Organic acids are widely used as hurdles to inactivate foodborne pathogens or spoilage microorganisms in food industry. Their inhibitory effect on bacterial spores is based on their lipophilic character by affecting membrane integrity of spores (van Melis et al., 2012). Yet, the composition and the structure of foodstuffs have also an effect on the microorganism growth. Thus, with the aim of increasing product shelf-life and improve their safety, it is also important to understand the relationships between food structure/composition and inhibitors. Our objective was to evaluate the mobility and the partition of organic acids in model emulsions by measuring their self-diffusion coefficients using Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR) spectroscopy. Emulsions were prepared with mineral oil mixed with distilled water using sonication, and were stabilized by Tween80 and Span80. Oil content was either 35 % (v/v) or 50 % (v/v) and each emulsion was studied in the presence of organic acid (acetic, lactic and hexanoic) at two pH levels (pH 5.5 and pH 6, reached by organic acid addition). Quality and stability of emulsions were characterized by multiple light scattering. Results showed that whatever the pH of the emulsions, the diffusion coefficient of the organic acids decreased when the oil/water ratio increased : rise of pH increased amount of undissociated forms (-COOH) which may be trapped in oil phase, and/or it may also occur a structure effect on diffusion coefficient. Furthermore, in 35 % (v/v) oil emulsion at pH 5.5 hexanoic acid showed lower values of D/D0 with pH decrease in comparison to AA and LA. Thus, specificity in the diffusion among organic acids was observed due to their different solubility in oil phase which depends on both pka and logP. Finally, in this latter emulsion, fraction of HA showed a completely restricted mean displacement and therefore may be trapped in oil droplets.