Why does boiling water make dough taste sweet?

Question

I was experimenting on dough for chapathi, which is basically wheat tortilla. This is how I normally prepare it,

Mix whole wheat flour and salt with room tap water, often 20 to 30 degree Celsius .

Knead with oil until I get a consistent dough.

Immediately press with a rolling pin and cook in a pan

In this method, the product is often crisp, never fluffy and no particular taste.

But today I experimented with hot boiling water as I read recently it denatures protein in food, which prompted me to experiment.

When I cooked my chapathi, those were extra tender but more importantly, it was very sweet, even though I added salt .

I hope to find a scientific explanation to this phenomenon.

Answer 1

Flour is mostly starch, and starches are long chains of sugar molecules. When you add hot water to starches they gelatinize and burst, and these gelatinized starches soften the dough. Gelatinization works faster at higher temperatures. There are enzymes in the flour which break the starch down into sugars, and they work more efficiently at high than room temperature as well, say 65°C.

Both these processes work at lower temperatures, but they work faster a higher temperatures, which is why adding boiling water gave you that result. At room temperature gelatinization works faster than enzymes action breaking starch down into sugars, so letting the dough rest will soften the dough without making it much sweeter.