A pectin and poly(lactic acid) (PLA) composite was compounded by extrusion. A model antimicrobial polypeptide, nisin, was loaded into the composite by diffusion. The incorporation of pectin into PLA resulted in a heterogeneous biphasic structure, as revealed by scanning electronic microscopy, confocal laser microscopy, and fracture-acoustic emission. The incorporation of pectin also created a rough and cragged surface, which was hydrophilic and facilitated the access and absorption of nisin. The nisin-loaded composite suppressed Lactobacillus plantarion growth, as indicated by agar diffusion and liquid-phase culture tests. The incorporation of pectin at the concentration of similar to 200% of the total mass did not alter the Young's modulus of the film from that of the pure PLA. The composite materials were able to retain their tensile strength, flexibility, and toughness to an extent that satisfied the requirements for packaging materials. Results from this research indicate the potential of pectin/PLA composites for applications in antimicrobial packaging. (c) 2007 Wiley Periodicals, Inc.