Show a process in a class diagram


I was wondering if it’s possible to show a process transforming one class into another in a class diagram.

For example, if we have two classes “flour” and “bread” and want to show the process of baking. Now I know that you can do that with an association named baking, but I want it to be more expressive. Any suggestions?

Perhaps the use of composition? That is, specify that a bread is composed of flour.