Could edible food packaging be the answer to Hong Kong’s plastic waste problems?

Researchers in the US are developing a packaging film similar to store-bought plastic wrap but made of milk protein, which not only reduces the use of plastic but could also prevent food spoilage and waste

PUBLISHED : Tuesday, 23 August, 2016, 12:30pm
UPDATED : Tuesday, 23 August, 2016, 12:30pm

At the supermarket, especially in Hong Kong, most food comes wrapped in plastic packaging. Imagine picking up that (needlessly) mummified organic apple and eating everything, cling wrap and all. Within a few years, it may well be reality.

Scientists in the US are developing an edible packaging film made almost entirely of the milk protein casein. The packaging looks similar to store-bought cling film, but it is less stretchy and is up to 500 times better at keeping oxygen away from food, thereby preventing food spoilage.

Because they are derived from milk, the films are biodegradable, sustainable and edible. They do not have much taste, the researchers say, but flavourings and nutritious additives such as vitamins, probiotics and nutraceuticals could be included in the future.

“The coating applications for this product are endless,” says Laetitia Bonnaillie, co-leader of the research team from the US Department of Agriculture’s Agricultural Research Service. “We are currently testing applications such as single-serve, edible food wrappers. For instance, individually wrapped cheese sticks use a large proportion of plastic – we would like to fix that.”

Bonnaillie and co-leader Peggy Tomasula presented their work over the weekend at the 252nd National Meeting & Exposition of the American Chemical Society in Philadelphia.

Bonnaillie says her team is currently creating prototype film samples for a small company in Texas, and the development has secured interest among other companies too. The researchers plan to keep making improvements, and Bonnaillie predicts this casein packaging will be on store shelves within three years.

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Typical plastic packaging is mainly petroleum-based, which is not biodegradable and also not sustainable, creating tonnes of plastic waste that sits in landfills for years. In Hong Kong, more than 2,000 tonnes of polystyrene, industrial and commercial plastic is thrown out daily – one of the highest waste-production rates per person in the world.

The New Plastics Economy report, released in January 2016 at the World Economic Forum, says global plastic production has surged from 15 million tonnes in 1964 to 311 million tonnes in 2014, and is expected to double in 20 years as demand grows. It forecasts that there could be more plastic than fish in the ocean (by weight) by 2050.

Typical plastic packaging is not great at preventing food spoilage, and some plastics are suspected of leaching potentially harmful compounds into food. In a study published in April 2016 by researchers at Milken Institute School of Public Health at George Washington University, it was found that people who reported consuming more fast food in a US national survey were exposed to as much as 40 per cent higher levels of potentially harmful chemicals known as phthalates.

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Phthalates belong to a class of industrial chemicals used to make food packaging, tubing for dairy products and other items used in the production of fast food. Other research suggests these chemicals can leach out of packaging and can contaminate highly processed food.

The USDA researchers have been working on the casein plastic packaging for more than 10 years.

Some commercially available edible packaging varieties are already on the market, but these are made of starch, which is more porous and allows oxygen to seep through. The milk-based packaging, however, has smaller pores and can keep oxygen out.

Although the researchers’ first attempt using pure casein resulted in a strong and effective oxygen blocker, it was relatively hard to handle and dissolved in water too quickly. They made some improvements by incorporating citrus pectin into the blend to make the packaging even stronger and more resistant to humidity and high temperatures.

In addition to being used as plastic pouches and wraps, this casein coating could be sprayed onto food, such as cereal flakes or bars. Right now, cereals keep their crunch in milk due to a sugar coating. Instead of all that sugar, manufacturers could spray on casein-protein coatings.

The spray also could line pizza or other food boxes to keep grease from staining the packaging, or to serve as a lamination step for paper or cardboard food boxes or plastic pouches.

But the Americans are not the only ones pursuing a plastic packaging alternative. Associate Professor Thian Eng San and his team at the National University of Singapore’s Faculty of Engineering revealed earlier this year an environmentally friendly food packaging material that is free from artificial chemical additives, by fortifying natural composite film derived from the shells of shrimp and other crustaceans with grapefruit seed extract.

This novel food packaging material is said to slow down fungal growth, doubling the shelf life of perishable food, such as bread.

“Increasing attention has been placed on the development of food packaging material with antimicrobial and antifungal properties, in order to improve food safety, extend shelf life and to minimise the use of chemical preservatives,” says Thian.