Effect of ferulic and cinnamic acids on the functional and antimicrobial properties in thermo-processed PLA films

Active Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Films Containing Phenolic Compounds with Different Molecular Structures

To obtain more sustainable and active food packaging materials, PHBV films containing 5% wt. of phenolic compounds with different molecular structures (ferulic acid, vanillin, and catechin) and proved antioxidant and antimicrobial properties were obtained by melt blending and compression molding. These were characterized by their structural, mechanical, barrier, and optical properties, as well as the polymer crystallization, thermal stability, and component migration in different food simulants. Phenolic compounds were homogenously integrated within the polymer matrix, affecting the film properties differently. Ferulic acid, and mainly catechin, had an anti-plasticizing effect (increasing the polymer glass transition temperature), decreasing the film extensibility and the resistance to breaking, with slight changes in the elastic modulus. In contrast, vanillin provoked a plasticizing effect, decreasing the elastic modulus without notable changes in the film extensibility while increasing the water vapor permeability. All phenolic compounds, mainly catechin, improved the oxygen barrier capacity of PHBV films and interfered with the polymer crystallization, reducing the melting point and crystallinity degree. The thermal stability of the material was little affected by the incorporation of phenols. The migration of passive components of the different PHBV films was lower than the overall migration limit in every simulant. Phenolic compounds were released to a different extent depending on their thermo-sensitivity, which affected their final content in the film, their bonding forces in the polymer matrix, and the simulant polarity. Their effective release in real foods will determine their active action for food preservation. Catechin was the best preserved, while ferulic acid was the most released.

New Functional Bionanocomposites by Combining Hybrid Host-Guest Systems with a Fully Biobased Poly(lactic acid)/Poly(butylene succinate-co-adipate) (PLA/PBSA) Binary Blend

In this study, we have developed innovative polymer nanocomposites by integrating magnesium-aluminum layered double hydroxide (LDH)-based nanocarriers modified with functional molecules into a fully biobased poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) matrix. These LDH-based hybrid host-guest systems contain bioactive compounds like rosmarinic acid, ferulic acid, and glycyrrhetinic acid, known for their antioxidant, antimicrobial, and anti-inflammatory properties. The bioactive molecules can be gradually released from the nanocarriers over time, allowing for sustained and controlled delivery in various applications, such as active packaging or cosmetics. The morphological analysis of the polymer composites, prepared using a discontinuous mechanical mixer, revealed the presence of macroaggregates and nano-lamellae at the polymer interface. This resulted in an enhanced water vapor permeability compared to the original blend. Furthermore, the migration kinetics of active molecules from the thin films confirmed a controlled release mechanism based on their immobilization within the lamellar system. Scaling-up experiments evaluated the materials' morphology and mechanical and thermal properties. Remarkably, stretching deformation and a higher shear rate during the mixing process enhanced the dispersion and distribution of the nanocarriers, as confirmed by the favorable mechanical properties of the materials.

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) with Phenolic Acids for Active Food Packaging

PHBV films incorporating 3, 6 and 9% ferulic acid (FA) or p-coumaric acid (PCA) were obtained by melt blending and compression moulding. The films' microstructures and thermal behaviours were analysed as well as their mechanical, optical and barrier properties. The overall and specific migration of the materials in different food simulants was also characterised. FA was homogeneously mixed with the polymer, whereas PCA was mainly dispersed as fine particles in the PHBV matrices due to its higher melting point. These structural features promoted differences in the physical properties of the films depending on the compound concentration. As the concentration of both compounds rose, the barrier capacity of the films to oxygen, and to a lesser extent water vapour, was enhanced. While FA promoted the extensibility of the films, 9% PCA enhanced their brittleness. Both compounds affected the crystallisation pattern of the polymer, promoting smaller crystalline formations and a slight decrease in crystallinity. Although the overall migration of every film formulation was lower than the overall migration limit (OML), the release of active compounds was dependent on the food simulant; almost total release was noted in ethanol containing simulants but was more limited in aqueous systems. Therefore, these films could be used as food contact materials, contributing to extending the food's shelf life.

Effect of ferulic acid derivative concentration on the release kinetics, antioxidant capacity, and thermal behaviour of different polymeric films

Ferulic acid displays poor thermal resistance during extrusion and compression moulding, slow 2,2-diphenyl-1-picrylhydrazyl (DPPH) reaction kinetics, and undetected release from polylactide (PLA) and polyhydroxyalkanoates (PHA)-based films into polar media. Thus, in this study, a ferulic acid derivative Bis-O-dihydroferuloyl-1,4-butanediol (BDF) was used as an active additive (up to 40 w%) in PLA, poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrices to produce blends by extrusion. These blends were then used to prepare films by solvent casting. The BDF displayed good stability with 86-93% retention. The release kinetics in Food Simulant A revealed higher BDF release amounts (1.16-3.2%) for PHA-based films as compared to PLA. The BDF displayed faster DPPH reaction kinetics as compared to ferulic acid. The PHA-based films containing BDF displayed > 80% of DPPH inhibition. The growth of crystals inside polymer matrix had a nucleation effect which reduced the glass transition temperature of the films.

Biodegradable sodium alginate films incorporated with lycopene and β-carotene for food packaging purposes

Incorporating carotenoids into sodium alginate films can give them functional properties for food packaging applications. The lycopene and β-carotene were included in the biopolymer matrix at 0.1%, 0.3%, and 0.5% (g carotenoid/g polymer). There was no significant difference (p > 0.05) in film thickness (45 ± 1 μm) of sodium alginate films with carotenoids. Nevertheless, the low quantity of carotenoids was enough to promote significant variations in the tensile properties of films. The films with lycopene or β-carotene showed lower tensile strength and elongation at break than control films. The carotenoid incorporation promoted a reduction (p < 0.05) in water vapor permeability, mainly by adding 0.5%. In the same way, it improved the light transmission and thermal stability of films and did not affect the water solubility of films. The scanning electron microscopy of films showed a homogeneous surface, but the films with lycopene or β-carotene showed a more compact structure than the control film. The sodium alginate films incorporated with 0.3% lycopene or β-carotene showed a remarkable protective effect on sunflower oil against oxidation compared with traditional commercial plastic packaging under accelerated storage conditions (heat and light). Therefore, they can be considered a potential material for food packaging purposes.

The Application of Phenolic Acids in The Obtainment of Packaging Materials Based on Polymers-A Review

This article provides a summarization of present knowledge on the fabrication and characterization of polymeric food packaging materials that can be an alternative to synthetic ones. The review aimed to explore different studies related to the use of phenolic acids as cross-linkers, as well as bioactive additives, to the polymer-based materials upon their application as packaging. This article further discusses additives such as benzoic acid derivatives (sinapic acid, gallic acid, and ellagic acid) and cinnamic acid derivatives (p-coumaric acid, caffeic acid, and ferulic acid). These phenolic acids are mainly used as antibacterial, antifungal, and antioxidant agents. However, their presence also improves the physicochemical properties of materials based on polymers. Future perspectives in polymer food packaging are discussed.

Beyond brewing: β-acid rich hop extract in the development of a multifunctional polylactic acid-based food packaging

Hops' (Humulus lupulus L.) phytochemicals are well known for their bioactivity. In the present study, the functional properties of hop extract rich in β-acids, as potassium-salts structures (KBA), were investigated to develop a sustainable active food packaging. Polylactic acid (PLA)-based sheets were incorporated with increasing concentrations of hop extract (0.1-5 % w/w in terms of KBA) and characterized through performance and bioactive properties. KBA-added sheets presented decreased crystallinity and affected mechanical and thermal properties, especially with higher KBA amounts. The sheets' surface hydrophobicity gradually decreased by KBA-extract addition, while the water vapor permeability was not affected. A Fickian diffuse behavior and a better fit to application in fatty foods were observed during release tests. UV-blocking and antioxidant properties were improved by KBA incorporation. Furthermore, results from antibacterial assays revealed great susceptibility of Staphylococcus aureus and Listeria monocytogenes towards sheets added with 5 % of KBA. Moreover, the atomic force microscopy (AFM) observations revealed that KBA led to strong effects on the cell membranes of both bacteria, including disruption of membrane integrity and cell death. Therefore, this study is a sign of great prospects of hop β-acids use, as KBA compound, in the production of sustainable active packaging for safe food shelf-life extension.

Active Starch-Polyester Bilayer Films with Surface-Incorporated Ferulic Acid

Bilayer films of cassava starch-based (with 10% gellan gum) and polylactic (PLA): Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) polyester blend (with 75% PLA) monolayers were obtained by melt-blending and compression-molding, and the subsequent thermocompressing of both monolayers. Ferulic acid (FA) was incorporated into the polyester sheet by spraying and drying. Films were characterized in terms of their microstructure and functional properties throughout two months of storage at 25 °C and 53% relative humidity. The laminates exhibited improved tensile and barrier properties compared to the respective monolayers, which makes them more adequate for food packaging purposes. Surface incorporation of ferulic acid did not significantly modify the barrier and mechanical properties of the films while providing them with antioxidant and antibacterial capacity when applied in aqueous systems, where a complete release of active compounds occurred. The physical properties of the bilayers and layer thermo-sealing were stable throughout storage. Likewise, the antioxidant and antimicrobial active properties were preserved throughout storage. Therefore, these active bilayers represent a sustainable packaging alternative to non-biodegradable, non-recyclable synthetic laminates for food packaging purposes, which could extend the shelf-life of food due to their antioxidant and antibacterial properties.

Antibacterial, Antifungal and Antiviral Polymeric Food Packaging in Post-COVID-19 Era

Consumers are now more concerned about food safety and hygiene following the COVID-19 pandemic. Antimicrobial packaging has attracted increased interest by reducing contamination of food surfaces to deliver quality and safe food while maintaining shelf life. Active packaging materials to reduce contamination or inhibit viral activity in packaged foods and on packaging surfaces are mostly prepared using solvent casting, but very few materials demonstrate antiviral activity on foods of animal origin, which are important in the human diet. Incorporation of silver nanoparticles, essential oils and natural plant extracts as antimicrobial agents in/on polymeric matrices provides improved antifungal, antibacterial and antiviral properties. This paper reviews recent developments in antifungal, antibacterial and antiviral packaging incorporating natural or synthetic compounds using preparation methods including extrusion, solvent casting and surface modification treatment for surface coating and their applications in several foods (i.e., bakery products, fruits and vegetables, meat and meat products, fish and seafood and milk and dairy foods). Findings showed that antimicrobial material as films, coated films, coating and pouches exhibited efficient antimicrobial activity in vitro but lower activity in real food systems. Antimicrobial activity depends on (i) polar or non-polar food components, (ii) interactions between antimicrobial compounds and the polymer materials and (iii) interactions between environmental conditions and active films (i.e., relative humidity, oxygen and water vapor permeability and temperature) that impact the migration or diffusion of active compounds in foods. Knowledge gained from the plethora of existing studies on antimicrobial polymers can be effectively utilized to develop multifunctional antimicrobial materials that can protect food products and packaging surfaces from SARS-CoV-2 contamination.