Fruitful endeavours in edible films

Materials World magazine
1 Jan 2011
A mango, yesterday

A film composed entirely of mango puree could provide an alternative to synthetic materials and increase the shelf-life of fresh-cut fruit.

In an attempt to make use of overripe mango and to prevent excessive waste, a team of Thai researchers at Kasetsart University has developed the edible film for use in modified atmosphere (MA) packaging.

Researcher Rungsinee Sothornvit explains the rationale behind using the film. ‘The mango puree consists of polysaccharide and protein, which presents an effective semi-permeable barrier to respiratory gases such as CO2 and oxygen and can create a modified atmosphere. This MA slows down respiration, metabolism and retards ethylene production, improving the quality and extending the shelf-life of fresh-cut mango’.

The film is created by pulping and degassing mango. The puree is then poured into a high-density polyethylene plate and dried at 50°C for 12 hours. In order to simulate realistic storage conditions, the films are stored at five and 30°C. It has also been subjected to a sensory evaluation test involving six semi-trained panellists. Mangoes were tested according to their aroma, flavour, colour, internal appearance and overall visual quality.

The researchers claim that storage life at 30°C is increased by one day compared to uncoated fresh mango, and also that the packaging caused no adverse flavours. 

However, there are shortcomings. Sothornvit says that the greatest challenge is, ‘the application of mango film on fresh-cut mango due to the hydrophilic nature of film,’ which causes the film to melt during storage. She also mentions that rough pulp is difficult to screen in the preparation process and that the film may cost more to produce than plastic packaging, though she adds that commercial equipment can be adjusted to accomodate it.

The pack is intended for use across the food industry, including nuts, fresh and processed fruits and dried and frozen food. In the future, the team intends to use lipids to improve the barrier properties of the mango film, and an antimicrobial agent for enhanced food safety. Alan Moffat, Packaging Development Manager at Heinz, UK, says that, ‘The results of this scientific work are genuine and welcome in highlighting the potential use of what otherwise would be a waste commodity, but there needs to be further questioning of both the validity and potential of this packaging material’.

He notes that the film’s exposure to high moisture levels could be problematic. He says, ‘The relative humidity in Thailand regularly reaches 100%. This would dissolve the mango film, thus rendering it useless’.

In addition, he questions the film’s commercial viability. ‘To be viable, they would require significantly more development time and investment to be able to commercialise the film and would rely on a constant supply of ripe mangos with the benefit being an improvement of a few days’ shelf-life. However, this shelf-life can also be achieved through low temperature storage and extended further through the use of MA packaging’.