heating food, insulated pouches?

a screw top jar covered with closed-cell-foam.

A plastic Jiffy peanut butter jar works well. (Just throw away the stuff inside.)

If you want to keep it *hot*, then you might have to go with a vacuum-insulated “thermos”-type bottle – which can now be found in all stainless steel and can double as a water bottle (not that water bottles need weigh very much).

If you want to keep it *warm*, you have a lot more options.  Any water-tight container can be placed in the middle of low-density, insulating clothes/quilt and will maintain its temp for many hours.  I routinely do this while transporting a few pounds of frozen salmon over three plane flights – 12 to 20 hours in transit.  Now, frozen food has the heat of fusion as an additional reservoir of cold and 70F-32F is not nearly as great a gradient as 190F-70F, so you’re not going to get days of insulation for a warm item.  But you should easily get 3-6 hours.

I’d just use a Nalgene or other water-tight container and wrap that. loosely, in my quilt, near the top of my pack (for easy access and so the insulation doesn’t get compressed).  But if you want it to stay even hotter or there’s any delay in getting it wrapped up in your quilt, you could make a Nalgene-sized cozy out of $1 of Reflectix.

It could do double-duty if you let your F-D dinner steep in the same, cozy-insulated container.

“A plastic Jiffy peanut butter jar works well. (Just throw away the stuff inside.)”

Not so fast! I have tried out a variety of lightweight plastic containers, and they all have heat issues. I use them for both hot and cold liquids, and some food mixing as well. Perhaps someone can help with a suggestion that addresses the OP and my concerns as well.

I like the Talenti gelato 8oz jars for their open mouth, but the wideness also makes it difficult to fit in my side pocket. When liquids are too hot, they start to bubble out at the bottom, and otherwise deform the jar:

I have tried a variety of 8 oz nut butter jars, mostly from Trader Joes, and while they have a better form factor for the side pocket, they deform even faster with hot water:

Nalgene offers an 8 oz wide-mouth straight-side jar that I have seen variously described as polypropolene and as lexan, there might be two versions, and I suspect that it can handle hot liquids, but it felt heavy in the hand when I spotted one. I can’t find a listed weight, but for sure it is heavy-ish. I wonder about some kind of modification to reduce the weight but am not sure if it will be enough:

Obviously, getting back to the OP, the hotter the liquid introduced, the longer it will stay hot, wrapped in bubble wrap, or whatever.

Plastic peanut-butter jars, soda bottles and other recycling symbol #1 – polyethylene Terephthalate (PETE) are NOT good for very hot water.  They deform in a dishwasher and fail immediately with boiling water.

Recycling symbol #2 – high-density polyethylene (HPDE) is good to well over boiling.  Classic Nalgene bottles and a variety of food products and household chemicals come in HDPE bottles and jars.  For wide-mouth, easy-to-eat-from (but not especially water-tight); Gatorade drink powder comes in short, wide HDPE screw-top jars.  Folger ground coffee comes in very large HDPE jars – I haven’t tested the seal of the lid.  Protein-powder jars tend to be larger but also a little sturdier and they seal better (the contents also cost more), but I see them in the recycling bins at times, in addition to behind Gold’s Gym.

Anyway, a little dumpster-diving at the recycling center will show you what the options are.  Because HDPE is dishwasher-safe, I run them through once or twice and figure that the very hot, caustic detergent will get them very clean.  Therefore I’m not terribly concerned about the prior contents.  Motor oil – so what?  Although I might pass on rat poison or Chromium-6-based plating solutions, etc.  Machine washing them is also handy after a trip to get all the odors out.

I used the talenti gelato container for 2200 miles this summer. Rehydrating my dinners with hot water every night. The container wrapped in a foam cover did distort on the sides but held up well. The tight foam cover allowed the plastic container to distort in an even symmetrical pattern around the outside. I will use the same container on my next trip.

There’s always the Crotch Pot.

Yeah, those gelato containers are really appealing – size, sturdiness, seal, ease or eating from, nice size for a cup.  If only they were good for another 15C, they’d be really versatile.  But for tabouli or cold oatmeal*, they’d be perfect.

Any Tupperware or Ziplock brand container is safe for the dishwasher or boiling water.  Some styles have screw tops.

*Just last night, I saw our Finish exchange student mixing up oatmeal, milk, raisins and nuts in a tupperware container and putting it in the fridge overnight.  I said, “Huh, does that soften it up enough to eat?”  Yes, she reported.  If she prepares it the same morning, she has to use boiling water and then let it cool down, but if she prepares it the night before, it’s ready to go in the morning.

Tap Plastics sells 16oz, 32oz wide mouth HDPE jars.  I think the 16oz weighs around 3oz.  Lids come with a gasket but I can’t speak to the seal from experience.  I cut the threaded lip off so it would fit in my 10cm Imusa mug and use as a cup.

https://www.tapplastics.com/product/plastics/plastic_containers/hdpe_wide_mouth_jar/554

Right @jringeorgia re: Crotch Pot.

Until you actually try it.

There’s a limit.

That “suggestion” was offered with tongue firmly in cheek. =)

I have done the overnight oatmeal before many times at home. Easy fix up for a weeks worth of meals.

https://www.theyummylife.com/Refrigerator_Oatmeal

Thank you to everyone who chimed in. It has given me some “Food For Thought”…….