Physicochemical and thermal characterization of poly (3-hydroxybutyrate-co-4-hydroxybutyrate) films incorporating thyme essential oil for active packaging of white bread

Enhancing the antioxidant properties and compatibility of protein/sodium alginate film by incorporating Zanthoxylum bungeanum essential oil Pickering emulsion

Zanthoxylum bungeanum essential oil (ZBEO) Pickering emulsion was incorporated into rice protein (RP)/sodium alginate (SA)-based film to enhance the antioxidant activity and compatibility. With increasing ZBEO content from 2 % to 4 %, the average size of ZBEO Pickering emulsion ranged from 124.28 to 165.65 nm. The best mechanical property with a tensile strength of 14.56 MPa and hydrophobicity with a water vapor permeability of 2.11 × 10-12 g⋅cm-1⋅s-1⋅Pa-1 of emulsion film were achieved with 0.8 % ZBEO. In addition, the loss of ZBEO in the emulsion films was reduced by 11-14 %. The DPPH radical scavenging activity of emulsion film with 1.2 % ZBEO was 65.54 % in 95 % ethanol. The results of Fourier transform infrared spectroscopy and molecular dynamics simulation showed that electrostatic interactions played a leading role in film formation. Overall, ZBEO Pickering emulsion is an effective method to enhance the antioxidant activity, mechanical strength and hydrophobicity of RP/SA film.

Physicochemical and thermal characterization of the edible shellac films incorporated with oleic acid to enhance flexibility, water barrier and retard aging

In this work, shellac plasticized with oleic acid was solvent cast to prepare the flexible and water-resistant film for packaging applications. The films were prepared with varying amounts of oleic acid and studied in detail for appearance, surface morphology, thermal, chemical, barrier, mechanical, and robustness. The surface morphology confirmed the smooth surface of films up to SH-OA20 (100:20 w/w; shellac: oleic acid). Fourier-transform infrared spectroscopy confirmed that oleic acid reduced the hydrogen bonding of the shellac matrix to provide a plasticization effect. Also, the thermal analysis showed a reduction in the melting enthalpy. Moreover, the plasticized films had a better barrier to water vapor due to increased smoothness and reduction in brittleness. Adding oleic acid also increased the elongation at break up to 40 % without any changes in tensile strength. The flexibility of the films increased with the oleic acid content, making them resistant to burst, crumbling, bending, rolling, and stretching. Oleic acid also showed the retardation of aging and thermal aging of shellac. In the future, the long-term stability and migration of the films can be investigated.

Synergistic effects of thyme and oregano essential oil combinations for enhanced functional properties of sericin/pectin film

This work aimed to assess the synergistic antibacterial effects of thyme and oregano essential oils in various ratios (thyme:oregano; 10:0, 8:2, 6:4, 4:6, 2:8, 10:0). We hypothesized that the synergistic combination of thyme and oregano essential oils can be effectively incorporated into sericin/pectin film to enhance its functional properties. Among the combinations tested, the mixture of thyme/oregano essential oil (TOE) at an 8:2 ratio exhibited the most potent synergistic activity against P. aeruginosa and S. aureus, with fractional inhibitory concentration index (FICindex) of 0.9. In this combination, thymol constituting 51.83 % of TOE (8:2), was the predominant component. TOE at an 8:2 ratio was selected to incorporate into sericin/pectin film. Different concentrations of TOE (0.8 %, 1.2 % and 1.6 %) were applied to evaluate their impact on film properties compared to a film without essential oil (control). It was found that increasing TOE concentration (control; 0 %) to 1.6 % reduced film moisture content (from 21.53 % to 16.91 %), decreased yellowness (from 18.24 to 15.92), diminished gloss (from 63.79 to 11.18), lowered swelling index (from 1.24 to 0.98), and reduced tensile strength (from 9.70 to 4.14 MPa). However, the addition of TOE showed higher film total phenolic content (8.59-31.53 mg gallic acid/g dry sample) and increased antioxidant activity (0.99-3.68 μmol Trolox /g dry sample). Moreover, the film with 1.2 % and 1.6 % of thyme/oregano essential oil exhibited inhibitory effects against all tested bacteria. Therefore, the thyme/oregano essential oil combination can provide the desirable physicochemical properties of the sericin/pectin film, as well as its antibacterial and antioxidant activities, making it a promising alternative for food packaging material applications.

Preparation and properties of films loaded with cellulose nanocrystals stabilized Thymus vulgaris essential oil Pickering emulsion based on modified tapioca starch/polyvinyl alcohol

Pickering emulsions were prepared by stabilizing thymus vulgaris essential oil (TEVO) with cellulose nanocrystals (CNCs), which formed composite films by loading the emulsions into modified tapioca/polyvinyl alcohol (PVA)-based films. The results showed that the 1.0 % CNCs-15 % TEVO emulsion had optimal stability and smaller particle size. The emulsion increased the thickness of the composite film in the form of solid material additions (thickness, 0.062-0.099 mm), which opacity given the laminating film's superior UV-blocking ability compared to blank film. The emulsion plasticizing effect enhanced the film's elongation at break (EAB, 123-159 %). In addition, due to the hydrophobicity and influencing the diffusion path of water molecules in the emulsion, the denser microstructure composite film had a lower water vapor transmission coefficient (WVP, 6.22 × 10-11-5.35 × 10-11g∙cm/cm2∙s∙Pa) to impede moisture penetration. Meanwhile, the composite film can effectively maintain the color and inhibit the growth of microorganisms to extend the storage time of fish fillets.

Soy protein isolate film activated by black seed oil nanoemulsion as a novel packaging for shelf-life extension of bulk bread

This paper investigates the addition of lecithin-emulsified black seed oil (BSO) nanoemulsions (LNEO) and whey protein isolate-stabilized Pickering emulsions (WPEO) to soy protein isolate (SPI)-based films and their effect on improving the shelf life of bread slices. The half-life of antioxidant activity, water vapor permeability, biodegradability, density, color difference, and film thickness significantly increased (p < .05) when BSO was added. However, the incorporation of BSO significantly reduced the solubility, tensile strength, strain to break (except for WPEO), and transparency (p < .05) of the samples. The interaction between SPI film and BSO-loaded nanocarriers, as well as the morphological properties of films, was evaluated using FT-IR and FE-SEM. SPI-based films containing LNEO-5% and WPEO-5% were selected based on their mechanical and barrier properties. The effect of films on the shelf life of bread slices was investigated for 17 days of storage. LNEO samples obtained the most acceptable results in the bread in terms of sensory evaluation and color properties. According to the results, bread slices packed in SPI film containing LNEO-5% showed no signs of mold growth until the 17th day of storage, whereas the sample packed in a low-density polyethylene bag began to corrupt on the 6th day. This study highlights the potential of BSO-loaded SPI films as a novel active packaging for the bakery industry.

Effects of antimicrobial nanocomposite films packaging on the postharvest quality and spoilage bacterial communities of mushrooms (Chanterelles)

Poly (lactic acid) (PLA) composite films with the addition of mesoporous silica nanoparticles MSN (0, 2, 4 and 6 wt%) loaded with 10 wt% citral (CIT) were prepared for application in Chanterelles packaging. Composite films with added MSN/CIT showed good mechanical properties, especially 4MSN/CIT/PLA. Changes in physicochemical properties and bacterial flora of Chanterelles during packaging and storage were tested. Compared with CIT/PLA, Chanterelles packed with 4MSN/CIT/PLA showed about 1.62-times lower browning value, 1.53-times lower electrolyte permeability, and 1.83- and 1.78-times lower PPO and POD, respectively, at 12 day. Better physicochemical properties of Chanterelles can be maintained. For bacterial flora changes, Chanterelles packaged with 4MSN/CIT/PLA had more stable flora (p < 0.05) and lower species diversity during storage (p < 0.05), effectively controlling the growth and reproduction of their dominant spoilage bacteria (Enterobacteriaceae spp). In conclusion, the composite membranes obtained by the addition of MSN/CIT to PLA have great potential in the storage of Chanterelles.

Innovative Biobased and Sustainable Polymer Packaging Solutions for Extending Bread Shelf Life: A Review

Sustainable packaging has been steadily gaining prominence within the food industry, with biobased materials emerging as a promising substitute for conventional petroleum-derived plastics. This review is dedicated to the examination of innovative biobased materials in the context of bread packaging. It aims to furnish a comprehensive survey of recent discoveries, fundamental properties, and potential applications. Commencing with an examination of the challenges posed by various bread types and the imperative of extending shelf life, the review underscores the beneficial role of biopolymers as internal coatings or external layers in preserving product freshness while upholding structural integrity. Furthermore, the introduction of biocomposites, resulting from the amalgamation of biopolymers with active biomolecules, fortifies barrier properties, thus shielding bread from moisture, oxygen, and external influences. The review also addresses the associated challenges and opportunities in utilizing biobased materials for bread packaging, accentuating the ongoing requirement for research and innovation to create advanced materials that ensure product integrity while diminishing the environmental footprint.

Extending shelf life and optimizing effective parameters by using clove oil (Syzygium aromaticum oleum)/orange oil (Citrus aurantium var dulcis oleum) in bread: thermal, morphological and sensory approach

The aim of the present study was to extend the shelf life of bread by using organic additives and optimization techniques. Quadruple effects of temperature (-18, + 4, + 20 °C), clove oil (0, 1, 2%), orange oil (0, 1, 2%), residence time (7, 14, 21 days) were investigated to determine optimum bread as moisture response. Quadratic model was found to be suitable with an accuracy of 0.9854 for moisture response. Rheological properties remained intact for 7 days at 20 °C in bread with 1% clove oil and 1% orange oil added. The effect of 4 effective parameters from 3 levels was examined with Box-Behnken in Design Expert. Optimum and control samples at two different temperatures were determined with SEM, TG-DTA and polarized light microscope. Consumer survey was conducted as appearance, colour, smell for optimum, control samples for bread and cake. It was concluded that bread samples could be stored with clove and orange oil at + 20 °C with period of 7 days without losing their quality properties.

Graphical abstract

Effect of thymol on properties of bionanocomposites from poly (lactic acid)/poly (butylene succinate)/nanofibrillated cellulose for food packaging application

The present study developed the formulation of active bionanocomposites films endowed with the abilities of high biodegradability and antimicrobials for active packaging applications. The aim of this work was to prepare poly (lactic acid)/poly (butylene succinate) (PLA/PBS) blended films reinforced with different concentrations of nanofibrillated cellulose (NFC) and 9 % of thymol essential oil (EO) using the casting method. The active films were further evaluated through Fourier transform infrared spectroscopy (FTIR); as well as mechanical, physical, water vapour permeability (WVP), thermal analysis (TGA), biodegradation, morphological, and antimicrobial (% reduction of bacteria) testing. The tensile strength (TS) of PLA/PBS blend films increased by 12 % with the incorporation of 2 wt% of NFC. The PLA/PBS/NFC with 9 % thymol EO has a good water barrier performance with its tensile strength, elongation at break, and tensile modulus was 13.2 MPa, 13.1 %, and 513 MPa respectively. The presence of NFC promoted the disintegration of PLA/PBS films by 70.5 %. These films promoted the antibacterial activity against S. aureus and E. coli. The study demonstrates that the developed films improved the qualities of chicken fillets and have great potential to be used as active bionanocomposites in food packaging applications.

Natural antimicrobial systems protected by complex polyhydroxyalkanoate matrices for food biopackaging applications - A review

Interest is growing in entrapping natural antimicrobial compounds (NACs) within polyhydroxyalkanoates (PHAs) to produce active food-biopackaging systems. PHAs are versatile polymeric macromolecules that can protect NAC activity by entrapment. This work reviews 75 original papers and 18 patents published in the last 11 years concerning PHAs as matrices for NACs to summarize the physicochemical properties, release, and antimicrobial activities of systems fabricated from PHAs and NACs (PHA/NAC systems). PHA/NAC systems have recently been used as active food biopackaging systems to inactivate foodborne pathogens and prolong food shelf life. PHAs protect NACs by increasing the degradation temperature of some NACs and decreasing their loss of mass when heated. Some NACs also transform the PHA/NAC systems into more thermostable, flexible, and resistant when interacting with PHAs while also improving the barrier properties of the systems. NAC release and activity are also prolonged when NACs are trapped within PHAs. PHA/NAC systems, therefore, represent ecologically friendly materials with promising applications.

Development of poly(hydroxybutyrate) film incorporated with nano silica and clove essential oil intended for active packaging of brown bread

The objective of current study was to develop Poly(hydroxybutyrate) (PHB) based active packaging film with long lasting antimicrobial potential in food-packaging applications. For developing such films, PHB was incorporated with poly(ethylene glycol) (PEG) as a plasticizer, nano-silica (n-Si) as strengthening material and clove essential oil (CEO) as an antimicrobial agent. These solvent-casted films with varying concentration of n-Si (0.5, 1, 1.5, 2 %) and 30 % CEO of total polymer matrix weight i.e., PHB/PEG (90/10) were prepared and studied on the basis of morphological, mechanical, thermal, degradation and antimicrobial behaviours. The presence of CEO and n-Si was confirmed by Fourier transform infrared spectroscopy (FTIR). Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to investigate homogeneous dispersal of n-Si in polymer matrix. PHB/PEG/CEO/Si 1.0 film was selected as optimized one after mechanical testing and therefore further carried for antimicrobial testing. This selected film extended the shelf-life of brown bread up to 10 days comparable to bread wrapped in polyethylene. This revealed that PHB/PEG/CEO/Si 1.0 exhibited superior antibacterial activity against the food borne microbes i.e., Escherichia coli, Staphylococcus aureus and Aspergillus niger. Our findings indicate that this film improved the shelf-life of packaged bread and has promising features for active food packaging.

Recent Development of Polyhydroxyalkanoates (PHA)-Based Materials for Antibacterial Applications: A Review

The diseases caused by microorganisms are innumerable existing on this planet. Nevertheless, increasing antimicrobial resistance has become an urgent global challenge. Thus, in recent decades, bactericidal materials have been considered promising candidates to combat bacterial pathogens. Recently, polyhydroxyalkanoates (PHAs) have been used as green and biodegradable materials in various promising alternative applications, especially in healthcare for antiviral or antiviral purposes. However, it lacks a systematic review of the recent application of this emerging material for antibacterial applications. Therefore, the ultimate goal of this review is to provide a critical review of the state of the art recent development of PHA biopolymers in terms of cutting-edge production technologies as well as promising application fields. In addition, special attention was given to collecting scientific information on antibacterial agents that can potentially be incorporated into PHA materials for biological and durable antimicrobial protection. Furthermore, the current research gaps are declared, and future research perspectives are proposed to better understand the properties of these biopolymers as well as their possible applications.

Production, characterization, and antimicrobial activity of almond gum/polyvinyl alcohol/chitosan composite films containing thyme essential oil nanoemulsion for extending the shelf-life of chicken breast fillets

In this study, thyme essential oil (TEO) nanoemulsion was immobilized within composite films based on almond gum (AG), polyvinyl alcohol (PVA), and chitosan (CS). The physical, mechanical, water barrier, microstructural and antimicrobial properties of composite films were assessed. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis confirmed the intermolecular interactions in the composite film matrix. The results indicated that the incorporation of TEO into the composite films increased thickness, moisture content, and water vapor permeability, while it reduced light transmittance and transparency value. The antimicrobial activity of films against gram-negative and gram-positive bacteria was tested using a disc diffusion method. The effect of composite on the microbiological properties of chicken breast fillets was investigated during refrigerated storage for 21 days. The microbial populations of total mesophilic, psychrotrophic, and lactic acid bacteria of the samples that were coated with the composite containing TEO were lower than the permitted limit after 21 days while for blank samples they were higher than 7 log CFU/g after 7 days which is considered as the maximum acceptable total count limit. Results disclosed that AG/PVA/CS composite films containing TEO nanoemulsion can be applied as eco-friendly active food packaging to enhance the shelf-life of food products.

The Green Era of Food Packaging: General Considerations and New Trends

Recently, academic research and industries have gained awareness about the economic, environmental, and social impacts of conventional plastic packaging and its disposal. This consciousness has oriented efforts towards more sustainable materials such as biopolymers, paving the way for the “green era” of food packaging. This review provides a schematic overview about polymers and blends of them, which are emerging as promising alternatives to conventional plastics. Focus was dedicated to biopolymers from renewable sources and their applications to produce sustainable, active packaging with antimicrobial and antioxidant properties. In particular, the incorporation of plant extracts, food-waste derivatives, and nano-sized materials to produce bio-based active packaging with enhanced technical performances was investigated. According to recent studies, bio-based active packaging enriched with natural-based compounds has the potential to replace petroleum-derived materials. Based on molecular composition, the natural compounds can diversely interact with the native structure of the packaging materials, modulating their barriers, optical and mechanical performances, and conferring them antioxidant and antimicrobial properties. Overall, the recent academic findings could lead to a breakthrough in the field of food packaging, opening the gates to a new generation of packaging solutions which will be sustainable, customised, and green.

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

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

Functional Polymer and Packaging Technology for Bakery Products

Polymeric materials including plastic and paper are commonly used as packaging for bakery products. The incorporation of active substances produces functional polymers that can effectively retain the quality and safety of packaged products. Polymeric materials can be used to produce a variety of package forms such as film, tray, pouch, rigid container and multilayer film. This review summarizes recent findings and developments of functional polymeric packaging for bakery products. Functional polymerics are mainly produced by the incorporation of non-volatile and volatile active substances that effectively retain the quality of packaged bakery products. Antimicrobial agents (either synthetic or natural substances) have been intensively investigated, whereas advances in coating technology with functional materials either as edible coatings or non-edible coatings have also preserved the quality of packaged bakery products. Recent patents demonstrate novel structural packaging designs combined with active functions to extend the shelf life of bakery products. Other forms of active packaging technology for bakery products include oxygen absorbers and ethanol emitters. The latest research progress of functional polymeric packaging for bakery products, which provides important reference value for reducing the waste and improving the quality of packaged products, is demonstrated. Moreover, the review systematically analyzed the spoilage factors of baked products from physicochemical, chemical and microbiological perspectives. Functional packaging using polymeric materials can be used to preserve the quality of packaged bakery products.

Fabrication of nanocellulose fibril-based composite film from bamboo parenchyma cell for antimicrobial food packaging

The development of nanocellulose fibril (NCF)-based films for use in food packaging has aroused tremendous attention because of their good biodegradability. In this work, NCFs isolated from bamboo parenchyma cell were used to fabricate the composite film with embedded silver nanoparticles (AgNPs). Results demonstrate that the low content of AgNPs, especially at content of 0.1 wt% in the composite film could slightly improve the tensile strength and Young's modulus of the composite film by about 11.0%, owing to the reduced thickness of cellulose crystallites and decreased amount of adsorbed water, as well as the increment in crystallinity and the hydrogen-bond intensity confirmed by X-ray diffraction measurement and Fourier transform infrared spectra. On the other hand, high content of AgNPs could enhance antimicrobial activity and thermal stability while showed negligible negative effect on tensile properties. Specifically, the maximum inhibition zone of the composite film (with AgNPs content of 0.1 wt%) was 13.5 ± 0.8 mm against Salmonella typhi (S. typhi) and 7.5 ± 0.3 mm against Escherichia coli (E. coli). The strong antimicrobial activity of NCF-based films highlights their potential as a biodegradable food packaging material.

Effects of Differing Monomer Compositions on Properties of P(3HB-co-4HB) Synthesized by Aneurinibacillus sp. H1 for Various Applications

Films prepared from poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers produced by Aneurinibacillus sp. H1 using an automatic film applicator were homogeneous and had a defined thickness, which allowed a detailed study of physicochemical properties. Their properties were compared with those of a poly (3-hydroxybutyrate) homopolymer film prepared by the same procedure, which proved to be significantly more crystalline by DSC and XRD. Structural differences between samples had a major impact on their properties. With increasing 4-hydroxybutyrate content, the ductility and release rate of the model hydrophilic active ingredient increased significantly. Other observed properties, such as the release of the hydrophobic active substance, the contact angle with water and ethylene glycol, or the surface morphology and roughness, were also affected by the composition. The identified properties predetermine these copolymers for wide use in areas such as biomedicine or smart biodegradable packaging for food or cosmetics. The big advantage is the possibility of fine-tuning properties simply by changing the fermentation conditions.