For premixed flames in the ＇＇flamelet＇＇ regime, where turbulence length scales are significantly greater than the flame thickness, it has been asserted that the principal contribution to flame surface area is generated by vortical structures present in the reacting gas mixture. Several direct numerical simulation (DNS) studies of premixed combustion implicitly follow this assumption by only considering a flame interacting with a single, well-defined vortical structure; however, the important issue of whether the majority of flame surface area is actually caused by vortical structures, as opposed to the featureless background turbulence has not been satisfactorily addressed. We consider this question using direct numerical simulations (DNS). As shown by She, Jackson and Orszag (Nature 344:226, 1990), scrambling the phase of the velocity held in Fourier space (or wave number space) eliminates coherent structures from the turbulent field. Consequently, DNS provides an opportunity to evaluate the importance of coherent structures by comparing flames propagating through Navier-Stokes turbulence with those passing through phase-scrambled (coherent-structure-free) turbulence. The idea of scrambling the phasing of the velocity components is extremely attractive since the scrambled velocity held is free of any coherent vortical structures yet is nearly identical to the Navier-Stokes velocity in all other respects. The results show that the turbulent burning velocity is predominantly influenced by the featureless background turbulence over the range of parameters considered, although there is approximately a 4-7% increase in the flame speed that results from the presence of structures. The topologies of the flame surfaces from the scrambled and unscrambled turbulence are also very similar.