(492h) Release Kinetics of Nisin Loaded in Spray-Dried Zein Microcapsules as Affected by Intrinsic Tween 20 and Glycerol

This work investigated the potential of achieving sustained release of nisin, a generally-recognized-as-safe antimicrobial, microencapsulated in corn zein capsules produced by spray-drying. Nisin was first extracted with 50% v/v aqueous ethanol from a commercial preparation with approximately 2.5% nisin. The extract was then reconstituted to 70% ethanol (v/v) to dissolve zein to a concentration of 2% w/v. The solution was additionally dissolved with a nonionic surfactant Tween 20 or a plasticizer glycerol to a zein: Tween 20 or zein: glycerol ratio from 1:0 to 1:2.5. Tween 20 was added to modify the interactions between nisin and zein and possibly microstructures of the formed microcapsules; glycerol was used for the purpose of modifying capsule microstructures. In vitro release studies showed that all samples had complete release of nisin in 30 min at pH 2. An intermediate Tween 20 concentration (zein: Tween = 50:1) corresponded to the most sustained release: 28-56% and 9%-19% cumulative release in 3 days at pH 6 and 8, respectively. Similar results were obtained when glycerol was used at a zein: glycerol ratio of 40:1. Our work showed that release kinetics of the encapsulated nisin can be manipulated by intrinsic compounds of surfactant or water-soluble plasticizer, which may be correlated to future studies focusing on effects of these compounds on interactions between nisin and zein and microcapsule internal structures.