Rotten from the Outside InJune 1, 2005 By: Sensors Staff Sensors
Remember reading The Picture of Dorian Gray way back there in high school? A painting of the handsome Dorian became uglier day by day as the young man abandoned himself to a life of shameless debauchery. Well, a new technology called "active packaging" can do a Dorian by providing a visual signal to tell you if those pretty pears will turn to mush by the time you get them home. Besides being a boon for shoppers whose sniffers just cannot tell a ripe cantaloupe from a rotten one, active packaging can save grocers the lost sales—and bad PR—that result when customers return spoiled food.
Several active packages rely on chemical changes to alert shoppers to a food's condition. The TTI from Temptime, for example, uses a label filled with a chemical that polymerizes with increasing speed as it's exposed to higher temperatures. As the polymerization proceeds, the label darkens. Higher temperature also speeds the growth of food bacteria; therefore, the darker the color, the more bacteria present.
Other packages monitor gases given off when frozen food decays. The National Center for Toxicological Research has come up with a dye-impregnated plastic disc that changes color if foods are heading down the primrose path.
Another take on active packaging controls the environment inside the package. Landec's Intelimer is a membrane wrapper that keeps foods at their optimal O2 and CO2 levels by changing its permeability in response to temperature changes.
Oxygen scavengers are another way to slow decay. Already, sachets filled with iron powder consume O2 as the iron oxidizes. In a newer variation from Sealed Air, the wrapper itself traps oxygen in its inner layer of oxidizable polymer.
There's still more. Toxin Alert is developing a sandwich wrap coated with antibodies that change color if unpleasant bugs show up in your tuna sub. And Hort Research is testing a package that indicates ripeness so consumers don't have to bruise the fruit.
Because of the extra development and manufacturing costs, active packaging has been coming along slowly. But given the benefits offered, at least one industry expert estimates that 20%–40% of all food packaging will one day be active. Watch out, Dorian Grape. We're onto you.
National Center for Toxicological Research, Jefferson, AR;
Sealed Air, Saddle Brook, NJ; 201-791-760,
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