Virginia Muriel-Galet

Antimicrobial food packaging film based on the release of LAE from EVOH

The aim of this work was to develop antimicrobial films for active packaging applications containing the natural antimicrobial compound LAE (lauramide arginine ethyl ester) in EVOH copolymers with different mol % ethylene contents (i.e. EVOH-29 and EVOH-44). EVOH-29 and EVOH-44 films were made by casting and incorporating 0.25%, 1%, 5%, and 10% LAE in the film forming solution (w/w with respect to polymer weight). Previously, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of LAE against Listeria monocytogenes, Escherichia coli, and Salmonella enterica were determined by a microdilution assay. The antimicrobial activity of the resulting films was tested in vitro against these microorganisms in liquid culture media. The activity of the films was also evaluated over time. The results showed that films containing 5% and 10% LAE produced total growth inhibition and viable counts decreased with 0.25% and 1% LAE. Finally, the effectiveness of the films was tested by applying them to an infant formula milk inoculated with L. monocytogenes and S. enterica and stored for 6 days at 4°C. The application of films with LAE to infant formula milk inoculated with L. monocytogenes reduced at the end of storage period about 4 log in case of 10% LAE and with S. enterica reduced 3.74 log and 3.95 log with EVOH 29 5% and 10%, respectively, and EVOH-44 5% and 10% LAE reduced 1 log and 3.27 log, respectively, at the end of storage. The antimicrobial capacity of EVOH-29 films was greater than that of EVOH-44 films in all the cases tested. In general, the films were more effective in inhibiting the growth of L. monocytogenes than S. enterica, this inhibition being more acute at the end of the storage time.

Chapter 22 – Antimicrobial Active Packaging Systems Based on EVOH Copolymers

Great attention is being paid to the potential applications of antimicrobial active packages that have resulted in diverse packaging systems commercialized for improved preservation of food products. This chapter reviews novel developments which make use of ethylene-vinyl alcohol copolymers (EVOH) as polymeric matrices for the design of antimicrobial active packages. EVOH copolymers are a family of materials that are widely used in package manufacturing, thanks to their excellent barrier properties to gases and organic vapors. They are highly hydrophilic and, in humid environments, tend to sorb large amounts of water, suffering a severe plasticization. This affects mechanical and barrier properties, and is commonly avoided by protecting EVOH between polyolefin layers. However, this water sensitivity can be beneficial, because plasticization can be used as a triggering mechanism in active packaging. Some of the antimicrobial active developments which make use of EVOH copolymers are reviewed in this chapter.

Chapter 24 – Ethyl Lauroyl Arginate (LAE): Usage and Potential in Antimicrobial Packaging

Ethyl lauroyl arginate (LAE) is a cationic surfactant, which is considered one of the most potent antimicrobial substances among novel food additives. It presents a broad spectrum of activity against bacteria, yeasts, and molds. The high antimicrobial properties of LAE have been attributed to its action on the cell membranes of microorganisms. Furthermore, LAE has been classified as non-toxic because it is hydrolyzed in the human body and metabolized rapidly into natural components. The potential use of LAE as an antimicrobial agent can include a wide range of food. Also, several studies have been related with the application of LAE in antimicrobial packaging systems, showing a great potential to improve the safety and quality of packaged food products.

Anchoring Gated Mesoporous Silica Particles to Ethylene Vinyl Alcohol Films for Smart Packaging Applications

This work is a proof of concept for the design of active packaging materials based on the anchorage of gated mesoporous silica particles with a pH triggering mechanism to a packaging film surface. Mesoporous silica micro- and nanoparticles were loaded with rhodamine B and functionalized with N-(3-trimethoxysilylpropyl)diethylenetriamine. This simple system allows regulation of cargo delivery as a function of the pH of the environment. In parallel, poly(ethylene-co-vinyl alcohol) films, EVOH 32 and EVOH 44, were ultraviolet (UV) irradiated to convert hydroxyl moieties of the polymer chains into –COOH functional groups. The highest COOH surface concentration was obtained for EVOH 32 after 15 min of UV irradiation. Anchoring of the gated mesoporous particles to the films was carried out successfully at pH 3 and pH 5. Mesoporous particles were distributed homogeneously throughout the film surface and in greater concentration for the EVOH 32 films. Films with the anchored particles were exposed to two liquid media simulating acidic food and neutral food. The films released the cargo at neutral pH but kept the dye locked at acidic pH. The best results were obtained for EVOH 32 irradiated for 15 min, treated for particle attachment at pH 3, and with mesoporous silica nanoparticles. This opens the possibility of designing active materials loaded with antimicrobials, antioxidants, or aromatic compounds, which are released when the pH of the product approaches neutrality, as occurs, for instance, with the release of biogenic amines from fresh food products.

Use of EVOH for Food Packaging Applications

Ethylene vinyl alcohol copolymers (EVOH) are a family of thermoplastic polymers with application in many industrial sectors including packaging, especially, in food packaging. The main characteristic of EVOH copolymers for packaging applications is their outstanding barrier to gases (oxygen, carbon dioxide, etc.) and organic vapors (food aroma). EVOH is applied in multilayer structures for bags, trays, cups, bottles, squeezable tubes, or jars to protect oxygen-sensitive products. However, the hydrophilic nature of EVOH must be taken in consideration in package design to minimize water uptake and polymer swelling during thermal treatment processes such as retorting. This article reviews EVOH applications in barrier packaging and in active packaging.