Using accepted testing methods heat seal integrity was measured in 11 factories containing 105 heat sealing units, packing a variety of ambient, fresh, chilled and frozen foods.

The team found that poor seal integrity could be a major cause of food and packaging waste.

While about 24% of packs measured exhibited seal problems judged liable to cause leakageproblems in the factory, distribution chain and \ or home, only 1% of packs were judged sufficiently damaged by factory tests to be rejected by the factory quality testing systems.

During the seal testing process, it was found that the most common quality check used in the factories was the ‘manual squeeze test’.  It was also noted that almost all testing is carried out ‘off-line’.

It was estimated that up to 480,000 tonnes of food waste per year could be generated through the production and lack of detection of unsound heat seals.

It was found that the most common reason for seal failure was product contamination in the seal area and that sealing problems were more common where products had liquid and crumb components.

Achieving adequate heat sealing was anticipated to be a greater problem in future as new packaging materials, such as PLA (polylactic acid), are introduced more widely.

The team identified some ‘best management practice’ procedures which could reduce waste generation but concluded that to achieve major improvements, technological changes were required.

These technological improvements should include better filling and heat sealing methods to reduce product contamination of the seal area and the development of robust in-line seal monitoring systems and associated control systems.

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