Immobilization of green tea extract on polypropylene films to control the antioxidant activity in food packaging

Effect of tea polyphenols on chitosan packaging for food preservation: Physicochemical properties, bioactivity, and nutrition

Chitosan packaging has been widely studied for food preservation, the application of which is expanded by the incorporation of tea polyphenols. This paper reviews the influence of tea polyphenols incorporation on chitosan-based packaging from the perspectives of physicochemical properties, bioactivity used for food preservation, and nutritional value. The physicochemical properties included optical properties, mechanical properties, water solubility, moisture content, and water vapor barrier property, concluding that the addition of tea polyphenols improved the opacity, water solubility, and water vapor barrier property of chitosan packaging, and the mechanical properties and water content were decreased. The bioactivity used for food preservation, that is antioxidant and antimicrobial properties, is enhanced by tea polyphenols, improving the preservation of food like meat, fruits, and vegetables. In the future, efforts will be needed to improve the mechanical properties of composite film and adjust the formula of tea polyphenols/chitosan composite film to apply to different foods. Besides, the identification and development of high nutritional value tea polyphenol/chitosan composite film is a valuable but challenging task. This review is expected to scientifically guide the application of tea polyphenols in chitosan packaging.

Nano-chitin: Preparation strategies and food biopolymer film reinforcement and applications

Current trends in food packaging systems are toward biodegradable polymer materials, especially the food biopolymer films made from polysaccharides and proteins, but they are limited by mechanical strength and barrier properties. Nano-chitin has great economic value as a highly efficient functional and reinforcing material. The combination of nano-chitin and food biopolymers offers good opportunities to prepare biodegradable packaging films with enhanced physicochemical and functional properties. This review aims to give the latest advances in nano-chitin preparation strategies and its uses in food biopolymer film reinforcement and applications. The first part systematically introduces various preparation methods for nano-chitin, including chitin nanofibers (ChNFs) and chitin nanocrystals (ChNCs). The nano-chitin reinforced biodegradable films based on food biopolymers, such as polysaccharides and proteins, are described in the second part. The last part provides an overview of the current applications of nano-chitin reinforced food biopolymer films in the food industry.

Fabrication and characterization of biodegradable active films with modified morphology based on polycaprolactone-polylactic acid-green tea extract

This research focused on developing an eco-friendly packaging for food products through blending polycaprolactone (PCL) and polylactic acid (PLA) as two biodegradable polymers, and green tea extract (GTE) as a natural antioxidant pushing the films toward active packaging; thereby, the morphological, mechanical, thermal, barrier, antioxidant, and biodegradation features of the composite films were analyzed. The films containing 30% PLA exhibited a reduction of 14.96%, 38.89%, 8.75%, and 35.55% in the hydrophilicity, water-solubility, water vapor permeability (WVP), and oxygen transition rate (OTR), respectively. Furthermore, GTE incorporation led to antioxidant behavior as well as better barrier properties (up to 6.25% decrease in WVP and 55.78% in OTR), mechanical properties (an increase of 14.96%, 38.89%, and 8.75% in elastic modulus, tensile strength, and elongation at break, respectively) and biodegradable rate (124.13%). Indeed, the presence of polyphenol compounds in green tea improved molecular interaction between the polymers and launched a co-continuous structure and an unparalleled level of compatibility, which was also approved by the changes in FTIR spectra of the PCL/PLA films. These results demonstrate the benefits of blending PLA with PCL and GTE integration in terms of operational enhancement and film activating, respectively, to provide reliable food packaging.

Integrating Antioxidant Functionality into Polymer Materials: Fundamentals, Strategies, and Applications

While antioxidants are widely known as natural components of healthy food and drinks or as additives to commercial polymer materials to prevent their degradation, recent years have seen increasing interest in enhancing the antioxidant functionality of newly developed polymer materials and coatings. This paper provides a critical overview and comparative analysis of multiple ways of integrating antioxidants within diverse polymer materials, including bulk films, electrospun fibers, and self-assembled coatings. Polyphenolic antioxidant moieties with varied molecular architecture are in the focus of this Review, because of their abundance, nontoxic nature, and potent antioxidant activity. Polymer materials with integrated polyphenolic functionality offer opportunities and challenges that span from the fundamentals to their applications. In addition to the traditional blending of antioxidants with polymer materials, developments in surface grafting and assembly via noncovalent interaction for controlling localization versus migration of antioxidant molecules are discussed. The versatile chemistry of polyphenolic antioxidants offers numerous possibilities for programmed inclusion of these molecules in polymer materials using not only van der Waals interactions or covalent tethering to polymers, but also via their hydrogen-bonding assembly with neutral molecules. An understanding and rational use of interactions of polyphenol moieties with surrounding molecules can enable precise control of concentration and retention versus delivery rate of antioxidants in polymer materials that are critical in food packaging, biomedical, and environmental applications.

Active Polypropylene-Based Films Incorporating Combined Antioxidants and Antimicrobials: Preparation and Characterization

Development of polypropylene (PP) films incorporating antioxidant-antimicrobial agents can inhibit microbial growth and reduce undesirable deteriorating reactions and can preserve the quality of food. This study was aimed to use a combination of sorbic acid (SA), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) to provide a synergistic effect at their reduced concentrations. A Combination of the additives was more effective in enhancing mechanical properties compared to their single state in film composition. The PP-2%SA-3%BHA film (T₃) had the highest tensile strength (17.9 MPa) and the lowest elongation at break (7.1%) than other films. The fourier-transform infrared (FTIR) proposed physical mixing of active additives within PP-matrix. Scanning electron microscopy showed uniform dispersion of the additives in PP-2%SA-1%BHT-1%BHA film (T₄) compared to others. BHT containing films decreased the storage and loss moduli leading to weakening of film viscoelastic behaviour and reducing film melting point. The prepared active films showed higher antioxidant activity than control PP-film following an order of T₄ > T₂ > T₃ corresponding to DPPH radical scavenging values of 89.1, 83.4 and 79.1%, respectively. All active films inhibited gram-negative and gram-positive bacteria growth. The results of this study indicated that the prepared active films possess desirable mechanical, thermal, antioxidant and antimicrobial properties enabling their use in food packaging.

Active packaging for Salmon stored at refrigerator with Polypropylene nanocomposites containing 4A zeolite, ZnO nanoparticles, and green tea extract

In this study, three types of Polypropylene-based (PP) films (two active nanocomposites and one control film) containing zinc oxide nanoparticles (ZnO NPs), 4A zeolite (4A Z), and green tea extract (GTE) were studied as modern active packaging's that can adjust the release of antimicrobial agents. The influence of PP nanocomposite with 3% (w/w) ZnO NPs/4A Z/GTE (treatment 1) and 6% (w/w) ZnO NPs/4A Z/GTE (treatment 2) on controlling microbial growth and preserving the sensory and chemical qualities of Salmon over nine days of storage at 4 ± 1°C was evaluated. The disk diffusion test revealed inhibition zones in the range of 10.98 ± 0.03 to 13.42 ± 0.01 m for treatments 1 and 2, respectively; the nanocomposite film with 6% ZnO NPs/4A Z/GTE had the highest antimicrobial effect against Gram-negative bacteria (p < .05). Chemical analysis revealed that the initial peroxide value of Salmon was 0.68 ± 0.0 mEq/kg, which increased by day 9 to 12.3 ± 0.03 mEq/kg in the control sample, but rising only to 9.9 ± 0.01 and 7.3 ± 0.02 mEq/kg in treatments 1 and 2, respectively (p < .05). The shelf life of Salmon given treatment 2 increased significantly to nine days relative to the control. Accordingly, these nanocomposite films are promising as new active packaging for preventing microbial growth and preserving the quality of salmon.

Polypropylene-MWCNT composite degradation, release, detection, and toxicity of MWCNT during accelerated aging

Nanomaterials (NM) are incorporated into polymers to enhance their properties. However, there are a limited number of studies on the aging of these nanocomposites and the resulting potential release of NM. To characterize NM at critical points in their life cycles, polypropylene (PP) and multiwall carbon nanotube filled PP (PP-MWCNT) plates with different thicknesses (from 0.25 mm to 2 mm) underwent accelerated weathering in a chamber that simulates solar irradiation and rainfall. The physicochemical changes of the plates depended on the radiation exposure, the plate thickness, and the presence of CNT fillers. Photodegradation increased with aging time, making the exposed surface more hydrophilic, decreasing the surface hardness and creating surface stress-cracks. Aged surface and cross-section showed crazing due to the polymer bond scission and the formation of carbonyls. The degradation was higher near the UV-exposed surface as the intensity of the radiation and oxygen diffusion decreased with increasing depth of the plates, resulting in an oxidation layer directly proportional to oxygen diffusion. Thus, sample thickness determines the kinetics of the degradation reaction and the transport of reactive species. Plastic fragments, which are less than 1 mm, and free CNTs were released from weathered MWCNT-PP. The concentrations of released NM that were estimated using ICP-MS, increased with prolonged aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability, were performed on the released CNTs. The toxicity of the released fragments and CNTs to A594 adenocarcinomic human alveolar basal epithelial cells was observed. The released polymer fragments and CNTs did not show significant toxicity under the experimental conditions in this study. This study will help manufacturers, users of consumer products with nanocomposites and policymakers in the development of testing guidelines, predictive models, and risk assessments and risk based-formulations of NM exposure.

Antimicrobial and Antioxidant Performance of Various Essential Oils and Natural Extracts and Their Incorporation into Biowaste Derived Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Layers Made from Electrospun Ultrathin Fibers

In this research, the antibacterial and antioxidant properties of oregano essential oil (OEO), rosemary extract (RE), and green tea extract (GTE) were evaluated. These active substances were encapsulated into ultrathin fibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from fruit waste using solution electrospinning, and the resultant electrospun mats were annealed to produce continuous films. The incorporation of the active substances resulted in PHBV films with a relatively high contact transparency, but it also induced a slightly yellow appearance and increased the films opacity. Whereas OEO significantly reduced the onset of thermal degradation of PHBV, both the RE and GTE-containing PHBV films showed a thermal stability profile that was similar to the neat PHBV film. In any case, all the active PHBV films were stable up to approximately 200 °C. The incorporation of the active substances also resulted in a significant decrease in hydrophobicity. The antimicrobial and antioxidant activity of the films were finally evaluated in both open and closed systems for up to 15 days in order to anticipate the real packaging conditions. The results showed that the electrospun OEO-containing PHBV films presented the highest antimicrobial activity against two strains of food-borne bacteria, as well as the most significant antioxidant performance, ascribed to the films high content in carvacrol and thymol. Therefore, the PHBV films developed in this study presented high antimicrobial and antioxidant properties, and they can be applied as active layers to prolong the shelf life of the foods in biopackaging applications.

Preparation and properties of polylactic acid-tea polyphenol-chitosan composite membranes

To study the properties of composite membranes consisting of polylactic acid (PLA), tea polyphenol (TP), and chitosan (CS), the stretch film method was employed to make PLA-TP- CS composite membranes of different concentrations. By testing the density, mechanical properties, heat-sealing performance, water vapor permeability, and solubility of the pure PLA membrane and the composite membranes, the comprehensive performance of the composite membranes were analyzed with regard to the actual use value. The results show that, compared with the pure PLA membrane, adding TP and CS significantly increases the heat-sealing strength, water vapor permeability, and solubility of the composite membrane. When the composite membrane is used for the preservation of cherries, it is found that the composite membrane with the mass ratio of TP to CS of 3:7 can decrease the rotting rate and mass loss rate significantly, postpone the consumption of soluble solids and vitamin C, maintain the quality of the cherries, and extend the shelf life, thus proving its potential for application in food packaging.

New Poly(lactic acid) Active Packaging Composite Films Incorporated with Fungal Melanin

In this work, fungal melanin was used for the first time to prepare poly(lactic acid)-based composites. The films of various melanin concentrations (0.025%, 0.05% and 0.2% w/w) were prepared using an extrusion method. The mechanical, antioxidant, antimicrobial, water vapor and UV-Vis barrier properties, as well as available polyphenolics on the surface, were studied. FT-IR and Raman spectroscopy studies were carried out to analyze the chemical composition of the resulting films. The hydrophobicity, color response, thermal, optical properties, and opacity values were also determined. The results of this study show that the addition of fungal melanin to poly(lactic acid) (PLA) as a modifier influenced mechanical and water vapor barrier properties depending on melanin concentration. In low concentration, melanin enhanced the mechanical and barrier properties of the modified films, but in larger amounts, the properties were decreased. The UV-Vis barrier properties of PLA/melanin composites were marginally improved. Differential Scanning Calorimetry (DSC) analysis indicated that crystallinity of PLA increased by the addition of melanin, but this did not affect the thermal stability of the films. Modified PLA/melanin films showed good antioxidant activity and were active against Enterococcus faecalis, Pseudomonas aeruginosa and Pseudomonas putida. The addition of melanin caused changes in color values, decreasing lightness and increasing the redness and yellowness of films. Based on the results of this study, fungal melanin has good potential to be exploited as a value-added modifier that can improve the overall properties of PLA.

Environmental aging and degradation of multiwalled carbon nanotube reinforced polypropylene

The degradation of polypropylene (PP) and PP-multiwalled carbon nanotube (PP-MWCNT) panels during environmental weathering resulted in an increased degree of crystallinity, making them brittle, and creating surface cracks. The degradation led to a breakdown of the panels and increased the potential for nanorelease. Thermal analysis revealed that the thickness of the test panels and reinforcement with MWCNTs had a significant influence on the stability of PP-MWCNT composites. Differential scanning calorimetry indicated that the MWCNTs acted as nucleation points, increasing the crystallization temperatures of PP-MWCNT, which reduced the extent of aging. Weathering decreased both the melting and crystallization temperatures of PP by as much as 20 o C. The reduction in the temperatures was inversely proportional to the thickness of the panels. The activation energy (E _a ) obtained using isoconversional kinetics of the TGA analysis showed that the effective thermo-oxidative degradations of PP changed during aging. The E _a for the initial stages of thermal degradation decreased from ~330 kJ/mol to ~100 kJ/mol for aged PP. During the late degradation stages, the E _a values increased to ~300 kJ/mol. These results suggest that early degradation were altered because of the changes in the molecular structure of the aged P and a shift in the degradation rate-limiting steps.

Functionalization of chitosan by a free radical reaction: Characterization, antioxidant and antibacterial potential

Chitosan was functionalized with epigallocatechin gallate (EGCG) by a free radical-induced grafting procedure, which was carried out by a redox pair (ascorbic acid/hydrogen peroxide) as the radical initiator. The successful preparation of EGCG grafted-chitosan was verified by spectroscopic (UV, FTIR and XPS) and thermal (DSC and TGA) analyses. The degree of grafting of phenolic compounds onto the chitosan was determined by the Folin-Ciocalteu procedure. Additionally, the biological activities (antioxidant and antibacterial) of pure EGCG, blank chitosan and EGCG grafted-chitosan were evaluated. The spectroscopic and thermal results indicate chitosan functionalization with EGCG; the EGCG content was 25.8mg/g of EGCG grafted-chitosan. The antibacterial activity of the EGCG grafted-chitosan was increased compared to pure EGCG or blank chitosan against S. aureus and Pseudomonas sp. (p<0.05). Additionally, EGCG grafted-chitosan showed higher antioxidant activity than blank chitosan. These results indicate that EGCG grafted-chitosan might be useful in active food packaging.

Enhanced antioxidant activity of polyolefin films integrated with grape tannins

BACKGROUND

A natural antioxidant derived from an agro-waste of the wine industry, grape tannin, was incorporated by melt blending into three different polyolefins (high-density polyethylene, linear low-density polyethylene and polypropylene) to introduce antioxidant functionality.

RESULTS

Significant antioxidant activity was observed at 1% tannin inclusion in all polymer blends. The antioxidant activity was observed to increase steadily with a greater concentration of grape tannins, the highest increases being seen with polypropylene. The mechanical and thermal properties of the polymer films following antioxidant incorporation were minimally altered with up to 3% grape tannins. All of the polyolefin-grape tannin films successfully passed the leachability test following USP661 standard protocol.

CONCLUSION

Superior antioxidant activity was established in polyolefin thin films by utilization of a bulk grape extract obtained from winery waste. Significant increases in antioxidant activity were seen with 1% extract inclusion. This not only demonstrates the potential for food packaging applications of the polyolefin blends, but also valorizes the agro-waste. © 2015 Society of Chemical Industry.

Development of antioxidant active films containing sodium ascorbate (SA) and ethylene vinyl alcohol (EVOH) to extend the shelf life of peanut

In this study, low-density polyethylene (LDPE) containing oxygen scavenger based on sodium ascorbate (SA) and ethylene vinyl alcohol (EVOH) at 5, 10 and 15 % concentrations were produced through extrusion method. In addition, the effect of size of SA, thickness LDPE (7.5, 15, 30 and 45 μm), and number of layers (monolayer, two-layers, three-layers and four-layers) were investigated. Oxygen and water vapor permeability, tensile stress, SA migration and antioxidant activity, thermal stability, scan electron microscopy (SEM), and FT-IR of the films were measured. Moreover, the performance of produced films to prevent of oxidation of packaged peanuts during storage at 40 °C was studied. The results revealed that the active films containing SA (especially at 10 % SA) present suitable performance and features to increase the shelf-life of peanuts.

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

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

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

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