Electrospun fibers from soy protein isolate (SPI)/poly(ethylene oxide) (PEO) blend and poly(lactic acid) were used for controlled release of a naturally occurring antimicrobial compound, allyl isothiocyanate (AITC). AITC was encapsulated in beta-cyclodextrin or added directly into the fiber-forming solutions. Scanning electron micrographs showed that the resulting electrospun SPI/PEO and PLA fibers possessed smooth morphology with diameters ranging from 200 nm to 2 mu m. Fiber morphologies were affected by the AITC concentration. The kinetics of AITC release under different relative humidity conditions and fiber morphologies were evaluated. Release of AITC was negligible under dry conditions, but increased dramatically as relative humidity increased. The interactive behaviour of these antimicrobial nanofibers may be promising in active packaging applications for foods. (C) 2009 Elsevier Ltd. All rights reserved.