Keeping Stuff Hot for Lunch

by Jenn @ Frugal Upstate on August 29, 2008

In the comments of yesterday’s post on Lunchbox Planning for School, one NH Mom of 3 asked:

Do your kids eat the Ramen Noodles, Mac N Cheese, etc cold? I’m wondering how we can successfully add that to the rotation.

I have to admit I’m not there when Princess opens her lunchbox,so I don’t know first hand how hot the food really is come lunchtime. I have quizzed her closely, and she says things are “warm” when she eats them.

To keep the food warm, I use either a children’s thermos (it looks like a crayon) or one of those short, wide mouth “soup” style thermoses, depending on what I am sending.

Both of mine are made of double walled plastic, which does not have the best heat retention properties. Honestly, one of the metal ones lined with glass would hold in the heat MUCH better. On the other hand when you have small children who might get rambuctious, then it’s probably best NOT to have glass in there.

The big secret is to preheat your thermos. Heat always tries to move into cold*-so the minute you put hot food into a cold (or even room temp) thermos the heat starts moving OUT of the food and INTO the thermos walls. That makes your food colder!

To prevent this you must fill the thermos with the hottest water you can (boiling if possible) and let it sit with the cap on for 3-5 minutes so that the heat can move into the thermos walls. At the same time you heat the food up as hot as you can (Thank you whoever invented the microwave!). Pour the water out and then immediately put the hot food into the hot thermos.

Viola! You have now greatly increased the chances that your food will still be hot (or at least warm) at lunch time.

For added insurance (since I’m using the aforementioned plastic) I like to wrap a kitchen towel around mine for extra insulation. I also try not to send anything that requires ice packs in the same lunchbox-because then you’ve got the hot and cold duking it out.

I’ve even on occasion resorted to using of those cheapo thin insulated lunchbags that I bought at the dollar store to put just the hot stuff in. Then I put the rest of the lunch in the regular lunchbox.

This may not be an issue with older kids. I’ve read (although not seen myself) that some middle and highschool cafeterias now contain a microwave. If that’s the case, you simply have to keep the food at a safe temperature until your student can heat it up.

Does anyone else have some brilliant ideas for how to keep the food hot until lunch?

*Note: Yeah, I know it’s a lot more technical than that-I’m giving the short, science for idiots version.

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{ 9 comments… read them below or add one }

Mama Squirrel August 29, 2008 at 10:08 am

Thanks again! I’m looking for all the technical stuff I can get on how to keep the hot hot and the cold cold–this is the first year I am sending an elementary-age student (been homeschooling up until now). Elementary schools here (southern Ontario) don’t tend to have cafeterias or even lunch rooms, so Thermoses and cold packs are all you have to work with.

My teenager is in her third year of public high school and her situation is quite different. They do have a full cafeteria but she usually takes her own lunch, often something frozen because they do have access to a microwave, and she says it’s easier for her to deal with frozen food than managing to just keep something cold until lunchtime. (If I just refrigerated the chili and sent it with a cold pack.) Sometimes it’s frozen leftovers (a square of lasagna, a cupful of leftover chili), sometimes we find a very good deal on individual frozen meals (we have found individually-wrapped burritos for a reasonable price).

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Harper August 29, 2008 at 11:08 am

I think it’s also worth noting that most kids are more sensitive to heat than adults are. So something that seems cold to us may seem warm to them, or they just don’t mind room temperature.

The other thing is that I remember when I brought lunch to school in a lunch box, the plastic box absorbed ambient heat. One of the things I hated was that my lunches were always supposed to be cold, but they always came out warm. And who wants warm pb+j, juice, and celery sticks. ew.

Great post.

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Martine August 29, 2008 at 4:14 pm

I have found that the double walled stainless steel thermos is better than the plastic at heat retention and is not breakable like glass lined ones.

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Your Frugal Friend, Niki August 29, 2008 at 4:56 pm

My mom used to boil soup for me and put it into a stainless steel thermos.

:)

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Barbara C. September 1, 2008 at 5:56 pm

Some people swear by insulated Bento containers like this one:

http://www.amazon.com/exec/obidos/ASIN/B000246GSE/catholichom0a-20

I think they put cold stuff in the bottom and hot stuff in the top with room temperature stuff in-between.

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Amanda September 2, 2008 at 12:40 pm

Love the terry towel idea to keep the thermos warm; newspaper and brown paper will also offer some insulation if you don’t want to send a cloth.

Note that when pre-warming a glass-lined thermos it should not be done with boiling water. Use hot tap water first to warm the vessel, and I even use a metal spoon or skewer to avoid cracking, while still warming the interior. Once it’s good and pre-heated you can put in boiling soups or whatever with no problem.

At one time I had a heat pad for take-along items. You warmed it in the microwave and sat your dish on it. Perhaps the same idea could be employed inside a lunch box? I often use a clean sock filled with rice as a heating pad. Those only stay warm for about 20 minutes when exposed to the air, but inside an insulated lunch box, I bet it would retain much more heat.

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Jenn @ Frugal Upstate September 2, 2008 at 12:49 pm

Amanda-great idea about the rice bag. I have those for my aches and pains, and to keep the tootsies warm on the sofa in the winter. Never though about making a small one to pop in the lunchbox. You RAWK!

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Anonymous January 11, 2009 at 4:52 am

this thermos mug from japan does a good job for keeping drinks warm
http://japansugoi.com/wordpress/sleek-thermos-coffee-mug-from-japan/

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Melody October 15, 2011 at 2:02 pm

I know I am reviving an old post but I’m now looking for products that’s can help me get my son a hot lunch some times… I have made every creative thing I can think of but we are ready for heat! I just came across something called Lunch and Go – has anyone tried it before?

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