It is easy to see the term "browning reactions" and assume that this is in reference to what's occurring in the coffee roaster.
The Maillard reaction, for example, is a type of nonenzymatic browning reaction that occurs during coffee roasting.
In many cases we (Homo sapiens sapiens, lacking fur, poor swimmers) very much enjoy the organoleptic results of the Maillard reaction.
However, the Maillard reaction can also be a problem with regard to food spoilage, as depicted in the Water Activity Stability Diagram.
"Pokorny et al (1975) mentioned that the Maillard reaction can sometimes start in green coffees stored at relatively high
temperatures and humid medium, producing a browningreaction" (Flament, 3.
The Maillard reaction and caramelization processes that occur during roasting occur under relatively high heat and low water activity.
출처 : CAFE IMPORTS
