Often the digestion of proteins from foods by digestive enzymes in the human or animal body is simulated in the laboratory. The same approach is also used to produce hydrolysates as food ingredients. It is difficult to predict the outcome of such process, i.e. the extent of protein hydrolysis/digestion. In this thesis, we developed a method to define expectations of the extent of protein hydrolysis, based on the properties of the proteins, the enzymes and the hydrolysis conditions. This method will enable a better understanding and comparison of the data of protein hydrolysis/digestion reported in literature. In addition, it would help the development of laboratory simulation of in vivo protein digestion as well as the development of the (bioactive) compounds production.