Nanoencapsulation of active compounds in chitosan by ionic gelation: Physicochemical, active properties and application in packaging.

The ionic gelation technique using chitosan to encapsulate active compounds has received lots of attention in the literature due to its ease-of-use and known biodegradability, biocompatibility and antimicrobial properties of the polymer. In this review, main studies from the last five years involving encapsulation of active compounds (natural and commercial/synthetic) are brought together in order to understand the encapsulation mechanisms of components with chitosan as well as the physical, chemical and morphological properties of the resulting particles. The application of these nanostructures in polymeric films was then investigated, since additives for packaging are an attractive premise and have only recently started being studied in the literature.

Evaluation of Different Pectic Materials Coming from Citrus Residues in the Production of Films.

This article explores the use of citrus residues as a source of different pectic materials for packaging film production: a water-soluble orange residue extract (WSE) (~5% pectin), semi-pure pectins extracted in citric acid (SP) (~50% pectin), and commercial pure citrus pectins (CP). First, these materials were characterized in terms of chemical composition. Then, films were produced using them pure or mixed with chitosan or glycerol through solvent-casting.

Water vapor transport properties of bio-based multilayer materials determined by original and complementary methods.

To enhance PLA gas barrier properties, multilayer designs with highly polar barrier layers, such as nanocelluloses, have shown promising results. However, the properties of these polar layers change with humidity. As a result, we investigated water transport phenomena in PLA films coated with nanometric layers of chitosan and nanocelluloses, utilizing a combination of techniques including dynamic vapor sorption (DVS) and long-term water vapor adsorption-diffusion experiments (back-face measurements) to understand the influence of each layer on the behavior of multilayer films.

Resilient high oxygen barrier multilayer films of nanocellulose and polylactide.

Nanocelluloses are promising high gas barrier materials for biobased food packaging, but they must be protected from water to preserve high performance. The respective O barrier properties of different types of nanocelluloses were compared (nanofibers (CNF), oxidized nanofibers (CNF TEMPO) and nanocrystals (CNC)). The oxygen barrier performance for all types of nanocelluloses was similarly high.

Multi-scale characterization of thermoplastic starch structure using Second Harmonic Generation imaging and NMR.

Starch granules can be extruded to obtain a thermoplastic material. Thermoplastic starch (TPS) usually requires a significant break down of the starch granular organization to form a continuous polysaccharide matrix. In this work, we extrude potato starch with and without a plasticizer and store samples at high humidity to generate recrystallization.

Shape-memory effect in amorphous potato starch: The influence of local orders and paracrystallinity.

In this paper, a detailed characterization of the mechanisms at the origin of the shape-memory effect in amorphous potato starch is presented. Using different treatments (annealing) and preparation methods (hot casting and extrusion), the local structures responsible for the shape-memory were disrupted, as evidenced in the first part of the article detailing the macroscopic properties: mechanical, calorimetric and shape-memory. In the second part the macromolecular scale is investigated using X-rays diffraction and CP-MAS NMR, and thus allows making the link between the structural differences and the macroscopic properties.

Interphase vs confinement in starch-clay bionanocomposites.

Starch-clay bionanocomposites containing 1-10% of natural montmorillonite were elaborated by melt processing in the presence of water. A complex macromolecular dynamics behavior was observed: depending on the clay content, an increase of the glass transition temperature and/or the presence of two overlapped α relaxation peaks were detected. Thanks to a model allowing the prediction of the average interparticle distance, and its comparison with the average size of starch macromolecules, it was possible to associate these phenomena to different populations of macromolecules.

Short versus long chain polyelectrolyte multilayers: a direct comparison of self-assembly and structural properties.

Successful layer-by-layer (LbL) growth of short chain (∼30 repeat units per chain) poly(sodium styrene sulfonate) (PSS)-poly(diallyl dimethylammonium chloride) (PDADMAC) multilayers is presented for the first time and compared with the growth of equivalent long chain polyelectrolyte multilayers (PEMs). A detailed study performed by quartz crystal microbalance with dissipation (QCM-D) is carried out and three main processes are identified: (i) initial mass uptake, (ii) adsorption-desorption during layer equilibration and (iii) desorption during rinsing. In contrast to the high stability and strong layer increment of high molecular weight (HMW) PEMs, layer degradation characterizes low molecular weight (LMW) multilayers.