Ziploc® bags are ideal for storing leftovers, ensuring a tight seal that keeps food fresh for days. However, we’ve all been in the same situation, pulling out a Ziploc full of pizza or chicken and wondering whether it’s safe to put in the microwave. It may be tempting to avoid dirtying a plate, but you’re not sure if it’s worth the risk.
The fact is, you can microwave a Ziploc bag. However, the hows and whys may be more complicated than you think. If you’re constantly microwaving Ziplocs, take a moment to learn a few safety tips that can improve your results.
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The Short Answer
The short answer is yes. Ziploc bags can be microwaved and are, in fact, designed to be used in this way. Part of the reason why some people hesitate to do so is because of the belief that heating plastic releases harmful chemicals into food.
However, the Ziploc company found that the harmful chemicals released when plastics are exposed to high heat only form at temperatures above 1500 degrees Fahrenheit. Since home microwaves don’t reach these temperatures, there is no risk of exposure to these chemicals.
The Long Answer
However, despite what manufacturers say about their products, there are still some dangers to be aware of. Even if you do plan on putting your resealable bag in the microwave, it’s a good idea to be aware of these factors.
Melting
Since Ziplock bags are made of thin plastic, they are prone to melting when exposed to high temperatures. This is especially true if the bag is empty or nearly empty when heated. A melted ziplock can fuse to food and burn skin, meaning it is a hazard worth taking seriously.
Steam
Even if your food turns out alright, there are still some safety hazards to be aware of when microwaving a Ziploc bag. If the plastic bag is sealed when cooked, steam can build inside. If not handled carefully, this can burn your hands enough to cause an injury.
That’s why it’s a good idea to leave the bag slightly open when microwaving. When handling it fresh from cooking, take care to avoid steam coming out of the bag.
Harmful Chemicals
Ziploc bags are made of plastic called polyethylene. This plastic is commonly used as a food-safe material as it does not contain harmful chemicals. However, polyethylene can release a chemical called dioxin when exposed to high heat.
As mentioned above, home microwaves don’t get hot enough to release dioxin. However, some believe that oils contained in food can concentrate heat to cause a health hazard. In the end, there is no definitive answer, leaving some preferring to play it safe.
Identifying the Product
If you’re not using name-brand Ziploc bags, it may be difficult to tell what exactly you’re putting in the microwave. Some resealable bags are made of PVC plastic, which is not as safe for reheating as polyethylene. Putting these products in the microwave can release harmful dioxin into your food.
How to Microwave a Ziploc Bag
As mentioned above, it’s not always a good idea to microwave a Ziploc bag. However, as long as you can keep the following steps in mind, you can mitigate many of the risks.
1. Choose the Right Bag
Ziploc does offer a line of bags designated Microwave Safe. Whether you’re using these or an off-brand option, make sure your bags are designed for use in the microwave. Other bags can melt or release harmful chemicals into your food.
It can also be a good idea to carefully check the label on your Ziploc’s packaging to learn more about how to use it. Some labels will include information about maximum temperatures and other helpful safety tips.
2. Fill Appropriately
The contents of your Ziploc bag are likely to expand and release steam when microwaved. That means even if the bag is cooked properly, it can cause a mess and a potential hazard. The best way to avoid this is to ensure it’s not too full.
Generally, your Ziploc should only be about half full, and the contents should not rise near the opening.
3. Place the Ziploc in a Microwave-safe Dish
Since Ziplock bags aren’t made to stand on end, they are still likely to tip over when microwaved. Also, any small holes or tears in the bag can leak, potentially damaging your microwave. For both of these reasons, it’s a good idea to place the bag in a shallow bowl or plate to catch any mess.
4. Unseal the Bag
Foods high in moisture will release steam when heated. This will make your food soggy as well as create pressure in the bag which may burst it. For both of these reasons, allow at least a small opening at the top of the bag to vent steam.
5. Choose a Low Power Setting
Generally, microwaving a Ziplock bag is only a good idea when defrosting or reheating food. The high temperatures required to cook food can lead to some of the dangers described in the sections above.
Stick with fifty percent power or below to avoid these dangers. This will be enough to defrost food or get it warm in a short time.
6. Never Overheat
Small quantities of food should only take 30 seconds or less to microwave. Any more than this can create unsafe temperatures in your Ziplock bag. If you need to microwave longer, do so in 30-second intervals, checking and adjusting the bag as you go.
7. Don’t Remicrowave
Even though reusing plastic bags can be good for the environment, it’s not a good idea to microwave them more than once. Over time, the plastic will degrade, releasing more chemicals into your food and risking leaks.
Alternatives to Ziploc Bags
The good news is if you’re hesitant to microwave Ziploc bags for health reasons, or you just don’t like the hassle, there are alternatives. Try one of these the next time you’re thinking about microwaving a Ziploc.
- Tupperware® may be made of plastic, but it is usually thick enough and durable enough to be a better fit for the microwave. However, just like with resealable bags, it’s best not to get them too hot.
- Paperware is an even better option than Tupperware, as it can be heated as long as you like without the risk of melting or releasing harmful chemicals. Of course, it’s not great for the environment.
- Ceramic Bowls and Plates, as long as they’re microwave-safe, are perfectly suited to microwave use. You do have to clean a dish when you’re done, but in the end, it’s the safest option.
Frequently Asked Questions
Still have questions about reheating food with a resealable bag? Take a look at these commonly asked questions below.
Ziploc bags are made of low-density polyethylene, which is formed into both the bag and its zip top. This is the same material used in rigid plastic containers like Tupperware and frozen dinners.
This material is ideal because it is able to withstand both high heat and freezing temperatures. It is also generally safe for use with food. The only point of caution is that high heat can cause this otherwise safe plastic to release toxins.
Since Ziplocs melt at a relatively low temperature, not many foods can be effectively cooked in them. Meat, eggs, and vegetables all require higher temperatures which would melt the plastic before they are fully cooked.
If you want to put a Ziploc bag in the microwave, use it only for reheating or defrosting. This will allow you to bring the food to an edible temperature without overheating the plastic.
Since Ziplock bags are made of thin plastic, they are prone to melting. At 195 degrees Fahrenheit, Ziplocks will begin to soften and warp. If exposed to this heat, it’s best to throw them away rather than reuse them.
If exposed to higher temperatures, especially water boiling at 212 degrees Fahrenheit, Ziplocks will melt completely. When resealable bags melt, they ruin food, release harmful toxins, and can harm your skin.
Freezer bags tend to be a bit thicker than other types of resealable bags, which leads some people to think they’re safe to microwave. However, unless labeled ‘microwave-safe,’ it is better to avoid doing so. This is because the microwave-safe bags are designed using slightly different materials which are better suited to high heat.
Since boiling occurs well above the melting point of low-density polyethylene, it is never safe to boil Ziploc bags. Doing so can ruin your food and cause a safety hazard. Also, pouring boiling water into a Ziploc can be especially hazardous and should be avoided.
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