Foil container lids are used for sealing, insulation or isolation. However, if the wrong material is used, it is easy to cause problems in use. For example, thin foil lids are easy to deform under heavy pressure or high temperature. In addition, some consumers like to mix all lids, such as using plastic lids to put directly into the oven, or using cardboard lids to store liquid food.
This article will summarize the improper use of aluminum foil container lids in daily life and explain the correct way.
Main Foil Container Lids
Cardboard lid, foil lid and plastic lid are three typical types of aluminum foil container lids. The following are their materials and temperature resistance:
The cardboard lid has white paper on one side and aluminum foil on the other. When in use, the white paper faces up and the aluminum foil side contacts the food. Aluminum foil container with cardboard lid products are mainly used for ready-to-eat foods and packaging containers. Cardboard lids can withstand -20°C to 100°C, depending on the liner material (such as PLA coating has a lower heat resistance of about 60°C; water-based barrier layer or PE coating can reach more than 90°C). It is also suitable for refrigeration.
The foil lid is made of aluminum foil, which can withstand -40°C to 220°C, suitable for oven, microwave heating and frozen storage. If the outer layer is plastic (such as PP or PET), the temperature resistance may drop to about 120°C. Aluminum foil containers with foil lids are suitable for takeaway boxes, baking containers and aluminum foil trays for ovens.
The temperature range of transparent plastic lids depends on the material. PP plastic lids can withstand -20°C to 120°C, suitable for microwave heating, but not high temperature baking. PET lids can withstand temperatures from -30°C to 70°C, suitable for refrigeration and avoid high temperatures. If you are not sure what material it is, you can directly refer to the instructions on the product packaging or contact the supplier for information.
Cases of Improper Use
Can I Microwave The Cardboard Lid
Can I leave the lid on or put it in direct contact with the oven when heating in the microwave? The cardboard lid has poor heat resistance. If it is in direct contact with the oven wall or heated at high temperatures for a long time, it will easily carbonize or release harmful substances. The cardboard lid is easily deformed or burned when heated in the microwave. It cannot be used directly in the microwave. It needs to be removed and heated separately or with a high-temperature resistant aluminum foil lid.
Are Plastic Lids Microwave Safe
Foil containers with plastic lids can be heated in the microwave for a short time at low temperatures, as long as the lid is marked “microwave safe”. If the PP plastic lid is used in the oven or high-temperature cooking, it may release harmful substances such as bisphenol A. Moreover, disposable plastic lids are easily worn and deformed after repeated washing, which is harmful to food safety.
Are Foil Lids Safe at High Temperatures
Using the foil lid in the oven or over an open flame to heat directly will cause a fire if the upper temperature limit is exceeded. The correct way is to use it for medium to low temperature heating (such as covering it for a short time after preheating the oven) to avoid direct contact with flames or prolonged high temperatures. At the same time, do not use the aluminum foil lid to wrap acidic foods such as lemons, vinegar, and tomatoes. It is recommended to choose an aluminum foil cover with a food-grade coating. Reusing a non-heat-sealed aluminum foil lid after washing will lose its sealing properties due to thinning or cracks in the material.