Two-phase flows occur in many fields such as liquid fuel injection, plunging waves, cavitation, sloshing, spray, phase change, pipeline of two-phase flows, etc. Regarding numerical developments, a lot of improvements have been realised to describe the interface between liquid and gas. Especially, the objective of Direct Numerical Simulations (DNS) is to solve all the scales of the considered flow. However, unlike the Kolmogorov scale in single phase flows, no theory about the smallest scale in a two-phase turbulent flow has been developed yet. Indeed, the liquid structures that break up, become smaller and smaller and make such theoretical work difficult. Two main scales are expected to have a strong influence in a two-phase system: one emerging from small scale turbulence-interface interactions and another linked to the smallest scale of wrinkling of the surface. The aim of this study is to investigate the latter and to provide a criterion to evaluate the interface resolution quality (IRQ) based on surface geometry. IRQ criteria have already been proposed in previous works with one based on the surface density used in ELSA (Eulerian Lagrangian Spray Atomization) approach or another one based on liquid volume fraction gradient. These criteria are not well adapted for DNS with interface capturing method coupled with a reconstruction technique. Consequently, an IRQ criterion based on curvature is here proposed to evaluate the accuracy of the interface resolution. The ARCHER code is used to simulate an Homogeneous Isotropic Turbulent (HIT) configuration to perform a mesh convergence study to evaluate the effect of various resolutions on important statistics (surface density, mean IRQ). Then, a diesel jet case (based on ECN Spray A) is presented to show the level of accuracy and pertinence of the IRQ criterion on this kind of configuration.