The whole package
Teresa Pitman |
September 26, 2014
If you’ve ever bought ready-to-eat sushi, you may have noticed a blob of wasabi on the tray. It’s a convenient way to add pungent flavour to your lunch, but it also serves another purpose: it protects your food from micro-organisms.
As food science professor Loong-Tak Lim explains, wasabi contains allylisothiocyanate, (AITC) a natural and potent anti-microbial that kills yeast and bacteria. Of course, not every food is enhanced by the strong flavour of wasabi, so Lim has developed a packaging system that offers the same antimicrobial benefits .
Lim derives his AITC from ground mustard powder, and uses a patented nanotechnological process to spin tiny fibres that encapsulate the naturally sourced agent in the packaging.
“The conventional approach to adding preservatives has been to add them to the food,” says Lim's research colleague Suramya Mihindukulasuriya. “But processing the food may break down the preservative. By having the preservative in the packaging, we don’t need as high a concentration to enhance the shelf-life, safety and quality of the food.”
So-called “active packaging,” responds to changes in the environment and the food itself, Lim says. In this case, the membrane responds to a certain level of moisture and releases a preservative to prevent spoiling. Other active packaging materials respond to heat and light.
Mihindukulasuriya works with a preservative called hexanal, the volatile organic compound you smell when you cut grass or slice a cucumber. Hexanal helps preserve cell membranes of fruits and vegetables so they don’t become soft or soggy as they ripen. The preservative also has some anti-microbial properties, which are activated by heat and humidity.
Mihindukulasuriya calls her technique of enclosing the preservative using ultra-high electrical forces “electrospinning.”
Lim jokes that “we are like Spiderman, spinning tiny fibres.” And the fibres are tiny – about 400 times smaller than a human hair. When exposed to humidity or water, these fibres become permeable and release the hexanal.
During her PhD studies, Mihindukulasuriya also developed an oxygen indicator that is activated by ultraviolet radiation. When there is little or no oxygen in the package, the indicator is white, but if the package is damaged or torn, allowing oxygen to enter, the indicator turns blue.
This matters because oxygen causes rapid deterioration of some foods, and higher levels of oxygen encourage the growth of more micro-organisms. These foods are sealed in vacuum packs or in packages flushed with nitrogen to remove the oxygen, but if the package becomes damaged at some point, oxygen can get inside. That’s where Mihindukulasuriya’s product comes in: a label with a blue line would indicate that the package should not be purchased.
What’s next in active and intelligent packaging? Mihindukulasuriya is planning to develop a compound that will detect the volatile compounds produced by food when it spoils and indicate to consumers that the food should not be eaten. The technique would supplement expiry dates, which are only estimates based on typical situations. Not only would such packaging warn people that food had spoiled, it could also reassure them when it was safe to eat – even if the expiry date had passed.
“People throw away lots of food that has expired but is still perfectly good to eat,” says Lim.
This article was originally published by the University of Guelph. It has been edited for brevity, clarity and style, and is republished here with permission.