Microstructure and physico-chemical evaluation of nano-emulsion-based antimicrobial peptides embedded in bioactive packaging films

Customized application of antimicrobial peptide (AMP) 'nisin' directly into food (neither in active packaging nor encapsulated form) is expensive and associated with loss of activity due to deactivation in complex food systems. The purpose of the present study was to fusion the two concepts for improved bioavailability i.e. AMP nanoencapsulation and biopolymer immobilizing to formulate the next generation biodegradable films embedded with either active agent, nano-encapsulated active agent or both of them. Nanoliposomes were prepared using soy-lecithin by microfluidizer at 2000 bar with 5 cycles to generate an average size of 151 +/- 4 nm with 50 +/- 3% encapsulation efficiency. For active films, nisin had demonstrated no negative impact on transparency, thickness and water sorption behavior obtained by GAB model (25 degrees C, 0-0.95 a(w)). For nano-active films, the results clearly illustrated that different physicochemical properties including barrier (oxygen and water vapor permeability), color and transparency (200-900 nm) remained comparable to native hydroxypropyl methylcellulose (HPMC) films and were significantly improved than using lecithin directly without nano-scale restructuring. The microstructure studies (topography and morphology) by scanning and transmission electron microscopes (SEM/TEM) revealed different (pore, lamellar, fusion) modes of nisin release from nanoliposomes embedded in HPMC matrix. As microbiological worth, nisin nano-emulsion (encapsulated and free nisin) films were effective against potential foodborne pathogen Listeria monocytogenes. This innovative concept of biodegradable nano-active films may thus be a preventive system toward improved food safety. (C) 2012 Elsevier Ltd. All rights reserved.