In this project, electrospinning technique was investigated to produce ultrafine soy protein isolate (SPI) and poly(lactic acid) (PLA) fibers. SPI fibers (~200 nm) were produced by electrospinning denatured protein (10-15% wt/wt) in aqueous solution (pH 12, 60 °C) in the presence of poly(ethylene oxide) (0.6-0.8% wt/wt) and Triton X-100 (0.5-1% wt/wt). In contrast, PLA fibers (~4 [mu]m) were spun from polymer (10% wt/wt) dissolved in a mixture of chloroform and dimethylformamide DMF (90:10). Fiber morphology can be manipulated readily by changing the fiber-forming formulation. An antimicrobial agent, allyl isothiocyanate (AITC), was incorporated in SPI and PLA electrospun fibers by direct addition of the antimicrobial into the fiber-forming solution. AITC concentration significantly affected the fiber morphology. AITC loss was reduced when cyclodextrins were used as a secondary carrier. Exposing these fibers to elevated humidity (>50% RH) triggered the release of AITC, with concomitant change in visual appearance and fiber micro-morphology. Preliminary studies showed that electrospun SPI fibers with AITC prevented mold growth on bread, indicating promising active and smart packaging applications.