28 August 2007

Food packaging not always a clear, safe choice

Packaging that lets you see what is inside may make you feel better as a consumer, but it is not good for the food.

Visible wavelengths of light cause taste and odor changes of food, according to research by Virginia Tech food scientists.

Materials research for protecting food from light damage focuses on ultraviolet (UV) light in the range of 200 to 400 nanometers, which is the range that can damage skin. "These are the same wave lengths that cause nutritional and sensory damage in food," said Susan Duncan, professor of food science and technology at Virginia Tech. For example, visible light degrades riboflavin in milk, interacts with flavor and odor molecules, and causes pigment damage in food.

UV wavelengths are not the only ones that cause damage but are important from the perspective of the food processors, who want beverages to look appealing. Packaging has moved away from paper board to polymers such as polyethylene, so the consumer can see the product. "Then they started to have color and flavor problems," Duncan said.

Adding UV absorbers to the packaging helped and still allowed the consumer to see the product, but it "didn't totally resolve the problem," she said. "The only way to completely protect the product is to use a totally opaque container. But generally, consumers like to see a product, particularly milk, to make sure it isn't curdled, or juice to make sure there is no sedimentation. But we also want a product to have a long shelf life."

Researchers tested new materials (not developed at Tech) not being used for food packaging. One material was a translucent sleeve over wrap with an iridescent shimmer that reflects wavelengths. "We found evidence of improvement, but still not as good as opaque," Duncan said.

She said material scientists can develop better materials once they become attuned to the challenges of food packaging. "We want to find manufacturers to work with us to develop packaging products that will work with milk and the visible wavelengths."