Manage water vapour and multiply your product's shelf-life

Food companies are missing opportunities to significantly lengthen the shelf-life of products because the effects of water vapour transmission are not fully understood, says a UK expert on materials testing.

"With packaged vegetables and fruit, for example, you can double or even quadruple the shelf-life," says Chris Roberts, md of testing equipment and services company Versaperm. "And 'freezer burn' can be practically eliminated if water vapour transmission is managed."

Roberts admits that no testing technique for water vapour transmission is 100% accurate. But he claims that the spread of results with traditional gravimetric tests is much higher (around 20%) than with instrumental or 'swept gas' testing (around 5% variation). This can lead to pack specifications which do not optimise shelf-life. There is also a general tendency, he says, for packaging departments to live with the specifications they have inherited rather than investigating possible improvements.

Jon De Roeck, zone application manager at film and materials supplier Sealed Air Cryovac, agrees that customers are often not aware of this particular issue. "The customer would tend to specify the overall barrier of the film rather than water vapour transmission rates."

UK sales development manager, fresh produce, at Amcor Flexibles Jane Bicknall agrees that water vapour transmission is an issue for very moist products in modified atmosphere packaging (MAP). Finding a film which contains MAP gases while remaining permeable to water vapour is something of a 'Holy Grail', she claims. Products such as stoned fruit and mushrooms are especially vulnerable to mould growth.

Versaperm maintains that water vapour and pack permeability constitutes the largest single cause of food spoilage in the UK, valued at £100m a year.