Sustained release of antimicrobials may be a viable solution to enhance the bioavailability during the shelf life of food products. In this work, spray-drying was used to encapsulate a model antimicrobial of lysozyme in corn zein. The effects of zein/lysozyme (20:1 to 4:1) and zein/thymol (1:0 to 4:1) ratios on the microstructures of microcapsules and in vitro release profiles of the encapsulated lysozyme were investigated. In all cases, less lysozyme was released at higher pH, resulting from stronger molecular attraction between zein and lysozyme. Nanoscalar matrix structures of microcapsules were correlated with release characteristics of the encapsulated lysozyme. At intermediate zein/lysozyme (10:1) and zein/thymol (50:1) ratios, microcapsules had a continuous matrix structure and showed sustained release (11.1-65.3%) of lysozyme at pH 6 over 49 days. This work may be developed into practical food grade delivery systems of antimicrobials.