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Can you microwave Ziploc bags?

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Can you put Ziploc sandwich bags in the microwave? Can Ziploc bags be heated? Are Ziploc bags microwave safe? 

If you have spent any time in a kitchen, both domestic and professional, chances are that you have witnessed someone microwaving food in a Ziploc bag. Is that safe and can you microwave Ziploc bags?

There continues to be debate whether or not plastics are safe to use around food. Name brands like Rubbermaid, Tupperware, and GladWare have built entire businesses around the guarantee that plastics are safe for food storage, however I continue to remain doubtful about the ability of plastics when stimulated with extreme heating.

What are Ziploc bags made of?

Ziploc bags, and many other brands of sandwich bags, are made with a product referred to as “film.” Film is a clear, thin plastic consisting of either high-density polyethylene, known as HDPE or recycling #2, or low-density polyethylene, known as LDPE or recycling #4. 

Plastic packaging resins are all assigned a number that corresponds with the polymers used in the container. The numbers are commonly located on the bottom of all plastic containers.

Although Ziploc bags are BPA-free, dioxin-free and designed to be recyclable, they are not made from recycled materials. 

At what temperature do Ziploc bags melt? Ziploc bags primarily consist of polyethylene plastic, which has a softening point of approximately 195°F or 90.5°C. As a result, the plastic bag could begin to melt if boiling water (water boils at 212°F or 100 °C) is poured inside the bag, or the bag is submerged into boiling water.

Can you microwave food in a Ziploc bag?  

I have bared witness to people successfully microwaving food in a Ziploc bag, however that doesn’t necessarily mean it is safe. While you may be able to effectively microwave food in a Ziploc bag, you may want to examine the manufacture’s directions a bit closer.

When label directions are followed, Ziploc® brand products can be used with confidence. All Ziploc® brand Containers and microwavable Ziploc® brand Bags meet the safety requirements of the U.S. Food and Drug Administration (FDA) for temperatures associated with defrosting and reheating food in microwave ovens, as well as room, refrigerator and freezer temperatures.

Ziploc

Can you defrost in Ziploc bag in microwave? Manufacture recommendations clearly state that the microwave Ziploc bags are only safe for defrosting and reheating foods.

Can you cook in a Ziploc bag? The answer is a resounding no. The manufacturer’s instructions do not recommend cooking in Ziploc bags.

Cooking requires temperatures that generally exceed the melting point of the polyethylene plastic. For this reason, the company only endorses microwave defrosting and reheating.

Can you steam veggies in a Ziploc bag? The answer is a strong no. Steaming actually accounts for a much higher heat transfer rate than direct contact with boiling water.

Steam burns are far more dangerous than burns from boiling water because there is more energy in steam. In fact, steam has 9 times more energy than water at the boiling point. 

By acknowledging this physics equation you understand that steaming veggies in a Ziploc bag creates a much higher temperature than polyethylene plastic is designed to withstand. 

Are sandwich bags microwave safe? Regular sandwich bags are not microwave safe. Unless the manufacturer clearly states that the sandwich bag is safe for microwave use, DO NOT use it in the microwave.

Can you microwave Ziploc freezer bags? Ziploc freezer bags are designed to defrost and reheat food, however caution should be exercised because the bag is not able to withstand high heat.

Ziploc bag manufacture warning label about microwaving
“CAUTION: For use in microwave, place bag on a “microwave safe” dish. Handle with care. Bag and contents may be hot. Do not overheat contents as bag may melt.”

How long can you microwave Ziploc bags? There are no clear defrosting and reheating standards set by the manufacturer. The only statement you can obviously discern is “Do not overheat contents as bag may melt.”

To meet these guidelines, microwave Ziploc bags on medium to low power and use 30-second increments. Make sure the bag is unsealed to prevent the buildup of steam inside the bag. Carefully inspect the Ziploc bag after each 30-second duration to ensure that the bag is not overheating. 

Things to know before you microwave Ziploc bags

Ziploc has created a specially designed line of sealable plastic bags that are designated microwave safe. However, there are key details to take away from the manufacture’s instructions.

The company recommends that you avoid overheating the contents inside the bag. Items with high fat and sugar contents should be microwaved with caution because they can heat to much higher temperatures than water molecules. The risk being that the hot temperatures may cause the plastic bag to overheat and melt.

In addition, the manufacturer’s instructions clearly state that foods should only be reheated or defrosted. Cooking is not recommended because the plastic bags are not designed to withstand the high heat required to cook foods.

Therefore, Ziploc plastic bags should be placed on a “microwave safe” dish and microwaved on a medium to low setting using 30-second intervals. The bag should be unsealed to prevent steam build up inside. Carefully examine the bag to make sure that the plastic is not beginning to overheat.

When you meal prep food in Ziploc bags, it is best to cut food up into smaller, uniform sized pieces. This will reduce the time required to reheat food. Furthermore, reduced microwave time minimizes the risk of overheating the plastic bag.

Conclusion

If you have found success using Ziploc bags in the microwave, then it’s easy and convenient to continue using the same methods. Even though the microwaveable Ziploc bags are “safe for microwave use,” there are noteworthy statements on the manufacturer’s instruction label.

After reviewing the subject with a deeper understanding, I believe that ceramic and glass microwave safe containers are a far better alternative to use rather than microwaving Ziploc bags.

Covered food heats up more efficiently because using a microwave food cover expedites the cooking, defrosting and reheating process by evenly distributing the heat and steam around the food.

Although Ziploc has developed new materials for their microwave bags, the manufacturer has provided guidelines that must be precisely followed when using microwave Ziploc bags:

  • Place bag on “microwave safe” dish
  • Do not seal bag in microwave
  • Defrost and reheat only
  • Do not overheat contents
  • Use medium to low heat
  • 30 seconds or less
  • Do not overfill bags

Even though Ziploc bags are washable, dryable and reusable, I would not recommend microwaving old Ziploc bags more than once. Doing so puts the food at risk of toxic release because the bag may have surpassed its microwave durability.

When it comes to the convenience of cooking, reheating and food storage, it’s important to understand the functionality and misapplications of the kitchen product you have. 

If you are comfortable using the microwave for Ziploc bags, then you should have zero concerns. However, if you find yourself questioning the safety of heating up plastic bags, then switch to ceramic or glass and just avoid using plastic in the microwave.

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