Thermal Cooker or thermal cooking pot is also known as a vacuum pot

Why use a thermal cooker when one has the slow cooker?

I like using the slow cooker to make chinese soups, but it can consume quite a bit of energy because it is turned on for at least 2 to 4 hours or even longer during cooking time.

If you are very environmental conscious, you might feel uncomfortable using the slow cooker. For others, energy costs may be a concern.

Thermal cooking

The Japanese was the first to invent the thermal cooker (also known as vacuum pot) as an energy saving pot. It saves energy because it uses trapped heat to cook food. It has three major components:

an inner pot, usually made of stainless steel
an outer container with insulation, and
an air-tight cover

Soup ingredients and water are brought to a boil in the inner pot over the stove. It is then placed into the insulated outer container. The outer container is sealed with the air-tight cover.

Since the outer pot is sealed and there is insulation all around, the heat in the inner pot has nowhere to go. It can "concentrate" on cooking the soup. Given sufficient time, the trapped heat will cook the soup and ingredients.

This is a very energy-efficient way to cook. The food also does not get burnt since the heat isn't high enough to burn.

The vacuum pot is very versatile. Besides soups, it has been used to cook many different food. I find it an ideal "green" soup making pot. The only problem is it is time-consuming...at least 6-8 hours. If you like your food fast, this is not the pot for you.

I have heard complaints that food are undercooked even when instructions are followed to the T. Do not underestimate the amount of time needed. 6 hours is the minimum for chinese clear soups with chunky ingredients. Less if the chinese soups have ingredients that cook easily. I would not recommend making pot roast in the thermal cooker, but if you want to try, you should cook it on the stove top for more than 20 minutes and let it thermal cook for at least 10 hours.

Top brands

The 2 best brands, in my opinion, are Zojirushi stainless thermal cooking pot and Tiger vacuum pot.

Both are Japanese brands. There are cheaper versions coming from Taiwan and China. Their quality and cooking effect are not as good as the Japanese ones but they can still do the job if given sufficient time.

Cooking Tips

It seems silly to say these, but just in case. Remember not to heat the outer pot directly, and not to put any food or ingredients in the outer pot.

It takes considerable time for the thermal pot to do its cooking work. Plan about 6 to 8 hours for the soups to be ready. It is ideal for overnight cooking.

Since the heat is trapped, so is the liquid. There will be little evaporation and therefore less reduction of the liquid. Prepare just enough water for the soups.

Do not cook chinese herbal soups in vacuum pots. The inner pot is made of steel or stainless steel, and certain chinese herbs react with metal. Not all chinese herbs have this reaction but it is better to avoid it especially if you like using pre-packed chinese herbal soup packs containing several different types of chinese herbs in varying quantities.

Caring tips

Do not soak the outer pot. To clean, just wipe with damp cloth and a small amount of detergent.

Wash the inner pot with detergent, rinse and wipe dry before placing back into outer pot.

Unconventional Uses

Besides slow cooking, it is also a great food warmer and portable food container. Because of the air-tight cover, it is spill-proof and leak-proof. Ideal for packing food for picnics and pot lucks.

Other unconventional uses include yoghurt incubator, thermo for hot tea, and ice cube holders / ice box for beers, especially for parties and barbeques.

Have you a new way of using the thermal cooker?