The extended Ambegaokar–Baratoff model was applied to calculate the critical current ($I_c$) of a superconductor/insulator/superconductor (S/I/S) Josephson junction with multiple tunnelling channels. We analysed the sensitivity of the critical current, multiplied by normal-state resistance (i.e.,$I_c$$R_n$ product), to the symmetries of the order parameter in the Bardeen-Cooper-Schrieffer (BCS)-type gap formula. In addition, we showed that the temperature dependence of the product $I_c$$R_n$ ($T$),which corresponds to multigap symmetry, exhibitsa shoulder-like feature and has a pronounced kink at $T$ ${\simeq}$10K for the SmFeAsO$_{0.9}$F$_{0.1}$ superconductor.