Can you microwave parchment paper?

Can you microwave parchment paper

Parchment paper is a versatile tool in the kitchen: used in the oven as a steaming packet for salmon, in toaster ovens for roasting vegetables and on frying pan surfaces for non-stick chicken breast.

But, can it’s versatility extend to microwave ovens? Let’s find out.

Can you microwave parchment paper? Yes, parchment paper can be used in the microwave for cooking and re-heating purposes. Parchment paper is largely transparent to microwave radiation because it's particles cannot absorb it. As a result, it doesn't heat up directly form the radiation but rather from food sources that have been heated by the radiation. And because it's treated to withstand temperatures upto 450°F, the food heating hardly affects it.

Here's why parchment paper is transparent to microwave radiation: The uses and other related questions are at the bottom of the page.

Microwave ovens work by generating low energy microwave radiation that is easily absorbed by polar molecules in food and converted to heat for cooking.

Polar molecules are molecules with two or more areas of different electrical charges otherwise known as permanent dipoles. Water molecules are a typical example: they have negative poles on one side and positive poles on the other—two sides, hence the name dipole.

The low energy radiation emitted from the microwave oven generates an oscillating electromagnetic field; which is basically an electric field and a magnetic field moving together at right angles to one another and constantly alternating between two directions in their respective axis. This oscillation happens 2.45 billion times per second.

Source: seos-project.eu

When these polar molecules are subjected to the microwave radiation, they interact with the constantly alternating electric field (blue) using the permanent dipole on them, to absorb energy and generate heat.

Here's how the interaction happens:

When the electric field is positive, it attracts the negative pole of the molecules and when it turns negative, it attracts the positive pole of the molecules. As an effect, a rapid back and forth rotation is induced in the molecules. Since the electric field is constantly changing from positive to negative 2.45 billion times per second, the molecules end up playing catch up. As a result, an intermolecular friction is created where each molecule rub against it's neighboring molecules and generates heat. The heat is then transferred to other parts of the food for cooking.

Water molecules in food are typical examples of polar substances that can interact with a microwave radiation in this manner and produce heat. They do so because their molecules fulfill the necessary conditions for the absorption of microwave radiation in ovens i.e [1] The energy of the microwave radiation exactly matches one of the energies at which the water molecules rotate [2] They have dipoles that can interact with the constantly alternating electric field generated by the microwave radiation to absorb it's energy and produce heat.

As for parchment paper, most of the particles that make up it's composition do not fulfill the microwave absorption criteria [1] [2], so the microwave radiation pass through it with little to no heating. This is also true for the air inside a microwave oven. The energy of the microwave radiation does not match any of the energies at which the air molecules rotate. So they appear transparent to it.

The only reason why the air inside of a microwave oven heats up after cooking is because it receives some radiating energy given off from food. Same thing goes for parchment paper; the food transfers some of it's heat energy directly to the parchment paper via conduction.

As a consequence, only food and not microwave radiation can actually heat a parchment paper past it's 450°F heating threshold. And that's more likely to happen with fatty tissues and oily foods, since the oils can easily reach temperatures above 400°F compared to water based food which can hardly exceed 212°F. Burnt foods can also raise the temperature of parchment paper past 450°F which cause browning or smoking.

As for most other scenarios where the above cases are checked and heating conditions aren't extreme, parchment paper should be safe to use without the risk of brittling or smoking. Besides, the cold air in the oven always keeps the surface temperature of the food lower than it's inside and the wet surface of parchment paper due to condensation of food, actually makes it difficult to heat up.

What are the uses of parchment paper in the microwave oven?

Parchment paper has the following uses in the microwave oven
  1. Reheat cooked food: Cover dishes with a sheet of parchment paper to hold in moist heat which can help destroy bacteria and ensure even heating.
  2. As a packet or wrap for cooking foods like salmon, fish, boneless meat, chicken, potato chips, corn, hot dogs etc.
  3. As a packet for roasting garlic. 
  4. To cover the top of foods that splatter i.e melting butter.
  5. To line microwave plates when cooking greasy food such as bacon.
  6. To defrost food; The food is covered with a sheet of parchment paper to hold in moist heat which ensures even heating. 
Note:
  • Ensure to press the parchment paper tightly around the body of the dish to prevent it from flying off the top of the dish in the oven. You can crumble and then flatten out the paper to achieve this.
  • Always use the right amount of parchment paper to avoid wastage.

Will parchment paper leach chemicals during microwaving?

The unbleached variant of parchment paper wont leak any harmful chemicals into food, but the bleached variant could. The chemicals are known as dioxins. They are formed during the chlorination step in the whitening of bleached papers and they could migrate into food during cooking or storage. However, they are transferred at insignificant amounts which do not appear to present any health risk to people.

What other materials can be used in the microwave?

All materials that are labeled "microwave safe" are fine to use in the microwave oven.

Here are other materials (according to USDA and other sources) that are fine to use in the microwave oven.
  • Wax papers: They are safe for wrapping water based food, but can be highly unpredictable with fatty tissues or oily foods. For that reason, always make sure to use wax papers form reliable brands such as Reynolds.
  • Silicone baking mats.
  • Oven cooking bags.
  • White microwave-safe paper towels.
  • Glass, ceramics and plastics containers and wraps with a clear microwave safe label.
  • Paper plates and bowls.
  • Styrofoam; Use Styrofoam to heat liquids like water or coffee tea. Do not use Styrofoam for fatty, oily foods, soups, or noodles.
  • Heat proof glass like Pyrex.
  • Wooden or straw basket.

Warning for plastics wraps:
  • Do not allow food to directly touch plastic wraps. The plastic wrap can melt and transfer into food.
  • Do not heat dry foods in a plastic container because the plastic container can melt.
  • When covering food during re-heating or defrosting, make sure to provide a small opening so steam can escape. This will ensure you don't get steam burned when you try to remove the wrap.

What can't be used in the microwave oven?

Never use the following items in the oven; (According to USDA and other sources)
  • Aluminum foil: they are only safe to use in small amounts, like when shielding small areas of poultry food to prevent over cooking. In large amounts, aluminum foil will prevent microwave radiation form reaching food and can cause arching which can damage ovens.
  • Thin plastic storage bags; they can melt and transfer harmful chemicals in to food.
  • One time storage containers: they can melt and transfer harmful chemicals into food. 
  • Brown paper bags: they can catch fire. 
  • Plastic grocery bags: they can melt and transfer chemicals
  • Newspapers: they are not sanitary and can leach ink.
  • Anything with metallic rim or handles: The metal can arc and damage oven.
  • Twist ties
  • Recycled materials
  • Materials with a "not microwave safe label".

What other things in food absorb microwave radiation apart form liquid water?

  • Fats and oils, although they are less effective at converting the microwave energy into heat energy compared to water. The reason is because their dipoles are not as free as those in water molecules, so they have difficulty rotating with the electric field. But even so, they are able to attain higher temperatures than water, because of their lower specific heat capacity compared to it. Fats and oils, are actually one of the main reasons why a parchment paper will brittle or smoke in a microwave oven. 
  • Sugars: They too can absorb microwave radiation when they are dissolved in foods.
  • Dissolved salt too, can absorb microwave radiation although their own mode of heating is via a method know as ionic conduction.

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