Root cause analysis for food safety incidents
How to use 5 Whys and a fishbone diagram to find the real cause, fix it and prove the fix worked.
Root cause analysis finds why a food safety problem happened, so you fix the system, not just the symptom. Use 5 Whys for a simple chain of events and a fishbone diagram when several causes are possible. Then set a corrective action for the immediate problem, a preventive action for the root cause, and a check that proves it worked before you close it.
Worked example: 5 Whys
Problem: a batch of cooked chicken was recorded at 71°C at CCP 2, below the 75°C critical limit.
| Why? | Answer |
|---|---|
| 1. Why was the core temperature low? | The batch came out of the oven early. |
| 2. Why did it come out early? | The operator went by the oven timer, not a probe reading. |
| 3. Why go by the timer? | The probe was out for repair and there was no spare. |
| 4. Why was there no spare? | Nobody owns the probe inventory, and calibration failures aren’t escalated. |
| 5. Why is nobody responsible? | The calibration program doesn’t name an owner or a minimum number of working probes. |
Root cause: a gap in the calibration program, not “operator error”.
Worked example: fishbone (6M)
Problem: repeat Listeria species positives in a drain in the packing room. More than one cause is possible, so list candidates under six headings, then test each one.
| Heading | Possible causes to check |
|---|---|
| People | Cleaning crew turnover; drain cleaning skipped on night shift |
| Method | Drain cleaning procedure missing the grate and trap |
| Machine | Cracked drain cover holding water |
| Materials | Sanitiser concentration below specification |
| Measurement | Swab taken after cleaning only, so trends are missed |
| Environment | Floor slope sends water from the wash area to this drain |
Illustrative. Confirm causes with evidence (records, observation, extra swabs) before you act on them.
Corrective, preventive, verified
Corrective action
Fixes the immediate problem. In the chicken example: hold and re-cook or discard the batch, and get a working probe on the line.
Preventive action
Removes the root cause. Name a calibration owner, keep a spare probe, and escalate any failed calibration the same day.
Verification
Proves the fix worked. Check four weeks of CCP 2 records for repeat deviations and audit probe availability before closing.
Common mistakes
- Stopping at “human error”. Ask why the system let the error happen.
- Retraining as the only action. It’s rarely the root cause on its own.
- Closing before verifying. Auditors look for evidence the fix worked.
- No owner or due date on the preventive action.
Corrective actions that get closed properly
In EthicalHub, a deviation or failed check opens a corrective action with fields for the root cause, the preventive action, an owner, a due date and the verification. Corrective actions are on every plan, and Professional adds deviation pattern alerts that flag repeat problems early. Plans start from $69 a month per site.
See a corrective action in EthicalHub
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Root cause analysis: common questions
What is root cause analysis in food safety?
When should I use 5 Whys and when a fishbone?
What’s the difference between corrective and preventive action?
How do I show a corrective action worked?
Fix it once, for good.
Root causes, actions and verification, recorded and tracked.