Direct application of active protein in practical food system suffers from the major disadvantage of protein inactivation caused by food components and environmental factors. This study is the first to encapsulate water-soluble protein into hydrophobic polystyrene (PS) polymer via emulsion electrospinning technique based on green chemical L-limonene to achieve sustained release of protein. Core-shell nanostructure with elongated domains was observed in electrospun fibers. In vitro release profiles suggest that a sustained release of protein was achieved. The increased release rate with PS molecular weight reveals that the release of protein could be well tuned by tailoring polymeric molecular weight, which is possibly attributed to the association of release rate with fiber inner structure and protein distribution in matrix. These results demonstrate that an excellent protein delivery system could be obtained via emulsion electrospinning based on green chemical for the application in antimicrobial packaging and filtration in food industry. (C) 2014 Wiley Periodicals, Inc.