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Equipment & Gear: Microwave Safe Containers
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Cooking For Engineers



Joined: 10 May 2005
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PostPosted: Fri May 13, 2005 5:43 pm    Post subject: Equipment & Gear: Microwave Safe Containers Reply with quote


Article Digest:
In the United States, food grade containers are containers manufactured with materials that the Food & Drug Administration (FDA) has approved as safe for use in food preparation and storage. Food grade materials are generally known to not leach harmful substances or react with food in a harmful manner.

In most home kitchens, we'll find an assortment of different materials used in our containers ranging from glass to plastic to ceramic to metals. But are all food grade materials similar? Should we care if a container is marked Microwave Safe? Let's take a closer look at some common materials used in food containers and if they are microwave safe.

Glass & Ceramics
Glass containers are often marked microwave safe. These containers can be heated in a microwave without a problem. The issue with glass that is not microwave safe is that micro-air bubbles may be present in the glass and as the glass heats in the microwave oven, the bubbles may expand to the point where the glass breaks or shatters. (Obviously, you shouldn't eat food where it's glass container has broken.) Pyrex glassware is an excellent example of microwave safe, heat resistant glass that can also be baked. Even Pyrex glass cannot withstand the intensity of direct heat, such as a range or a broiler, for long, so don't use glassware with such heating methods. Also, all glass is susceptible to thermal cooling shock (rapid cooling, for example, dunking in cold water while hot) and may crack.

One popular method of testing if a particular glass is microwave safe is to microwave the container while it is empty for one minute. If the container is hot, then it is not microwave safe. If the container is warm, it should be fine for heating food. If the container remains cool, you can cook in the microwave with that container. Personally, I choose to either check to see if it's marked as microwave safe or ask the manufacturer before using in a microwave.

Any glass container with a metallic trim should never be microwaved. The electrical currents induced by the microwave radiation in the metals can cause sparking and pinpoint heating of the glass. Sometimes this can result in marring or even breaking of the glassware. Also, make sure any glassware with a colorful coating, finish, or stain should be marked for use with food or microwave safe before attempting to use in food preparation. The dyes, pigments, or stains may not be food grade. Almost always, decorative plates are not for use with food.

Food safe ceramic uses glazes that are made from harmless materials like silica, dolomite, kaolin, feldspar, ball clay, and others. In these glazes, the inevitable leaching that occurs is only a functional and aesthetic issue and has no health impact. Glazes that contain metals such as lithium, lead, or barium may present a health issue. Ceramic containers made with such glazes cannot be sold in the United States without either a permanent marking stating it is "Not for Food Use - May Poison Food" or have a hole in the container (presumably rendering it useless for food preparation). If you make your own ceramics, make sure you use a food grade glaze if you plan to use it in your kitchen.

Plastics
Food grade plastics are made from a specific list of plastics approved by the FDA (which may include dyes and recycled plastic that have not been determined to be harmful to humans). Once a plastic container has been used to store non-food items (like detergent or paint), it can no longer be considered food grade. Plastics containers that are not food grade may leach plasticizers into food on contact. Due to the nature of plastics, they have a high affinity for fats. Plastics that come in contact with an oil-based substance will almost always be irrevocably altered and the plastic may never become truly clean once again. Contact to foods that are high in fat may cause leaching of the original oil-based substance into the food even if the plastic was originally food grade.

Microwave safe plastics are food grade plastics (which do not leach plasticizers) that are known to be able to withstand higher than normal temperatures. Plastics that are not microwave safe may leach harmful substances when heated in a microwave oven. (There was an internet e-mail scare/hoax that was passed around claiming the USDA or FDA and independent researchers showed that dioxin (a plasticizer) leached out of plastic wrap onto food being microwaved. This is untrue since all microwave safe plastics are dioxin free. Saran and Ziploc both maintain that their product lines are completely plasticizer free. The temperatures necessary to create dioxin (around 1500įF) are beyond the normal operating conditions of household and commercial microwave ovens.)

Do not microwave food in plastic containers or covered with plastic wrap that is not microwave safe.

Also, don't brine (or store) foods in containers that are not intended for food preparation - such as a "clean/brand new" mop bucket, plastic trash bag, or trash can.

Lexan is a food grade polycarbonate plastic that has gained a large following in the food service community. It is hard, durable, and resistant to reacting with oils resulting in a virtually stain and odor proof material. It is capable of handling a range of temperatures from below freezing to boiling. However, it is advisable to recycle and purchase new polycarbonate containers when they crack, chip or cloud up.

Recently, Sierra magazine published a report claiming that polycarbonate plastics leach an endocrine disruptor called Bisphenol-A (BPA). Unfortunately, the studies the article was based on cannot be directly related to use in the food industry since the tests were performed on non-food grade polycarbonate mouse cages (which affected the growth cycle of the mice). No evidence of food grade polycarbonates (such as Lexan) being a health hazard has been uncovered. Further studies are ongoing to determine if a potential for such a hazard even exists.

The S.C. Johnson Company says that the larger Ziploc brand bags are microwave safe. All Ziploc bags are made of microwave safe materials, but bags smaller than 1 quart size may be too thin to withstand the temperature of the food being microwaved. Be sure to vent Ziploc bags to allow steam to escape during microwaving. Please note that not all resealable plastic bags are microwave safe, you'll want to check with the manufacturer.

Additional information can be found at:
foodsafety.gov
Food Grade Containers for Brining


Last edited by Cooking For Engineers on Tue Jun 21, 2005 1:59 pm; edited 1 time in total
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Tz'Akh
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PostPosted: Sat May 14, 2005 3:03 pm    Post subject: an interesting story Reply with quote

I work for a company that is a plastics compounder - which means they getplastic directly from the nuclear power plants that cook it out of petroleum, mix it into different forms, and then ship it out to other companies that make products. The chemists that design the melts (plastic recipe runs) refuse to use 'microwave safe' or any other plastic containers in a food settling where the container gets hot.

The plastics that are labeled 'safe' for such conditions are the same plastics that would normally be unsafe, mixed with a strengthening additive. When, over the course of time and exposure to heat & other radiation, the plastic itself does not break down rapidly, but instead the additive 'takes the hit' and comes out of the container (with small quantities of plsatic).

The problem is that the strengthening additives are highly toxic - with various kinds having known connection with organ failures and nervous system problems. The safety tests done on the plastic compounds I've been able to research don't have any awareness of whether the small quantities of an additive that comes off from the plsatic container are stored in our body or pass through it. No sense of whether there is a internal system threshold for our body, even though it's known that people can reach thresholds through job exposure to some of them. ('Threshold' meaning once you're exposed to a certain amount of it you experience dramatic physiological reactions (vomiting, loss of consciousness, etc) when exposed further.

To wrap up the rest of this disclosure; I am highly sensititive to many chemicals - what is safe and/or unnoticable to other people can make me sick. For the month or two that I worked in the plastics plant (before I began telecommuting) there would be days that I would become nauseous, couldn't stay awake, sharp headaches, etc. My arguement is that the notion of a "food grade" plastic is probably best taken with a small footnote of caution (probably provided by me via this post Wink

-Zak
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Jason
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PostPosted: Sat May 14, 2005 5:05 pm    Post subject: Reply with quote

I thought nuclear power plants don't use petroleum - radioactive uranium or plutonium, steam, turbines, sure, but petroleum? Why did you even start witht hat "tidbit" of (mis?)information?

It makes me suspect your whole story...
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lena
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PostPosted: Sat May 14, 2005 6:55 pm    Post subject: Reply with quote

Interesting article, this is exactly a topic I am interested in at the moment.
Quote:
Also, don't brine (or store) foods in containers that are not intended for food preparation - such as a "clean/brand new" mop bucket, plastic trash bag, or trash can.


I have a large (25 kg) bag of whole wheat, that I mill at home. Any suggestions on how to store this? Food grade containers that I can find are way too expensive. Large ones do not even seem to exist in my country, and multiple small ones would cost hundreds of dollars. I now keep them in the original paper bag, and cover that with a plastic trash bag. So the grains do not actually touch the plastic. I wonder if the mill where I bought the grains stored them in food grade containers, by the way.

Any suggestions would be much appreciated. The solution I now have is not ideal because mice will still eat through the trash bag, of course.
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shpoffo
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PostPosted: Mon May 16, 2005 3:59 pm    Post subject: OT: to note on "(mis?)information" Reply with quote

Quote:
petroleum..... It makes me suspect your whole story...


Nuclear power plants have a "waste heat" cycle, where the system is producing heat that they can't use for turbines, etc. Rather than let that heat be wasted (dissipated into the atmosphere) they use it to heat giant vats of petroluem. The heat causes the petroleum to separate into layers of material; gasoline, ployethene, other plastics, sludge, etc.

I never said the nuclear reactors use petroluem for their fuel source. I shared it because it is a fun tidbit that reveals part of the way our system works. Thanks for being polite enough to make it a question, though...


Zak


Last edited by shpoffo on Mon May 16, 2005 4:05 pm; edited 2 times in total
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shpoffo
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PostPosted: Mon May 16, 2005 4:03 pm    Post subject: large food grade containers Reply with quote

lena, had you considered finding a wooden barrel? You could inquire into a local winery as to their source of barrels, as you can then be sure the barrel is not being treated with any dangerous chemicals (and barrel-makers are hard to find outside of the wine industry these days)

Otherwise look for a large food-safe plastic bag to use as a liner in and otherwise inappropriate container.



Zak
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Johneegeek



Joined: 12 May 2005
Posts: 21
Location: Kenosha, WI

PostPosted: Mon May 16, 2005 4:47 pm    Post subject: Reply with quote

lena wrote:
Interesting article, this is exactly a topic I am interested in at the moment.
Quote:
Also, don't brine (or store) foods in containers that are not intended for food preparation - such as a "clean/brand new" mop bucket, plastic trash bag, or trash can.


I have a large (25 kg) bag of whole wheat, that I mill at home. Any suggestions on how to store this? Food grade containers that I can find are way too expensive. Large ones do not even seem to exist in my country, and multiple small ones would cost hundreds of dollars. I now keep them in the original paper bag, and cover that with a plastic trash bag. So the grains do not actually touch the plastic. I wonder if the mill where I bought the grains stored them in food grade containers, by the way.

Any suggestions would be much appreciated. The solution I now have is not ideal because mice will still eat through the trash bag, of course.

I think I remember that in Alton Brown's book: I'm Just Here For More Food (http://snipurl.com/exjv)
He uses a metal trash can (The fancy ones you put your foot on to open the top) to store flour. Of course this goes against the advice that you use food grade containers. :?
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PostPosted: Thu May 19, 2005 4:12 pm    Post subject: Reply with quote

lena wrote:
Interesting article, this is exactly a topic I am interested in at the moment.
Quote:
Also, don't brine (or store) foods in containers that are not intended for food preparation - such as a "clean/brand new" mop bucket, plastic trash bag, or trash can.


I have a large (25 kg) bag of whole wheat, that I mill at home. Any suggestions on how to store this? Food grade containers that I can find are way too expensive. Large ones do not even seem to exist in my country, and multiple small ones would cost hundreds of dollars. I now keep them in the original paper bag, and cover that with a plastic trash bag. So the grains do not actually touch the plastic. I wonder if the mill where I bought the grains stored them in food grade containers, by the way.

Any suggestions would be much appreciated. The solution I now have is not ideal because mice will still eat through the trash bag, of course.


You might try going to the pet store and looking at the containers they sell to store dog/cat food. They generally hold about 40lb of kibble and cost around $35-50. Smile [/quote]
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Claudia
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PostPosted: Tue Jun 21, 2005 4:09 am    Post subject: Large food storage container Reply with quote

Lena,
The Baker's Catalogue has a 22 quart container. Here is the page:
http://shop.bakerscatalogue.com/items/item6069.html
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Julie
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PostPosted: Fri Aug 26, 2005 10:54 pm    Post subject: Storage container for milled wheat Reply with quote

What about using a galvanized steel can? I might be way off here, but it may be possible to store the grain in the bag inside of the steel can. Just a suggestion....good luck!
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drsimpson
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PostPosted: Wed Sep 21, 2005 8:45 pm    Post subject: Large food grade containers Reply with quote

I stumbled on your fine forum searching for inexpensive containers for long term water storage (disaster preparedness). Since I like to cook I like the concept of Cooking for Engineers.

I have been using galvanized steel cans for storing bird seed and dog food on the back porch. I do use the food every day. Am I killing the wildlife and my dog?

Thanks for any feedback... Unsure
Dianne
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an0n
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PostPosted: Wed Jul 26, 2006 1:03 am    Post subject: RE: Large food grade containers - water storage Reply with quote

You can find used food grade barrel suppliers at www.pharmacal.com/recond.htm
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arete
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PostPosted: Tue Aug 01, 2006 3:43 pm    Post subject: largeish containers, metal bird seed, etc Reply with quote

One largish (20 qt) container that I use is a 5-gallon bucket. In particular, a 5 gallon bucket originally used to ship pickles to a fast food establishment, which they were happy to give me for free.

Considering the many plastic issues, even still I only use it for short-term cold temperature applications to reduce leaching. A wine barrel is an awesome idea. I have no idea how voluminous 25kg of wheat is.


Regarding your bird feed: I think your galvanized can is _probably_ fine, for several reasons:
1. Metals tend to be relatively nonporous and metals finishes (like galvanization) tend to be relatively robust and strong. I wouldn't necessarily sandpaper the finish and eat the dust, though.

2. You're not heating it, heating encourages everything (but especially plastics) to release all sorts of chemicals.

3. You're not soaking it. Filling something with a liquid vastly increases leeching from the container compared to storing solids, because it's easier to leech into the liquid and because the liquid will touch every last bit of the sides of the container. (A seed, for instance, will only touch a tiny piece of container but "block" a bunch more from being touched by other pieces; there are lots of tiny air pockets.)
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guest
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PostPosted: Wed Aug 02, 2006 9:20 am    Post subject: microwave safe ???? Reply with quote

First all plastics regardless of name brand or what have you give of chemical products that they were made from as like all chemical formulations they break down over time. What disturbs me is the lengths that the industry goes to silence any leak of facts that show microwaves are not healthy. just look at what happened to the two swiss researchers who were prosecuted for exposing the dangers of microwaved food. it was claimed they were interfering with commercial trade. fortunately the european court lifted the prosecution on appeal.
From my point of view after indepth research is never to eat anything out of a microwave oven. Im able to readily do this as im in control of my free will to decide what i eat and how its cooked, its that simple. Remember you are what you eat (what you do is what you get back, second natural law).
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Larry
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PostPosted: Tue Sep 12, 2006 12:27 am    Post subject: Microwave safe Reply with quote

Letís get a grip. Microwaving food is a good thing. Microwaves are non-ionizing, and do not leave any residual radiation of any sort. Itís good because it kills the micro organisms in the food that you are cooking or defrosting. You know the ones that can make you sick (like salmonella). Donít use plastic, use Pyrex.

Larry
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