Some microwave packaging may disintegrate when exposed to high cooking temperatures, causing potentially harmful chemicals to enter food, a federal report stated.
Those containers most likely to pose problems are known as heat susceptors designed to elevate temperatures--some to 500 degrees F.--during microwaving.
The packaging is used on such traditional microwave products as popcorn, pizza, French fries, fish sticks and Belgian waffles, according to the U.S. Food and Drug Administration.
Typically, the susceptors are marketed as “browning” or “crisping” devices. The microwave would be unable to brown food--as is the case in conventional ovens--without the presence of these items in the packaging.
The agency’s concern also extends to plastic “dual ovenables,” or those containers prepared for use in either the conventional or microwave oven.
“The FDA is concerned . . . . that such high-temperature use of these materials may cause packaging components such as adhesives, polymers, paper and paperboard--known as indirect food additives--to migrate into food at excessive levels,” said a recent report in FDA Consumer magazine.
The agency identified at least two compounds that have migrated from microwave packaging directly into food. In a September, 1989, test of microwave French fried potatoes, federal researchers found minute levels of polyethylene terephthalate in addition to diethylene glycol dibenzoate.
Since 1987, the agency has requested that the packaging and food industries voluntarily provide research indicating that partial dissolution of these materials, and subsequent migration of the chemicals into food, is safe. The information has not been forthcoming.
As a result, FDA has stepped up its efforts and published a notice last year that establishes a deadline for manufacturers to submit the data.
The FDA must approve all additives--direct or indirect--that may be consumed in processed food. Even unintended results, such as the leaching of chemicals from microwave packaging, must receive the agency’s approval.
Yet, in its report on the problem, the FDA made an unusual concession. It stated that the agency had not been “ready” for the introduction of these packaging innovations and was surprised to learn that the devices could raise microwave oven temperatures to 500 degrees.
Now, the agency admits it is “working to keep up” with the technology and is placed in a position where it must retroactively determine the safety of a processing technique that has been in use for years. Sales of microwaved-packaged foods are expected to reach $3 billion by 1992, according to the FDA.
In preliminary tests, agency researchers found that these heat susceptor pads reach such high temperatures that they actually become charred and can cause a fire.
“The food-contact surface of heat susceptor packaging is usually a metalized polyethylene terephthalate film laminated to paperboard with adhesive. This metalized film absorbs the microwave energy in the oven and, with most of the microwave absorbed, the package becomes a little ‘frying pan’ that actively participates in the cooking,” according to an FDA account of the problem.
Although the FDA approved some of these compounds for food packaging as early as 1958, the approval was based on oven temperatures of only 300 degrees F., not the high levels being created by today’s products. In fact, the dual ovenables are also a concern because consumers often heat the containers at 350 degrees to 400 degrees in conventional ovens for long periods of time and thus risk some disintegration of the packaging.
The FDA has stated that research to date does not indicate any public health problem with heat susceptors or dual ovenables. The agency also claims that this type of packaging represents only a small portion of the total microwave packaging category.
Nonetheless, the federal government has issued a series of guidelines for consumer protection.
--Do not exceed microwaving times recommended on package instructions.
--If packaging, such as popcorn bags, becomes extremely brown or charred do not consume the product.
--Carefully watch the microwave oven when microwaving popcorn because heat buildup can cause a fire. Time heating precisely according to label instructions. Favor the shorter recommended cooking times (some ovens can scorch popcorn in two minutes).
--Do not reuse heat susceptors, and do not use them for a purpose other than that originally intended by the manufacturer. Handle these packages very carefully because they can be very hot to the touch.
--Avoid letting plastic wrap touch foods during microwaving because the plastic can melt, causing compounds known as plasticizers to enter food.
--Never heat foods in brown grocery bags or newspapers because both contain recycled materials and metals that could cause a fire.