There's now potentially one more use for discarded shrimp shells. Already, scientists have used chitosan – a natural antibacterial polymer found in crustacean shells – as an ingredient in self-healing paint, proton-conducting transistors, and coatings that keep fruit fresh longer. Now, it turns out that chitosan can also be used to create a plastic film wrap that doubles the shelf life of some foods.

Chitosan itself is well-suited to the task, since besides being antibacterial it's also antifungal, non-toxic, and is easily formed into thin films.

Scientists at the National University of Singapore decided to boost such a film, however, by fortifying it with grapefruit seed extract. The extract likewise has antibacterial and antifungal properties, although it's also an antioxidant, antiseptic and anti-viral.

The composite film is claimed to be similar to regular synthetic polyethylene film in strength and flexibility, while also blocking the transmission of ultraviolet light – in so doing, it slows down the oxidation and photochemical deterioration of foods contained within it. In lab tests, bread samples wrapped in the film lasted twice as long as control samples wrapped in traditional film.

Once commercialized, the chitosan film could be a greener alternative to polyethylene, as it utilizes raw ingredients that would otherwise be discarded, it will biodegrade once it itself is discarded, and it should reduce food waste.