How to qualify pouch and tray seals
Qualify the exact packaging and product on the intended filling line. Establish settings that pass clean and realistic contaminated-seal trials, then check leakage, peel strength and opening after relevant storage and handling. Agree acceptance limits before testing. Coordinate factory samples and records with Cambridge China Bridge.
Define what the line trial must prove
Use the supplier qualification guide for supplier approval gates. Here, approve a specific pouch or tray-and-lidding combination for the intended filling line, product and use. Record material construction, sealant layer, dimensions, tooling, fill condition and intended opening route. Identify who owns the trial and who can release the packaging.
If you package food yourself, you must use packaging suitable for food use. Keep food-contact suitability separate from seal performance: a leak test does not establish chemical suitability. Use the plastic food-contact declaration guide alongside the trial. Agree leakage limits, peel acceptance, opening behaviour, sampling and test timing before running.
Challenge product contamination at the seal
Run clean seals as the baseline, then challenge the seal area with realistic product residues, such as oil, sauce, powder or particles. Define the amount, location and application method in the trial brief. Include tray corners, pouch folds and other difficult sealing areas. Keep deliberately challenged packs identified and outside saleable stock.
Record residue and wrinkles before sealing, then photograph failures and their locations. If contaminated seals fail, investigate filling accuracy, splashing, seal-area cleaning and pack geometry as well as material choice. Do not approve unrestricted contamination tolerance from a successful isolated sample; define the conditions tested and the actions when the seal area falls outside them.
Establish a working range of sealing settings
Treat the supplier's suggested settings as a starting point. On the intended line, vary temperature, contact time and pressure through an agreed trial matrix, including combinations near the proposed operating limits. Record line speed, actual jaw or platen temperature, alignment, tooling condition and cooling. A controller setting alone does not describe the conditions at the seal.
Include start-up, steady running, stops and restarts, and each sealing lane or cavity. Select a working range where leakage, strength and opening all pass, rather than a setting that only produces the strongest seal. If packs are loaded while seals remain hot, challenge that handling stage too. Record the approved recipe and the response to settings drifting outside it.
Test leakage and peel strength separately
Inspect seal continuity, channels, wrinkles and damaged film, then use a leak method selected for the pack construction and defect risk. Ask the laboratory to explain whether bubble, pressure-decay or dye testing suits the filled pack, what it can detect and what it can miss. Use known leaking and intact controls to check the method. Record the leak location; visual inspection alone is insufficient for qualification.
For peel testing, agree strip location and width, conditioning, pull speed, support arrangement and reporting units. Keep these consistent between supplier and buyer. Sample around the seal, including difficult areas, and retain force traces and failure descriptions. Distinguish seal separation from film tearing, stretching or laminate separation. A strong strip result does not establish that the whole pack is leak-free.
Working out your own order? Send us the product on WhatsApp and we reply the same working day: WhatsApp us
Check opening and release with recorded limits
Open complete filled packs using the intended tab, notch or peel direction. Assess starting effort, continuing pull, sudden release, splashing, tearing and fragments. Repeat leakage, peel and opening checks after relevant storage, transport handling and any intended heating or freezing. Set an upper opening-force limit where needed as well as a minimum strength. Seal results alone do not validate food shelf life.
Release only the combination and operating range supported by the trial. Retain packaging batch details, settings, individual results, photographs, deviations and signed approval. Define routine checks, stock containment and requalification triggers, including sealant, laminate, tray, tooling or line changes. Cambridge China Bridge's own staff in China can coordinate supplier samples and records; the buyer retains filling-line approval.
Frequently asked questions
Can I approve packaging from empty sample seals?
Use empty seals for initial screening. Final approval should use the intended line and product, including realistic seal-area residue, handling and opening trials.
What peel strength should a pouch or tray seal have?
Agree application-specific limits and a repeatable test method. Consider leakage, handling and opening together; a higher peel result may make the pack difficult to open.
Does a passed peel test prove there are no leaks?
No. A tested strip may be strong while a channel elsewhere leaks. Use a suitable whole-pack leak check alongside peel testing and record where defects occur.
Can we increase sealing temperature to fix leaks?
Trial the change within the agreed settings matrix. Check for film damage, distortion and difficult opening, and investigate residue, alignment, contact time and pressure before release.