Zein-Based Films Containing Monolaurin/Eugenol or Essential Oils with Potential for Bioactive Packaging Application

Abstract

Zein is renewable plant protein with valuable film-forming properties that can be used as a packaging material. It is known that the addition of natural cross-linkers can enhance a film’s tensile properties. In this study, we aimed to prepare antimicrobial zein-based films enriched with monolaurin, eugenol, oregano, and thyme essential oil. Films were prepared using the solvent casting technique from ethanol solution. Their physicochemical properties were investigated using structural, morphological, and thermal techniques. Polar and dispersive components were analyzed using two models to evaluate the effects on the surface free energy values. The antimicrobial activity was proven using a disk diffusion method and the suppression of bacterial growth was confirmed via a growth kinetics study with the Gompertz function. The films’ morphological characteristics led to systems with uniform distribution of essential oils or eugenol droplets combined with a flat-plated structure of monolaurin. A unique combination of polyphenolic eugenol and amphiphilic monoglyceride provided highly stretchable films with enhanced barrier properties and efficiency against Gram-positive and Gram-negative bacteria, yeasts, and molds. The prepared zein-based films with tunable surface properties represent an alternative to non-renewable resources with a potential application as active packaging materials.

Physicochemical and Antimicrobial Characterization of Chitosan and Native Glutinous Rice Starch-Based Composite Edible Films: Influence of Different Essential Oils Incorporation

“…This could be due to the different compositions of EOs that slightly influenced the film’s appearance. This is in accordance with the study by Sedlarikova et al [ 73 ]. Furthermore, weak interaction between the chitosan and native starch-based edible films and EOs with high active components could induce a higher coalescence between EO globules, thus creating irregular film patterns [ 16 , 55 , 74 ].…”

Bioactive zein/chitosan systems loaded with essential oils for food‐packaging applications

“…In another recent study, 20 the surface tension of zein solutions in acetic acid was measured by the same method and similar values as in our case (from 27 to 30 mN m −1 ) were obtained. Zein polymer plays a dominant role here 21 . The decrease in average relative viscosity after adding bioactive compound can be the consequence of weakened inter‐ or intramolecular forces of zein and chitosan polymer after the active molecule incorporation into their matrix.…”

“…Zein polymer plays a dominant role here. 21 The decrease in average relative viscosity after adding bioactive compound can be the consequence of weakened inter-or intramolecular forces of zein and chitosan polymer after the active molecule incorporation into their matrix. In this way, the previously ordered network structure can be disturbed while new hydrogen bonds arise.…”