There are important discrepancies in the results of detonation studies of starch particle suspensions in various gaseous atmospheres. The problem of heterogeneous detonation of this kind is studied with the help of a numerical model based on the same main assumptions as have been used previously for modeling non-ideal detonations in suspensions of aluminium particles in gaseous explosive mixtures. It is assumed that starch particles decompose by pyrolysis after their temperature has reached some critical value, and the burning is controlled by their gasification time. The model demonstrates that the differences between existing experimental results can be attributed to the changes in particle size and shock tube diameter and length. When applied to the two-phase hybrid stoichiometric H-2/O-2 mixtures with starch particles in suspension studied by Peraldi and Veyssiere [AAIA, NY 106:490-504, 1986], the model confirms their experimental results: the detonation velocity weakly depends on starch particle concentration for the studied 20 mu m particles and significantly exceeds the thermodynamic equilibrium CJ detonation velocity. On the other hand, the second discontinuity observed in these hybrid mixtures has a nature different from that of the double-front detonation in hybrid mixtures with aluminium particles. A hypothesis is proposed to explain the origin of this.