The goal of this study was to demonstrate the ability of carbohydrate nanoparticle‐stabilized emulsion to prolong the efficacy of bacteriocin against food pathogens. An amphiphilic, negatively charged carbohydrate nanoparticle, phytoglycogen octenyl succinate (PG‐OS), was used to form oil‐in‐water emulsion for delivering bacteriocin nisin against the food pathogen Listeria monocytogenes. Dynamic light scattering test showed that in emulsion all PG‐OS nanoparticles were adsorbed at the surface of oil droplets. Zeta‐potential analysis indicated an effective adsorption of positively charged nisin molecules at the surface of PG‐OS interfacial layer. Nisin depletion model showed that, during 50 days of storage, the anti‐listerial activity of nisin‐containing PG‐OS‐stabilized emulsion was substantially greater than that of nisin solution. In contrast, the emulsion stabilized with a neutral, small‐molecule surfactant (Tween 20) or negatively charged, hyperbranched carbohydrate polymer (modified starch) was either ineffective or less effective than the nanoparticle‐stabilized emulsion to retain nisin activity during storage. Biotechnol. Bioeng. 2011; 108:1529–1536. © 2011 Wiley Periodicals, Inc.