Thermoformed Meal Trays: CPET, PP and the Engineering of Catering Packaging

A meal tray looks like the simplest object in food packaging until you list what it has to survive: a blast chiller, a domestic microwave or a 200°C convection oven, a sealing head that has to make a leak-free lid weld, stacking in a galley cart, and a food-safety regime that leaves no room for compromise. Thermoformed meal trays — the ready-meal and airline catering kind — are a genuine materials-engineering problem dressed up as disposable packaging.

The material decision: CPET vs PP

Two materials dominate, and the choice hinges on how the meal will be reheated.

• CPET (crystallised PET) is the dual-ovenable specialist. Ordinary APET softens in a hot oven, but by inducing crystallinity in the sheet — through the resin and a heated tool that sets the crystalline structure during forming — CPET holds its shape from freezer temperatures up to around 220°C. That “freezer-to-oven” range is exactly what a chilled or frozen ready meal needs. CPET trays are the standard for meals that will see a real oven, not just a microwave.
• PP is the microwave-and-chemical champion. It is food-safe, microwaveable, tolerant of hot-fill and grease, lighter than CPET, and can carry an integrated hinge or a co-extruded EVOH barrier layer for extended shelf life. PP is the choice where the meal is microwaved rather than oven-baked, or where oxygen barrier drives shelf life.

Picking the wrong one is unforgiving: a PP tray in a convection oven deforms, and a CPET tray is heavier and costlier than a microwave-only meal needs.

Compartment design

Multi-compartment trays are where forming skill shows. Each compartment is effectively a separate deep draw, and the dividing walls between them thin the most because material is pulled in two directions at once. Good compartment design means:

• Generous corner radii so material distributes into the deep corners instead of thinning to failure.
• Draw depths matched to the starting gauge, with the finished wall in the deepest compartment specified as the controlling dimension.
• A flat, dimensionally stable sealing flange around the whole perimeter — because the lid seal is only as good as the flange it lands on.

Sealing and MAP

Most catering and ready-meal trays are lidded by heat-sealing a film to the flange. For extended shelf life this is done as modified-atmosphere packaging (MAP) — the air in the pack is flushed and replaced with a controlled gas mix (typically nitrogen and carbon dioxide) before the lid is sealed, slowing spoilage without preservatives. MAP puts two hard demands on the tray: the flange must be clean, flat and consistently formed so the seal is hermetic, and the tray (or its barrier layer) must itself resist oxygen ingress. A tray with flange gauge variation leaks, and a leaking MAP pack is a failed pack.

Food-grade compliance is non-negotiable

Everything that touches the meal has to be documented. That means FDA food-contact grades of sheet, ISO 9001:2015 process control behind the forming, and full traceability from resin lot to formed tray. For airline catering — where packs cross borders and buyers audit hard — that paper trail is as important as the part itself. This is where controlling the sheet extrusion in-house pays off: the food-grade compliance, gauge tolerance and (for PP) barrier structure are all verified upstream, so the formed tray carries a clean provenance rather than a supplier’s word.

Why the sheet source decides tray quality

CPET only crystallises correctly if the sheet and the heated tool are matched; PP MAP trays only seal reliably if flange gauge is tight; barrier shelf life only holds if the EVOH layer is intact. All three are decided at extrusion, not forming. Running sheet extrusion, tooling and thermoforming as one integrated operation — wide-web food-grade sheet, in-house heated tooling, and CNC-trimmed flanges — is what makes a meal tray dependable at catering volumes.

If you’re sourcing meal or catering trays and need the material and seal engineered together, talk to our team or review food-grade options on our materials page.