The work describes a new method of simulating the chemical reactions in a complex chemical system so as to predict the products actually formed. Using the Maillard reaction as example the program, called Iterated Reaction Graphs (IRG), consists of a Soup of molecules, a reaction database of Maillard reactions and a probability table representing the probabilities of reactions occurring. Reactants were taken from the Soup, reacted, and the products returned to the Soup. The reaction database and probability table were updated by comparison of the simulated output with the main products found by gc/ms analysis of real reaction mixtures. Novel in the system is that only a subset of the possible chemical reactions was chosen so that only the volatile components were simulated (<5% of the total), reaction rates were included as probabilities and, to increase efficiency, the reactions were grouped into blocks. The program gave insight into the major paths followed as well as information on how the pH influenced these.