Sunday, 19 July 2015

Using the Microwave Oven: Boiling Water, and Eggs

For a while now I have driven around with the Microwave in the back. I had tested it right after Christmas, when I cooked one of those meals specifically made for microwave cooking. It had worked fine, but now I wanted to do a more thorough testing.

So I decided to heat 0.5l of water and observe the boiling process. The microwave oven is specifically manufactured for use in a motorhome and therefore does have less power than any usual household microwave oven. This is because campsites often only provide limited electric power, sometimes only 4A at 240V, which is around 1kW. The heating power of this microwave oven is 425W, compared to 700W or more for a small household oven. Therefore, it is to be expected that the boiling duration would take longer. Also, this has to be considered when cooking meals: the times given for certain microwave powers need to be extended for use with this oven.

0.5l is quite a large amount. This is about 3 cups of coffee/tea and is sufficient for any soup that I would want to cook. I measured 0.5l, then used a microwaveable cup to heat the water.

Then I heated the water in intervals and measured the surface temperature with a remote infrared thermometer. The plot of the temperature rise is shown here:

The graphs seems not to show that the water is brought to a boil - but actually the water was boiling in the end, blubbering, even though the surface temperature seemed not to increase beyond 87 C.

The next experiment was to boil eggs. Usually eggs are very difficult to boil in a microwave oven: the power needs to be deliberately reduced to achieve a slow cooking. Here is where the reduced power of this oven becomes really useful. I used a plastic egg boiling container specifically made for microwave cooking.

To avoid that an explosion would throw egg around in the oven I affixed the top cover with a rubber band.

After about 45 seconds of heating I heard an explosion. Nothing really happened, just the egg cracked a bit. I took it out after 1 minute, and here is how it looked:

Not yet fully hard-cooked, the egg white was still partially transparent. So I boiled it for another minute. Here is how it looked then:

Well done, a hard-boiled egg in 2 minutes!

The next experiment was to boil 2 eggs in the special microwave cooking device which my friend Falk had given me a few years ago (knowing my cooking style). This is a plastic container in which one can either cook 2 eggs or one slice of bacon.

I opened 2 eggs, one in each of the compartments, as shown in the picture above. After 45 seconds there was again an explosion. Here is how they looked after 1 minute:

Only the right one seemed to be done, whereas the left one remained uncooked. After another minute the result was this:

Clearly there was an issue with the internal distribution of the microwaves: apparently the power was stronger in the right part of the oven. I ate the well-done egg and boiled again the not-yet-boiled one, for 1:30 min. Perfectly done then!

My final experiment for the day was to boil again two eggs, this time just switching sides after 1 minute. Did this, and after the rotation I did cook them for another minute.

They tasted excellent!

Wednesday, 1 July 2015

The next step: Microwave Oven

Slowly the equipment in the MicroCamper gets completed. What was missing up to now is a cooking facility. I had put the coffee maker onto the work board, but that had to be shifted due to space restrictions - it will be again mounted on a slightly different location. But there is another item which my brother Winfried gave me as a present: a microwave oven specifically for campervans! Its specific features are a low power, so that it can be operated in low current settings, for example on camp sites which only provide a few Amps. any regular microwave oven would blow the fuses at those sites, but this microwave oven does not.

I already had cooked a ready-made meal in it a few months ago, but now it is time to do a real-world test in the actual camper.

So far I only have placed it in its location, affixed with a bungee cord. Will have to do some actual cooking soon. I will first use only its main connection, which can be a standard 220-240V mains power. It also has two battery-powered modes, which sound a bit scary: the "low power" setting will draw 20A from the 12V battery, and it will produces 100W microwave power. The 20A will move my electric system close to its 30A limit - I will have to watch that I do not blow it. Also, the cooking / boiling will take a while in this low power setting; I will take some measurements on how long it takes to heat up a cup of water to the boiling point.
There is the other, "high power" setting for using the battery. And that one will draw a full 55A. Cannot run this through my electronics, but will have to connect it directly to the battery. With the car alternator connected and running. Am a bit afraid of that test....

In any case, for both tests the leisure battery will need to be fully charged, as after these tests it will most likely be fully drained.