Fish and seafood
Tuna, sardines and mackerel in oil or brine; oily, salty contents test the sealant and adhesive.
Retort lidding foil
Retortable Aluminium Foil for Peel-Off Ends
Retortable peel-off end foil is a laminated or coated aluminium membrane that is heat-sealed to a metal ring, seamed onto a food can, and must then survive steam sterilisation at around 121 °C or higher before the consumer peels it open by hand. It is usually based on 8011 foil with a polypropylene-compatible heat-seal layer. This guide explains the structure, performance demands and how to specify reels for lid makers; Metline supplies the aluminium lidding foil worldwide.
- Base alloy
- 8011 aluminium foil
- Process
- Retort sterilisation, about 121 °C+
- Reel width
- Typically 700 – 800 mm
- Cores
- 76 mm or 152 mm ID
What a peel-off end is and why the foil matters
A peel-off end (POE) replaces the familiar ring-pull easy-open end on a food can. Instead of a scored metal panel, it uses a flexible aluminium membrane sealed to a narrow metal ring. The ring is double-seamed onto the can body on a standard seamer, and the consumer opens the can by pulling a tab that peels the membrane away.
POEs are lighter than full metal ends, leave no sharp edge when opened, and give a wide, clean opening that suits fish, pâté, pet food and premium products. They also allow attractive printing and embossing on the lid.
Everything depends on the membrane. It must be a complete barrier for the life of the product, bond strongly enough to stay sealed through retort pressure and transport, and yet peel cleanly with a comfortable force. Aluminium foil supplies the barrier; the coatings and laminates supply the seal and peel behaviour.
Typical structure of retortable lid foil
| Layer (outside to inside) | Purpose |
|---|---|
| Print primer and overlacquer | Holds printing and protects it through retort without colour change or blistering |
| Printing and embossing | Brand graphics, text and tactile patterns |
| Aluminium foil (typically 8011, soft or semi-hard temper) | Full barrier to oxygen, moisture, light and odour; gives dead-fold and embossability |
| Adhesive or tie layer | Bonds the foil to the sealant film and must resist hydrolysis during retort |
| Heat-seal layer (often PP-based film or lacquer) | Seals to the coated ring and controls the peel force |
Exact gauges depend on the lid design, ring coating, sealing equipment and food. Lid makers usually specify the foil gauge and temper, the coating or film type and weight, and the sealing window. Present your existing structure or lid drawing when enquiring so the foil can be matched to it.
The peel mechanism is designed in. In a well-made structure the seal to the ring is stronger than the internal bond that fails when the lid is peeled, so opening is clean and predictable instead of tearing the foil or leaving fragments on the ring.
Why 8011 is the standard alloy
8011 is an Al-Fe-Si foil alloy. Its iron and silicon form fine particles that refine the grain, which gives higher strength and better puncture resistance than pure 1xxx foil at the same gauge, along with fewer pinholes. In the annealed O temper it embosses and forms well; partial-hard tempers are chosen where more stiffness is wanted. 8079 and 1235 are occasionally used for specific structures.
| Property | 8011 foil | Why it matters for POE |
|---|---|---|
| Composition | Al-Fe-Si (Fe about 0.6 – 1.0 %, Si about 0.5 – 0.9 %) | Fine grain, strength and low pinhole count |
| Common tempers | O, H22, H24 | O for embossing and formability; harder tempers for stiffness |
| Barrier | Complete barrier when pinhole-free | Long shelf life for oxygen-sensitive foods |
| Food contact | Composition to EN 602 for food-contact aluminium | Regulatory compliance in many markets |
The ring itself is usually tinplate or aluminium, and the can body may be tinplate or aluminium (3003 and 5xxx sheet are common for drawn aluminium bodies). The ring coating and the foil sealant must be designed as a pair.
Foods packed under retortable peel-off ends
Meat and ready meals
Pâté, luncheon meat and meals; long retort cycles at elevated temperature.
Vegetables and fruit
Acidic contents demand corrosion-resistant inner layers.
Pet food
Wet cat and dog food in shallow trays and cans, a major user of peel-off ends.
Speciality and premium foods
Products such as bird's nest drinks and dairy desserts where opening experience and printing matter.
Infant and medical nutrition
Powder and liquid products where clean opening and hygiene matter.
Performance requirements and how they are tested
| Requirement | What to check | Typical test |
|---|---|---|
| Seal integrity after retort | No leaks, delamination, blisters or wrinkles in the seal area | Retort simulation followed by visual and leak or burst testing |
| Peel force | Opens smoothly with an acceptable force, cleanly and in one piece | Peel test on sealed lids before and after retort |
| Barrier | No pinholes in the foil | Light-table pinhole inspection; oxygen transmission on laminate |
| Print and coating resistance | No discolouration, blushing or ink loss after retort | Retort test on printed samples |
| Emboss quality | Clear, even embossing without cracking the foil | Visual inspection of finished lids |
| Reel quality | Correct width, core, splice count and winding tension | Dimensional and visual inspection per reel |
Retort conditions vary: a fish cannery may run a different temperature and time from a pet food plant. Always qualify a new foil on your own sealing line and retort cycle before production, and keep retained samples from each lot.
What to include in an enquiry
Reel specification
- Structure
- Foil alloy, temper and gauge; coating or laminate type; heat-seal layer
- Width
- Commonly 700 – 800 mm for printing and slitting, or slit to your lid press
- Core
- 76 mm or 152 mm inner diameter; paper, aluminium or steel core according to reel weight
- Printing
- Artwork, colours, registration and embossing pattern
- Retort conditions
- Temperature, time, retort type and food contents
- Ring and can
- Ring material and coating, can diameter and curl design
- Documents
- Food-contact declarations, test reports and batch traceability for your market
Metline supplies the aluminium lidding foil in reels to lid makers and converters. The lids themselves are made by the lid maker, which cuts, seals and forms the membrane onto rings.
Three mistakes cause most problems with new lid foil: changing the ring coating without re-qualifying the sealant, judging peel force only before retort (it often changes afterwards), and specifying foil by gauge alone while ignoring temper and coating weights. Write all three into the specification and test them together on your own line.
References and standards
- EN 546-2 – Aluminium and aluminium alloys, foil: mechanical properties
- EN 602 – Wrought aluminium products for food contact: chemical composition
- Regulation (EC) No 1935/2004 – Materials and articles intended to come into contact with food
- US FDA 21 CFR Part 113 – Thermally processed low-acid foods packaged in hermetically sealed containers
Retortable aluminium (aluminum) peel-off end foil: FAQs
What is retortable lidding foil?
It is aluminium foil laminated or coated with heat-seal and protective layers that withstand steam sterilisation, used as the peelable membrane in peel-off ends for food cans.
How is it different from ordinary aluminium foil?
Plain foil has no sealant and no retort-resistant coatings. Retortable lid foil adds a heat-seal layer matched to the ring, adhesives that resist hydrolysis, and print coatings that survive 121 °C or higher.
Which alloy is used?
Usually 8011, for its strength, low pinhole count and good embossing. 8079 and 1235 are used in some structures.
Do you supply finished peel-off lids?
No. Metline supplies the aluminium lidding foil in reels; lid makers cut, seal and form it onto rings to make the finished ends.
What retort temperature must the foil withstand?
Low-acid foods are typically sterilised at about 121 °C or higher. Give us your actual temperature, time and retort type so the structure can be matched and tested.
Can the foil be printed and embossed?
Yes. Printed graphics, colours and embossed patterns are common, using inks and overlacquers designed to survive retort without fading.
Need retortable lidding foil?
Send the structure, reel size, printing and retort conditions. We reply with a matched specification, documents and a delivered price.
