Intrinsic Tween 20 improves release and antilisterial properties of co-encapsulated nisin and thymol.

Antimicrobial delivery systems have been proposed as potential solutions to improve effectiveness of antimicrobials in food matrixes by shielding antimicrobials from contacting food matrix components and releasing them continuously. In this work, spray-dried capsules were produced from zein solutions with the same concentrations of nisin and thymol but with varying Tween 20 contents for characterization of release kinetics of antimicrobials and antilisterial properties. At intermediate levels of Tween 20, sustained and more complete release of antimicrobials was observed at pH 6.0 and 8.0. Most capsule samples were more effective than free antimicrobials against Listeria monocytogenes in 2% reduced fat milk, and the best capsule treatment reduced the bacterial population by 2 log CFU/mL more than comparable free antimicrobials after 4 h incubation at 25 °C. Our work demonstrated that nonionic surfactant can be conveniently used to modulate characteristics of delivery systems to effectively improve antimicrobial functions in food systems.