat a control limit as a critical limit, or vice versa. A control chart that signals is not a food safety deviation, and a process comfortably inside its control limits can still be sitting dangerously close to a critical one. They answer different questions and they belong on different lines.
Where SPC fits in the HACCP system
- Principle 4, monitoring. A chart is a monitoring record that also carries a trend. Same data, same frequency, far more information.
- Principle 5, corrective action. A signal with a recorded cause and a named person who closed it is precisely the evidence an auditor is looking for, and it is stronger than a ticked box.
- Principle 6, verification. "Is the HACCP plan working?" is a question about a system over time, which is what a control chart is for. Charted CCP data across a quarter answers it far better than a sample of checksheets.
- Prerequisite programmes. Hygiene swabs, ATP results, water testing, glass-and-hard-plastic checks — count data, best charted as counts, and mostly never charted at all.
What the audit standards ask for
BRCGS, IFS and FSSC 22000 do not mandate control charts. What they require — and what the auditors probe — is: monitoring at a defined frequency, records that show it happened, evidence of trend analysis, and demonstrated corrective action. Trend analysis is the clause where a spreadsheet of pass/fail ticks starts to look thin, and it is the reason plants end up building charts anyway.
Where this platform helps
- One place for everything the line measures — fill weights, temperatures, pH, Brix, seal strength, swab counts — rather than one system per instrument.
- Frozen limits with a recorded baseline, so a recipe or seasonal change is a documented re-baseline, not a chart that quietly moved.
- Rules evaluated on arrival, with an alert. A drift starting at 02:00 gets noticed at 02:00.
- A line-side display operators can see, and share links for a retailer's technologist.
Where it does not
- This is not a HACCP or food safety management system. No hazard analysis, no CCP register, no corrective-action workflow, no traceability, no supplier approval, no document control.
- No p, np or u charts — rejects per batch with a varying batch size is a u-chart and we do not draw one. Straight counts per equal interval work.
- No statutory average-weight reporting.
- Not a LIMS.
Use it for the trend, keep your food safety system where it is. The worked example — a filling line where the legal limit is never threatened and the giveaway is costing real money — is on the food and beverage page.