In foodstuffs, interactions between spores, inhibitors and food components may occur (i.e. physicochemical interactions and/or physical constraints). Then, the objective of this study was to understand such phenomena using a model emulsion as a microbial medium to improve, in the long term, bacterial spores control. Emulsions were prepared with mineral oil mixed with distilled water using sonication and were stabilized by Tween 80 and Span 80. Oil content was either 35 % (v/v) or 50 % (v/v) and each emulsion was studied in the presence of organic acid (acetic, lactic or hexanoic) at two pH levels (5.5 and 6). Bacillus weihenstephanensis (strain KBAB4) was used as a model of a high prevalence food spoiler. It was enumerated by a most probable number assay in microplate. Growth in a Bioscreen® and flow cytometry were used to quantify antimicrobial effect on spores and cells. Self-diffusion coefficients of emulsion components were measured by Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR). Main results are that the antimicrobial activity depends on oil volume ratio. In the same conditions, spores germinated/grew by more than 25% more in the 50/50 O/W emulsion than in the 35/65. This could be explained by a Tween 80 antimicrobial effect, dependant on pH, and by the distribution of organic acids between oil and water phases. Tween 80 effect has been hardly described in the literature and this study will be continued on spores of different species.