Can this aluminum tray be used in the microwave? The answer is in standard NF D21-314.

This may seem counterintuitive to an entire generation of consumers who would have been careful never to put metal utensils in the microwave. And yet, aluminum trays and other steel containers are microwave-safe. This is a boon at a time when the push for recycling and reuse is encouraging people to choose these materials.

Microwave-safe, provided they have passed the necessary tests! In this case, the NF D21-314 standard , published in January 2023 in the AFNOR series, describes a method for determining the suitability for microwave reheating of metallic or partially metallic items (bare or coated) used as food or beverage containers, whether intended for single-use or multiple-use. These items have distinct advantages: “In a metal tray, the food is reheated through the opening; the microwaves do not pass through the metal, but the result is very uniform,” explains Gilles Mangin, a research engineer at ArcelorMittal and the lead author of this document, to Enjeux magazine. “85.5% of steel packaging sold (such as cans) is recycled. Furthermore, it is sturdy and does not break.”

No sharp edges

The standard specifies the principles, equipment, test specimens, calibration of the microwave oven (determination of effective power), test procedures (performance tests, safety tests), marking, labeling, and the user manual (which must be provided to consumers), as well as the test report. “Tests were conducted by independent laboratories, which verified that nothing abnormal occurred inside the oven and that the packaging was suitable for use,” explains Gilles Mangin. “The shape of the packaging is important; there must be no sharp edges.” The top priority is ensuring user safety. Recommendations must be provided on proper use: place the container in the center of the oven, not near the walls; do not use a metal lid… The safety instructions are described in the standard. "The method used aims to exclude both items that could damage the oven—for example, by causing an electric arc—and items that could be damaged by microwave heating."

The NF D 21-314 standard fills a real gap, according to the expert. Currently, claims regarding the microwave-safety of metal items are sometimes based on the NF EN 15284 standard, which covers kitchenware made of ceramic, glass, glass-ceramic, or plastic… It’s a completely different matter! There was therefore a need for a reference document, and the plan to bring this French standard to CEN will help achieve this goal on a European scale.