Josep Pasqual Cerisuelo

Preparation and characterization of chitosan/HP-β-cyclodextrins composites with high sorption capacity for carvacrol

The aim of this work was to design new polymer-based systems exhibiting an adjustable loading capacity of carvacrol depending on the film formulation. For this purpose, biocomposite films were developed employing chitosan (CS) as the polymer matrix and hydroxypropyl-β-cyclodextrins (HP-βCDs) as an adjuvant to improve the sorption of carvacrol in the polymer matrix. The morphology, optical, mechanical and barrier properties of the resulting films were investigated, and the sorption capacity of carvacrol evaluated. Biocomposites resulted highly transparent with higher mechanical resistance and moisture barrier properties. Sorption of carvacrol was greatly affected by the humidity (RH) and glycerol (G) content of the biocomposites. The highest sorption values were achieved for composites incorporating 35% glycerol and conditioned at 75% these composites retained 216% carvacrol (g/100 g dry matter). These results indicate that inclusion of carvacrol in the films could be occurring by mechanisms other than formation of inclusion complexes.

Contact probe electrochemical characterization and metal speciation of silver LLDPE nanocomposite films

A contact probe methodology, based on the voltammetry of immobilized microparticle approach, is used for characterizing silver species present in linear low density polyethylene (LLDPE) films with different Ag(I)/Ag(0) ratios and silver nanoparticle features usable as food contact polymers. The films displayed characteristic voltammetric features in contact with aqueous acetate buffer, in particular signals for the stripping oxidation of nanoparticulate Ag systems. Significant differences between the studied films were also observed by means of electrochemical impedance spectroscopy and detected at the nanoscopic scale using electrochemical scanning microscopy. Differences in optical and thermal properties of the studied films are associated with the presence of silver nanoparticles. The silver oxidation state as well as nanoparticle size also had influence on the oxidative resistance of the LLDPE films; indeed, films containing cationic silver showed the lowest oxidation induction time value.

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.

Gas Transport Properties in Packaging Applications

Polymers are among the preferred materials in packaging design mainly because of their versatility. In some of these applications such as in food, pharmaceutical, or dangerous product packaging, the knowledge and control of gas transport properties are crucial to achieve packaging objectives: to present, preserve, and protect the contained product. In this chapter, the implications of mass transport properties in diverse packaging technologies, such as appertized, vacuum, modified atmosphere, or barrier packaging are discussed. The control of gas permeation, sorption, or release and the incidence on products are commented and the main methodologies to obtain adequate barrier, control gas exchange with the environment, or control gas exchange with the product are introduced. The effect of on-purpose perforation of films on final mass transport properties is also discussed.

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.