A review of poly(lactic acid)-based materials for antimicrobial packaging

Development of poly(lactic acid)-based natural antimicrobial film incorporated with caprylic acid against Salmonella biofilm contamination in the meat industry

Using a solvent-casting method, a poly(lactic acid) (PLA) film incorporated with caprylic acid (CA) was developed as an active packaging against Salmonella enterica ser. Typhimurium and S. enteritidis to reduce the risk of microbial contamination during distribution and storage of meat. According to the minimum inhibitory concentration (MIC) test results of the natural antimicrobial, CA was introduced at 0.6, 1.2, 2.4, and 4.8 % (v/v) into neat PLA. The biofilm inhibitory effect and antimicrobial efficacy of CA-PLA film against both Salmonella strains, as well as the intermolecular interactions and barrier properties of CA-PLA film, were evaluated. Biofilm formation was reduced to below the detection limit (<1.0 log CFU/cm2) for both S. typhimurium and S. enteritidis when co-cultured overnight with 4.8 % CA-PLA film. The 4.8 % CA-PLA film achieved maximum log reductions of 2.58 and 1.65 CFU/g for S. typhimurium and 2.59 and 1.76 CFU/g for S. enteritidis on inoculated chicken breast and beef stored at 25 °C overnight, respectively, without any quality (color and texture) losses. CA maintained its typical chemical structure in the film, as confirmed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra. Furthermore, film surface morphology observations by field emission scanning electron microscopy (FESEM) showed that CA-PLA film was smoother than neat PLA film. No significant (P > 0.05) changes were observed for water vapor permeability and oxygen permeability by the addition of CA into PLA film, suggesting that CA-PLA film is a promising strategy for active packaging to control Salmonella contamination in the meat industry.

Demonstrating the key role of Bacillus in poly lactic acid film degradation through statistical analysis and strain screening

Plastic films are extensively utilized in agriculture, construction, and manufacturing, with their annual production reaching staggering figures. Addressing the global plastic pollution crisis is imperative. One promising approach is the augmentation of plastic films degradation through microbial agents. Consequently, we undertook composting experiments employing various plastics, including Polyethylene (PE), Poly lactic acid (PLA), and a treatment without plastic films addition (CK), mixed with kitchen waste. Employing bipartite association networks and difference significance analysis methods, we scrutinized the impact of different plastics on the microbial community within the compost piles. There were significant disparities in the microbial community composition among three composting piles. To pinpoint the key microorganisms responsible for PLA degradation, we conducted a comparative analysis of microbial species present on PLA compost piles and PLA film surfaces (PLAS), utilizing variance analysis, co-occurrence network analysis, and Spearman's correlation analysis. Our findings identified Bacillus as the pivotal microorganism involved in PLA degradation. Furthermore, employing function prediction by PICRUSt 2, we identified K00016 as the crucial gene facilitating PLA degradation by Bacillus. Subsequently, employing strain screening techniques, we isolated a highly effective PLA-degrading bacterium, Bacillus amyloliquefaciens strain ML274. The PLA films degradation rate of ML274 reached 3.18%. and other strains was lower than 3.0%. Thus, Bacillus emerges as the primary microorganism driving PLA degradation, emphasizing the significance of focusing on Bacillus genus microorganisms in the development of plastic-degrading bacterial agents for future endeavors.

Preparation and Characterization of Poly(lactic acid)-Based Poly(ethylene glycol) and Daphne Essential Oil-Loaded Smart Nanofibers for Thermal Protection

Phase change material (PCM) stores latent heat energy, and poly(ethylene glycol) (Mw: 4000) (PEG 4000) is also a solid-liquid PCM. PEG and poly(lactic acid) (PLA) polymers are biodegradable. Essential oils are known as plant extracts with antimicrobial properties. In this study, daphne essential oil (DEO) obtained by the distillation method and PLA/PEG/DEO composite nanofibers were prepared by the electrospinning method with PLA, PEG 4000, and daphne (Laurus nobilis L.) essential oil in certain ratios (100/100/20, 100/120/20, and 100/150/20). DEO showed an antibacterial effect against Staphylococcus aureus and Escherichia coli bacteria. Thermal behaviors of the nanofibers were characterized by differential scanning calorimetry and thermogravimetric analysis. Morphological features were observed by scanning electronic microscopy (SEM), crystal behavior by X-ray diffraction analysis, and molecular structures were examined by Fourier transform infrared spectroscopy. Essential oil composition was determined by GC-MS. The thermal decomposition temperatures of the nanofibers were found between 250 and 276 °C, and the latent heat storage energies of nanofibers were 69.06, 86.76, and 96.39 J g-1 at temperatures 59.0 and 54.37 °C. High PCM added fiber was observed as 182 nm diameter with 3.264 μm diameter spheres. The produced nanofiber matrix has the potential to be used in applications such as medicine, textile, and hot food logistics.

Electrospun high hydrophilicity antimicrobial poly (lactic acid)/silk fibroin nanofiber membrane for wound dressings

Antimicrobial wound dressings can aid wound healing by preventing bacterial infection. This is particularly true of electrospun ones, which have a porous structure and can be easily loaded with antimicrobial drugs. Here, Poly lactic acid (PLA), Silk Fibroin (SF) and antimicrobial agents of Silver nanoparticles (Ag NPs) and Silver oxide (Ag2O) to prepare the PLA/SF composites antimicrobial nanofiber membrane by electrospinning. The PLA with 30 % SF nanofiber membrane show the water vapor permeability (WVP) and the liquid absorption of 36 g·mm/(m2·d·kPa) and 1721 %. With the increasing of SF contents, the degradation rate and surface hydrophilicity of the nanofiber membrane increase significantly. The nanofiber membrane exhibited excellent antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) with the inhibition circle reach at 18.2 mm. The resultant nanofiber membrane showed high cytosolic activity, good cytocompatibility and strong antimicrobial ability, which laid a theoretical foundation for the construction of a new PLA/SF composites antimicrobial fiber membrane.

The effect of Dunaliella salina extracts on the adhesion of Pseudomonas aeruginosa to 3D printed polyethylene terephthalate and polylactic acid

Polyethylene terephthalate (PET) and polylactic acid (PLA) are among the polymers used in the food industry. In this study, crude extracts of Dunaliella salina were used to treat the surface of 3D printed materials studied, aiming to provide them with an anti-adhesive property against Pseudomonas aeruginosa. The hydrophobicity of treated and untreated surfaces was characterized using the contact angle method. Furthermore, the adhesive behavior of P. aeruginosa toward the substrata surfaces was also studied theoretically and experimentally. The results showed that the untreated PLA was hydrophobic, while the untreated PET was hydrophilic. It was also found that the treated materials became hydrophilic and electron-donating. The total energy of adhesion revealed that P. aeruginosa adhesion was theoretically favorable on untreated materials, while it was unfavorable on treated ones. Moreover, the experimental data proved that the adhesion to untreated substrata was obtained, while there was complete inhibition of adhesion to treated surfaces.

Shelf Life of Minced Pork in Vacuum-Adsorbed Carvacrol@Natural Zeolite Nanohybrids and Poly-Lactic Acid/Triethyl Citrate/Carvacrol@Natural Zeolite Self-Healable Active Packaging Films

Enhancing food preservation and safety using environmentally friendly techniques is urgently needed. The aim of this study was to develop food packaging films using biodegradable poly-L-lactic acid (PLA) as biopolymer and carvacrol (CV) essential oil as an antioxidant/antibacterial agent for the replacement of chemical additives. CV was adsorbed onto natural zeolite (NZ) via a new vacuum adsorption method. The novel nanohybrid CV@NZ with a high CV content contained 61.7%wt. CV. Pure NZ and the CV@NZ nanohybrid were successfully dispersed in a PLA/triethyl citrate (TEC) matrix via a melt extrusion process to obtain PLA/TEC/xCV@NZ and PLA/TEC/xNZ nanocomposite films with 5, 10, and 15%wt CV@NZ or pure NZ content. The optimum resulting film PLA/TEC/10CV@NZ contained 10%wt. CV@NZ and exhibited self-healable properties, 22% higher tensile strength, 40% higher elongation at break, 45% higher water barrier, and 40% higher oxygen barrier than the pure PLA/TEC matrix. This film also had a high CV release content, high CV control release rate as well as 2.15 mg/L half maximal effective concentration (EC50) and 0.27 mm and 0.16 mm inhibition zones against Staphylococcus aureus and Salmonella enterica ssp. enterica serovar Typhimurium, respectively. This film not only succeeded in extending the shelf life of fresh minced pork, as shown by the total viable count measurements in four days but also prevented the lipid oxidation of fresh minced pork and provided higher nutritional values of the minced meat, as revealed by the heme iron content determination. It also had much better and acceptable sensory characteristics than the commercial packaging paper.

Morphologies, Compatibilization and Properties of Immiscible PLA-Based Blends with Engineering Polymers: An Overview of Recent Works

Poly(L-Lactide) (PLA), a fully biobased aliphatic polyester, has attracted significant attention in the last decade due to its exceptional set of properties, such as high tensile modulus/strength, biocompatibility, (bio)degradability in various media, easy recyclability and good melt-state processability by the conventional processes of the plastic/textile industry. Blending PLA with other polymers represents one of the most cost-effective and efficient approaches to develop a next-generation of PLA-based materials with superior properties. In particular, intensive research has been carried out on PLA-based blends with engineering polymers such as polycarbonate (PC), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and various polyamides (PA). This overview, consequently, aims to gather recent works over the last 10 years on these immiscible PLA-based blends processed by melt extrusion, such as twin screw compounding. Furthermore, for a better scientific understanding of various ultimate properties, processing by internal mixers has also been ventured. A specific emphasis on blend morphologies, compatibilization strategies and final (thermo)mechanical properties (tensile/impact strength, ductility and heat deflection temperature) for potential durable and high-performance applications, such as electronic parts (3C parts, electronic cases) to replace PC/ABS blends, has been made.

Bioactivity and Antibacterial Analysis of Plasticized PLA Electrospun Fibers Reinforced with MgO and Mg(OH)2 Nanoparticles

In this work, we focused on the bioactivity and antibacterial behavior of PLA-based electrospun fibers, efibers, reinforced with both MgO and Mg(OH)2 nanoparticles, NPs. The evolution of PLA-based efibers was followed in terms of morphology, FTIR, XRD, and visual appearance. The bioactivity was discussed in terms of hydroxyapatite growth after 28 days, considered as T28, of immersion in simulated body fluid, SBF. In particular, the biomineralization process evidenced after immersion in SBF started at T14 in both systems. The number of precipitated crystals increased by increasing the amount of both NPs. The chemical composition of the precipitated crystals was also characterized in terms of the Ca/P molar ratio after T28 of immersion in SBF, indicating the presence of hydroxyapatite on the surface of both reinforced efibers. Moreover, a reduction in the average diameter of the PLA-based efibers was observed, reaching a maximum reduction of 46 and 60% in the average diameter of neat PLA and PLA:OLA efibers, respectively, after 28 days of immersion in SBF. The antibacterial behavior of the MgO and Mg(OH)2 NPs in the PLA-based electrospun fibers was tested against Escherichia coli, E. coli, as the Gram-negative bacteria, and Staphylococcus aureus, S. aureus, as the Gram-positive bacteria, obtaining the best antibacterial activity against the Gram-negative bacteria E. coli of 21 ± 2% and 34 ± 6% for the highest concentration of MgO and Mg(OH)2 NPs, respectively.

Fabrication of Flexible Films for Supercapacitors Using Halloysite Nano-Clay Incorporated Poly(lactic acid)

In the past few years, significant research efforts have been directed toward improving the electrochemical capabilities of supercapacitors by advancing electrode materials. The present work signifies the development of poly(lactic acid)/alloysite nano-clay as an electrode material for supercapacitors. Physico-chemical characterizations were analyzed by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and a universal testing machine. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques were employed to evaluate electrochemical characteristics. The optimized poly(lactic acid)/halloysite nano-clay film revealed the highest specific capacitance of 205.5 F g-1 at 0.05 A g-1 current density and showed 14.6 Wh kg-1 energy density at 72 W kg-1 power density. Capacitance retention of 98.48% was achieved after 1000 cycles. The microsupercapacitor device presented a specific capacitance of 197.7 mF g-1 at a current density of 0.45 mA g-1 with 10.8 mWh kg-1 energy density at 549 mW kg-1 power density.

Potential Use of PLA-Based Films Loaded with Antioxidant Agents from Spent Coffee Grounds for Preservation of Refrigerated Foods

The aim of this work concerned the production of an active food packaging suitable for refrigerated foods. Polylactic-acid-based films were produced by optimizing the solvent casting technique and testing different loadings of extracts obtained from spent coffee grounds. Indeed, an extract obtained by high-pressure and -temperature extraction (HPTE) and a further purified extract by liquid-liquid extraction (LLE) were separately used as active agents, and the effects on packaging features and active compounds migration were analyzed. The selected active agents showed antioxidant and lipid peroxidation inhibition effects on food simulants (peroxide values of 9.2 ÷ 12.0 meqO2/kg extra virgin olive oil), demonstrating the possibility of enhancing food shelf life. In addition, significant effects on the packaging structure due to the presence of the extract were observed, since it can enhance gas barrier properties of the polymer (O2 permeability of 1.6 ÷ 1.3 × 10-9 cm2/s) and confer better processability. In general, the HPTE extract exhibited better performances than the further purified extract, which was due to the presence of a complex pool of antioxidants and the browning effect on the film but a limited loading capacity on the polymer (840 μg caffeine/g PLA), while higher loading capabilities were enabled using LLE extract.

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.

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.

Current Insights in Fungal Importance-A Comprehensive Review

Besides plants and animals, the Fungi kingdom describes several species characterized by various forms and applications. They can be found in all habitats and play an essential role in the excellent functioning of the ecosystem, for example, as decomposers of plant material for the cycling of carbon and nutrients or as symbionts of plants. Furthermore, fungi have been used in many sectors for centuries, from producing food, beverages, and medications. Recently, they have gained significant recognition for protecting the environment, agriculture, and several industrial applications. The current article intends to review the beneficial roles of fungi used for a vast range of applications, such as the production of several enzymes and pigments, applications regarding food and pharmaceutical industries, the environment, and research domains, as well as the negative impacts of fungi (secondary metabolites production, etiological agents of diseases in plants, animals, and humans, as well as deteriogenic agents).

High value valorization of lignin as environmental benign antimicrobial

Lignin is a natural aromatic polymer of p-hydroxyphenylpropanoids with various biological activities. Noticeably, plants have made use of lignin as biocides to defend themselves from pathogen microbial invasions. Thus, the use of isolated lignin as environmentally benign antimicrobial is believed to be a promising high value approach for lignin valorization. On the other hand, as green and sustainable product of plant photosynthesis, lignin should be beneficial to reduce the carbon footprint of antimicrobial industry. There have been many reports that make use of lignin to prepare antimicrobials for different applications. However, lignin is highly heterogeneous polymers different in their monomers, linkages, molecular weight, and functional groups. The structure and property relationship, and the mechanism of action of lignin as antimicrobial remains ambiguous. To show light on these issues, we reviewed the publications on lignin chemistry, antimicrobial activity of lignin models and isolated lignin and associated mechanism of actions, approaches in synthesis of lignin with improved antimicrobial activity, and the applications of lignin as antimicrobial in different fields. Hopefully, this review will help and inspire researchers in the preparation of lignin antimicrobial for their applications.

Production and characterization of biodegradable bi-layer films from poly(lactic) acid and zein

Recently, packaging industry has turned to biodegradable packaging, and poly(lactic acid) has become the most remarkable polymer. However, the high oxygen permeability of PLA films significantly limits their use. Therefore, this study, it was aimed to improve the oxygen barrier properties of PLA films without adversely affecting the mechanical and water vapor barrier properties. Biodegradable PLA-Zein bi-layer films were produced by changing PLA and zein thickness. Transparent and UV barrier bi-layer films were obtained. Mechanical properties of PLA films were improved by the production of bi-layer films. Water vapor permeability of bi-layer films increased whereas the permeance decreased with zein coating of PLA. Multi-criteria decision hierarchy was used to select the best bi-layer films based on mechanical, permeance, and opacity results. Oxygen barrier properties of PLA film significantly improved by zein coating, and hydrophobicity of PLA film was not affected by zein coating. The crystallization and melting temperatures of films decreased when compared to PLA films, supporting the mechanical results. Homogeneous, non-porous, and smooth film surface was obtained and zein layer was in good compatibility with PLA layer. These results suggest that zein coatings could be used to decrease oxygen permeability of PLA films without negatively affecting other properties.

Correlation between chain structures of corn starch and properties of its film prepared at different degrees of disorganization

This study investigated the relationship between the chain structure of corn starch and the properties of corn starch-based films formed with starch pastes with different degrees of disorganization (70, 80, and 90 °C). The degree of gelatinization, chain length distribution, amylose content, and molecular weight of the corn starch were determined by the water absorption index, ion chromatography, spectrophotometry, and gel chromatography, respectively. The thickness, surface roughness, solubility, water content, water vapor permeability, mechanical properties, and maximum thermal degradation rate of corn starch-based films formed with starch pastes with different degrees of disorganization were evaluated. The moisture content, thickness and surface roughness of films formed with the starch pastes decreased. At the same time, the solubility, elongation at break, water vapor permeability, and molecular weight distribution increased with increasing heat treatment temperature. The maximum thermal degradation rate and tensile strength of the corn starch-based films formed with the starch pastes decreased with increasing heat treatment temperature. The gradual decrease in the amylose content of corn starch-based films formed with starch paste with increasing heat treatment temperature led to a change in the performance of the corn starch-based films.

Effect of polylactic acid on the micellization of SDS and CTAB: physicochemical studies on surfactants aggregation

This study reports the aggregation behavior of polylactic acid (PLA) with ionic surfactants e.g. sodium dodecyl sulphate (SDS) and hexadecyltrimethylammonium bromide (CTAB) at different temperatures. Surface tension and conductivity techniques were used to investigate these physicochemical properties. Surface tension measurements were carried out to find out critical micelle concentration (CMC), free energy change of micellization (ΔG m), free energy change of adsorption (ΔG ads) and surface excess concentration (Γ). Conductivity measurements were used to determine CMC, degree of ionization (α) and degree of counter ion binding (β). The values of α and β obtained for SDS were (0.389 and 0.611 respectively), while for CTAB the values of α and β were (0.239 and 0.761 respectively). This type of electrostatic interactions is very important which can be applied in various industrial applications (e.g. pharmaceutical, industrial foaming, oil recovery etc.).

Study on Rapid Detection Method for Degradation Performance of Polyolefin-Based Degradable Plastics

In order to accurately determine the degradation performance of polyolefin-based degradable plastics, the concept of bioassimilated carbon is proposed for the first time in this paper; the bioactive and hydrophilic organic carbon in plastic degradation products is defined as bioassimilation carbon. A method for the detection of the carbonyl index and bioassimilated carbon conversion rate in polyolefin degradable plastics was developed to quickly identify its degradation performance. The measurement results show that the bioassimilated carbon conversion rate of more than 70% can be used to replace the biodegradation rate index to achieve the purpose of quickly identifying the degradation performance of plastics. The deterioration detection cycle proposed by the current common standards implemented in American Society of Testing Materials: ASTM D6400 "Specification for Composting Plastics" can be shortened from 1 year to 1 month. The standard system for catalytic degradation of plastics provides detection methods for polyolefin-based catalytic degradation materials (microplastics), and solves the problems of long detection cycle and poor detection efficiency. Thus, this method has promise for use as a relevant standard method for accurately providing a reference for the assessment.

From Classical to Advanced Use of Polymers in Food and Beverage Applications

Polymers are extensively used in food and beverage packaging to shield against contaminants and external damage due to their barrier properties, protecting the goods inside and reducing waste. However, current trends in polymers for food, water, and beverage applications are moving forward into the design and preparation of advanced polymers, which can act as active packaging, bearing active ingredients in their formulation, or controlling the head-space composition to extend the shelf-life of the goods inside. In addition, polymers can serve as sensory polymers to detect and indicate the presence of target species, including contaminants of food quality indicators, or even to remove or separate target species for later quantification. Polymers are nowadays essential materials for both food safety and the extension of food shelf-life, which are key goals of the food industry, and the irruption of smart materials is opening new opportunities for going even further in these goals. This review describes the state of the art following the last 10 years of research within the field of food and beverage polymer's applications, covering present applications, perspectives, and concerns related to waste generation and the circular economy.

Highly Permeable Polylactic Acid Membrane Grafted with Quaternary Ammonium Salt for Effective and Durable Water Disinfection

Given the increasing usage of drinking water purifiers, highly permeable membranes with strong antimicrobial functions are desperately desirable for effective and durable water disinfection. Hereby, we prepared such antimicrobial membranes by chemical grafting of quaternary ammonium salt (QAS) molecules, 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride (TPMMC), onto air plasma pretreated biodegradable polylactic acid (PLA) substrates. The high chemical grafting density promoted very strong and positive zeta potential charge of the resulted PLA-QAS membrane, contributing to effective and broad-spectrum antimicrobial efficiencies (>99.99%) against different microbes, including fungi and conventional and drug-resistant bacteria. The solid grafting of QAS molecules produced a durable antimicrobial performance of the PLA-QAS membrane. In addition, the pleated filter (0.45 m²) of PLA-QAS membrane showed outstanding bacteria rejection properties (>99.99%) and excellent washing durability (up to 20 m³ water) even at very high water filtration rates (up to 4 L/min). The disinfection mechanism was clarified that negatively charged bacteria could be rapidly adsorbed to positively charged PLA-QAS spinnings, followed by devastating cell membrane damage to bacterial debris, leaving a clean environment without significant biofilm and biofouling formation.

Strength Characteristics of Electrospun Coconut Fibre Reinforced Polylactic Acid: Experimental and Representative Volume Element (RVE) Prediction

Environmental conservation and waste control have informed and encouraged the use of biodegradable polymeric materials over synthetic non-biodegradable materials. It has been recognized that nano-sized biodegradable materials possess relatively good properties as compared to conventional micron-sized materials. However, the strength characteristics of these materials are inferior to fossil-based non-biodegradable materials. In this study, biodegradable polylactide (PLA), reinforced with treated coconut husk particulates (CCP) for improved mechanical properties, was fabricated using an electrospinning process and representative volume element (RVE) technique, and some of the obtained mechanical properties were compared. It was observed that the electrospun CCP-PLA nanofibre composites show improved mechanical properties, and some of these mechanical properties using both techniques compared favourably well. The electrospun fibres demonstrate superior properties, mostly at 4 wt.% reinforcement. Thus, achieving good mechanical properties utilising agro waste as reinforcement in PLA to manufacture nanocomposite materials by electrospinning method is feasible and provides insight into the development of biodegradable nanocomposite materials.

Recent advances and future prospects of cellulose, starch, chitosan, polylactic acid and polyhydroxyalkanoates for sustainable food packaging applications

Cellulose, starch, chitosan, polylactic acid, and polyhydroxyalkanoates are seen as promising alternatives to conventional plastics in food packaging. However, the application of these biopolymers in the food packaging industry on a commercial scale is limited due to their poor performance and processing characteristics and high production cost. This review aims to provide an insight into the recent advances in research that address these limitations. Loading of nanofillers into polymer matrix could improve thermal, mechanical, and barrier properties of biopolymers. Blending of biopolymers also offers the possibility of acquiring newer materials with desired characteristics. However, nanofillers tend to agglomerate when loaded above an optimum level in the polymer matrix. This article throws light on different methods adopted by researchers to achieve uniform dispersion of nanofillers in bionanocomposites. Furthermore, different processing methods available for converting biopolymers into different packaging forms are discussed. In addition, the potential utilization of agricultural, brewery, and industrial wastes as feedstock for the production of biopolymers, and integrated biorefinery concept that not only keep the total production cost of biopolymers low but are also environment-friendly, are discussed. Finally, future research prospects in this field and the possible contribution of biopolymers to sustainable development are presented. This review will certainly be helpful to researchers working on sustainable food packaging, and companies exploring pilot projects to scale up biopolymer production for industrial applications.

Electrospinning of PLA Nanofibers: Recent Advances and Its Potential Application for Food Packaging

Poly(lactic acid), also abbreviated as PLA, is a promising biopolymer for food packaging owing to its environmental-friendly characteristic and desirable physical properties. Electrospinning technology makes the production of PLA-based nanomaterials available with expected structures and enhanced barrier, mechanical, and thermal properties; especially, the facile process produces a high encapsulation efficiency and controlled release of bioactive agents for the purpose of extending the shelf life and promoting the quality of foodstuffs. In this study, different types of electrospinning techniques used for the preparation of PLA-based nanofibers are summarized, and the enhanced properties of which are also described. Moreover, its application in active and intelligent packaging materials by introducing different components into nanofibers is highlighted. In all, the review establishes the promising prospects of PLA-based nanocomposites for food packaging application.

Synthesis and Thermal Analysis of Non-Covalent PS-b-SC-b-P2VP Triblock Terpolymers via Polylactide Stereocomplexation

Polylactides (PLAs) are thermoplastic materials known for their wide range of applications. Moreover, the equimolar mixtures of poly(L-Lactide) (PLLA) and poly(D-Lactide) (PDLA) can form stereocomplexes (SCs), which leads to the formation of new non-covalent complex macromolecular architectures. In this work, we report the synthesis and characterization of non-covalent triblock terpolymers of polystyrene-b-stereocomplex PLA-b-poly(2-vinylpyridine) (PS-b-SC-b-P2VP). Well-defined ω-hydroxy-PS and P2VP were synthesized by "living" anionic polymerization high-vacuum techniques with sec-BuLi as initiator, followed by termination with ethylene oxide. The resulting PS-OH and P2VP-OH were used as macroinitiators for the ring-opening polymerization (ROP) of DLA and LLA with Sn(Oct)₂ as a catalyst to afford PS-b-PDLA and P2VP-b-PLLA, respectively. SC formation was achieved by mixing PS-b-PDLA and P2VP-b-PLLA chloroform solutions containing equimolar PLAs segments, followed by precipitation into n-hexane. The molecular characteristics of the resulting block copolymers (BCPs) were determined by ¹H NMR, size exclusion chromatography, and Fourier-transform infrared spectroscopy. The formation of PS-b-SC-b-P2VP and the effect of molecular weight variation of PLA blocks on the resulting polymers, were investigated by differential scanning calorimetry, X-ray powder diffraction, and circular dichroism spectroscopies.

Polylactide-Based Films with the Addition of Poly(ethylene glycol) and Extract of Propolis-Physico-Chemical and Storage Properties

Polymeric films based on polylactide (PLA) with the addition of poly(ethylene glycol) (PEG) and a chloroformic extract of propolis were obtained. In the case of the studied films, polylactide (PLA) played the role of polymeric matrix and poly(ethylene glycol) was used as a plasticizer, while the extract of propolis was incorporated as a compound that could significantly affect the properties of the obtained materials, especially the water vapour permeation rate and the stability of the food products. Moreover, changes in structure, morphology, mechanical and storage properties as well as differences in colour, thickness and transparency after introducing propolis into the PLA-PEG system were determined. Based on the obtained results, it was established that the addition of the chloroformic extract of propolis significantly influences the most important properties taken into account during food packaging. It was also noticed that films with incorporated propolis were characterised by a significant improvement in the water vapour barrier property. Moreover, the obtained results prove that packaging containing a chloroformic propolis extract allow for the maintenance of the quality of the fruit stored for an extended period of time. To summarise, the application of a chloroformic propolis extract enables the formation of packaging materials that extend the shelf life of stored food products.

Biodegradable blend films of poly(ε-caprolactone)/poly(propylene carbonate) for shelf life extension of whole white button mushrooms

Blend films with poly(ε-caprolactone)(PCL) and poly(propylene carbonate)(PPC)with thickness of approximately 40 μm and 60 μm, respectively, were prepared using a uniaxial-stretching extrusion process to modify the property of PCL. PCL/PPC blend films with better comprehensive properties with thickness about 60 μm were used for equilibrium-modified atmosphere packaging of button mushrooms at 5 °C. The gas barrier property together with water vapor permeability were evaluated as well as its effects on the shelf life button mushrooms. The results showed that the PCL/PPC20 and PCL/PPC50 blend films have suitable gas barrier property and water vapor permeability, which was helpful to generate an appropriate storage environment and more importantly no condensation occurred in these two packages. The lower weight loss of button mushrooms was observed for PCL/PPC20 and PCL/PPC50 blend films 4.43 and 4.46, respectively. The PCL/PPC blend films was more effective in decreasing the activity of PPO and preserving the color of the button mushrooms. The over market acceptability of button mushrooms packaged in PCL/PPC blend films still maintained good and within the limit of marketability after 17 days of storage.

Active PLA Packaging Films: Effect of Processing and the Addition of Natural Antimicrobials and Antioxidants on Physical Properties, Release Kinetics, and Compostability

The performance characteristics of polylactic acid (PLA) as an active food packaging film can be highly influenced by the incorporation of active agents (AAs) into PLA, and the type of processing technique. In this review, the effect of processing techniques and the addition of natural AAs on the properties related to PLA performance as a packaging material are summarized and described through a systematic analysis, giving new insights about the relation between processing techniques, types of AA, physical–mechanical properties, barriers, optical properties, compostability, controlled release, and functionalities in order to contribute to the progress made in designing antioxidant and antimicrobial PLA packaging films. The addition of AAs into PLA films affected their optical properties and influenced polymer chain reordering, modifying their thermal properties, functionality, and compostability in terms of the chemical nature of AAs. The mechanical and barrier performance of PLA was affected by the AA’s dispersion degree and crystallinity changes resulting from specific processing techniques. In addition, hydrophobicity and AA concentration also modified the barrier properties of PLA. The release kinetics of AAs from PLA were tuned, modifying diffusion coefficient of the AAs in terms of the different physical properties of the films that resulted from specific processing techniques. Several developments based on the incorporation of antimicrobial and antioxidant substances into PLA have displayed outstanding activities for food protection against microbial growth and oxidation.

Surface-initiated atom-transfer radical polymerization (SI-ATRP) of bactericidal polymer brushes on poly(lactic acid) surfaces

We have modified the surface of poly(lactic acid) (PLA) by bromination in the presence of N-bromosuccinimide (NBS) under UV irradiation. This new approach to impart functionality to the surface does not effect the bulk of the material. Brominated PLA surfaces served as initiators for atom-transfer radical polymerization (SI-ATRP) of 2-(methacryloyloxy)ethyl]trimethylammonium chloride, a quaternary ammonium methacrylate (QMA). Grafting of poly(QMA) brushes rendered PLA films hydrophilic and these films displayed a three-order of magnitude increase in antimicrobial efficacy against Gram-negative bacteria such as Escherichia coli as compared to unmodified PLA. The two-step strategy described here to modify PLA surface represents a useful route to modified PLA materials for biomedical and antimicrobial packaging applications.

Development of Antibacterial Biocomposites Based on Poly(lactic acid) with Spice Essential Oil (Pimpinella anisum) for Food Applications

Among the main biodegradable food packaging materials, poly-lactic acid (PLA) is a commercially successful polymer used notably in the food packaging industry. In this study, active PLA films containing different percentage of anise essential oil (AE) (0, 0.5, 1 and 1.5% v/v) were developed, and characterized by physical, mechanical and antibacterial analysis. Based on physical examinations, thermal stability of PLA/AE films was greater than the neat PLA film, and the minimum water vapor permeability (WVP) was recorded for PLA/0.5AE film (1.29 × 10 ¹¹ g/m s), while maximum WVP was observed for PLA/1.5AE (2.09 × 10¹¹ g/m s). Moreover, the lightness and yellowness of the composites were decreased by the addition of AE. For the PLA composites with 1.5% AE, the tensile strength decreased by 35% and the elongation break increased by 28.09%, comparing to the pure PLA. According to the antibacterial analysis, the minimum inhibitory concentrations of PLA/AE film were 5 to 100 mg/mL and the active composite could create visible inhibition zones of 14.2 to 19.2 mm. Furthermore, the films containing AE inhibited L. monocytogenes and V. parahaemolyticus in a concentration-dependent manner. The confirmation of the success of the incorporation of EOs into the PLA films was further evaluated using principal component analysis, where positive results were obtained. In this context, our findings suggest the significant potency of AE to be used as an antibacterial agent in active food packaging.

Flexible mats as promising antimicrobial systems via integration of Thymus capitatus (L.) essential oil into PLA

Aim: To develop electrospun mats loaded with Thymus capitatus (L.) essential oil (ThymEO) and to study their morpho-mechanical and antimicrobial properties. Materials & methods: Poly(lactic acid) (PLA) mats containing ThymEO were prepared by electrospinning. The effect of ThymEO on the morpho-mechanical properties of fibers was assayed by scanning electron microscopy and dynamometer measurements. The antimicrobial activity of ThymEO delivered either in liquid or vapor phase was assessed through killing curves and invert Petri dishes method. The cytotoxicity was also investigated. Results: The mechanical properties were enhanced by integrating ThymEO into PLA. Both liquid and vapors of ThymEO released from mats caused reductions of microbial viable cells. Negligible cytotoxicity was demonstrated. Conclusion: PLA/ThymEO delivery systems could be suitable for treating microbial infections.

Preparations of Poly(lactic acid) Dispersions in Water for Coating Applications

A green, effective methodology for the preparation of water-based dispersions of poly(lactic acid) (PLA) for coating purposes is herein presented. The procedure consists of two steps: in the first one, an oil-in-water emulsion is obtained by mixing a solution of PLA in ethyl acetate with a water phase containing surfactant and stabilizer. Different homogenization methods as well as oil/water phase ratio, surfactant and stabilizer combinations were screened. In the second step, the quantitative evaporation of the organic provides water dispersions of PLA that are stable, at least, over several weeks at room temperature or at 4 °C. Particle size was in the 200-500 nm range, depending on the preparation conditions, as confirmed by scanning electron microscope (SEM) analysis. PLA was found not to suffer significant molecular weight degradation by gel permeation chromatography (GPC) analysis. Furthermore, two selected formulations with glass transition temperature (Tg) of 51 °C and 34 °C were tested for the preparation of PLA films by drying in PTFE capsules. In both cases, continuous films that are homogeneous by Fourier-transform infrared spectroscopy (FT-IR) and SEM observation were obtained only when drying was performed above 60 °C. The formulation with lower Tg results in films which are more flexible and transparent.

Lignin reinforced, water resistant, and biodegradable cassava starch/PBAT sandwich composite pieces

Following the stipulation to replace nondegradable plastics with biodegradable materials in China, cost-effective and water-resistant packaging materials have become increasingly necessary. In this work, lignin reinforced thermoplastic cassava starch (TPS) pieces were prepared by filling glycerol and lignin powder into starch via a melt blending process and then being pressed into thin pieces. A mechanical properties test showed that following the addition of 3 wt% lignin, the tensile strength of the TPS piece was improved to 16.15 MPa from 3.71 MPa of the original TPS piece. The porous structures of the lignin powder tie the TPS macromolecular chains, induce higher crystallization, and thus provide higher tensile strength and lower elongation at break. After sandwiching two pieces of poly (butylene adipateco-terephthalate) (PBAT)/peanut shell powder composite thin film to each side of the TPS piece, the PBAT/TPS/PBAT sandwich gains excellent water resistance properties. However, as soon as the sandwich piece is cut into smaller ones, they absorb water quickly, implying such pieces can be biodegraded rapidly. These characteristics make it especially suitable for use in the preparation of cabinet waste bags, which are generally stirred into organic fertilizer with the cabinet waste. Slow degradation may negatively affect soil health and farm production.

Preparation of cypress (Cupressus sempervirens L.) essential oil loaded poly(lactic acid) nanofibers

This study investigated the production of poly(lactic acid) (PLA) nanofibers containing cypress (CUP) essential oil (EO) via electrospinning. The nanofibers were produced from polymer solution prepared with different percentages of cypress EO. Cypress EO-containing PLA nanofibers were characterized and some mechanical and thermal properties were examined using thermogravimetric analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and dynamic mechanical analysis. The thermal stability of the nanofibers was reduced depending on the percentage of the cypress EO. As the ratio of the cypress EO to polymer matrices was increased, it was observed that the glassy transition temperatures of the nanofibers decreased and their flexibility increased. The T g value was determined to be 53.74°C for the neat PLA nanofiber, while 51.83°C for the PLA-CUP nanofiber (containing 15% cypress EO). According to the results of releasing trial, the increased amount of cypress EO resulted in less cypress EO releasing from polymer matrices. The nanofibers were observed to exhibit antibacterial activity against Escherichia coli and Staphylococcus aureus. The inhibition zone diameter of the nanofibers containing 10% cypress EO was 20 mm for S. aureus and 16 mm for E. coli, while 10 mm in the presence of Kanamycin.

Antimicrobial Food Packaging with Biodegradable Polymers and Bacteriocins

Innovations in food and drink packaging result mainly from the needs and requirements of consumers, which are influenced by changing global trends. Antimicrobial and active packaging are at the forefront of current research and development for food packaging. One of the few natural polymers on the market with antimicrobial properties is biodegradable and biocompatible chitosan. It is formed as a result of chitin deacetylation. Due to these properties, the production of chitosan alone or a composite film based on chitosan is of great interest to scientists and industrialists from various fields. Chitosan films have the potential to be used as a packaging material to maintain the quality and microbiological safety of food. In addition, chitosan is widely used in antimicrobial films against a wide range of pathogenic and food spoilage microbes. Polylactic acid (PLA) is considered one of the most promising and environmentally friendly polymers due to its physical and chemical properties, including renewable, biodegradability, biocompatibility, and is considered safe (GRAS). There is great interest among scientists in the study of PLA as an alternative food packaging film with improved properties to increase its usability for food packaging applications. The aim of this review article is to draw attention to the existing possibilities of using various components in combination with chitosan, PLA, or bacteriocins to improve the properties of packaging in new food packaging technologies. Consequently, they can be a promising solution to improve the quality, delay the spoilage of packaged food, as well as increase the safety and shelf life of food.

Can Sustainable Packaging Help to Reduce Food Waste? A Status Quo Focusing Plant-Derived Polymers and Additives

The promotion of sustainable packaging is part of the European Green Deal and plays a key role in the EU’s social and political strategy. One option is the use of renewable resources and biomass waste as raw materials for polymer production. Lignocellulose biomass from annual and perennial industrial crops and agricultural residues are a major source of polysaccharides, proteins, and lignin and can also be used to obtain plant-based extracts and essential oils. Therefore, these biomasses are considered as potential substitute for fossil-based resources. Here, the status quo of bio-based polymers is discussed and evaluated in terms of properties related to packaging applications such as gas and water vapor permeability as well as mechanical properties. So far, their practical use is still restricted due to lower performance in fundamental packaging functions that directly influence food quality and safety, the length of shelf life, and thus the amount of food waste. Besides bio-based polymers, this review focuses on plant extracts as active packaging agents. Incorporating extracts of herbs, flowers, trees, and their fruits is inevitable to achieve desired material properties that are capable to prolong the food shelf life. Finally, the adoption potential of packaging based on polymers from renewable resources is discussed from a bioeconomy perspective.

Design and development of Schiffs base (SB)-modified polylactic acid (PLA) antimicrobial film for packaging applications

SB compounds were synthesized from (para, ortho, meta)-phenylenediamine as a cross-linking agent through vanillin. The chemical structure of the formed SB complexes is confirmed by FT-IR spectroscopy. Among the three complexes, para-phenylenediamine (p-SB), possessing a stable resonance structure with the lowest steric repulsion, was obtained in the highest yield of 87%. Hence, the present work focused on reducing the brittle behavior and improving the antimicrobial activity of PLA by reacting it with p-SB. FT-IR investigation revealed the existence of an intermolecular hydrogen bonding between PLA and SB, which led to an increased toughness in the PLA–p-SB complex. This is further confirmed through SEM analysis. The tensile and contact angle measurements determined an improvement in mechanical properties and hydrophobic nature of the PLA–p-SB film. DSC results demonstrated an increase in flexibility, which indicated a 10 °C reduction in glass transition temperature (T_g) of PLA–p-SB films. The antimicrobial activity of the PLA–p-SB films had a maximum of 15 mm zone of inhibition, which was found to be more effective than the neat PLA film. PLA–p-SB coating on Kraft paper showed improved mechanical and barrier properties than neat PLA coatings and could be tried as a possible replacement for conventional synthetic packaging materials.

Migration kinetic of silver from polylactic acid nanocomposite film into acidic food simulant after different high-pressure food processing

The migration study of nano-Ag migration from polylactic acid (PLA) films was studied. Samples treated by high-pressure food processing (0, 100, 200, 300, and 400 MPa pressure) were soaked in acetic acid solution and incubated at 20 °C for 90 days. At the end of storage, nano-Ag particles (AgNPs) migration from the PLA/AgNPs composite film treated under 200 MPa high pressure was the lowest. However, AgNPs migration was accelerated under 400 MPa high pressure. High-pressure processing (200 MPa) could cause denser structure and higher crystallinity degree in films than other treatments. Lower amount of AgNPs induced a decline in the intensity of specific characteristic peaks. The diffraction peak intensity of α-crystal for the film sample treated with 400 MPa was the lowest on day 60. The crystallization index of the PLA matrix changed with different high-pressure processing. The result indicated that appropriate high-pressure food processing could effectively suppress AgNPs migration from PLA-based film while contacting with acidic acid food simulant. PRACTICAL APPLICATION: The release of nanoparticles from food packaging material is a very important matter when the migration is concerned with regulatory and toxicity issues. The study described the migration kinetic of AgNPs from PLA nanocomposite film into acidic food simulant after different high-pressure food processing. The results indicated that the PLA/AgNPs nanocomposite film was safe for acidic food after high-pressure treatment.