What is the best way to approach thermos cooking?

Question

I have a series of hard days in my near future. I want to prepare quick and easy lunches. I have the idea of taking lentils putting them trough a blender to get lentil flour.

If you add the lentil flour to a thermos flask add salt and spices and add boiling water. Could you then have lentil soup of some sort to help you get trough the day?

You would off course preheat your flask. Would it better to prepare the lentils on the morning you consume them or is it possible to do this the previous evening?

If the soup is only luke warm after 12 hours in the flask it is OK.

Even if it is cold a minute or two in the microwave is still OK.

What would be the best way to do thermos cooking?

Answer 1

In general, when using a thermal cooker, the basic procedure is this:

1. Start some water boiling
2. Bring your soup base to a boil (separately)
3. Pour the boiled water into your insulated flask
4. Make your soup and let it boil for a few minutes (fully cook any meat, typically, but not more than 5 minutes)
5. Dump the water out of your flask (it was just to pre-heat it)
6. Pour the soup into the flask with any items that shouldn’t be boiled and seal it
7. Wait a few hours
8. Eat

You can find recipes by searching for ‘thermal cooker recipes’, but some are for appliances which have their own cooking element in them, so don’t require the pre-heating step. You can also try searching for ‘soup bento’ recipes to try to find something similar to base your initial ratios on, and then adjust from there to your taste and time delay.

Answer 2

"The best way" is a matter of opinion, and thus off-topic.

For a matter of food safety, test your thermos routine with a thermometer to see how long the food is maintained at a safe temperature. Then limit your timing to the number of hours it stays above 140°F / 60°C in your particular preheated flask when prepared as you do, .vs. when you would eat it.

Guidelines permit up to 4 hours below the safe temperature limit, after which the food should be discarded (not reheated) so there are distinct limits on "luke warm" or "cold" actually being OK, rather than a hazard to your health.

Answer 3

The best way is to not try to cook it in the thermos itself, but to precook, dehydrate and store, then rehydrate in the thermos. This will save you from nasty surprises, especially undercooked food. It is not that your idea cannot work, it is just that it might fail just when you cannot afford it to.

There are a lot of recipes for this kind of cooking, just look around the web for making your own trail food packs.

Also, you will elegantly sidestep any food safety problems, because when you go that route, you are supposed to pack dehydrated portion sizes, then rehydrate one per meal and consume it outright.