Sustained release of lysozyme from zein microcapsules produced by a supercritical anti-solvent process

Delivery systems with sustained release of antimicrobials are possible solutions to minimize the binding between antimicrobials and food matrices, thereby enhancing the efficacy of antimicrobials during shelf-lives of foods. In this work, GRAS (generally recognized as safe) corn zein was used as a carrier material and 90% aqueous ethanol was used as a solvent to microencapsulate GRAS hen egg white lysozyme using a supercritical anti-solvent (SAS) process. The microcapsules showed a continuous matrix with internal voids. The release of lysozyme was observed over 36 days at room temperature, with slower release at a higher pH between 2 and 8. At pH 4, release kinetics was further slowed by the addition of sodium chloride. Stronger molecular attraction between lysozyme and carrier zein was attributed to slower release at a higher pH and a higher ionic strength at the same pH. Our work demonstrated that SAS may be a feasible process to manufacture GRAS delivery systems to enhance antimicrobial efficacy.