Sugars. Caramelization. Timing. And why sweet sauces are often added at the last moment to dishes like chai tow kway.
“Watch what you eat!” is advice we are often told. Good advice for healthy eating. But here, we also like to say “Watch what you cook!”. Why? Because it is a great way to learn about science!
Just watch this video of the cooking of this popular dish in Southeast Asia. It is called “chai tow kway“, where cake cubes of rice flour, water and daikon (a kind of winter radish – see above) are stir-fried.
Chai tow kway comes in a “black” version and a “white” version. The former is fried with a sweet black sauce, giving it a special kick. Watch the video closely and you will see the sweet black sauce is added just before the cooking is complete.
Why is this so? It has to do with science, specifically the science of caramelization. The flavors the sweet black sauce gives to chai tow kway are created when the sugars in the sauce undergoes caramelization, which releases hundred of new and complex compounds.
Caramelization happens because at the temperatures used for stir-frying, the sucrose in the sugar is broken down by heat into its simple sugars fructose and glucose. As these sugars lose water, what is left of the sugar molecules combine to form a larger molecule. These large molecules react further to form the delicious new compounds and polymers mentioned earlier.
But overdo this though, and it becomes black and burnt, and most importantly, unpleasant to taste. All this can happen very quickly. Which is why the sweet black sauce is only added near the end, just before the stir-frying is done, so that the sugars in the sauce do not burn.
We are all in fact more familiar with this phenomenon than we imagine. Watch how crème brûlée is prepared and caramelization is what we see in the slightly burnt thin top layer of sugar (read about it in the 1-Minute NomNom “Burn (sugar) baby burn“). The torching of this layer is also done very briefly.
We can get a sense of how quickly sugars burn by watching coffee roasting. When the roasting temperature rises quickly, the time from the coffee beans’ second crack to becoming burnt is a matter of seconds (read the 1-Minute NomNom “How to be a crack at roasting coffee“). And if the chai tow kway is stir-fried in a wok, all we need to do is watch foods being wok-fried to see that the temperature can get very intense quickly (read the 1-Minute NomNom “Hei, wok’s up?“).
So don’t just watch what you eat, watch the cooking too, because you will be amazed what you can learn!
Like this? Unlike sugars, any time is a good time to add and like me to discover more? All you need is a minute a day to explore the world’s marvels through the phenomenon of food!