DEAR DR. BLONZ: I have questions about foods sold in plastic containers at my local store. Can a microwave be used to defrost chicken and beef broths in these containers? These foods are produced in small quantities, sold only at this store, and have no markings aside from a label indicating the food inside. Should I be concerned about plastics leaching into the food? -- B.B., Portland, Oregon
DEAR B.B.: Many different materials are used in food packaging, and there may be cause for concern if a substance migrates from the packaging into the food it contains. These are referred to as incidental food additives, and are regulated by the Food and Drug Administration. Attention is required if a food-packaging substance is found to be harmful, but there should also be concern if the packaging affects the food's quality, appearance or shelf life. Two concerns with plastics are bisphenol A, also known as BPA, once common in can-lining materials and plastics, and plasticizers known as phthalates. (More about BPA at b.link/dzukfd, and phthalates at b.link/skx9fz5e.)
Your local store packages its minimally labeled foods in plastic containers, then stocks them in their freezer for sale. Foods prepared in a retail establishment and sold only in that establishment are exempt from the requirement to display nutrition labeling. (For more on this, see b.link/6ex3bwrr.)
But that does not absolve you of the need to know how to treat these foods and their containers appropriately -- especially as they may be sold in single-use containers unsuitable for the microwave.
Check for a "microwave-safe" symbol on the carton or label before putting that container in the microwave. "Microwave-safe" is usually an icon with horizontal wavy lines. (For examples of food and equipment symbols, including those signifying "microwave-safe," see b.link/hdsuug2b. For more on general microwave safety, see b.link/js6iw9yw.)
If you don't see the "microwave-safe" symbol, it's best to assume the container is not microwave-safe. What to do with that store-packaged frozen broth? Defrost it in your refrigerator. You can also use a brief hot-water bath to loosen up the contents and then transfer it to a designated microwave-safe container for the rest of the defrosting in the fridge.
If the container has a symbol of a 5 in a triangle, often with a "PP," it is made from polypropylene, which is generally considered microwave-safe. Still, it's best to find those squiggly, microwave-safe lines. The responsibility is on the consumer to check with the store to verify that they use microwave-safe containers. You can encourage the store to post information about the containers they use.
One final point: Containers, particularly plastic ones, do not have an indefinite life span. Discard single-use containers after the contents are gone, and toss any plastic container if it shows signs of cracking or discoloration.
Send questions to: "On Nutrition," Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.