Study highlights industry's need for 'perfect' film

By Charlotte Eyre

- Last updated on GMT

Related tags: Light, Sheffield hallam university, Chemical reaction

The holy grail of clear food packaging, film that prevents
light damage, is still a quest for the food industry, according to
new research.

A study focused on clear packaging film, carried out by food scientists at the University of Virginia, shows that more work needs to be done if the popular clear packaging is going to be as protective as opaque materials, especially for pathogen-friendly foods such as meat and fresh vegetables. According to the research team, led by Susan Duncan with Janet Webster, consumers generally prefer transparent or translucent packaging materials, as they feel more secure in their choice if they can observe the food they are going to consume. "Generally, consumers like to see a product, particularly milk, to make sure it isn't curdled, or juice to make sure there is no sedimentation,"​ Duncan said. Picking up on the trend in recent years, manufacturers moved away from older forms of packaging, such as paper board, and started using clear polymers like high density polyethylene (HDPE) and polyethylene terephthalate (PET), she added. However, it was at this point that producers "started to have colour and flavour problems"​ especially as food products are often displayed in stores under florescent lights. Many foods and beverages then undergo harmful oxidation reactions, as the photosensitisers in the product, such flavanoids and cholorophyl, absorb certain wavelengths of UV or visible light. This chemical reaction leads to an off-odour, Duncan explained, and the destruction of vitamins and nutrients. The team therefore carried out research into materials that provide package clarity in order "to meet consumer expectations",​ yet still protect against oxidation damage. When examining clear packaging for milk, for example, the Virginia Tech team observed the chemical changes that occur during photo-oxidation when the product was packaged in a range of single and multi-layers of iridescent film. The oxidation process was then observed by using gas chromatography, a process that involves separating complex mixtures by moving the product along a stationary material. In regards to packaging materials, Duncan and her team concluded that film over-wraps do reduce the production of volatile and odour-active compounds in milk, compared to milk with no over-wrap, and that multi-layer over-wraps are more effective than single-layer. However, none of the over-wraps are as effective as a complete light block, such as foil, Duncan said. The results also suggested that exposure to UV wavelengths (200-400 and 395 nm), the same wavelengths that damage human skin, and full light, produced the highest amounts of volatile compounds. Many companies are investing in new packaging for food, as manufacturers are looking for environmentally friendly, practical film that complies with regulatory demands. Recent innovations include a new oxygen barrier film made by Swedish company Xylophane, while many companies are carrying out research into films made using nanotechnology. At Sheffield Hallam University in the UK, work is underway on the design of nanoclay particles, which are expected to significantly improve the barrier properties and mechanical strength of new biopolymer films and coatings. Studies: Changes in aromatic chemistry and sensory quality of milk due to light wavelength​ and Packaging solutions for sensory degradation of foods and beverages due to photooxidation ​Authors: J. B. Webster, S. E. Duncan, S. F. O'Keefe, J. E. Marcy, S. Sims

Related topics: Processing & Packaging

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