Bread turns brown when we put it in a toaster because the dry heat removes any trace of moisture from within the bread and carbohydrates and proteins in bread react chemically in the presence of heat. The chemical process is called ‘Maillard Reaction’, in which there is a chain of reactions that gradually break down carbohydrates in bread into simple sugars. The carbon molecules of sugars and starches in bread react chemically with the protein and amino acids in bread. As carbohydrates react completely with the amino acids, eventually a layer of carbon forms on top of the toast.
Why does bread turn crispy when toasted?
