Food Preservation: No Silver Lining

Plus: Best Buys in Vacuum Sealers

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In January, there was much ado about the invention of “killer paper” that’s coated with colloidal silver nanoparticles. According to an article that was published in American Chemical Society’s journal Langmuir, those tiny silver bits, each one-50,000th of the width of a human hair, lengthen the life of food. The silver kills E. coli and other bacteria bad guys.

Some food-storage containers use nanosilver, and their packaging touts this. The manufacturer of one line says its nanosilver technology keeps salad greens edible for 3 weeks. (That’s about 2 weeks longer than typical.)

These claims about silver might catch the attention of U.S. families who are examining ways in which they can deal with tough financial times as food prices soar. (Americans throw out more than 25 percent of the food that they purchase, according to numerous studies.)

Is silver truly the food-saving solution?

NO GOLD MEDAL. Unfortunately, we didn’t uncover anything beyond manufacturers’ claims that clearly supports the effectiveness of silver that’s in containers for extending food freshness. In fact, what we found deepens our skepticism.

Troy Benn, who is an environmental engineer, studied the incorporation of silver nanoparticles in two consumer products: socks and humidifiers. He acknowledges silver’s antimicrobial nature but stops short of vouching for its addition to products. His main question: “Do the [food-storage] products contain enough silver to be effective?”

The only information about the effectiveness of silver-coated containers that Benn found is consumers’ reactions. But it’s obvious that laymen’s experience isn’t suitable for judgment, however.

When Benn conducted his studies on the silver-laced socks, he found that the silver often washed away after a few laundry cycles. (Socks that are infused with silver are designed to kill the bacteria that cause odor.) That fact made us wonder whether silver in food containers might wash away. Benn could see the embedding of silver in plastic products producing a permanency that seemingly didn’t exist for the socks, but he concedes that that’s just a theory, because he hasn’t performed those studies. One manufacturer of silver-embedded containers wouldn’t provide data that support its stance that the silver remains throughout the life of the product. Another declined to respond to our queries.

There also is concern about the safety of nanosilver in products, food-storage or not. Silver has fairly low toxicity in humans, although if you ingest enough colloidal silver, your skin will turn gray or blue, a harmless but permanent condition that’s called argyria. But silver that’s incorporated at the nano-level—in hundreds of products, from soap to toothpaste to baby pacifiers—might be a different story. Nevertheless, food-storage containers that use nanosilver and are marketed under the Go Green brand are approved as safe for human use by Food and Drug Administration.

Noting the lack of real answers to questions about this, Nichole Burnett, who is a dietician and a family and consumer-science agent at Kansas State University Research and Extension, advises consumers to go low-tech—meaning forget silver until there’s definitive proof about silver’s effectiveness in food-storage products. For example, Burnett, who teaches food-preservation classes, extends the life of lettuce by about a week by reducing moisture with a salad spinner and refrigerating the lettuce in a container that is lined with a paper towel. Moisture can promote bacterial growth, which speeds up deterioration. Plus, rinsing reduces nutrients. Similarly, she avoids specialized produce bags, finding their performance unimpressive. These bags typically are lined with oya. (Oya is a clay compound that’s found in mountain caves in Japan. Zeolite is a natural drying agent in oya.)

Burnett is of the mind that if there isn’t definitive proof about silver’s effectiveness in food-storage products, there isn’t any reason for her to buy them. “You’re trying to save time and money,” she said. “So more expensive products . . . defeat the purpose.”

Stacy Downs has been the Home reporter for The Kansas City Star for 8 years.

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