Hydrophilic–lipophilic deviation (HLD) concept is well developed in the fields of cosmetics, pharmaceutics and enhanced oil recovery and therefore, it is adopted for emulsification process in a predictive and controlled way. To apply this concept, it is necessary to get the knowledge of optimum formulation (i.e. emulsion’s environmental parameters at which the affinity of emulsifier for aqueous and oil phase is equal) through formulation scans. In above fields optimum formulation of the oil–water–emulsifier system is commonly detected through simple techniques like visual observation, light scattering, and interfacial tension measurements. Unfortunately, such techniques are not suitable for food emulsion systems, because of the complexities associated with the emulsifiers and vegetable oils. This study deals with the detection of optimum formulation (formulation scan with respect to salt concentration) of food grade emulsion system through spectrophotometric assay of emulsifier molecule in the aqueous and oil phase, and in microemulsion. It is shown that the spectrophotometric method associated with formulation scans is a relatively more accurate method to detect optimum formulation. This method was studied with a model system which resembles to a mayonnaise, i.e. sunflower oil–water–lecithin. Spectrophotometric method associated with formulation scans put forward a better understanding of transitional inversion which is pre-requisite to make a formulation–composition map of an emulsion system.