In recent years, we've heard about bacteria-killing food packaging materials that incorporate sorbic acid, silver, and montmorillonite clay. One of the latest such developments along those lines is a film that protects meat from spoilage using essential oils or nanoparticles. Additionally, because the film is edible, it could even be incorporated right into meat products.
The film is being developed by a team at Pennsylvania State University, led by Prof. Catherine Cutter.
In the four different versions that have been created, the antibacterial ingredients have consisted of rosemary or oregano essential oils, or zinc oxide or silver nanoparticles. Those elements are embedded within a layer of pullulan, which is a tasteless edible polymer created by the Aureobasidium pulluns fungus. Pullulan is commonly used in breath-freshening strips, and may also soon be finding its way into water-testing pills.
Once meat is wrapped in the film, the pullulan actually adheres to its surface, gradually dissolving and slowly releasing its payload of oils or nanoparticles into the meat. The rate at which it dissolves can be tweaked by adding compounds to the film such as guar gum, xanthan gum or glycerol ... this means it doesn't break down as fast as a Listerine breath strip would in the same situation.
But just how safe is it to eat zinc oxide or silver nanoparticles? "In this study, we were attempting to demonstrate 'proof of concept'," Cutter told us. "It is my understanding that the FDA requires manufacturers provide evidence that the nanoparticles will not be harmful when ingested."
In lab tests, meat products were first inoculated with bacterial pathogens, then vacuum-packed in the film and stored in a fridge for up to three weeks. When they were subsequently analyzed, they were found to be considerably fresher than control samples that had been packed in regular polyethylene film.
Because the pullulan is edible, the film could conceivably be eaten as part of the food product, perhaps not unlike a sausage casing. Cutter thinks it's more likely, however, that it will take the form of a separate, disposable wrapping material. Due to the fact that pullulan isn't as oxygen-impermeable as plastic, the film also likely wouldn't replace polyethylene film, but instead be used along with it.
That said, Cutter is hoping to develop a method of producing plastic film with the antimicrobial pullulan film bonded to it, so that meats wouldn't have to be wrapped in two separate layers of material.
A paper on the research was recently published in Journal of Food Science.
Source: Penn State
