Why does bacon sizzle?

Bacon sizzles when it is cooked due to the Maillard reaction. This is a chemical reaction between amino acids and reducing sugars that occurs when food is heated above a certain temperature. The reaction produces a variety of compounds, including melanoidins, which are responsible for the brown colour and flavour of cooked bacon.

When bacon is cooked, the fat melts and the proteins begin to break down. This releases water vapour and other volatile compounds, which create the sizzle. The Maillard reaction also produces carbon dioxide gas, which bubbles through the fat and contributes to the sizzle.

The sizzle of bacon is a sign that it is cooking properly. When the sizzle stops, the bacon is done.