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. (C) 2011 Wiley Periodicals, Inc.