Effect of a toroidal vortex on a laminar flame surface and inner structure is investigated using Rayleigh scattering and shadowgraph techniques. Vortex characteristics are kept identical whereas flame parameters are varied. Based on the flame surface observations, two distinct phases are observed. In the first phase, the flame undergoes a passive perturbation where the local flame apex curvature is driven by the vortex size. In the second phase, driven by the fuel reactivity, the laminar burning velocity is responsible for generating a structure with a very large negative curvature, thickening the flame inner structure. Only the thermal zone is modified during the flame-vortex interaction whereas the reaction zone remains unchanged.