- Tray sealer machines apply a lidding film to pre-filled trays using heat and pressure, producing hermetically sealed packs for fresh and processed food.
- Three structural types exist: tabletop, semi-automatic, and inline automatic — each suited to different production volumes and automation levels.
- Tray sealers can operate in standard air, MAP (modified atmosphere), and VSP (vacuum skin packaging) modes on the same machine platform.
- Material compatibility between tray substrate and lidding film is critical — peelable and non-peelable seals require different film and tray surface combinations.
- Modern inline tray sealers achieve 20–120 trays per minute with integrated gas dosing, vision inspection, and label application.
What Is a Tray Sealer Machine?
A tray sealer machine is a packaging system that applies a plastic, aluminium, or compostable lidding film to a pre-filled tray using heat, pressure, and — where required — modified gas atmosphere. The result is a hermetically sealed package that protects the food contents from contamination, oxygen ingress, and moisture loss while enabling consumer-friendly presentation on refrigerated retail shelves.
Tray sealing is one of the dominant packaging formats for ready meals, fresh meat, poultry, fish, dairy products, fresh produce, and prepared salads. Its combination of flexible automation levels (from manual tabletop to high-speed inline) and multi-mode capability (standard atmosphere, MAP, VSP) makes it the packaging workhorse of the modern food processing plant.
Unlike thermoforming, which forms the tray from a roll of bottom web film on the packaging machine, tray sealing uses pre-made trays — either purchased or formed offline — and applies only the lidding film on the sealer. This distinction has important implications for capital cost, changeover time, tray geometry flexibility, and carbon footprint per pack.
How Tray Sealing Works
The tray sealing process varies slightly between machine types, but the core sequence is consistent:
- Tray loading: Pre-filled trays are placed into a die tool either manually (tabletop/semi-automatic) or automatically via conveyor and indexing (inline systems). The die tool positions the tray precisely under the sealing head.
- Chamber closure: On MAP and VSP machines, the sealing chamber closes around the tray, forming an airtight enclosure. On standard air machines, the sealing head simply descends onto the tray flange.
- Atmosphere modification (MAP/VSP): For MAP, residual air is evacuated and replaced with the target gas mix (typically CO₂, N₂, O₂). For VSP, a deeper vacuum is drawn and maintained as the top film is heated and drawn down over the product.
- Film application and sealing: The lidding film unwinds from a top-mounted reel and is advanced over the tray. The heated sealing platen presses the film onto the tray flange, forming a seal bond via heat and pressure.
- Cutting and discharge: A cutting tool trims the film around the tray perimeter and the sealed pack is discharged from the die. On multi-cavity machines, several trays are sealed simultaneously per cycle.
Tray Sealer Types by Structure
Tabletop Tray Sealers
Tabletop tray sealers are compact, low-investment machines designed for small-scale production environments — artisan food producers, delicatessens, catering operations, and R&D/NPD kitchens. An operator places the filled tray into the sealing mould, lowers the sealing head manually or via a foot pedal, and the machine completes the seal cycle automatically. Output typically ranges from 4 to 15 trays per minute depending on cycle time and operator speed.
Tabletop sealers are available in single-cavity and multi-cavity variants, with some models offering optional MAP capability through manual gas flush. They require minimal maintenance and can be operated with minimal training, making them an accessible entry point for processors new to tray sealing.
Semi-Automatic Tray Sealers
Semi-automatic tray sealers motorize the film advance, sealing, and cutting functions while retaining manual tray loading and unloading. They bridge the gap between tabletop simplicity and full-line automation, offering outputs of 15–40 trays per minute with significantly improved consistency over tabletop machines. MAP and VSP capability is standard on most semi-automatic platforms, and die change systems allow format switching in 15–30 minutes.
Inline Automatic Tray Sealers
Inline tray sealers are fully automated systems designed to integrate into continuous food production lines. Trays are automatically fed from a denester or upstream conveyor, indexed through filling stations, transferred to the sealing station, sealed, and discharged — all without manual intervention. Output ranges from 30 to 120+ trays per minute (for single-cavity machines) and can exceed 300 trays per minute on multi-cavity high-speed platforms.
Modern inline tray sealers from manufacturers such as MULTIVAC, Sealpac, Ishida, and Proseal feature integrated die change systems with indexed quick-lock clamps, reducing format change times to under 15 minutes. Industry 4.0 connectivity via OPC-UA, SCADA integration, and remote diagnostics are standard features on current-generation equipment.
- Tabletop: Output under 15 trays/min, limited floor space, artisan/NPD/catering use
- Semi-automatic: Output 15–40 trays/min, MAP/VSP required, medium investment
- Inline automatic: Output 40+ trays/min, full line integration, consistent high-volume production
Sealing Modes: Standard, MAP, VSP
Standard Atmosphere Sealing
Standard atmosphere tray sealing seals the tray in ambient air. It is suitable for products with short shelf life requirements (same-day to 3–5 days) or products inherently resistant to oxidation — bakery items, prepared salads, fresh pasta, and sandwiches. It offers the highest machine speed and lowest capital cost among sealing modes.
MAP Tray Sealing
Modified atmosphere packaging (MAP) replaces the headspace air in the sealed pack with a controlled gas mix to retard microbial growth, oxidation, and enzymatic spoilage. The appropriate gas mix depends on the product: fresh red meat typically uses 70–80% O₂ / 20–30% CO₂ to maintain bloom colour; poultry and fish prefer low O₂ / high CO₂ mixes; and cooked meats use N₂ / CO₂ to exclude oxygen entirely. Shelf life extension of 100–300% compared to standard air packing is achievable depending on product and gas combination.
VSP (Vacuum Skin Packaging)
In VSP mode, the tray sealer draws a deep vacuum before applying a high-barrier skin film that conforms tightly over the product surface, eliminating residual headspace entirely. This produces visually premium packs with enhanced drip control, superior oxygen exclusion, and shelf lives of 14–28 days for fresh red meat — significantly longer than standard MAP. VSP also allows the use of trays without a flat flange, enabling presentation on non-flat substrates including boards and skin boards. For a detailed technical overview of VSP, see Vacuum Skin Packaging (VSP): Complete Guide to Premium Food Packaging.
Tray and Film Material Selection
| Tray Material | Common Applications | Recyclability (EU) | Notes |
|---|---|---|---|
| CPET | Ready meals (oven-safe) | Limited — dark colourant | Dual-ovenable; high temp resistance |
| APET | Fresh meat, salads, sushi | Recyclable (clear) | High clarity; cold chain only |
| PP | Deli, dairy, bakery | Recyclable | Microwave-safe; good chemical resistance |
| Aluminium foil | Caterer packs, cook-in | Recyclable | Opaque; excellent heat conduction |
| Pulp / cardboard | Sustainable fresh produce | Compostable/recyclable | Limited moisture resistance; growing adoption |
| Foam PS | Legacy meat / fish | Non-recyclable | Being phased out under PPWR |
Lidding film selection must be matched to tray substrate for optimal seal performance. Peelable seals — required for consumer convenience — use a controlled-release coating or a peel-initiation layer that allows the film to be cleanly removed from the tray flange without tearing the film or delaminating the tray. Non-peelable (permanent) seals are used where tamper evidence or hermetic integrity are the primary requirements and consumer access is via cutting.
Comparing Tray Sealer Formats
| Parameter | Tabletop | Semi-Automatic | Inline Automatic |
|---|---|---|---|
| Output (trays/min) | 4–15 | 15–40 | 30–300+ |
| MAP capability | Optional | Standard | Standard (multi-gas) |
| VSP capability | Rare | Available | Standard on premium models |
| Changeover time | 5–10 min | 15–30 min | Under 15 min (quick-lock) |
| Capital cost | Low | Medium | High |
| Floor footprint | 0.3–0.5 m² | 0.5–2 m² | 3–15+ m² (full line) |
| Operator requirement | 1 (semi-skilled) | 1–2 | 1 (line supervisor) |
Technical Specifications
| Specification | Typical Range |
|---|---|
| Sealing temperature | 130–220°C (product-dependent) |
| Sealing pressure | 1–6 bar |
| Vacuum level (MAP) | 5–50 mbar residual |
| Gas dosing accuracy | ±0.5% composition |
| Tray size range | 60×40 mm to 350×250 mm (typical) |
| Film width range | 50–400 mm |
| Seal width | 3–12 mm |
| Electrical supply | Single or three-phase 230/400V |
How to Select a Tray Sealer
1. Define your output requirement. Calculate peak throughput in trays per hour and add 20–30% headroom for line imbalances, changeovers, and planned maintenance. This defines the minimum speed class of machine you need.
2. Confirm your sealing mode. If MAP or VSP shelf life targets are required, budget for the appropriate vacuum and gas handling equipment. Not all entry-level machines offer true hermetic MAP capability — verify burst pressure specification with the manufacturer.
3. Validate material compatibility. Obtain film and tray samples from your chosen suppliers and run sealing trials on the shortlisted machine. Test peelability, seal strength, and hermeticity across the full operating temperature range of your product (cold fill vs. hot fill).
4. Assess changeover flexibility. If you run multiple tray formats, quick-lock die change systems and programmable sealing recipes significantly reduce downtime. Budget for one die set per tray format.
5. Consider downstream integration. Modern tray sealers are designed to feed directly into checkweighers, metal detectors, X-ray systems, labellers, and case packers. Ensure the machine’s discharge height and conveyor speed are compatible with your downstream equipment.
For complementary reading on the MAP gas science that underpins MAP tray sealing, see Modified Atmosphere Packaging (MAP): Complete Guide for Food Manufacturers. For film material selection guidance relevant to lidding films, see Food Packaging Films: Types, Materials & Selection Guide. For the full sustainable packaging materials context for tray selection, see Sustainable Packaging Materials: The 2026 Selection Guide.
Frequently Asked Questions
What is the difference between a tray sealer and a thermoformer?
A tray sealer applies a lidding film to pre-made trays. A thermoformer forms the tray from a roll of bottom web film on the machine before filling and sealing. Thermoformers offer greater tray geometry flexibility and typically lower per-unit material cost at high volumes; tray sealers offer lower capital cost, faster changeovers, and the ability to use pre-formed premium tray materials like CPET that cannot be thermoformed inline.
What gas mixes are used in MAP tray sealing?
Gas mix selection depends on product biology. Fresh red meat: 70–80% O₂ / 20–30% CO₂ (maintains oxymyoglobin bloom). Poultry: 30% CO₂ / 70% N₂ (inhibits bacterial growth). Fish: 40% CO₂ / 30% O₂ / 30% N₂. Cooked meats: 20–30% CO₂ / 70–80% N₂ (zero oxygen). Baked goods: 100% N₂ (prevents oxidative rancidity).
How do I choose between peelable and non-peelable lidding film?
Peelable films are required for most retail consumer applications — the consumer must be able to open the pack without tools. Non-peelable (weld) seals are used in foodservice and industrial applications where tamper evidence and hermetic integrity take priority over openability. Peelable seals require careful calibration of sealing temperature and pressure to achieve consistent peel force (typically 5–15 N/15mm).
Can a tray sealer run both MAP and VSP on the same machine?
Yes — most modern inline tray sealers offer MAP and VSP as selectable modes, with die sets and film rolls changed between formats. Some manufacturers offer universal sealing heads that switch between MAP gas flush and VSP vacuum cycle via software, enabling format changes without die exchange.
What tray materials are compatible with MAP sealing?
APET, CPET, PP, and aluminium foil trays are all compatible with MAP sealing, provided the tray has an adequate sealing flange width (minimum 4 mm recommended). The tray material must have sufficient gas barrier properties to maintain the gas atmosphere — OTR below 5 cc/m²/day is typical for red meat MAP trays.
How do I calculate the number of trays per reel of lidding film?
Trays per reel = (reel length in mm ÷ tray pitch in mm). Tray pitch = tray length + inter-seal gap (typically 8–15 mm). For a 5,000 m reel sealing 200 mm trays at 15 mm pitch: 5,000,000 mm ÷ 215 mm ≈ 23,250 trays per reel. Reel weight and core size determine frequency of reel changes.
What are typical seal strength requirements for retail meat packs?
Retail MAP meat packs typically require a seal burst pressure of 0.3–0.6 bar (45–90 psi) and a peel force of 8–20 N/15mm for consumer peelability. Seal strength validation should include testing at both refrigerated temperatures (4°C) and ambient distribution temperatures (up to 25°C) to account for temperature-dependent film properties.