Why does chocolate only melt smoothly in a pot inside hot water, but not in a pot that is directly heated?
In: 479
Because it burns. When the chocolate is in a pot over boiling water, its temperature never rises above the water’s temperature, which is 100°C. When placed directly over the heat, it can pass 200°C, where the chocolate burns.
A pot is being heated more intensely. the chocolate doesn’t have time to melt because the little liquid content in it gets burned out. Where as in like a glass bowl in water or more recommended above steaming water the steam is released heat that’s not directly heating the chocolate, but gently heating the vessel if that makes sense.
Chocolate burns way too easy if the pot its in is exposed to flame or coils, placing the pot of chocolate into another pot with water to boil makes it so the chocolate is not directly exposed to intense heat and the heat of the steam is enough to melt the chocolate.
When a pot is heated, only the bottom of the pot is heated, the sides are only heated via internal thermal transmission inside the metal.
Water is a fluid, as the water at the bottom is heated it rises to the top, letting cool water circulate down to be heated. (Convection)
If you put a bowl into a pot of hot water, the bowl is heated uniformly, and not intensely in one spot (the bottom) because the water circulates as it is heated,
The other part is that water boils at 100 C, water that is continuously heated will not go above 100 C but will instead boil faster. meaning the water and thus the bowl will never exceed 100 C.
The metal at the bottom of the pan has no such limitations. it will heat up until the metal melts
(Note: You can superheat water, but that requires special equipment, and much higher pressure)
Well, when chocolate is heated directly in a pot, it can get too hot too quickly, causing it to become grainy and lumpy
But when it’s melted in a pot inside hot water, the gentle heat from the water helps the chocolate melt slowly and smoothly.
The double boiler method regulates temperature around 100 degrees celcius due to boiling water / steam contacting the bottom of the bowl of chocolate, not the heating element which can heat closer to 200 degrees and burn the chocolate. Burning occurs in the 140 – 160 degree range.
For the same reason that analogue Rice Cookers work.
Water evaporates at 100degC (at Sea level) so the temperature of water never gets above 100c and thus neither does the Chocolate. However the metal pot can get above 100c and if the chocolate is in direct contact with it so too will the chocolate and thus burn.
Analogue Rice cookers are genius in their simplicity. A bi-Metalic switch in contact with the metal Rice bowl will disengage the power when its temperature goes above about 100degC. As long as there is water in the Rice bowl, it evaporates and takes away excess heat and the bowl stays at about 100c and so the switch stays engaged keeping the power flowing. However when all the water in the metal rice bowl is both absorbed by the rice and evaporated (ie. The rice is done), now there is nothing to take away excess heat from the metal bowl and its temperature rises above the trigger temperature of the bi-metalic switch which then disengages the power.
Many Modern Rice Cookers now use thermostats and Fuzzy Logic and are much more functional too and you can cook more things in them but you can still buy the old simple analogue style with the bimatalic switches too.
You put a thermometer in a pot of water as it boils, that thermometer stays at 100c until all the water boils off even though the stovetop is many hundred degrees higher. You put a pot of chocolate inside that water, pretty much guarantees the chocolate never gets past 100c as long as there’s still water in the bottom of the first pot, even though the stovetop is many hundreds of degrees higher. This let’s chocolate heat slowly and melt evenly. You put chocolate directly on the stovetop, then too soon one part of the chocolate is many hundred degrees and burning while another part is not even melted.
The water boiling in open pot not going past 100c (at sea level) is the latent heat (enthalpy) of vaporization.
Chocolate has a lot of sugar inside it
Sugar tends to breakdown into carbon and water when heated strongly, and is more commonly referred to as burning
This obviously is not desireable. Carbon is the same stuff pencil lead and charcoal is made of, so not exactly nice to eat
Putting directly over a flame is heating strongly, the pot can easily get up to 300c or above, more than enough to burn sugar
However if you put it over boiling water, the max temperature would only be 100c, since thats the boiling point of water and anything higher would mean the water is already steam
Yes you technically do not exactly **need** a pot of boiling water and can try to use a small flame, but having the boiling water bath ensures that you wont burn the chocolate and just makes the whole thing much easier
Melting something using a boiling water bath also isnt exclusive to only chocolates, its good to do this for anything heat sensitive, such as other sweets or special techniques used in baking which cook stuff like eggs while they are still fully liquid
Liquid water is never over 100C at standard pressure. You could think of this like the water is ablatively insulating the chocolate from any higher temperature, preventing it from burning.
Latest Answers