Antioxidants Release from Solvent-Cast PLA Film: Investigation of PLA Antioxidant-Active Packaging

The release study of natural antioxidants, i.e., ascorbyl palmitate and α-tocopherol, and synthetic phenolic antioxidants including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate, and tert-butylhydroquinone (TBHQ) from polylactic acid (PLA) film into food simulants were accomplished. PLA antioxidant films were placed in contact with 95, 50, and 10 % ethanol at 40 and 20 °C. Released antioxidants were regularly measured by high-performance liquid chromatography system for 60 days. Ascorbyl palmitate was completely degraded during film preparation and is not a suitable antioxidant for PLA antioxidant-active packaging. The diffusion coefficient (D) and partition coefficient (K) of antioxidants were calculated based on obtained data. Diffusion of the antioxidants from PLA to the simulants showed a Fick’s behavior with the diffusion coefficient (D) value between 10^?9 and 10^?11 cm² s^?1 with 0–100 % of release. Faster and higher release of antioxidants occurred at 40 °C according to Arrhenius law. At 40 °C, TBHQ in 95 % ethanol decomposed to 2-tert-butyl-1,4-benzoquinone and other quinone derivatives, and α-tocopherol in 50 % ethanol decomposed to some unknown neoformed compounds. Antioxidants molecular weight, Log P, simulant polarity, and temperature were the most influencing factors on antioxidants release rate from PLA films in contact with food simulants. The D and K coefficients of studied antioxidants from PLA in three food simulants and two temperatures can be used to create PLA antioxidant-active packaging to continually control the oxidation reactions in diverse foodstuffs to ensure higher food qualities. The PLA antioxidant-active packaging approach also permits to reduce the amounts of directly added antioxidants in foods to provide safer foods.     

Controlled Release System by Active Gelatin Film Incorporated with β-Cyclodextrin-Thymol Inclusion Complexes

Essential oils such as thymol are added to food packaging film to obtain active films with antimicrobial and antioxidant properties. However, thymol is insoluble in water, and release rate of thymol is usually too fast. Therefore, a need exists to increase thymol solubility and to deliver thymol in a controlled manner from film matrix to food surface. In this study, spray dried inclusion complexes of β-cyclodextrin/thymol (1:1 molar ratio) was incorporated into gelatin solution to obtain active gelatin films. Both inclusion complexes and active films showed sustained release of thymol. Physical properties and thymol release kinetics were evaluated for active films. For gelatin films with 8.25% (mass ratio) inclusion complexes, complete thymol release took 235 h, compared with 38 h for thymol release from inclusion complexes. The diffusion coefficient reached 2.04?×?10^?15 m² s^?1.     

The Release of Carotenoids from a Light-Protected Antioxidant Active Packaging Designed to Improve the Stability of Soybean Oil

An antioxidant active packaging was developed by coextruding two layers of high-density polyethylene (HDPE). Bags were made with the film in which the inner layer, designed to be in contact with food, contained marigold flower (Tagetes erecta) extract rich in carotenoids. The outer layer of the film was added with titanium dioxide (TiO₂) to decrease the effect of commercial lighting on the degradation of carotenoids. Four bilayer films were produced: added with TiO₂ and carotenoids, added with carotenoids, added with TiO₂, and with no additives at all (control film). Degradation of color and astaxanthin in the films was delayed by the addition of the TiO₂ when they were stored under commercial lighting at 25 °C. Bags made of these films produced an improvement on the soybean oil stability at 25 °C as a result of a synergic effect of light protection by TiO₂ and carotenoids release. This release was measured as diffusion coefficients of carotenoids from the films toward soybean oil at 10, 25, and 40 °C (2.10–19.26?×?10^?11 cm² s^?1) with activation energy of 53.66 kJ mol^?1. In conclusion, the combination of the two layers of HDPE added with TiO₂ and carotenoids introduced opacity and permitted to extend the active effect of the films in contact with soybean oil. Moreover, the effect of temperature on the diffusion of carotenoids showed that this new active packaging is able to exert its function in conditions of transport, storage, and commercialization of food.     

Effect of temperature,pH and film thickness on nisin release from antimicrobial whey protein isolate edible films

BACKGROUND: An active packaging film based on whey protein isolate (WPI) was developed by incorporating nisin to promote microbial food safety. The effect of temperature and pH on the release of nisin from edible films of different thickness was investigated. The film mechanical properties and inhibitory effect were also evaluated. RESULTS: Nisin release was significantly favoured by low pH, with the highest release after 24 h (1325 IU), which was not significantly affected by temperature (5 or 10 °C). Thickness significantly affected film elongation, with thicker films showing the highest elongation (54.3 ± 2.7%). Water vapour permeability (0.15 ± 0.4 g mm m^?2 kPa^?1 h^?1) and elastic modulus were not significantly affected by thickness. The highest nisin effective diffusivity (5.88 × 10^?14 m² s^?1) was obtained using a solution at pH 4, 112 µm film thickness and a temperature of 5 °C. More than four log cycles of Brochotrix thermosphacta were reduced from the surface of a ham sample after 8 days of incubation at 4 °C by the active WPI film containing 473 IU cm^?2 nisin. CONCLUSION: Nisin diffusivity from WPI edible films was favoured at lower pH and film thickness. This active packaging film may be used to preserve the quality and safety of meat products. Copyright © 2009 Society of Chemical Industry     

Effects of nano‐clay type and content on the physical properties of sesame seed meal protein composite films

Sesame seed meal protein (SSMP)/nano‐clay composite films were prepared, and the physical properties of the films were determined. The SSMP film was prepared with 5 g of SSMP and 2 g of glycerol in 100 mL of film‐forming solution, and the tensile strength (TS), elongation (E) and water vapour permeability (WVP) of the SSMP film were 2.51 MP, 21.84% and 3.23 × 10^?9 g m m^?2s^?1 Pa^?1, respectively. Two types of nano‐clays were incorporated to enhance the physical properties of the SSMP film. The TSs of the SSMP film with 5% Cloisite Na⁺ and 7% Cloisite 10A were 6.32 and 5.76 MPa, respectively, and the WVPs of the SSMP nanocomposite films were 2.04 × 10^?9 g m m^?2s^?1 Pa^?1 compared with the SSMP film without nano‐clay, which was 3.23 × 10^?9 g m m^?2s^?1 Pa^?1. Therefore, these results indicate that the SSMP nanocomposite film can be applied in food packaging.     

Release Kinetics of Nisin from Chitosan–Alginate Complex Films

Understanding the release kinetics of antimicrobials from polymer films is important in the design of effective antimicrobial packaging films. The release kinetics of nisin (30 mg/film) from chitosan–alginate polyelectric complex films prepared using various fractions of alginate (33%, 50%, and 66%) was investigated into an aqueous release medium. Films containing higher alginate fractions showed significantly lower (P < 0.05) degree of swelling in water. Total amount of nisin released from films into an aqueous system decreased significantly (P < 0.05) with an increase in alginate concentration. The mechanism of diffusion of nisin from all films was found to be Fickian, and diffusion coefficients varied from 0.872 × 10^?9 to 8.034 ×10^?9 cm²/s. Strong complexation was confirmed between chitosan and alginate polymers within the films using isothermal titration calorimetry and viscosity studies, which affects swelling of films and subsequent nisin release. Complexation was also confirmed between nisin and alginate, which limited the amount of free nisin available for diffusion from films. These low‐swelling biopolymer complexes have potential to be used as antimicrobial packaging films with sustained nisin release characteristics.     

Migration analysis,antioxidant, and mechanical characterization of polypropylene-based active food packaging films loaded with BHA,BHT, and TBHQ

Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at < 2%, BHT at > 2%, and TBHQ at all added concentrations significantly reduced elongation at break (E_b) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower E_b and TS values, higher WVP, and greater migration).     

Antioxidant migration resistance of SiOx layer in SiOx/PLA coated film

As novel materials for food contact packaging, inorganic silicon oxide (SiO_x) films are high barrier property materials that have been developed rapidly and have attracted the attention of many manufacturers. For the safe use of SiO_x films for food packaging it is vital to study the interaction between SiO_x layers and food contaminants, as well as the function of a SiO_x barrier layer in antioxidant migration resistance. In this study, we deposited a SiO_x layer on polylactic acid (PLA)-based films to prepare SiO_x/PLA coated films by plasma-enhanced chemical vapour deposition. Additionally, we compared PLA-based films and SiO_x/PLA coated films in terms of the migration of different antioxidants (e.g. t-butylhydroquinone [TBHQ], butylated hydroxyanisole [BHA], and butylated hydroxytoluene [BHT]) via specific migration experiments and then investigated the effects of a SiO_x layer on antioxidant migration under different conditions. The results indicate that antioxidant migration from SiO_x/PLA coated films is similar to that for PLA-based films: with increase of temperature, decrease of food simulant polarity, and increase of single-sided contact time, the antioxidant migration rate and amount in SiO_x/PLA coated films increase. The SiO_x barrier layer significantly reduced the amount of migration of antioxidants with small and similar molecular weights and similar physical and chemical properties, while the degree of migration blocking was not significantly different among the studied antioxidants. However, the migration was affected by temperature and food simulant. Depending on the food simulants considered, the migration amount in SiO_x/PLA coated films was reduced compared with that in PLA-based films by 42–46%, 44–47%, and 44–46% for TBHQ, BHA, and BHT, respectively.     

Modelling natamycin release from alginate/chitosan active films

In antimicrobial active films, the active agent is incorporated in the polymeric matrix and is released from the film to the product surface where most deterioration processes take place. In this study, films structured solely by alginate and by blends of alginate:chitosan (82.5:17.5 and 65:35) were obtained by casting. The film formulations received natamycin (4 and 8 g/100 g biopolymer) as antimicrobial agent. Films were characterised according to their thickness and morphology. Diffusion experiments in water indicated very slow release kinetics of the antimicrobial, being markedly hindered in the alginate and chitosan composite films, probably due to electrostatic interactions between chitosan and natamycin. Fickian diffusion prevailed and the diffusion coefficients found for the films varied from 2.6 × 10^?11 to 2.5 × 10^?12 cm² s^?1.     

Biocomposite Films Based on κ-Carrageenan/Locust Bean Gum Blends and Clays: Physical and Antimicrobial Properties

The aims of this work were to evaluate the physical and antimicrobial properties of biodegradable films composed of mixtures of κ-carrageenan (κ-car) and locust bean gum (LBG) when organically modified clay Cloisite 30B (C30B) was dispersed in the biopolymer matrix. Film-forming solutions were prepared by adding C30B (ranging from 0 to 16 wt.%) into the κ-car/LBG solution (40/60 wt.%) with 0.3 % (w/v) of glycerol. Barrier properties (water vapour permeability, P _vapour; CO₂ and O₂ permeabilities), mechanical properties (tensile strength, TS, and elongation-at-break, EB) and thermal stability of the resulting films were determined and related with the incorporation of C30B. Also, X-ray diffraction (XRD) was done in order to investigate the effect of C30B in film structure. Antimicrobial effects of these films against Listeria monocytogenes, Escherichia coli and Salmonella enterica were also evaluated. The increase of clay concentration causes a decrease of P _vapour (from 5.34?×?10^?11 to 3.19?×?10^?11 g (m s?Pa)^?1) and an increase of the CO₂ permeability (from 2.26?×?10^?14 to 2.91?×?10^?14 g (m s?Pa)^?1) and did not changed significantly the O₂ permeability for films with 0 and 16 wt.% C30B, respectively. Films with 16 wt.% clay exhibited the highest values of TS (33.82 MPa) and EB (29.82 %). XRD patterns of the films indicated that a degree of exfoliation is attained depending on clay concentration. κ-car/LBG–C30B films exhibited an inhibitory effect only against L. monocytogenes. κ-car/LBG–C30B composite films are a promising alternative to synthetic films in order to improve the shelf life and safety of food products.     

Novel Intact Bitter Cassava: Sustainable Development and Desirability Optimisation of Packaging Films

Novel biomaterials and optimal processing conditions are fundamental in low-cost packaging material production. Recently, a novel biobased intact bitter cassava derivative was developed using an intrinsic, high-throughput downstream processing methodology (simultaneous release recovery cyanogenesis). Processing of intact bitter cassava can minimise waste and produce low-cost added value biopolymer packaging films. The objective of this study was to (i) develop and characterise intact bitter cassava biobased films and (ii) determine the optimal processing conditions, which define the most desirable film properties. Films were developed following a Box-Behnken design considering cassava (2, 3, 4 % w/v), glycerol (20, 30, 40 % w/w) and drying temperature (30, 40, 50 °C) and optimised using multi-response desirability. Processing conditions produced films with highly significant (p?<?0.05) differences. Developed models predicted impact of processing conditions on film properties. Desirable film properties for food packaging were produced using the optimised processing conditions, 2 % w/v cassava, 40.0 % w/w glycerol and 50 °C drying temperature. These processing conditions produced films with 0.3 %; transparency, 3.4 %; solubility, 21.8 %; water-vapour-permeability, 4.2 gmm/m²/day/kPa; glass transition, 56 °C; melting temperature, 212.6 °C; tensile strength, 16.3 MPa; elongation, 133.3 %; elastic modulus, 5.1 MPa and puncture resistance, 57.9 J, which are adequate for packaging applications. Therefore, intact bitter cassava is a viable material to produce packaging films that can be tailored for specific sustainable, low-cost applications.     

The Potential Application of Antimicrobial Silver Polyvinyl Chloride Nanocomposite Films to Extend the Shelf-Life of Chicken Breast Fillets

Silver (Ag) nanoparticles (NPs) were synthesised and characterised, and their antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Pseudomonas fluorescens and microflora derived from raw chicken, beef or cooked ham was determined. Polyvinyl chloride (PVC) films or antimicrobial Ag/PVC nanocomposite films were manufactured via a solvent casting method and the mechanical and thermal properties of these materials determined. Manufactured antimicrobial Ag/PVC nanocomposite films were used to wrap chicken breast fillets, followed by modified atmosphere packaging (using conventional laminates and employing a gas mix of 60 % N₂/40 % CO₂), and compared against PVC control films. In general, Gram-negative bacteria were more sensitive to Ag NPs than Gram-positive bacteria and microflora isolated from meat products were more resistant than pure culture bacteria. However, the most sensitive bacteria to Ag NPs were Pseudomonas fluorescens. No significant differences (p?>?0.05) in tensile strength and elongation at break were observed, but glass transition temperatures (T _g) of Ag/PVC nanocomposite films were lower (p?<?0.05) when compared to PVC control films. Results also indicated that antimicrobial Ag/PVC nanocomposite films significantly (p?<?0.05) extended the shelf-life of chicken breast fillets and reduced lipid oxidation of chicken breast fillets compared to PVC-wrapped equivalents. Overall, results indicated that antimicrobial Ag/PVC nanocomposite films can potentially be used as antimicrobial packaging for food packaging applications.     

Direct FTIR Analysis of Free Fatty Acids in Edible Oils Using Disposable Polyethylene Films

To simplify a previously reported Fourier transform infrared (FTIR) method for the direct determination of free fatty acid (FFA), a new technique was designed to facilitate mid-FTIR transmission analysis of viscous edible oil samples using disposable polyethylene (PE) films as a spectral acquisition accessory. In the PE-film-based procedures, the viscosities of oil samples were reduced by mixing hexane for allowing the samples to readily deposit onto PE films to form oil films when the solvent evaporated (PE film as spectral background), and the path length of each oil film was normalized to a fixed path length of 0.15 mm. The relationship between FFA content (expressed as percentage of oleic acid) and the absorbance of FFA at 1711 cm^?1 relative to a baseline at 1600 cm^?1 (baseline was 1600 cm^?1) in thenormalized spectra was expressed by a linear calibration equation. To remit the interference from the absorbance due to triglyceride esters (approximately 1,746 cm^?1) in the wave numbers used in FFA determination (1,711 cm^?1), the intensity of the first overtone of the ester vibration (3,471 cm^?1/3,527 cm^?1) in FFA-free oil samples was used to determine the intensity of the interfering signal at 1,711 cm^?1. Moreover, a linear relationship between the two absorbances was established. Consequently, the absorbance measured at 1,711 cm^?1/1,600 cm^?1 by FFA determination in the oil samples was corrected for the linear equation. FFA determination in oil samples with known FFA content (0 to 3 %) was carried out in parallel by using the American Oil Chemists’ Society titrimetric method and the PE-film-based FTIR procedures. A comparison indicated that the PE-film-based FTIR method can be used to determine FFA content in different kinds of edible oils.     

Diffusion of Acetic and Propionic Acids from Chitosan-based Antimicrobial Packaging Films

The diffusion of acetic or propionic acids from thin (44 to 54 μm) chitosan‐based antimicrobial packaging films in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7, 6.4, or 7.0) and temperature (4 °C, 10 °C, or 24 °C) on diffusion were investigated. The kinetics of acetic‐ and propionic‐acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in the range of values tested, but a decrease in temperature from 24 °C to 4 °C resulted in a reduction of diffusion coefficients from 2.59 × 10^?12 m².s^?1 to 1.19 × 10^?12 m².s^?1 for acetic acid and from 1.87 × 10^?12 m².s^?1 to 0.91 × 10^?12 m².s^?1 for propionic acid. The effect of temperature on diffusion was well (r² > 0.9785) described by an Arrhenius‐type model with activation energies of 27.19 J.mole^?1 (acetic) and 24.27 J.mole^?1 (propionic). Incorporation of lauric acid or essential oils (cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in the diffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehyde incorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.     

Effects of Interactions between the Constituents of Chitosan-Edible Films on Their Physical Properties

The main objective of this work was to evaluate the effect of chitosan and plasticizer concentrations and oil presence on the physical and mechanical properties of edible films. The effect of the film constituents and their in-between interactions were studied through the evaluation of permeability, opacity and mechanical properties. The effects of the studied variables (concentrations of chitosan, plasticizer and oil) were analysed according to a 2³ factorial design. Pareto charts were used to identify the most significant factors in the studied properties (water vapour, oxygen and carbon dioxide permeability; opacity; tensile strength; elongation at break and Young’s modulus). When addressing the influence of the interactions between the films’ constituents on the properties above, results show that chitosan and plasticizer concentrations are the most significant factors affecting most of the studied properties, while oil incorporation has shown to be of a great importance in the particular case of transport properties (gas permeability), essentially due to its hydrophobicity. Water vapour permeability values (ranging from 1.62?×?10^?11 to 4.24?×?10^?11 g m^?1 s^?1 Pa^?1) were half of those reported for cellophane films. Also the mechanical properties (tensile strength values from 0.43 to 13.72 MPa and elongation-at-break values from 58.62% to 166.70%) were in the range of those reported for LDPE and HDPE. Based on these results, we recommend the use of 1.5% (w/w) chitosan concentration to produce films, where the oil and plasticizer proportions will have to be adjusted in a case-by-case basis according to the use intended for the material. This work provides a useful guide to the formulation of chitosan-based film-forming solutions for food packaging applications.     

Antimicrobial Polylactic Acid Packaging Films against Listeria and Salmonella in Culture Medium and on Ready-to-Eat Meat

The contamination of Listeria monocytogenes and Salmonella spp. in ready-to-eat (RTE) meat products has been a concern for the meat industry. In this study, edible chitosan-acid solutions incorporating lauric arginate ester (LAE), sodium lactate (NaL), and sorbic acid (SA) alone or in combinations were developed and coated on polylactic acid (PLA) packaging films. Antimicrobial effects of coated PLA films on the growth of Listeria innocua, L. monocytogenes, and Salmonella Typhimurium in a culture medium (tryptic soy broth, TSB) and on the surface of meat samples were investigated. Antimicrobial PLA films containing 1.94 mg/cm² of chitosan and 1.94 μg/cm² of LAE were the most effective against both Listeria and Salmonella in TSB and reduced them to undetectable level (<0.69 log CFU/ml). The same PLA films with LAE significantly (p?L. innocua, L. monocytogenes, and S. Typhimurium on RTE meat during 3 and 5 weeks’ storage at 10 °C, achieving 2–3 log reduction of Listeria and 1–1.5 log reduction of Salmonella as compared with controls. PLA films coated with 1.94 mg/cm² of chitosan, 0.78 mg/cm² of NaL, and 0.12 mg/cm² of SA significantly reduced the growth of L. innocua but were less effective against Salmonella. The combination of NaL (0.78 mg/cm²) and SA (0.12 mg/cm²) with LAE (1.94 μg/cm²) did not generate additional or synergetic antimicrobial effect against Listeria or Salmonella on the meat surface. L. innocua had a similar sensitivity to the film treatments as L. monocytogenes, suggesting that L. innocua may be used as a surrogate of L. monocytogenes for further scaleup and validation studies. The film treatments were more effective against the microorganisms in TSB culture medium than in RTE meat, which suggests that in vivo studies are a necessary step to develop antimicrobial packaging for applications in foods.     

Diffusion behaviour of the acetaldehyde scavenger 2-aminobenzamide in polyethylene terephthalate for beverage bottles

Polyethylene terephthalate (PET) bottles are widely used as packaging material for natural mineral water. However, trace levels of acetaldehyde can migrate into natural mineral water during the shelf life and might influence the taste of the PET bottled water. 2-Aminobenzamide is widely used during PET bottle production as a scavenging agent for acetaldehyde. The aim of this study was the determination of the migration kinetics of 2-aminobenzamide into natural mineral water as well as into 20% ethanol. From the migration kinetics, the diffusion coefficients of 2-aminobenzamide in PET at 23 and 40°C were determined to be 4.2 × 10^?16 and 4.2 × 10^?15 cm² s^–1, respectively. The diffusion coefficient for 20% ethanol at 40°C was determined to be 7.7 × 10^?15 cm² s^–1, which indicates that 20% ethanol is causing swelling of the PET polymer. From a comparison of migration values between 23 and 40°C, acceleration factors of 9.7 when using water as contact medium and 18.1 for 20% ethanol as simulant can be derived for definition of appropriate accelerated test conditions at 40°C. The European Union regulatory acceleration test based on 80 kJ mol^–1 as conservative activation energy overestimates the experimentally determined acceleration rates by a factor of 1.6 and 3.1, respectively.     

Kinetic Study of the Quenching Reaction of Singlet Oxygen by Common Synthetic Antioxidants (tert-Butylhydroxyanisol, tert-di-Butylhydroxytoluene, and tert-Butylhydroquinone) as Compared with α-Tocopherol

ABSTRACT: Effects of synthetic phenolic antioxidants (BHA, BHT, and TBHQ) on the methylene blue (MB) sensitized photooxidation of linoleic acid as compared with that of α‐tocopherol have been studied. Their antioxidative mechanism was studied by both ESR spectroscopy in a 2,2,6,6‐tetramethylpiperidone (TMPD)‐methylene blue (MB) system and spectroscopic analysis of rubrene oxidation induced by a chemical source of singlet oxygen. Total singlet oxygen quenching rate constants (k_ox?Q+k_q) were determined using a steady state kinetic equation. TBHQ showed the strongest protective activity against the MB sensitized photooxidation of linoleic acid, followed by BHA and BHT. TBHQ (1 × 10^?3 M) exhibited 86.5% and 71.4% inhibition of peroxide and conjugated diene formations, respectively, in linoleic acid photooxidation after 60‐min light illumination. The protective activity of TBHQ against the photosensitized oxidation of linoleic acid was almost comparable to that of α‐tocopherol. The data obtained from ESR and rubrene oxidation studies clearly showed the strong singlet oxygen quenching ability of TBHQ. The k_ox?Q+k_q of BHA, BHT, and TBHQ were determined to be 3.37 × 10⁷, 4.26 × 10⁶, and 1.67 × 10⁸ M^?1 s^?1, respectively. The k_ox?Q+k_q of TBHQ was within the same order of magnitude of that of α‐tocopherol, a known efficient singlet oxygen quencher. There was a high negative correlation (r² = ?0.991) between log (k_ox?Q+k_q) and reported oxidation potentials for the synthetic antioxidants, indicating their charge‐transfer mechanism for singlet oxygen quenching. This is the 1st report on the kinetic study on k_ox?Q+k_q of TBHQ in methanol as compared with other commonly used commercial synthetic antioxidants and α‐tocopherol.     

Release property and antioxidant effectiveness of tocopherol-incorporated LDPE/PP blend films

Low-density polyethylene (LDPE)/polypropylene (PP) blend films in various blending ratios containing 3000?mg?kg^?1 of tocopherol were manufactured by an extrusion process. Tocopherol release properties were characterised and correlated with antioxidant effectiveness in retarding the oxidation of linoleic acid contacting the films at 40°C. The conditions without tocopherol (control) and with instant tocopherol addition corresponding to the amount included in the films were also prepared and compared with the film-contacting solutions. The effect of tocopherol inclusion and the blending ratio on their physical properties was also examined. A wide range of tocopherol diffusivity in 6.6?×?10^?16–4.6?×?10^?14?m^2?s^?1 were obtained by blend films. As PP content increases, the diffusivity decreased sharply at the beginning and levelled off later. The slower release of tocopherol in LDPE/PP blend films corresponding to lower tocopherol diffusivity retained the higher tocopherol concentration in the linoleic acid system providing better antioxidant effectiveness of the extended induction period in oxidation. The tocopherol inclusion reduced tensile strength and transparency significantly in an affordable range with higher tensile strength given by a higher PP ratio. LDPE/PP blending can be a useful tool to modulate the release profile of tocopherol and thus the antioxidant effectiveness of the tocopherol-incorporated antioxidant packaging film.