I made a toaster waffle for myself this morning. Growing impatient, I popped it out before it was all the way done. As I was buttering it, I noticed parts of the waffle were still cold. Since there was already butter and syrup on it, I couldn’t put it back in the toaster. I threw it in the microwave for 20 seconds and it came out floppy instead of crispy. What gives?
In: Technology
Microwave heating penetrates into food a little bit – certainly enough to get to the middle of a slice of bread. It heats all the bread evenly, and microwaves are really good at heating up water (no, this is not because they’re set to the resonant frequency of water – that is a myth). So all the water in the middle of your bread gets heated up, some of it turns to vapor, and your bread gets steamed. Steaming foods generally makes them soft and floppy. This also prevents the heat from reaching above 100 C – any more heat than that will just go into boiling that water – and 100 C is not enough to have crispification occur.
Toasters, on the other hand, use infrared radiation which cannot penetrate food that well. This heat hits just the surface of the bread, boils off the water on the surface, and goes on to get the surface much hotter than 100 C. This is hot enough to set off the famous Maillard reaction, which combines sugars and amino acids in the bread into those yummy brown polymers we love to eat.
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