The white, powdery film that can develop on microwaved foods is usually caused by mineral deposits, specifically calcium and magnesium, that are present in the water used during cooking or in the food itself. When the water evaporates during the microwaving process, these minerals can remain behind and form a residue on the surface of the food.
The phenomenon is commonly referred to as "microwave arcing" or "microwave sparks," although no actual sparks occur. The minerals in the water or food can accumulate and create tiny white spots or a powdery film on the food's surface.
To minimize the occurrence of this residue, you can try the following tips:
Use distilled or filtered water: Using purified water with lower mineral content can reduce the likelihood of the residue forming.
Cover food with a microwave-safe lid or microwave-safe plastic wrap: This helps retain moisture and prevent the minerals from being concentrated on the surface.
Stir or rotate the food: Stirring or rotating the food during cooking can distribute the minerals more evenly and reduce the chance of a concentrated buildup.
Clean the microwave regularly: Regularly cleaning the interior of your microwave can help prevent mineral buildup and keep your food from coming into contact with residue.
While the white film may not be harmful, some people find it unappetizing or may prefer to avoid consuming it. If you encounter this residue, you can simply wipe it off or rinse the affected area before consuming the food.