Interaction and release of catechin from anhydride maleic-grafted polypropylene films

Agri-Food Extracts Effectiveness in Improving Antibacterial and Antiviral Properties of Face Masks: A Proof-of-Concept Study

The European dependencies for raw materials supply from foreign countries have been unquestionably shown by COVID-19 outbreak and have become particular evident from the slow response to the need for high quality personal protective equipment (PPEs). Among all medical devices, surgical face masks have earned themselves a primary role for the containment of the epidemic. In this context, our work aims at improving the barrier effect of surgical mask by depositing on their external surface a mixture of bioactive compounds, mainly polyphenols, extracted from agronomical sources. The main objective is the integration of the biorefining of agri-food solid wastes with the potential virucidal properties of the polyphenolic extracts for the treatment of PPEs.

Antioxidant Bilayers Based on PHBV and Plasticized Electrospun PLA-PHB Fibers Encapsulating Catechin

The main objective of this work was to develop bio-based and biodegradable bilayer systems with antioxidant properties. The outer layer was based on a compression-molded poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)-based material while antioxidant electrospun fibers based on poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) blends formed the inner active layer. In particular, PLA was blended with 25 wt% of PHB to increase the crystallinity of the fibers and reduce the fiber defects. Moreover, in order to increase the stretchability and to facilitate the electrospinning process of the fiber mats, 15 wt% of oligomeric lactic acid was added as a plasticizer. This system was further loaded with 1 wt% and 3 wt% of catechin, a natural flavonoid with antioxidant activity, to obtain antioxidant-active mats for active food packaging applications. The obtained bilayer systems showed effective catechin release capacity into a fatty food simulant. While the released catechin showed antioxidant effectiveness. Finally, bilayer films showed appropriate disintegration in compost conditions in around three months. Thus, showing their potential as bio-based and biodegradable active packaging for fatty food products.

Evaluation of a Novel Collagenous Matrix Membrane Cross-Linked with Catechins Catalyzed by Laccase: A Sustainable Biomass

Collagen, a sustainable and biodegradable biomass material, has many applications in different scope including application in food packaging. However, owing to its poor mechanical properties, this kind of application is limited. In this work, collagen was cross-linked with catechin under the incubation of laccase to improve the mechanical properties of collagen, and the cross-linked collagen exhibited properties of excellent antioxidant capacity and lower swelling ratio. Meanwhile, Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) results provide evidence for changes in the structure of collagen after being cross-linked with the catechin. From the aspects of the thermal stability, tensile strength, elongation, antioxidant capacity, swelling, solubility, and morphological analysis, the cross-linked collagen has better physical properties in comparison with natural collagen. This indicates that the physical properties and antioxidant capacity of collagen after being cross-linked with catechins were improved significantly. Therefore, the cross-linked collagen can be used as green food-packaging materials.

Antimicrobial Carvacrol-Containing Polypropylene Films: Composition, Structure and Function

Significant research has been directed toward the incorporation of bioactive plant extracts or essential oils (EOs) into polymers to endow the latter with antimicrobial functionality. EOs offer a unique combination of having broad antimicrobial activity from a natural source, generally recognized as safe (GRAS) recognition in the US, and a volatile nature. However, their volatility also presents a major challenge in their incorporation into polymers by conventional high-temperature-processing techniques. Herein, antimicrobial polypropylene (PP) cast films were produced by incorporating carvacrol (a model EO) or carvacrol, loaded into halloysite nanotubes (HNTs), via melt compounding. We studied the composition-structure-property relationships in these systems, focusing on the effect of carvacrol on the composition of the films, the PP crystalline phase and its morphology and the films’ mechanical and antimicrobial properties. For the first time, molecular dynamics simulations were applied to reveal the complex interactions between the components of these carvacrol-containing systems. We show that strong molecular interactions between PP and carvacrol minimize the loss of this highly-volatile EO during high-temperature polymer processing, enabling semi-industrial scale production. The resulting films exhibit outstanding antimicrobial properties against model microorganisms (Escherichia coli and Alternaria alternata). The PP/(HNTs-carvacrol) nanocomposite films, containing the carvacrol-loaded HNTs, display a higher level of crystalline order, superior mechanical properties and prolonged release of carvacrol, in comparison to PP/carvacrol blends. These properties are ascribed to the role of HNTs in these nanocomposites and their effect on the PP matrix and retained carvacrol content.

Chilean berry Ugni molinae Turcz. fruit and leaves extracts with interesting antioxidant, antimicrobial and tyrosinase inhibitory properties

The knowledge of the biological properties of fruits and leaves of murta (Ugni molinae Turcz.) has been owned by native Chilean culture. The present study investigated the phenolic content, the antioxidant, antimicrobial and anti-tyrosinase activities of different murta fruit and leaves extracts to approach their uses on future food, pharmaceutical and cosmetic applications. Extractions of murta fruit and leaves were carried out under water, ethanol and ethanol 50%. Phenolic content of these extracts was measured through Folin Ciocalteu test and the antioxidant power by four different antioxidant systems (ORAC, FRAP, DPPH and TEAC assays) owing to elucidate the main mechanism of antioxidant. Some flavonoids, such as rutin, isoquercitrin and quercitrin hydrate were identified and quantified through HPLC analysis. Antimicrobial activity was determined measuring minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values against Escherichia coli and Listeria monocytogenes, and the effect of these extracts on L. monocytogenes was confirmed by flow cytometry. Highest contents of polyphenol compounds were obtained in hydroalcoholic extracts (28±1mggallicacid/g dry fruit, and 128±6mggallicacid/g dry leaves). The same trend was found for the values of biological properties: hydroalcoholic extracts showed the strongest activities. Leaves presented higher antioxidant, antimicrobial and anti-tyrosinase properties than murta fruit. Highest antioxidant activity values according to ORAC, FRAP, TEAC and DPPH were 80±8mgTrolox/g, 70±2mgTrolox/g, 87±8mgTrolox/g and 110±12mgTrolox/g, respectively, for murta fruit samples, and 280±10mgTrolox/g, 192±4mgTrolox/g, 286±13mgTrolox/g and 361±13mgTrolox/g, respectively, for murta leaves. These activities were confirmed by HPLC analysis that revealed highest presence of analyzed compounds on leaves hydroalcoholic extract. Regarding to antimicrobial analysis, hydroalcoholic leaves extract presented the highest activity presenting the lowest MIC value for L. monocytogenes (0.07mg/mL). This extract also performed the highest anti-tyrosinase activity (CE₅₀ values of 1.6±0.3 (g/L) and 8.9±1.2 (g/L) for leaves and fruit, respectively).

Plasticized poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends incorporated with catechin intended for active food-packaging applications

Active biobased packaging materials based on poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends were prepared by melt blending and fully characterized. Catechin incorporation, as antioxidant compound, enhanced the thermal stability, whereas its release was improved by the addition of acetyl(tributyl citrate) (ATBC) as plasticizer. Whereas the incorporation of ATBC resulted in a reduction of elastic modulus and hardness, catechin addition produced more rigid materials due to hydrogen-bonding interactions between catechin hydroxyl groups and carbonyl groups of PLA and PHB. The quantification of catechin released into a fatty food simulant and the antioxidant effectiveness after the release process were demonstrated. The effect of the materials' exposure to a food simulant was also investigated. PHB-added materials maintained their structural and mechanical properties after 10 days in a test medium that represents the worst foreseeable conditions of the intended use. Thus, plasticized PLA-PHB blends with catechin show their potential as biobased active packaging for fatty food.

Controlled release properties of zein-fatty acid blend films for multiple bioactive compounds

To develop edible films having controlled release properties for multiple bioactive compounds, hydrophobicity and morphology of zein films were modified by blending zein with oleic (C18:1)Δ⁹, linoleic (C18:2)Δ(9,12), or lauric (C₁₂) acids in the presence of lecithin. The blend zein films showed 2-8.5- and 1.6-2.9-fold lower initial release rates for the model active compounds, lysozyme (LYS) and (+)-catechin (CAT), than the zein control films, respectively. The change of fatty acid chain length affected both CAT and LYS release rates while the change of fatty acid double bond number affected only the CAT release rate. The film morphologies suggested that the blend films owe their controlled release properties mainly to the microspheres formed within their matrix and encapsulation of active compounds. The blend films showed antilisterial activity and antioxidant activity up to 81 μmol Trolox/cm². The controlled release of multiple bioactive compounds from a single film showed the possibility of combining application of active and bioactive packaging technologies and improving not only safety and quality but also health benefits of packed food.

Green aqueous surface modification of polypropylene for novel polymer nanocomposites

Polypropylene is one of the most widely used commercial commodity polymers; among many other applications, it is used for electronic and structural applications. Despite its commercial importance, the hydrophobic nature of polypropylene limits its successful application in some fields, in particular for the preparation of polymer nanocomposites. Here, a facile, plasma-assisted, biomimetic, environmentally friendly method was developed to enhance the interfacial interactions in polymer nanocomposites by modifying the surface of polypropylene. Plasma treated polypropylene was surface-modified with polydopamine (PDA) in an aqueous medium without employing other chemicals. The surface modification strategy used here was based on the easy self-polymerization and strong adhesion characteristics of dopamine (DA) under ambient laboratory conditions. The changes in surface characteristics of polypropylene were investigated using FTIR, TGA, and Raman spectroscopy. Subsequently, the surface modified polypropylene was used as the matrix to prepare SiO2-reinforced polymer nanocomposites. These nanocomposites demonstrated superior properties compared to nanocomposites prepared using pristine polypropylene. This simple, environmentally friendly, green method of modifying polypropylene indicated that polydopamine-functionalized polypropylene is a promising material for various high-performance applications.