Chemistry (including Biochemistry)/Non-melting decorating powder
My father was in his youth an apprentice pastry cook and 10 years ago I followed some cooking course here in Belgium. In both cases I remember there was an artififial substance being used "to present it better" to replace powdered sugar because that melts too easily. Only recently I found it in a specialised baking shop after all that time.
I studied Chemistry myself (though I never practised it) and I have been looking everywhere I could, but I still have no clue what the Chemistry of the product it is (the labeling does not realy provide any clues).
Somewhere I read it is just dextrose = glucose (but would not that melt as well ?) and elsewhere that it is plain starch (but that not behave differently ?).
Similar products exist on other continents, for instance : https://www.kingarthurflour.com/shop/items/snow-white-non-melting-topping-sugar-16-oz.
Any insights from your end ?
Take home message: its the starch and titanium additives with the oil that collectively give you this effect.
More in depth -
There are lots of sugars out there: here is a break down of what we call the melting point (the theoretical temperature at which the sold becomes converts to flowable fluid)
monosaccharides (single molecule sugars)
Glucose/Dextrose - 146 C
Fructose - 103 C
Galactose - 167 C
Disaccharides (double molecule sugars)
Sucrose (Glucose+Fructose)- 186 C
Maltose (Glucose+Glucose)- 102 C
Lactose (Glucose+Galactose)- 203 C
Given typical confection bake temperatures (175-190 C) it is not reasonable to suppose that any of the conventional sugars would remain a solid during most baking process, especially given the moist environment. Certainly the dextrose will melt.
So what else do we have in there:
Starch (a crosslinker that binds particles together), Titanium dioxide (a common food additive that I try to avoid - gives a white color even if the sugar is no longer white), and the hydrogenated oil (serves as a thickener and flow control material as it is a much larger molecule than dextrose).
Here is how the chemistry breaks down: The dextrose melts eventually, but not before the little powder particles that the dextrose are in does some chemistry - specifically, the starch binds to the TiO2 and then makes a network with dextrose stuck in it. The dextrose eventually melts and blends with the hydrogenated oil, making a very thick liquid. The liquid cannot readily flow out of the starch/Ti02 network. When you finish baking, the liquid solidifies at cooler temperatures and you have retained your sugar on top.
But the manufacturer is even trickier by adding the TiO2... even if your sugar flows into your baked good (because you are baking hotter or longer than usual), the TiO2 is very very white. So the customer will not know that the sugar has melted into the baked good and the final product still looks and tastes like there is sugar on top, even if it has melted into your pastry.
Personally I avoid TiO2 foods, though TiO2 has been being used in the food industry for ages.
I hope this helps.