Recently, there is an increasing interest to prepare wound healing agents based on bio-polymers, due to their non-toxicity, biocompatibility and biodegradability. Despite this interest, nanocomposite ...films were prepared based on chitosan and gelatin reinforced with chitosan-sodium tripolyphosphate nanoparticles (CS-NPs). Nanoparticles were incorporated onto films at different weight ratios (2, 4 and 6 wt%, dry base). Nanocomposite films enriched with nanoparticles were characterized by a higher UV-barrier property, compared to the control film. Films were characterized in terms of physical, mechanical and thermal properties, as well as their bioactivity. An increase in the tensile strength was observed with CS-NPs incorporation, while the elongation at break was adversely affected by nanoparticles amount. Thermal analyses confirmed the compatibility and miscibility between the different film components. Further, CS-NPs addition increased the surface wettability (polar component and surface free energy) of nanocomposite films. The biological properties of films, as well as their wound healing ability were explored. Results showed that nanoparticles incorporation improved significantly the antioxidant and antibacterial efficacies of nanocomposite films. Moreover,
in-vivo
wound healing test showed that the rate of wound reduction was greatly elevated with a rapid re-epithelialization for treated group with nanocomposite films. Consequently, films were suitable and promising alternatives biomaterials for wound healing and skin regeneration.
Composite films based on chitosan and lignin biopolymers were investigated for their mechanical, barrier, surface, and antioxidant properties and linked to an extensive microscopic analysis of their ...external and internal structure. In particular, the fluorescence properties of lignins were exploited, using two-photon microscopy, to achieve a 3D representation of its distribution within the chitosan matrix. The lignin incorporation generated small aggregates homogeneously distributed in the film. The aggregates slightly weakened the network as reflected by the mechanical properties. Lignin as an antioxidant provided to the film a radical scavenging activity, essentially governed by a surface activity mechanism. Accordingly, the film surface showed a chemical reorganization induced by the presence of lignin as highlighted by surface hydrophobicity and X-ray photoelectron spectroscopy. On the molecular scale, solid state NMR also revealed the absence of covalent bonds between lignin and chitosan and the establishment, but to a small extent, of low energy dipole–dipole interactions. Finally, lignin is a promising compound for a good added-value due to radical scavenging in a chitosan matrix.
Chitosan and pectin films were enriched with blackcurrant pomace powder (10 and 20% (
/
)), as bio-based material, to minimize food production losses and to increase the functional properties of ...produced films aimed at food coatings and wrappers. Water vapor permeability of active films increased up to 25%, moisture content for 27% in pectin-based ones, but water solubility was not significantly modified. Mechanical properties (tensile strength, elongation at break and Young's modulus) were mainly decreased due to the residual insoluble particles present in blackcurrant waste. FTIR analysis showed no significant changes between the film samples. The degradation temperatures, determined by DSC, were reduced by 18 °C for chitosan-based samples and of 32 °C lower for the pectin-based samples with blackcurrant powder, indicating a disturbance in polymer stability. The antioxidant activity of active films was increased up to 30-fold. Lightness and redness of dry films significantly changed depending on the polymer type. Significant color changes, especially in chitosan film formulations, were observed after exposure to different pH buffers. This effect is further explored in formulations that were used as color change indicators for intelligent biopackaging.
Poly(lactic acid) or PLA is currently considered as one of the most promising substitutes of conventional plastics, with low environmental impact, especially for food packaging applications. ...Nevertheless, some drawbacks, such as high permeability to oxygen, are still limiting its industrial applications. The objective of this study was to highly increase the oxygen barrier performance of PLA without compromising its sustainable nature and following the principles of circular economy perspective. Coproducts coming from mill industries, such as wheat gluten proteins (WG), were used to produce PLA-WG-PLA multilayer complexes with improved barrier performance. Different technologies of industrial interest were considered: high-pressure homogenization of WG film forming dispersions, corona treatment of industrial PLA films, wet casting and spin coating for tailoring the WG coating thickness, and hot-pressing for shaping the multilayers. The impact of all these strategies on the properties (surface and bulk) and performances (barrier and adhesion) were investigated on the single constituent layers as well as on the final laminate. The most efficient complex increased more than 20 times (or 2000%) the barrier properties to oxygen and ∼20% the barrier properties to water vapor, considering application conditions (50% relative humidity and 25 °C). The low thickness (∼60 μm) of this complex also matched the requirement for flexible packaging applications. High-pressure homogenization, WG coating thickness, and hot-pressing positively and highly impacted the final properties of the multilayer, while the contribution of corona treatment was limited. This study unambiguously evidenced the potential of PLA-WG-PLA complexes as a valid sustainable substitute for high performing conventional plastics, and it could open an unexplored PLA market opportunity. In addition, it could motivate further investigations on PLA-based laminates for industrial interest, using other biopolymers from agro-industrial waste or byproducts.
As starch is an inexpensive, filmogenic, easily processable and a widely available material, it is a material that can be utilized in the creation of biodegradable films and containers, presenting as ...a viable alternative to polymers derived from petrol. Moreover, starch could also be used to create edible coatings for fresh foods in order to extend shelf life. As such, wheat starch films with two glycerol contents were formulated to mimic the effects of compounds currently used to coat fruit. Their structural and functional properties were characterized. This study found that the transfer properties of starch films containing 33% of plasticizer was less effective than film comprised of 50% glycerol. Water diffusivity, oxygen permeability, and water vapor permeability at two different humidity gradients, surface tension, works of surface adhesion and cohesion, and moisture sorption were tested. Glycerol content does not play a significant role on the color or mechanical properties. This work shows that glycerol can strongly affect the functional properties of starch-based coatings and films.
Food preservation is mostly related to packaging in oil-based plastics, inducing environmental problems, but this drawback could be limited by using edible/biodegradable films and coatings. Physical ...and chemical properties were assessed and reflect the role of the starch type (wheat, corn or potato) and thus that of the amylose/amylopectin ratio, which influences thickness, colour, moisture, wettability, thermal, surface and mechanical properties. Higher amylose content in films induces higher moisture sensitivity, and thus affects the mechanical and barrier properties. Films made from potato starch constitute a greater barrier for oxygen and water vapour though they have weaker mechanical properties than wheat and corn starch films. Starch species with higher amylose content have lower wettability properties, and better mechanical resistance, which strongly depends on the water content due to the hydrophilic nature of starch films, so they could be used for products with higher water activity, such as cheese, fruits and vegetables. It especially concerns wheat starch systems, and the contact angle indicates less hydrophilic surfaces (above 90°) than those of corn and potato starch films (below 90°). The starch origin influences optical properties and thickness: with more amylose, films are opalescent and thicker; with less, they are transparent and thinner.
In order to improve the quality of food and to extend their shelf life, a new generation of active edible films is being especially intended after the incorporation of organic acids, enzymes, ...antimicrobial proteins, phenolic compounds, or other functional ingredients such as probiotics, flavors, vitamins and nutraceuticals. These active compounds have different mechanisms of action related to their structure, their concentration, the nature of micro-organism targeted, the process of encapsulation or incorporation in the biopolymer film-networks. The application of the active films by direct contact or indirect contact via the head space also affects the bioactivity of these compounds. This article critically reviews the published work on active edible-films and their applications for food preservation. The classes of active compounds and their action mechanisms are firstly discussed. Then, an extended overview on their effect on model food (simulants) or on real food during storage was also addressed. Edible films offer two main advantages over the direct incorporation of the antimicrobial or antioxidant agents into the bulk food: 1) to control the diffusion of active compounds at the surface of the food and 2) to reduce the amount of preservatives added in the food.
Edible films may act as carriers of active molecules, such as flavors. This possibility confers to them the status of active packaging. Two different film-forming biopolymers, gluten and ...ι-carrageenans, have been compared. d-Limonene was added to the two film formulations, and its release kinetics from emulsion-based edible films was assessed with HS-SPME. Results obtained for edible films were compared with d-limonene released from the fatty matrix called Grindsted Barrier System 2000 (GBS). Comparing ι-carrageenans with gluten-emulsified film, the latter showed more interesting encapsulating properties: in fact, d-limonene was retained by gluten film during the process needed for film preparation, and it was released gradually during analysis time. d-Limonene did not show great affinity to ι-carrageenans film, maybe due to high aroma compound hydrophobicity. Carvone release from the three different matrices was also measured to verify the effect of oxygen barrier performances of edible films to prevent d-limonene oxidation. Further investigations were carried out by FT-IR and liquid permeability measurements. Gluten film seemed to better protect d-limonene from oxidation. Gluten-based edible films represent an interesting opportunity as active packaging: they could retain and release aroma compounds gradually, showing different mechanical and nutritional properties from those of lipid-based ingredients.
Sustainable hydrocolloid-based films containing natural antioxidants, caffeic and p-coumaric acids at different concentrations of 0.5%, 1%, 5%, and 10% w/w of polymers, were designed for packing ...fatty foods. Antioxidant activities and kinetics for all film formulations were assessed using radical scavenging activity (DPPH), reducing power, and iron chelating ability. Release kinetics of the antioxidants from the films into a food simulant (96% ethanol) were analyzed. The intermolecular interactions between antioxidants and polymers chains were assessed by Fourier transform infrared attenuated total reflectance (FTIR-ATR) and related to the film properties. Antioxidant activity of pure compounds (powder), showed that caffeic acid (IC50 = 4 μg/mL) had higher activity than p-coumaric acid (IC50 = 33 μg/mL). Films containing caffeic acid exhibited higher antioxidant activity, reducing power, and iron chelating ability than p-coumaric acid films. The antioxidant activity is concentration dependent. However, the percentage of release (PR) in ethanol (96%) is not influenced by the initial concentration. PR is 88% ± 9% and 82% ± 5%, respectively, for caffeic and p-coumaric acids. Determination of the partition (K p) and the apparent diffusion (D) coefficients allowed better characterization of the release kinetic mechanisms. The partition coefficients of caffeic acid (K p = 454) and p-coumaric acid (K p = 480) are not influenced by the initial concentration. The diffusion coefficients (D) of caffeic and p-coumaric acids were of same order, but they slightly increased with the antioxidant concentration and probably related to antioxidant activity. FTIR displayed that amide B and amide-III are involved in the interactions occurring between polymer chains and antioxidants. However, interactions are of only low energy and unable to significantly affect the structure of films and consequently the release kinetics.
Nowadays, a new generation of edible films is being especially designed for incorporating antimicrobials, antioxidants, enzymes or functional ingredients. Edible films made from natural biopolymers ...become the focus of many research works as an alternative to synthetic food packaging due to their edibility, biodegradability and compostability as well as to their use as active packaging. Active compounds incorporated in edible films could protect foods against deterioration during storage and therefore extend their shelf life. These active films were mainly studied for the bioactivity, as antimicrobial or antioxidant. However, they could also improve the structure and the physicochemical properties of films through chemical linkage with reactive groups of the polymer chains for instance. Moreover, changing the film structure under cross-linking reaction may increase the cohesion between polymer chains and active compounds, and therefore their retention in the polymer network to better control their release.
This manuscript provides an overview on the effect of bio-active compounds incorporation on the film structure and functional properties. Depending on their structure, concentration, reactive groups,.., active compounds can act as plasticizer, but also as anti-plasticizer or cross-linking agents in the biopolymer matrix, and can thus ameliorate the water vapour and gas permeability. Therefore, the retention of bioactive compounds in the polymer network and their release can be better controlled. They can also provide a negative plasticizing effect on the film structure. Hence, the improvement of edible active film functionalities has been investigated to achieve suitable applications on foods.
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