Internet Version [Naruhodo no Mori] Vol.47

by Yumiko Mori

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Vol.47   September 15th, 1999

Baking sweet potatoes in hot stones

Home science experiments for mothers of elementary school children

Mom collects gravels, puts them into a wok, and starts heating them.
Satoshi: "What? Are you going to heat stones?"
Mom: "That's right. We can bake sweet potatoes in the hot stones."
Then she puts sweet potatoes under the gravels.
After a while, nice smell of baked sweetpotatoes start coming from the wok.

Tae: "Are they ready soon?"
Mom: "Let me check if they are ready. Oh, it's very hot!"
Tae: "Mom, you must be careful not to get burnt. "
Mom: "Yes, I have to be careful. I turn off stove. I am going to finish baking by residual heat. "

While eating baked sweetpotatoes,
Satoshi: "Today's experiment was very easy."
Mom: "I am not sure this was so easy. This experiment took time and the hot stones were difficult to handle."
Satoshi: "Think what I did in this experiment. Just eating."

Materials

Gravels	Enough to fill your wok (approximately 2 kg)
	(You may be able to obtain from a gardening store.)
Sweet potatoes	Several
	(need to be washed before baking)
A wok
Pot lid
Cotton work gloves
Stove
A stainless bowl and a sieve
Old newspapers

How to bake sweet potatoes

1. Wash gravels in a stainless bowl.
   Drain water from the gravels through a sieve.

2. Dry the gravels on old newspapers.

3. Heat the gravel at medium heat for 15 minutes.

   

   

4. Wear cotton work gloves and push sweet potatoes into the gravels.
   (The potatoes don't have to be buried completely.)
   Turn the heat to low.
   Cover the wok.
   (If you cover the wok completely, the temperature inside the wok will become too hot.)

5. Rotate the potatoes every 15 minutes.
   Make sure to wear the cotton work gloves.

6. When the potatoes are cooked (approximately 1 hour), turn off the heat.

7. Feel the potatoes whether they are a little soft or still hard. If they are still hard, the potatoes need to be cooked longer. Put back the potatoes to the gravels and cook them in the residual heat.

* The gravel is very hot. Make sure not to get burnt!
I measured the temperature inside the gravel. It was 180 degree Centigrade. It was hotter than the water boiling temperature (which is 100 degree centigrade).

* Baked sweet potatoes taste good because they were cooked slowly for a long time.
Sweet potatoes contain amylase, which converts starch into maltose.

* You may want to try baking potatoes, aroids, or eggplants in the similar way.

Cooking delicious baked sweet potatoes

I just wanted to bake delicious sweet potatoes. This is why I wanted to try this experiment. But I got very excited at this unusual cooking method. I know this is cooking rather than an experiment. It's also very easy. You must to try this one!