Search

Plastic pollution and food waste are two global issues with much in common. Plastic containers were introduced as a practical and easy remedy to improve food preservation and reduce the risk of creating waste, but ironically, to address one problem, another has been made worse. The spread of single-use containers has dramatically increased the amount of plastic that has to be discarded, and the most urgent task is now to find a solution to what has become part of the problem. An innovative way around it consists of promoting the valorization of food residues by turning them into novel materials for packaging. Although the results are promising, the aim of completely replacing plastics with biodegradable materials still seems far from being achieved. This review illustrates the main strategies adopted thus far to produce new bioplastic materials and composites from waste resources and focuses on the pros and cons of the food recovery process to look for the aspects that represent an obstacle to the development of the circular food economy on an industrial scale.

Fibrous membranes of thermoplastic polyurethane (TPU) were fabricated through a uni-axial electrospinning process. Fibers were then separately charged with two pharmacological agents, mesoglycan (MSG) and lactoferrin (LF), by supercritical CO2 impregnation. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis proved the formation of a micrometric structure with a homogeneous distribution of mesoglycan and lactoferrin. Besides, the degree of retention is calculated in four liquid media with different pHs. At the same time, angle contact analysis proved the formation of a hydrophobic membrane loaded with MSG and a hydrophilic LF-loaded one. The impregnation kinetics demonstrated a maximum loaded amount equal to 0.18 ± 0.20% and 0.07 ± 0.05% for MSG and LT, respectively. In vitro tests were performed using a Franz diffusion cell to simulate the contact with the human skin. The release of MSG reaches a plateau after about 28 h while LF release leveled off after 15 h. The in vitro compatibility of electrospun membranes has been evaluated on HaCaT and BJ cell lines, as human keratinocytes and fibroblasts, respectively. The reported data proved the potential application of fabricated membranes for wound healing.

In this work, novel bio-based hydrogel beads were fabricated by using soybean extract as raw waste material loaded with Lambrusco extract, an Italian grape cultivar. The phenolic profile and the total amount of anthocyanins from the Lambrusco extract were evaluated before encapsulating it in soybean extract-based hydrogels produced through an ionotropic gelation technique. The physical properties of the produced hydrogel beads were then studied in terms of their morphological and spectroscopic properties. Swelling degree was evaluated in media with different pH levels. The release kinetics of Lambrusco extract were then studied over time as a function of pH of the release medium, corroborating that the acidity/basicity could affect the release rate of encapsulated molecules, as well as their counter-diffusion. The pH-sensitive properties of wine extract were studied through UV-Vis spectroscopy while the colorimetric responses of loaded hydrogel beads were investigated in acidic and basic solutions. Finally, in the framework of circular economy and sustainability, the obtained data open routes to the design and fabrication of active materials as pH-indicator devices from food industry by-products.

In this paper gelatin beads reinforced with natural hemp hurd have been produced as pH sensitive devices for the release of eugenol, as green pesticide. The composites beads, with a mean diameter of about 1 mm, were obtained by polymer droplet gelation in sunflower oil. Thermal properties were evaluated showing no noticeable difference after the introduction of hemp hurd. Barrier properties demonstrated an improvement of hydrophobization. The introduction of 5% w/w of hemp hurd led to a reduction of sorption coefficient of about 85% compared to unloaded gelatin beads. Besides, the diffusion coefficient decreased, introducing 5% w/w of hemp hurd, from 8.91 × 10−7 to 0.77 × 10−7cm2/s. Swelling and dissolution phenomena of gelatin beads were studied as function of pH. The swelling of gelatin beads raised as pH increased up to 2.3 g/g, 9.1 g/g and 27.33 g/g at pH 3, 7 and 12, respectively. The dissolution rate changed from 0.034 at pH 3 to 0.077 h−1at pH 12. Release kinetics of eugenol at different pH conditions were studied. The released eugenol after 24 h is 98%, 91%, 81 and 63% w/w (pH 3), 87%, 62%, 37 and 32 wt% (pH 7) and 81%, 68%, 60 and 52 wt% (pH 12) for unloaded gelatin beads and gelatin beads with 1%, 3 and 5% of hemp hurd, respectively. The eugenol release behavior was demonstrated to be highly sensitive to the pH release medium, which allows to tune such devices as green pesticide release systems in soils with different level of acidity/basicity.

This paper reports the possibility of functionalizing hemp fibers (HF) through a mechano-chemical treatment assisted by an easily scalable top-down technology. The mechanical action was able to remove non-cellulosic material and to cause exposure of the cellulose microfibrils. Its influence on structure, morphology, and properties of hemp fibers has been analyzed by means of the scanning electron microscopy, X-Ray, FTIR and Raman spectroscopy. The milling process induced a change in crystalline content of hemp fibers, which decreased after a treatment time of 30 min. The crystallinity index and cellulose chain arrangement influence the thermal stability of hemp fibers. In order to compare the improved properties of mechanochemically treated HF respect to the HF modified with conventional alkalization, they were introduced, as green reinforcement, into a pectin matrix. Thermal and mechanical properties demonstrated the effectiveness of milling treatment in improving the considered physical properties of the pectin matrix.

The paper reports the preparation of a novel material composed of pectin chemically modified with polycaprolactone (PCL). PCL was firstly functionalized through radical grafting of maleic anhydride and glycidyl methacrylate in the molten state and then used as grafting agent onto pectins from apple, using a solvent free process. The obtained material was submitted to melt process on laboratory scale and films obtained. Structural, thermal, mechanical, and barrier properties to water vapor were evaluated and compared with pure pectin and modified PCL’s films. The used strategy allowed to overcome the processability problems of a natural polymer, like pectin, that undergoes degradation with the temperature and is not processable without additives and plasticizers. The proposed green process represents a good opportunity to manufacture waste materials from fruits to obtain flexible and fully biodegradable polymers for food packaging applications, as interesting alternative to not biodegradable traditional thermoplastics.

The present study reports on the development by thermoforming of highly sustainable trays based on a bilayer structure composed of paper substrate and a film made of a blend of partially bio-based poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA). The incorporation of the renewable succinic acid derived biopolyester blend film slightly improved the thermal resistance and tensile strength of paper, whereas its flexural ductility and puncture resistance were notably enhanced. Furthermore, in terms of barrier properties, the incorporation of this biopolymer blend film reduced the water and aroma vapor permeances of paper by two orders of magnitude, while it endowed the paper structure with intermediate oxygen barrier properties. The resultant thermoformed bilayer trays were, thereafter, originally applied to preserve non-thermally treated Italian artisanal fresh pasta, “fusilli calabresi” type, which was stored under refrigeration conditions for 3 weeks. Shelf-life evaluation showed that the application of the PBS–PBSA film on the paper substrate delayed color changes and mold growth for 1 week, as well as reduced drying of fresh pasta, resulting in acceptable physicochemical quality parameters within 9 days of storage. Lastly, overall migration studies performed with two food simulants demonstrated that the newly developed paper/PBS–PBSA trays are safe since these successfully comply with current legislation on plastic materials and articles intended to come into contact with food.

In order to mitigate the social and ecological impacts of post-consumer plastic made of conventional petrochemical polymers, the market of (bio)degradable plastics have recently become more widespread. Although (bio)degradable plastics could be an environmentally friendly substitute of petrochemical ones, the consequences of their presence in the waste management system and in the environment (if not correctly disposed) are not always positive and plastic pollution is not automatically solved. Consequently, this work aims to review how plastic (bio)degradability affects the municipal solid waste management cycle. To this end, the state-of-the-art of the intrinsic (bio)degradability of conventional and unconventional petrochemical and bio-based polymers has been discussed, focusing on the environment related to the waste management system. Then, the focus was on strategies to improve polymer (bio)degradability: different types of eco-design and pre-treatment approach for plastics has been investigated, differently from other works that focused only on specific topics. The information gathered was used to discuss three typical disposal/treatment routes for plastic waste. Despite many of the proposed materials in eco-design have increased the plastics (bio)degradability and pre-treatments have showed interesting results, these achievements are not always positive in the current MSW management system. The effect on mechanical recycling is negative in several cases but the enhanced (bio)degradability can help the treatment with organic waste. On the other hand, the current waste treatment facility is not capable to manage this waste, leading to the incineration the most promising options. In this way, the consumption of raw materials will persist even by using (bio)degradable plastics, which strength the doubt if the solution of plastic pollution leads really on these materials. The review also highlighted the need for further research on this topic that is currently limited by the still scarce amount of (bio)degradable plastics in input to full-scale waste treatment plants.

Grape pomace, as by-product of wine making, is a source of polyphenols, fibers, fatty acids, metals, and organic acids, which could be used as raw component for the production of sustainable materials. Novel biodegradable films based on pomaces, from Negroamaro (red) and Fiano (white), Italian grape cultivars, were fabricated. Physical, chemical and antioxidant properties of material produced were characterized. In particular, migration tests of phenols from pomace films to aqueous food simulant medium were investigated. Data obtained allowed to evaluate the antioxidant activity in terms of total phenol assay and Trolox Equivalent Antioxidant Capacity assay and phenols profile. The characterization of phenolic composition confirmed the peculiarity of some compounds such as anthocyanins (191.17 ± 10.3 μg/g film) in red skin pomace film (NPF) and a great amount of flavanols (76.36 ± 1.72 μg/g film) in white skin pomace film (FPF). Antioxidant activity of polyphenols resulted in active films and was confirmed in migration test with aqueous food simulants. Physical properties of produced films were then studied in terms of morphological, thermal, mechanical and barrier properties. Finally, in the framework of sustainability and circular economy, the presented data paves the way to the design and production of active materials for packaging application starting from a widely available by-product derived from wine-making chain.

In the original publication [...]

The synthesis of novel block copolymers, namely poly(limonene-phthalate)-block-poly(pentadecalactone) and poly(limonene-phthalate)-block-poly(pentadecalactone) is here described. To achieve this synthesis, a bimetallic aluminum based complex (1) was used as catalyst in the combination of two distinct processes: the ring-opening polymerization (ROP) of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) and the ring-opening copolymerization (ROCOP) of limonene oxide (LO) and phthalic anhydride (PA). The synthesis of di-block polyesters was performed in a one-pot procedure, where the semi-aromatic polyester block was firstly formed by ROCOP of LO and PA, followed by the polyethylene like portion produced by ROP of macrolactones (PDL or HDL). The obtained di-block semiaromatic polyesters were characterized by NMR and GPC. The structural organization was analyzed through XRD. Thermal properties were evaluated using differential thermal analysis (DSC) and thermogravimetric measurements (TGA) either in air or in nitrogen atmosphere.

The study reports on the preparation and characterization of an active packaging based on pouches composed of a coupled system nylon/polyethylene (PE). The PE layer was filled with and active nano-hybrid of layered double hydroxide (LDH) on which it was anchored salicylate, as antimicrobial molecule. The release of the salicylate anchored to the LDH was compared to the release of the molecule free dispersed into the PE and resulted much slower. It was evaluated the efficiency of the active packaging to inhibit Pseudomonas aeruginosa, Escherichia coli, Listeria monocytogenes, Salmonella typhimurium, and Campylobacter. Global migration tests on the PE active layer, using ethanol (50% v/v) as food simulant, demonstrated the possibility of such active nanocomposite to be used for food contact being the migration limits in compliance with those imposed from the EU regulation. Fresh milk was packed into the active pouches and pouches with unfilled PE layer, as control. The pH reduction as function of the time, due to the production of lactic acid, resulted much slower in the active packaging. Total bacterial count (TBC) was evaluated on the milk, either packed into the active packaging or the control, up to 50 days of storage at 4 °C. Shelf life of the milk was evaluated using the Gompertz model. It was demonstrated an increasing of the shelf life of milk packaged in active pouches from 6 days up to 10 days.

Nanoparticles (NPs) in the biomedical field are known for many decades as carriers for drugs that are used to overcome biological barriers and reduce drug doses to be administrated. Some types of NPs can interact with external stimuli, such as electromagnetic radiations, promoting interesting effects (e.g., hyperthermia) or even modifying the interactions between electromagnetic field and the biological system (e.g., electroporation). For these reasons, at present these nanomaterial applications are intensively studied, especially for drugs that manifest relevant side effects, for which it is necessary to find alternatives in order to reduce the effective dose. In this review, the main electromagnetic-induced effects are deeply analyzed, with a particular focus on the activation of hyperthermia and electroporation phenomena, showing the enhanced biological performance resulting from an engineered/tailored design of the nanoparticle characteristics. Moreover, the possibility of integrating these nanofillers in polymeric matrices (e.g., electrospun membranes) is described and discussed in light of promising applications resulting from new transdermal drug delivery systems with controllable morphology and release kinetics controlled by a suitable stimulation of the interacting systems (nanofiller and interacting cells).

Novel biodegradable films based on rice flour loaded with hemp hurd powder and grapefruit seed oil, as a mixture of natural compounds with potential antimicrobial activity, were fabricated and morphologically analyzed. Mechanical and thermal analysis were correlated to the hemp hurd content showing that no increase in thermal stability occurred for the rice flour composite while a noticeable improvement in mechanical properties was achieved after the addition of hemp hurd (up to 300 % of the pure rice flour film for a reinforcement loading of 20 % wt). Barrier properties were then studied aiming of evaluating the effect of hemp hurd on water sorption and diffusion. The decrease in polar site of rice flour and the hydrophobic character of either hemp hurd or essential oil led to a reduction of either the sorption parameter (about 85 % with a hemp hurd amount of 20 %wt) or the diffusion one (up to 96 % with a hemp hurd amount of 20 %wt). Optical properties appeared to not be pretty sensitive to hemp hurd presence. The release of a grapefruit seed oil was then studied through a second-order model and correlated with the effect of hemp hurd loading.

This paper concerns the facile preparation of alginate beads encapsulating layered double hydroxide (LDH) intercalated with diclofenac sodium as drug delivery systems. To better evaluate the effect of LDH carrier, alginate beads loaded with free diclofenac were also prepared. Composites hydrogel beads were ionotropically crosslinked in CaCl2 solution at 4 °C. Thermal and barrier properties were evaluated and correlated with the presence of the inorganic phase. Swelling behavior was investigated over time. Release kinetics of diclofenac at different pH and temperatures were evaluated. The diclofenac release behavior appeared to be affected by the presence of LDH, the pH of release medium and the temperature allowing for fabricating a sustainable composite characterized by a triggered drug release rate. Finally, empirical relationships correlating the drug diffusion as a function of temperature and pH were extrapolated.

In this paper it is reported the preparation of a food packaging based on isotactic polypropylene (PP) coated with layered double hydroxide (LDH) hosting sorbate as active molecule. The active nano-hybrid (LDH-sorbate) was dispersed into a food grade resin and used as coating. The release of the sorbate anchored to the LDH was compared to the release of the molecule free dispersed into the food grade resin and resulted much slower. It was evaluated the efficiency of the active packaging to inhibit Salmonella enterica subsp. arizonae, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Campylobacter jejuni, and the global migration using two food simulant (i.e. poly (2,6-diphenyl-p-phenylene oxide) and vegetable oil). Experimental data, in compliance with the migration limits of the European Union regulation, demonstrated the suitability of the prepared material for food contact. White bread was packed into the active PP film and untreated PP, as control. Organoleptic characteristics, moisture analysis, peroxide evolution and mold count showed that the bread packaged in the active film retained its starting characteristics up to 12 days of storage at ambient temperature.

The wettability of hemp fibers, to be applied in fiber-reinforced foams, can be improved with several chemical treatments. In this paper, a innovative treatment with sodium ascorbate was evaluated. Untreated and treated fibers have been characterized using FTIR spectroscopy and TGA measurements. Furthermore, the feasibility of treated fibers was evaluated preparing diatomite-based fiber-reinforced foams. These materials were finally characterized by mechanical compressive strength and thermal properties (thermal conductivity). The fiber-reinforced foams have been produced using a diatomite natural source as a matrix. A suitable amount of Si powder and vegetable surfactant were used as chemical and physical foaming agents while a polysilicate solution was used as reactive crosslinker. The foams highlight low density, around 350 kg/m3, and low thermal conductivity (0.06 W/mK).

Solvent-free syntheses provide an alternative path that reduces the use of hazardous substances. In this work, a sustainable synthesis of nanometric layered double hydroxide particles grafted over halloysite nanotubes (HNT@LDH) is reported using a mechanochemical technique. Samples loaded with different LDH percentage (100%, 50%, 40%, 30%, 20%, 10% with respect to the HNT content) were prepared and characterized. Spectroscopic and morphological characterizations allowed to select the sample with 20% by weight of LDH as the best composite (HNT@LDH20), wherein no LDH phase segregation was observed and the nanosheets were homogeneously grafted throughout the surface of the halloysite nanotubes. The combination of cationic and anionic clays in one filler enables the preparation of a composite which can be easily dispersed in a polymer and release active molecules. To this end, salicylate ions were incorporated into the layered double hydroxide nanoflakes of HNT@LDH20 and three intercalation strategies, comprising both solvent-free and traditional intercalating routes, were tested. Results of salicylate release tests indicate that the intercalating route used affects the amount of species hosted, the strength of the salicylate-LDH interactions and the drug release time, thus offering the possibility of selecting the most suitable method of drug incorporation to tune the salicylate content depending on a specific aim.

The photo-oxidative studies of ethylene vinyl acetate copolymer (EVA) matrix, filled with Layered Double Hydroxide (LDH) modified with methacrylic anion (MA), were herein reported, together with gas permeation tests. The formulation of nano-hybrid LDHs was characterized using X-ray diffractometry (XRD) and thermogravimetric analysis (TGA), demonstrating the partial intercalation of the 30% of MA anion between the LDH’s galleries. The as-modified filler was introduced into an EVA matrix by mechanical milling, producing free-standing films subjected to accelerated aging. Fourier transform infrared spectroscopy (FT-IR) results suggested that the nanohybrid presence determined a stabilizing effect up to 45 days of UV irradiation, especially if compared to the EVA/LDH references for all formulated EVA hybrid nanocomposites. Conversely, the presence of nanohybrid in the matrix did not significantly change the thermal stability of EVA samples. The dispersion of modified MA-LDH in the EVA matrix produces defect-free samples in the whole range of investigated loadings. The samples show a slight decrease in gas permeability, coupled with a substantial stabilization of the original CO2/O2 selectivity, which also proves the integrity of the films after 30 days of UV irradiation.

Recently two-dimensional nanomaterials, such as graphene and molybdenum disulfide (MoS2), have received much attention as adsorbent materials for the effective removal of organic contaminants. MoS2 is attracting attention, not only for its chemical-physical properties, but also for its wide availability in nature as a constituent of molybdenite. The aim of this investigation was to assess the effects of different MoS2 concentrations (5 × 10−1, 5 × 10−2 and 5 × 10−3 mg/ml) on the embryonated eggs of Gallus gallus domesticus, according to Beck method. We evaluated the toxic effect of the MoS2 powder purchased at Sigma-Aldrich indicated as “received” and MoS2 powder treated via mechanical milling indicated as “ball mille”. Subsequently, the embryos were sacrificed at different times of embryonic development (11th, 15th and 19th day after incubation) in order to evaluate their embryotoxic and teratogenic effects. The alterations of the embryonic development were studied by morphological and immunohistochemical analysis of the tissues. The results obtained have shown the toxicity of both powders of MoS2 with a high percentage of deaths and growth delays. Moreover, the immunohistochemical analysis performed on several tissue sections showed a strong positivity to the anti-metallothionein1 antibody only for the erythrocytes.