Innovative Systems for the Delivery of Naturally Occurring Antimicrobial Volatiles in Active Food-Packaging Technologies for Fresh and Minimally Processed Produce: Stimuli-Responsive Materials.

Certain naturally occurring volatile organic compounds are able to mitigate food spoilage caused by microbial growth. Their considerable vapor pressure enables them to create an antimicrobial atmosphere within a package, and this property can be used for the development of active food-packaging technologies. The volatility of these molecules, however, makes their stabilization difficult and limits their effectiveness. Whilst much research is being undertaken on the use of natural antimicrobial volatiles for inhibiting microbial growth in food, less attention has been paid to the design of controlled-release mechanisms that permit the efficient application of these compounds. Most studies to date either spray the volatile directly onto the fresh product, immerse it in a solution containing the volatile, or embed the volatile in a paper disc to create a vapor in the headspace of a package. More sophisticated alternatives would be delivery systems for the sustained release of volatiles into the package headspace. Such systems are based on the encapsulation of a volatile in organic or inorganic matrices (cyclodextrins, electrospun non-wovens, polymer films, micelles, molecular frameworks, etc.). However, most of these devices lack an efficient triggering mechanism for the release of the volatile; most are activated by humidity. All of these techniques are revised in the present work, and the most recent and innovative methods for entrapping and releasing volatiles based on reversible covalent bonds are also discussed.

Agro-Industrial Protein Waste and Co-Products Valorization for the Development of Bioplastics: Thermoprocessing and Characterization of Feather Keratin/Gliadin Blends.

Biopolymers based on plant and animal proteins are interesting alternatives in the development of films with future prospects as food packaging. Considering that in recent years there has been an increasing interest in the valorization of agro-industrial residues and by-products and that the blending of polymers can lead to materials with improved properties, in this work, keratin-rich feather fibers and gliadins were blended at different ratios in order to develop sustainable and biodegradable films. Control gliadin G100, feather F100 films, and their blends at 3:1 (G75F25), 2:2 (G50F50), and 1:3 (G25F75) ratios were successfully developed through thermoprocessing. The physical properties were differentiated as a function of the concentration of both polymeric matrices. Although gliadins showed higher hydrophilicity as confirmed by their highest swelling degree, films with high gliadin ratios exhibited lower water vapor permeability values at low and medium relative humidities. On the other hand, the feather fiber-based films displayed the highest Young's modulus values and provided an oxygen barrier to the blends, principally at the highest relative humidity. In conclusion, the blend of these protein-based polymers at different ratio resulted in interesting composites whose physical properties could be adjusted.

Improving and measuring the solubility of favipiravir and montelukast in SC-CO2 with ethanol projecting their nanonization.

Supercritical carbon dioxide (SC-CO2)-based approaches have become more popular in recent years as alternative methods for creating micro- or nanosized medicines. Particularly, high drug solubility is required in those techniques using SC-CO2 as a solvent. During the most recent pandemic years, favipiravir and montelukast were two of the most often prescribed medications for the treatment of COVID-19. In this study, ethanol at 1 and 3 mol% was utilized as a cosolvent to increase the solubility of both medicines in SC-CO2 by a static approach using a range of temperatures (308 to 338 K) and pressure (12 to 30 MPa) values. The experimentally determined solubilities of favipiravir and montelukast in SC-CO2 + 3 mol% ethanol showed solubility values up to 33.3 and 24.5 times higher than that obtained for these drugs with only SC-CO2. The highest values were achieved in the pressure of 12 MPa and temperature of 338 K. Last but not least, six density-based semi-empirical models with various adjustable parameters were used to perform the modeling of the solubility of favipiravir and montelukast.

Designing an Oxygen Scavenger Multilayer System Including Volatile Organic Compound (VOC) Adsorbents for Potential Use in Food Packaging.

Oxygen scavengers are valuable active packaging systems because several types of food deterioration processes are initiated by oxygen. Although the incorporation of oxygen scavenger agents into the polymeric matrices has been the trend in recent years, the release of volatile organic compounds (VOC) as a result of the reaction between oxygen and oxygen scavenger substances is an issue to take into account. This is the case of an oxygen scavenger based on a trans-polyoctenamer rubber (TOR). In this work, the design of an oxygen scavenger multilayer system was carried out considering the selection of appropriate adsorbents of VOCs to the proposed layer structure. Firstly, the retention of some representative organic compounds by several adsorbent substances, such as zeolites, silicas, cyclodextrins and polymers, was studied in order to select those with the best performances. A hydrophilic silica and an odor-adsorbing agent based on zinc ricinoleate were the selected adsorbing agents. The principal VOCs released from TOR-containing films were carefully identified, and their retention first by the pure adsorbents, and then by polyethylene incorporated with the selected compounds was quantified. Detected concentrations decreased by 10- to 100-fold, depending on the VOC.

Feasibility of Valorization of Post-Consumer Recycled Flexible Polypropylene by Adding Fumed Nanosilica for Its Potential Use in Food Packaging toward Sustainability.

The food industry has a current challenge of increasing the recycling of post-consumer plastics to reduce plastic waste towards a circular economy, especially flexible polypropylene, which is highly demanded in food packaging. However, recycling post-consumer plastics is limited because service life and reprocessing degrade their physical-mechanical properties and modify the migration of components from the recycled material to the food. This research evaluated the feasibility of valorization of post-consumer recycled flexible polypropylene (PCPP) by incorporating fumed nanosilica (NS). For this purpose, the effect of concentration and type (hydrophilic and hydrophobic) of NS on the morphological, mechanical, sealing, barrier and overall migration properties of PCPP films was studied. Incorporating NS improved Young's modulus and, more significantly, tensile strength at 0.5 wt% and 1 wt%, where a better particle dispersion was confirmed by EDS-SEM, but it diminished elongation at breakage of the films. Interestingly, NS tended to increase the seal strength of PCPP nanocomposite films more significantly at higher NS content, showing a seal failure of the adhesive peel type which is preferred for flexible packaging. NS at 1 wt% did not affect the water vapor and oxygen permeabilities of the films. Overall migration of PCPP and nanocomposites exceeded the limit value of 10 mg dm-2 allowed by European legislation at the studied concentrations of 1% and 4 wt%. Nonetheless, NS reduced the overall migration of PCPP from 17.3 to 15 mg dm-2 in all nanocomposites. In conclusion, PCPP with 1 wt% of hydrophobic NS presented an improved overall performance of the studied packaging properties.

Developing Post-Consumer Recycled Flexible Polypropylene and Fumed Silica-Based Nanocomposites with Improved Processability and Thermal Stability.

Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal-mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This work determined the effect of incorporating two fumed nanosilica (NS) types on processability improvement of post-consumer recycled flexible polypropylene (PCPP) through ATR-FTIR, TGA, DSC, MFI and rheological analysis. Presence of trace polyethylene in the collected PCPP increased the thermal stability of the PP and was significantly maximized by NS addition. The onset decomposition temperature raised around 15 °C when 4 and 2 wt% of a non-treated and organically modified NS were used, respectively. NS acted as a nucleating agent and increased the crystallinity of the polymer, but the crystallization and melting temperatures were not affected. The processability of the nanocomposites was improved, observed as an increase in viscosity, storage and loss moduli with respect to the control PCPP, which were deteriorated due to chain scission during recycling. The highest recovery in viscosity and reduction in MFI were found for the hydrophilic NS due to a greater impact of hydrogen bond interactions between the silanol groups of this NS and the oxidized groups of the PCPP.

Developing Core/Shell Capsules Based on Hydroxypropyl Methylcellulose and Gelatin through Electrodynamic Atomization for Betalain Encapsulation.

Betalains are bioactive compounds with remarkable functional and nutritional activities for health and food preservation and attractiveness. Nevertheless, they are highly sensitive to external factors, such as oxygen presence, light, and high temperatures. Therefore, the search for new structures, polymeric matrices, and efficient methods of encapsulation of these compounds is of great interest to increase their addition to food products. In this work, betalains were extracted from red beetroot. Betacyanin and betaxanthin contents were quantified. Subsequently, these compounds were successfully encapsulated into the core of coaxial electrosprayed capsules composed of hydroxypropyl methylcellulose (HPMC) and gelatin (G). The effect of incorporating the carbohydrate and the protein both in the core or shell structures was studied to elucidate the best composition for betalain protection. Morphological, optical, and structural properties were analyzed to understand the effect of the incorporation of the bioactive compounds in the morphology, color, and chemical interactions between components of resulting electrosprayed capsules. The results of the thermogravimetric and encapsulation efficiency analysis coincided that the incorporation of beetroot extract in G in the core and HPMC in the shell resulted in the structure with greater betalain protection. The effectiveness of the core/shell structure was confirmed for future food applications.

Hollow Iron Oxide Nanospheres Obtained through a Combination of Atomic Layer Deposition and Electrospraying Technologies.

In the present study, we report on the successful synthesis of hollow iron oxide nanospheres. The hollow Fe3O4 nanospheres were synthesized following a four-step procedure: electrospraying spherical PVP particles, coating these particles with alumina (Al2O3) and hematite (Fe2O3) through atomic layer deposition and, finally, a thermal reduction process to degrade the polymer (PVP) and convert hematite (Fe2O3) into magnetite (Fe3O4). A structural analysis using X-ray diffraction (XRD) confirmed the effectiveness of the thermal reduction process. A morphological analysis confirmed that the four-step procedure allowed for the obtainment of hollow iron oxide nanospheres, even though the reduction process caused a contraction in the diameter of the particles of almost 300 nm, but did not affect the thickness of the walls of the hollow spheres that remained at approximately 15 nm. Magnetic properties of the hollow iron oxide nanospheres enable their use in applications where the agglomeration of magnetic nanostructures in liquid media is commonly not allowed, such as in drug encapsulation and delivery.

Electrospinning and cyclodextrin inclusion complexes: An emerging technological combination for developing novel active food packaging materials.

This review was focused on describing the combination of electrospinning and cyclodextrin inclusion complexes as one of the newest alternatives for the development of food packaging materials with antimicrobial and/or antioxidant properties. The advantages of this technological combination, the routes to design the active materials, the characterization and application of such materials were reviewed. Electrospinning has allowed developing active packaging materials composed by fibrillary structures with a high ratio surface-to-volume. On the other hand, cyclodextrin inclusion complexes have maintained the properties of active compounds when they have been incorporated in packaging materials. Both methods have been recently combined and novel active food packaging materials have been obtained through three different routes. Polymeric solutions containing preformed (route 1) or in-situ formed (route 2) cyclodextrin inclusion complexes have been electrospun to obtain packaging materials. Furthermore, cyclodextrin inclusion complexes solutions have been directly electrospun (route 3) in order to produce those materials. The developed packaging materials have exhibited a high active compound loading with a long lasting release. Therefore, the protection of different foodstuff against microbial growth, oxidation and quality decay as well as the maintenance of their physical and sensory properties have been achieved when those materials were applied as active packaging.

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.

Natural antimicrobials and antioxidants added to polylactic acid packaging films. Part I: Polymer processing techniques.

Currently, reducing packaging plastic waste and food losses are concerning topics in the food packaging industry. As an alternative for these challenges, antimicrobial and antioxidant materials have been developed by incorporating active agents (AAs) into biodegradable polymers to extend the food shelf life. In this context, developing biodegradable active materials based on polylactic acid (PLA) and natural compounds are a great alternative to maintain food safety and non-toxicity of the packaging. AAs, such as essential oils and polyphenols, have been added mainly as antimicrobial and antioxidant natural compounds in PLA packaging. In this review, current techniques used to develop active PLA packaging films were described in order to critically compare their feasibility, advantages, limitations, and relevant processing aspects. The analysis was focused on the processing conditions, such as operation variables and stages, and factors related to the AAs, such as their concentrations, weight losses during processing, and incorporation technique, among others. Recent developments of active PLA-based monolayers and bi- or multilayer films were also considered. In addition, patents on inventions and technologies on active PLA-based films for food packaging were reviewed. This review highlights that the selection of the processing technique and conditions to obtain active PLA depends on the type of the AA regarding its volatility, solubility, and thermosensitivity.

Effect of Organic Modifier Types on the Physical-Mechanical Properties and Overall Migration of Post-Consumer Polypropylene/Clay Nanocomposites for Food Packaging.

The deterioration of the physical-mechanical properties and loss of the chemical safety of plastics after consumption are topics of concern for food packaging applications. Incorporating nanoclays is an alternative to improve the performance of recycled plastics. However, properties and overall migration from polymer/clay nanocomposites to food require to be evaluated case-by-case. This work aimed to investigate the effect of organic modifier types of clays on the structural, thermal and mechanical properties and the overall migration of nanocomposites based on 50/50 virgin and recycled post-consumer polypropylene blend (VPP/RPP) and organoclays for food packaging applications. The clay with the most hydrophobic organic modifier caused higher thermal stability of the nanocomposites and greater intercalation of polypropylene between clay mineral layers but increased the overall migration to a fatty food simulant. This migration value was higher from the 50/50 VPP/RPP film than from VPP. Nonetheless, clays reduced the migration and even more when the clay had greater hydrophilicity because of lower interactions between the nanocomposite and the fatty simulant. Conversely, nanocomposites and VPP/RPP control films exhibited low migration values in the acid and non-acid food simulants. Regarding tensile parameters, elongation at break values of PP film significantly increased with RPP addition, but the incorporation of organoclays reduced its ductility to values closer to the VPP.

Designing Biodegradable and Active Multilayer System by Assembling an Electrospun Polycaprolactone Mat Containing Quercetin and Nanocellulose between Polylactic Acid Films.

The design of multilayer systems is an innovative strategy to improve physical properties of biodegradable polymers and introduce functionality to the materials through the incorporation of an active compound into some of these layers. In this work, a trilayer film based on a sandwich of electrospun polycaprolactone (PCL) fibers (PCLé) containing quercetin (Q) and cellulose nanocrystals (CNC) between extruded polylactic acid (PLA) films was designed with the purpose of improving thermal and barrier properties and affording antioxidant activity to packaged foods. PCLé was successfully electrospun onto 70 µm-thick extruded PLA film followed by the assembling of a third 25 µm-thick commercial PLA film through hot pressing. Optical, morphological, thermal, and barrier properties were evaluated in order to study the effect of PCL layer and the addition of Q and CNC. Bilayer systems obtained after the electrospinning process of PCL onto PLA film were also evaluated. The release of quercetin from bi- and trilayer films to food simulants was also analyzed. Results evidenced that thermal treatment during thermo-compression melted PCL polymer and resulted in trilayer systems with barrier properties similar to single PLA film. Quercetin release from bi- and trilayer films followed a similar profile, but achieved highest value through the addition of CNC.

Designing active mats based on cellulose acetate/polycaprolactone core/shell structures with different release kinetics.

Core/shell electrospun mats based on cellulose acetate (CA) and polycaprolactone (PCL) were developed as novel active materials for releasing quercetin (Quer) and curcumin (Cur). The effect of polymeric uniaxial and coaxial electrospun systems and the chemical structures of Quer and Cur on the structural, thermal, and mass transfer properties of the developed mats were investigated. Release modelling indicated that the diffusion of the active agents from the uniaxial PCL fibers was highly dependent on the type of food simulant. Higher diffusion coefficients were obtained for both active agents in acid food simulant due to the higher swelling of the electrospun mats. In addition, CA/PCL coaxial structures slowed down the diffusion of both active agents into both food simulants. CA increased the retention of the active compounds in the polymer structure, resulting in partition coefficients values higher than the values obtained for uniaxial active PCL mats.

Development of Biodegradable Films Loaded with Phages with Antilisterial Properties.

The inhibitory and bactericidal capacity of Listex P100 bacteriophage has been studied against different concentrations of Listeria monocytogenes in stationary and exponential phases. Three different matrices were employed to developed films incorporating Listex P100: (1) sodium caseinate, (2) sodium alginate mixed with gelatin, and (3) polyvinyl alcohol (PVOH). All the films were successfully developed by casting at room temperature. These active biodegradable films were optical, structural, and thermally characterized, and their antimicrobial capacities against L. monocytogenes were studied. The incorporation of phages did not affect the morphology, colour, opacity, and thermal stability of polymers. The antimicrobial analysis revealed the bacteriophage presented a high antimicrobial capacity against L. monocytogenes in the stationary phase (4.40 and 6.19 log reduction values or bactericide effect depending on the initial inoculum of the pathogen). Developed films showed antimicrobial capacity close to 1 log after 24 h of incubation at 30 °C. The effectiveness of PVOH films was greater under refrigeration conditions, reaching 2 log reduction after eight days of incubation. The use of these films as a coating in a food or as part of a packaging could improve food safety against the growth of pathogenic microorganisms such as Listeria monocytogenes.

The use of nanoadditives within recycled polymers for food packaging: Properties, recyclability, and safety.

Nanotechnology is considered a highly valued technology to reduce the current environmental problem that is derived from plastic accumulation. The need to recycle and reuse packaging materials is essential to create a sustainable society towards a circular economy. However, the reprocessing of polymers leads to the deterioration of their characteristic mechanical, optical, thermal, and barrier properties due to the degradation of their polymeric chains. When recycled polymers are reinforced with nanoadditives, aforementioned properties improve and their use in the circular economy is more viable. In this review, different types of nanoadditives and recent advances in the development of recycled polymer nanocomposites reinforced with nanoadditives will be presented. In addition, there is a description of two research topics of current interest, recyclability of nanocomposites and safety for food packaging applications. Recyclability of nanocomposites requires a study that includes the nature of the polymer matrix, the type of polymer and the concentration of nanofiller, the morphology, the presence of additives, and the conditions of the thermal-mechanical cycles. Finally, safety section is dedicated to clarify the migration process in nanoreinforced-recycled polymers in order to assess their safety for food contact applications.

Development of Bilayer Biodegradable Composites Containing Cellulose Nanocrystals with Antioxidant Properties.

The interest in the development of novel biodegradable composites has increased over last years, and multilayer composites allow the design of materials with functionality and improved properties. In this work, bilayer structures based on a coated zein layer containing quercetin and cellulose nanocrystals (CNC) over an extruded poly(lactic acid) (PLA) layer were developed and characterized. Bilayer composites were successfully obtained and presented a total thickness of approx. 90 µm. The coated zein layer and quercetin gave a yellowish tone to the composites. The incorporation of the zein layer containing CNC decreased the volatile release rate during thermal degradation. Regarding to mechanical properties, bilayer composites presented lower brittleness and greater ductility evidenced by a lower Young's modulus and higher elongation values. Water permeability values of bilayer composites greatly increased with humidity and the zein coated layer containing quercetin increased this effect. Experimental data of quercetin release kinetics from bilayer structures indicated a higher release for an alcoholic food system, and the incorporation of cellulose nanocrystals did not influence the quercetin diffusion process.

Enhancing Thermal Stability and Bioaccesibility of Açaí Fruit Polyphenols through Electrohydrodynamic Encapsulation into Zein Electrosprayed Particles.

The açaí fruit (Euterpe oleracea Mart.) is well known for its high content of antioxidant compounds, especially anthocyanins, which provide beneficial health properties. The incorporation of this fruit is limited to food products whose processing does not involve the use of high temperatures due to the low thermal stability of these functional components. The objective of this work was the encapsulation of açaí fruit antioxidants into electrosprayed zein, a heat-resistant protein, to improve their bioavailability and thermal resistance. First, the hydroalcoholic açaí extract was selected due to its high polyphenolic content and antioxidant capacities, and, subsequently, it was successfully encapsulated in electrosprayed zein particles. Scanning electron microscopy studies revealed that the resulting particles presented cavities with an average size of 924 nm. Structural characterization by Fourier transform infrared spectroscopy revealed certain chemical interaction between the active compounds and zein. Encapsulation efficiency was approximately 70%. Results demonstrated the effectiveness of the encapsulated extract on protecting polyphenolic content after high-temperature treatments, such as sterilization (121 °C) and baking (180 °C). Bioaccesibility studies also indicated an increase of polyphenols presence after in vitro digestion stages of encapsulated açaí fruit extract in contrast with the unprotected extract.

Novel Antimicrobial Titanium Dioxide Nanotubes Obtained through a Combination of Atomic Layer Deposition and Electrospinning Technologies.

The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 µg/mL concentration.

Modifying an Active Compound's Release Kinetic Using a Supercritical Impregnation Process to Incorporate an Active Agent into PLA Electrospun Mats.

The main objective of this work was to study the release of cinnamaldehyde (CIN) from electrospun poly lactic acid (e-PLA) mats obtained through two techniques: (i) direct incorporation of active compound during the electrospinning process (e-PLA-CIN); and (ii) supercritical carbon dioxide (scCO2) impregnation of CIN within electrospun PLA mats (e-PLA/CINimp). The development and characterization of both of these active electrospun mats were investigated with the main purpose of modifying the release kinetic of this active compound. Morphological, structural, and thermal properties of these materials were also studied, and control mats e-PLA and e- PLA CO 2 were developed in order to understand the effect of electrospinning and scCO2 impregnation, respectively, on PLA properties. Both strategies of incorporation of this active compound into PLA matrix resulted in different morphologies that influenced chemical and physical properties of these composites and in different release kinetics of CIN. The electrospinning and scCO2 impregnation processes and the presence of CIN altered PLA thermal and structural properties when compared to an extruded PLA material. The incorporation of CIN through scCO2 impregnation resulted in higher release rate and lower diffusion coefficients when compared to active electrospun mats with CIN incorporated during the electrospinning process.