Why does bread turn brown when toasted?

Answer: Maillard reaction browns it

Sugar caramelizes from heat — Wrong. While caramelization can occur, it requires higher temperatures (above 160°C) than typical toasting. The primary browning in toast comes from a different reaction between amino acids and sugars, not just sugar alone.

Maillard reaction browns it ✓ — Correct! The Maillard reaction is a chemical reaction between amino acids (from proteins) and reducing sugars when heated. This creates hundreds of flavor compounds and brown pigments called melanoidins. It's the same reaction that browns meat, coffee beans, and baked goods. The reaction starts around 140°C, perfect for toasting!

Carbon from burning — Wrong. Toast isn't burning - that would make it black and taste burnt. The brown color comes from the Maillard reaction, a complex chemical process that creates new flavor compounds and brown pigments without charring the bread.