Walk-in Failure Before a 42-Cover Sashimi Service
At 07:40 on a Saturday the sous-chef finds the sashimi walk-in reading 9.4°C. The door was left ajar at the 23:00 close, and the data logger shows the room passed 4°C at about 01:15 and sat between 7 and 10°C for roughly six hours. Inside are a 4.2 kg vacuum-packed block of hon-maguro delivered Friday 09:00 with a 3°C core and a surface now at 8.9°C; 3 kg of unwrapped sashimi-grade tai fillets at 9.1°C; 60 peeled amaebi at 9°C; last night's cooked sushi rice, cooled and kept for staff meal; and unopened vacuum-packed salmon. The restaurant's HACCP plan requires ≤4°C for raw fish and a 24-hour limit on thawed product. Service starts at 11:30 with 42 sashimi covers and 28 nigiri sets. The head chef wants to rinse the tuna in iced 3% salt water, trim the surfaces and serve everything as planned.
1. Set the disposition for each of the five items in the walk-in: serve raw, rework for cooked service, or discard. Give the reasoning that drives each call.
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The plan's 4°C limit is a validated control, so the assessment turns on three questions: was the core temperature kept, is the exposed surface the surface that will be eaten, and does the species carry a hazard that survives reworking?
- Tai fillets, unwrapped - discard. The surface is the sashimi surface, has been at 9°C for about six hours, and there is no core to verify. No downstream step would make it safe for raw service.
- Amaebi, peeled - discard. Unwrapped, high surface-to-mass ratio, heavily handled, and a recognised vehicle for Vibrio and Listeria. Same rule as the tai.
- Cooked sushi rice - discard. Rice held in the 7–10°C band is the classic Bacillus cereus setting; cereulide is heat-stable, so reheating or frying is not a control.
- Salmon, unopened vacuum pack - hold, then rework. Probe the core: if it is ≤4°C the pack insulated the product and it can go to a cooked application the same day. It is not returned to the raw menu because the room history, not the pack, is the control.
- Maguro block - no raw service. Vacuum and 4.2 kg of thermal mass mean the core may still be low, so probe it. If the core is ≤4°C it can be downgraded to a cooked item; if the core exceeded 4°C, discard. Either way it does not go on the sashimi counter, because tuna is a scombroid species.
Log core temperatures, times and every disposition before anything moves.
2. The head chef argues that trimming and salt-rinsing makes the maguro safe. Explain why this does not restore the product, naming the specific hazards at issue.
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There are two separate hazards, and the proposed treatment addresses neither.
Bacterial contamination. A 3% salt dip is roughly a 3% NaCl solution. That is far below the 15–20% needed to inhibit most vegetative bacteria, and it has no sporicidal or toxin-destroying effect. Rinsing does not sterilise a surface; it redistributes cells across it and into cut tissue, and it adds water that raises surface water activity. The bacteria are also not only on the surface: they sit in the cut faces, the connective tissue and the channels along the spine.
Histamine. Maguro is a scombroid fish. Decarboxylase-positive bacteria convert free histidine to histamine, and histamine is heat-stable: it is not destroyed by salt, trimming, cooking or freezing. Trimming the outer centimetre lowers the bacterial count, but it does not reliably remove histamine that has already formed and diffused into the block, and the core history of a 4.2 kg block is unverified.
So the question is not whether the fish can be made to look and smell acceptable. It is whether a control has been met, and it has not. The maguro is withdrawn from the raw menu; if the core checks out it goes to a cooked application, and the decision is recorded as a deviation.
3. Write the corrective-action plan you would complete before the 11:30 service and the records you would file.
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Before service:
- Segregate and label. Move all suspect product to a clearly marked holding area, tagged 'not for raw service', so no one plates it under pressure at 11:25.
- Probe and log. Core temperatures of the vacuum packs and the maguro block; record time, item, temperature and who took it.
- Discard the tai, amaebi and cooked rice into a recorded waste log.
- Sanitise the walk-in, the door frame and the gasket, and check that the door closes and the alarm works.
- Verify the instruments - logger calibration and a second thermometer check - before trusting any of the readings.
- Re-source: call the alternate supplier for sashimi-grade fish by 08:30. If nothing arrives, rewrite the 11:30 menu with cooked items (grilled fish set, seafood donburi) and put the sashimi on the 86 list.
- Brief the floor on the 86 list and the script for guests.
Records to file: the deviation report (time discovered, duration above limit, product and quantities), disposition records, corrective action and root cause (door left ajar at close), verification that the door alarm and closing checklist were corrected, and the signature of the HACCP-responsible person. If the head chef wants to override the limit, that instruction must be documented and signed by the person with HACCP authority - not settled verbally in the kitchen.