Bakery Tunnel Oven — Hot-Clean Allergen Changeover
A high-volume bakery line cut its allergen changeover time from 14 hours to 4 hours by replacing chemical cleaning with dry ice — without a single shift lost.
A high-volume bakery line cut its allergen changeover time from 14 hours to 4 hours by replacing chemical cleaning with dry ice — without a single shift lost.
The brief
A Melbourne specialist bakery runs three product lines on a single 32-metre tunnel oven. Two of the lines share a major allergen (egg) and the third is allergen-free. Each switch from the egg-containing products to the allergen-free product required a validated allergen changeover — including a full sanitation cycle on the oven, conveyor and downstream packaging machinery.
Their existing process was chemical-based: cool the oven (3 hours), apply alkaline cleaner (2 hours dwell), rinse (1 hour), wait for cleaning to dry (2 hours), warm the oven back up (3 hours), validate with ATP swabs (1 hour), restart. Round trip: 12-14 hours per changeover, twice a week.
That’s a shift lost each time. The QA lead had been looking for alternatives for 18 months.
The work
Phase 1 — Trial. We ran a single trial cycle on a planned changeover. Existing chemical clean ran in parallel as a fallback. Dry ice clean was scoped to: oven walls, bake plates, conveyor belt, oven exit zone, packaging filler. ATP swabs from same locations as their existing protocol.
The dry ice cycle ran while the oven was at 110°C — well below operating temperature but no cool-down required. The whole sequence took 4 hours including ATP validation. Swab readings matched or beat the chemical clean comparison.
Phase 2 — Validation. QA wrote the procedure, ran swab studies over 8 changeovers, and got sign-off from the food safety lead. The process was added to the HACCP plan.
Phase 3 — Production. We’ve been on a contract since with crews dedicated to their two scheduled changeovers per week. Each cycle takes 4 hours instead of 12-14.
The result
- Cleaning time: 12-14 hours → 4 hours (66-70% reduction)
- Production gained: ~16 hours per week of additional run time
- Chemical inventory: Eliminated for this part of the regime
- Water usage: Eliminated — sanitation regime now uses no water for these surfaces
- Operator exposure: No more alkaline-cleaner handling near hot equipment
ATP results have been stable across the 6 months we’ve been on the contract. The QA team has put forward a proposal to extend the dry ice protocol to the egg-and-cream line as well.
“We weren't losing the allergen change — we were losing 10 hours of production each time we did it. Dry ice flipped that. Cleaning happens during the change, not before and after it. We've effectively gained a shift a week.”
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