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Shear-induced formation of crystal nuclei in polyamide 11 (PA 11) was studied using a conventional parallel-plate rheometer. Crystallization of PA 11 after shearing the melt at different rates for 60 s was followed by the evolution of the complex viscosity. The sheared samples showed in an optical microscope a gradient structure along the radius, due to the increasing shear rate from the center to the edge. The critical shear rate for shear-induced formation of nuclei was identified at the position where a distinct change of the semicrystalline superstructure is observed, being at around 1 to 2 s−1. Below this threshold, a space-filled spherulitic superstructure developed as in quiescent-melt crystallization. Above this value, after shearing at rates between 1 and 5 s−1, an increased number of point-like nuclei was detected, connected with formation of randomly oriented crystals. Shearing the melt at even higher rates led to a further increase of the nuclei number and growth of crystals oriented such that the chain axis is in parallel to the direction of flow. In addition, optical microscopy confirmed formation of long fibrillar structures after shearing at such condition. The critical specific work of flow of PA 11 was calculated to allow a comparison with that of polyamide 66 (PA 66). This comparison showed that in the case of PA 11 more work for shear-induced formation of nuclei is needed than in the case of PA 66, discussed in terms of the chemical structure of the repeat unit in the chains. Graphical abstract

Bio-based composites made of poly(L-lactic acid) (PLLA) and β-cyclodextrin/d-limonene inclusion complex (CD-Lim) were prepared by melt extrusion. Encapsulation of volatile d-limonene molecules within β-cyclodextrin cages was proven to be a successful strategy to prevent evaporation during high-temperature processing. However, small amounts of limonene were released upon processing, resulting in the plasticization of the polymeric matrix. Morphological analysis revealed good dispersion of the filler, which acted as a nucleating agent, favoring the growth of PLLA crystals. The composites′ lowered glass transition temperature upon the addition of CD-Lim was also proved by thermomechanical analysis (DMA). Moreover, DMA revealed constant stiffness of modified materials at room temperature, which is crucial in PLLA-based formulations.

In this study, chitosan (C) tripolyphosphate (T) sub-micro particles containing ungeremine (CTUn), an alkaloid particularly active against Penicillium roqueforti, a fungus responsible of the bakery products deterioration, were prepared through external gelation crosslinking process. The particles were included in a thermoplastic starch based polymer Mater-Bi (MBi), and MBi/CTUn bioactive biocomposites were obtained. The films showed bioactivity against P. roqueforti. In particular, the bioassays were performed on films with different concentration of CTUn and at different pH values. CTUn particles influenced MBi crystallization (DSC analysis) and promoted thermal degradation of MBi starch component (TGA). Morphological analysis confirmed even distribution of sub-micro particles into the polymeric matrix. Water permeability slightly increased, as expected, whereas oxygen permeability decreased. Tensile tests showed CTUN sub-microparticles improved rigidity and tensile strength of the films at the expense of ductility. Finally, MBi/CTUn biocomposites evidenced interesting performances potentially exploitable in bioactive bakery based food packaging materials.

Cardoon seed oil (CO), derived from the nonedible Cynara cardunculus plant, growing in marginal and contaminated soils of Mediterranean regions, was successfully epoxidized (ECO) in a fed-batch modality. The cost-effective and environmentally friendly oils have been used as bioplasticizers of poly(lactic acid) (PLA), to improve the overall properties and broaden its industrial applications as a biodegradable packaging material. Hence, physical blends and films of PLA, containing 3% by weight of CO and ECO, were prepared by melt extrusion and compression molding, and the effect of the both bioplasticizers on structural, thermal, and mechanical properties of the obtained films was investigated. Cardoon oils induced the decreasing of glass transition temperature due to PLA free volume enhancement. This effect was particularly marked in PLA–ECO film. Thermal stability of PLA was meaningfully improved upon addition of the oils, and the mechanical properties made evident the increase of PLA ductility, particularly enhanced in the PLA–ECO system, where the polymeric matrix and the oil showed stronger physical interaction and improved phase compatibility, as also revealed by spectroscopic and morphological analyses. Therefore, the plasticization action exerted by very low concentrations of epoxidized cardoon oil efficiently overcomes PLA drawbacks, thus encouraging the feasibility of its use as a bioplastic for packaging material.

Cynara Cardunculus plant was used as source of seed oil. The epoxidized oil (ECO) and presscake waste fibers (CP) recovered from post-oil extraction, were recombined for developing PLA functional biocomposites, according to “zero waste” circular economy approach. Different compositions of PLA/CP and PLA/CP/ECO were prepared in form of platelets and investigated by thermal, morphological, structural and mechanical analyses. The poor interfacial adhesion between the hydrophobic PLA matrix and short, hydrophilic and randomly dispersed presscake fibers, well evidenced by morphological analysis, was responsible of PLA thermal degradation hastening, Tg decreasing and tensile properties dropping down, since no mechanical stress transfer occurred from the polymer to the dispersed phase. The inclusion of ECO slightly improved the above properties due to its mild compatibilizing action inducing a fairly tightening of the macromolecular structure. The recycling of CP waste fibers was effective in hastening the polymer biodegradation in common soil under environmental conditions. Indeed, biocomposites recovered after 90 days of soil burial tests evidenced morphological features typical of late stage PLA biodegradation, a drastic dropping down of molecular weights and a decreasing of PLA thermal stability. These experimental evidences, not detected in soil buried neat PLA, assessed that the inclusion of CP waste fibers inside PLA matrix, represented a valid route to promote a fast and easy PLA biodegradation if compared to the composting method commonly used, for which severe atmosphere conditions and specific microbial population are necessary.

Active packaging refers to packaging systems with active functions beyond the inert passive containment and protection of the product. It is commonly used with foods, as it helps extend shelf life, improve safety or sensory properties and maintain food quality [1]. Most diffused active packaging systems include the use of oxygen scavengers, carbon dioxide or ethylene emitters and scavengers, ethanol releaser, as well as antimicrobial and antioxidant agents. The active agent may be placed in the package with the food, within a small sachet or pad of permeable material, able to release volatile antimicrobial agents without allowing a direct contact with the food product. Incorporation of volatile active agents into polymers is a technological challenge, due to the need to avoid evaporation of the additive during melt processing of the polymer. Such challenge can be solved by incorporation of the volatile molecules within cyclodextrins (CD), as detailed in this contribution. Cyclodextrins are biocompatible, biodegradable cyclic oligosaccharides produced from a renewable natural material, starch [2]. Cyclodextrins can form inclusion complexes with various non-polar, aliphatic and aromatic compounds, including antibacterial molecules, whose release could enhance the quality of the packaged product and extend its shelf life [3]. In the research detailed below, b-CD was used as cage to include D-limonene (4-isopropenyl-1-methylcyclohexene), the major constituent in several citrus-derived essential oils, which is also a natural antimicrobial agent [4-6]. D-limonene is listed in the Code of Federal Regulations and generally recognized as safe flavoring agent and food preservative [7]. Its outstanding antimicrobial activities have already been tested with different species of food-related microorganisms, such as staphylococcus aureus, Listeria monocytogenes, Salmonella enterica, Saccharomyces bayanus [8, 9]. Unfortunately, D-limonene is susceptible to oxidative degradation, which directly results in its loss of activity [7, 10]. Moreover, similar to other volatile essential oils, limonene aroma could be easily released to the packaged food, thus contaminating it. In order to overcome to these drawbacks, D-limonene was included into CDs, and the inclusion complex CD-Lim thus obtained was dispersed into a biodegradable and bio-based polymer matrix, namely poly(butylene succinate) (PBS). PBS is a biodegradable and bio-based polyester, currently used for food packaging, and its use in this market area is expected to largely increase in the coming years [11]. The aim of this paper is to prepare a novel biodegradable polymeric-based system, as potential bioactive food packaging material, by dispersing CD-Lim inclusion complex into PBS polymeric matrix and to investigate the chemical-physical properties of the obtained blends.

In this paper, a novel and sustainable process for the fruit dehydration was described. Specifically, edible coatings based on pectin and honey were prepared and used as dehydrating and antimicrobial agents of cut fruit samples, in this way promoting the fruit preservation from irreversible deteriorative processes. Pectin-honey coating was tested on apple, cantaloupe melon, mango and pineapple. The analysis were performed also on uncoated dehydrated fruits (control). The coated fruit evidenced enhanced dehydration percentage, enriched polyphenol and vitamin C contents, improved antioxidant activity and volatile molecules profile. Moreover, the antimicrobial activity against Pseudomonas and Escherichia coli was assessed. Finally, morphological analysis performed on fruit fractured surface, highlighted the formation of a non-sticky and homogeneous thin layer. These outcomes suggested that the novel fruit dehydration process, performed by using pectin-honey coating, was able to both preserve the safety and quality of dehydrated fruits, and enhance their authenticity and naturalness.

The performances of a commercial Mg/Al hydrotalcite (Pural© MG76) in biodiesel production have been tested in an autoclave and in a continuous packed bed reactor. The obtained results have shown that calcined Mg/Al hydrotalcite (Pural© MG76) is a promising heterogeneous catalyst for biodiesel production because is sufficiently active, deactivates slowly and can easily be regenerated.

In this work, biodegradable films based on poly (lactic acid) (PLA) and corn thermoplastic starch (TPS), additivated with epoxidized cardoon oil plasticizer (ECO) at 3% by weight with respect to PLA mass fraction, were prepared by melt extrusion process and compression molding. The effect of ECO on structural, thermal, mechanical, barrier, and spectral optical properties of the films was investigated. Spectroscopic analysis evidenced the development of physical interaction between oil and polymers, mainly PLA. In addition, no oil migration occurrence was detected after six months of film preparation, as evidenced by oil mass evaluation by precipitation as well as by 1H-NMR methods, thus highlighting the good inclusion of oil inside the polymeric network. The plasticizing action of the oil induced a lean improvement of the interfacial adhesion between hydrophobic PLA and hydrophilic TPS, particularly accentuated in PLA80_ECO composition, as evidenced by morphological analysis of blend fracture surfaces. TGA data underlined that, differently from TPS-based films, PLA-based systems followed one degradative thermal profile suggesting a slight compatibilization effect of epoxidized oil in these films. The shifting of Tg values, by differential scanning calorimetry (DSC) analysis, indicated a weak miscibility at molecular level. Generally, in the investigated blends, the phase separation between PLA and TPS polymers was responsible for the mechanical properties failing, in particular, the tensile strength evidenced a negative deviation from the rule of mixtures, particularly marked in TPS-based blends, where no physical entanglements occurred between the polymers since their immiscibility even in presence of ECO. The epoxidized oil strongly improved the barrier properties (water vapor permeability (WVP) and oxygen permeability (O2P)) of all the films, likely developing a physical barrier to water and oxygen diffusion and solubilization. With respect to neat PLA, PL80 and PL80_ECO films evidenced the improvement of surface wettability, due to the presence of polar groups both in TPS (hydroxyl residues) and in epoxidized oil (oxirane rings). Finally, following to the conditioning in climatic chamber at T = 25 &deg, C and RH = 50%, PLA80 film became opaque due to TPS water absorption, causing a light transmittance decreasing, as evidenced by spectral optical analysis.

Structural, morphological and thermal properties of films based on poly(butylene succinate) (PBS) and inclusion complex (IC) of beta-cyclodextrins (beta-CD) and D-limonene were studied, in order to prepare novel bio-active food packaging materials. Formation of the inclusion complex was proved by infrared spectroscopy, nuclear magnetic resonance, and X-ray diffraction. The IC contains 7 wt% of D-limonene, as quantified by precipitation, as well as by C-13 NMR and by thermogravimetry. Inclusion within beta-CD cavity stabilizes D-limonene against evaporation, which allows melt compounding with PBS. Infrared spectroscopy of compression molded composite films, evidenced both the D-limonene encapsulation inside beta-CD cages, and the occurrence of interactions between hydroxyl groups of beta-CD-lim complex and the carbonyl groups of PBS units. Optical micrographs showed a phase separated morphology, with homogeneous distribution of the IC within the PBS matrix, probably due to interactions between the polar groups of the composite components. DSC analysis highlighted the anti-nucleating action of beta-CD-lim complex towards PBS, evidenced by a significant delay in crystallization kinetics of PBS. (C) 2016 Elsevier Ltd. All rights reserved.