Toasting bread triggers a chemical reaction known as the Maillard reaction. This process is the reaction between amino acids and reducing sugars in the presence of heat.
Toasting bread is both a physical change and a chemical change…Let me explain.
Imagine freeze-fried bread. It undergoes a whole lot of physical changes with few minimal chemical changes. The object loses moisture and other volatile substances, like smell chemicals.
Freeze-dried bread is quite similar to toast. Yes, if there were no chemical reactions going on – it isn’t brown, and it doesn’t smell like toast. It will smell closer to fresh bread but muted.
The aim of toasting fresh bread is to induce a chemical reaction that browns the toast and created new smells and chemical types, too. But the bread is also losing plenty of its volatile moisture, like when you freeze dry bread. But not all of the moisture: You can freeze dry toast to make it even drier. So, toast bread is not simply dried bread.
The chemical reactions that begin and spread once the bread are being toasted generally need moisture in order to correctly form: So I couldn’t just put freeze-dried bread into a toaster and make toast.
ALSO SEE: Is Boiling Water Physical Or Chemical Change?
Yes, it might get brown or burn, but the smell it will release will not smell like a piece of toasted bread.
I hope the explanation was simple enough. Cheers.