In a food processing chain, a process is a succession of unit operations leading to the food product. As a first step, we will use a single assertional conceptual graph to represent the process steps. But reasoning with expert rules on this assertional graph raises some issues (activation of rules, readability). We propose an extension of the conceptual graph model, in order to introduce the 'Becomes' relation to structure the set of concept types in the support. This extension allows one to consider an extended set of concept types and conformity relation and to create another kind of graph rules and assertional graph representing the process, resolving these issues. We present the application of this extension to the case of the expert knowledge base about durum wheat transformation process.