Antibacterial activity in gelatin-bacterial cellulose composite film by thermally crosslinking with cinnamaldehyde towards food packaging application

Gelatin/dextran active films incorporated with cinnamaldehyde and α-tocopherol for scallop (Patinopecten yessoensis) adductor muscle preservation

Scallops are rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid but perishable due to their microbial growth and lipid oxidation. In this study, gelatin/dextran films containing cinnamaldehyde and α-tocopherol (0% + 0%, 0.3% + 0.3%, 0.6% + 0.6%, 0.9% + 0.9%, and 1.2% + 1.2%, w/w) as active fillers were developed by solution casting method, and their preservation effects on scallop adductor muscle refrigerated at 4°C for 0, 3, 6, 9, and 12 days were evaluated. Inclusion of the two active fillers did not influence the thermal stability of the films but created heterogenous and discontinuous film microstructure and increased the film hydrophobicity. Increase in the concentrations of active fillers lowered the mechanical properties and water vapor permeability of the films but increased their crystallinity, thickness, water contact angle, opacity, antibacterial property, and antioxidant property. The longest release times for both cinnamaldehyde and α-tocopherol were found in 95% (v/v) ethanol solution. The gelatin/dextran films containing 1.2% (w/w) of active fillers (Gelatin [Ge]/Dextran [Dx]/1.2 film) improved the chemical stability of refrigerated scallop adductor muscle. The total viable count (TVC) of the unpackaged scallop adductor muscle exceeded the recommended limit of 7 lg CFU/g on day 6 (7.07 ± 0.50 lg CFU/g), whereas the TVC of the Ge/Dx/1.2 film-packaged scallop adductor muscle was still below the limit on day 9 (5.60 ± 0.50 lg CFU/g). Thus, the Ge/Dx/1.2 film can extend the shelf life of refrigerated scallop adductor muscle by at least 3 days. Overall, the developed gelatin/dextran active packaging films are promising for the preservation of aquatic food products.

Spontaneous nanoemulsification of cinnamon essential oil: Formulation, characterization, and antibacterial and antibiofilm activity against fish spoilage caused by Serratia rubidaea BFMO8

The contemporary food industry's uses of nanoemulsions (NEs) include food processing, effective nutraceutical delivery, the development of functional chemicals, and the synthesis of natural preservatives, such as phytocompounds. Although cinnamon essential oil (CEO) is widely used in the cosmetic, pharmaceutical, and food industries, it is difficult to add to aqueous-based food formulations due to its weak stability and poor water solubility. This study describes the formulation of a CEO nanoemulsion (CEONE) by spontaneous emulsification and evaluates its antibacterial and antibiofilm properties against biofilm-forming Serratia rubidaea BFMO8 isolated from spoiled emperor fish (Lethrinus miniatus). Bacteria causing spoilage in emperor fish were isolated and identified as S. rubidaea using common morphological, cultural, and 16S RNA sequencing methods, and their ability to form biofilms and their susceptibility to CEONE were assessed using biofilm-specific methods. The spontaneous emulsification formulation of CEONE was accomplished using water and Tween 20 surfactant by manipulating organic and aqueous phase interface properties and controlling particle growth by capping surfactant increases. The best emulsification, with highly stable nano-size droplets, was accomplished at 750 rpm and a 1:3 ratio concentration. The stable CEONE droplet size, polydispersity index, and zeta potential values were 204.8 nm, 0.115, and -6.05 mV, respectively. FTIR and high-resolution liquid chromatography-mass spectrometry (HR-LCMS) analyses have revealed carboxyl, carbonyl, and phenol-like primary phytochemical functional groups in CEO and CEONE, which contribute to their antibacterial and antibiofilm properties.

PEG-crosslinked O-carboxymethyl chitosan films with degradability and antibacterial activity for food packaging

This study developed a kind of PEG-crosslinked O-carboxymethyl chitosan (O-CMC-PEG) with various PEG content for food packaging. The crosslinking agent of isocyanate-terminated PEG was firstly synthesized by a simple condensation reaction between PEG and excess diisocyanate, then the crosslink between O-carboxymethyl chitosan (O-CMC) and crosslinking agent occurred under mild conditions to produce O-CMC-PEG with a crosslinked structure linked by urea bonds. FT-IR and 1H NMR techniques were utilized to confirm the chemical structures of the crosslinking agent and O-CMC-PEGs. Extensive research was conducted to investigate the impact of the PEG content (or crosslinking degree) on the physicochemical characteristics of the casted O-CMC-PEG films. The results illuminated that crosslinking and components compatibility could improve their tensile features and water vapor barrier performance, while high PEG content played the inverse effects due to the microphase separation between PEG and O-CMC segments. The in vitro degradation rate and water sensitivity primarily depended on the crosslinking degree in comparison with the PEG content. Furthermore, caused by the remaining -NH2 groups of O-CMC, the films demonstrated antibacterial activity against Escherichia coli and Staphylococcus aureus. When the PEG content was 6% (medium crosslinking degree), the prepared O-CMC-PEG-6% film possessed optimal tensile features, high water resistance, appropriate degradation rate, low water vapor transmission rate and fine broad-spectrum antibacterial capacity, manifesting a great potential for application in food packaging to extend the shelf life.

Active whey protein/hydroxypropyl methylcellulose edible films incorporated with cinnamaldehyde: Characterization, release kinetics and application to Mongolian cheese preservation

Edible films with modulated release of antimicrobial agents are important for food preservation. Herein, antimicrobial edible films were prepared using whey protein (WP) and hydroxypropyl methylcellulose (HM) as polymer matrix materials and cinnamaldehyde (CIN) as antimicrobial agent. The mass ratios of WP and HM were 100/0, 75/25, 50/50, 25/75 and 0/100. The release kinetics of CIN through the film was studied, applying the Fickian model, power law and Weibull model. The films were also characterized by physical and structural characteristics, and antibacterial activity. In comparison to other films, the CIN-loaded film with a WP/HM ratio of 50/50 had better moisture resistance, water vapor barrier properties and mechanical properties. High correlation factors were obtained by fitting the CIN release data with the power law (R2 > 0.96) and Weibull model (R2 > 0.97). The diffusion mechanism of CIN was pseudo-Fickian. The diffusion coefficients (D1 and D2) had a positive linear relationship with the HM ratio, suggesting that a high HM ratio was beneficial to the CIN release. Finally, the WH50-C film was successfully used to preserve Mongolian cheese. This research provides a new perspective on the design of active packaging film with sustained-release characteristics.

Enhanced antioxidant and antibacterial activities of chitosan/zein nanoparticle Pickering emulsion-incorporated chitosan coatings in the presence of cinnamaldehyde and tea polyphenol

Pickering emulsions were prepared by using zein/chitosan nanoparticles as stabilizer and then incorporated into chitosan coatings. To improve the stability and performances, tea polyphenol and cinnamaldehyde (CA) were used to modulate the formation and functionalities of Pickering emulsions. The oil phase in Pickering emulsions were set at 5 % and 20 % to alter the hydrophobicity of chitosan coatings. Physical, structural, antioxidant and antibacterial activities of chitosan coatings with Pickering emulsions were characterized. Tea polyphenol significantly enhanced antioxidant capacity of chitosan coatings from 2.09 % to 57.61 % of DPPH value and from 2.63 % to 38.85 % of ABTS value. CA effectively increased the antibacterial activity of chitosan coatings against S. aureus and E. coli. Under 20 % oil content, the inhibition zones on S. aureus and E. coli increased from 3.03 ± 0.23 mm to 18.39 ± 1.22 mm and 7.66 ± 1.61 mm to 15.70 ± 1.75 mm, respectively. The preservative effect of chitosan coatings on fresh pork was further confirmed that the shelf-life of fresh pork could be extended by >4 days. These results suggested a great potential application of Pickering emulsion-incorporated chitosan coatings in the preservation of fresh pork.

Antimicrobial and hydrophobic cellulose paper prepared by covalently attaching cinnamaldehyde for strawberries preservation

The demand for paper-based packaging materials as an alternative to incumbent disposable petroleum-derived polymers for food packaging applications is ever-growing. However, typical paper-based formats are not suitable for use in unconventional applications due to inherent limitations (e.g., excessive hydrophilicity, lack antimicrobial ability), and accordingly, enabling new capabilities is necessity. Herein, a simple and environmentally friendly strategy was proposed to introduce antimicrobial and hydrophobic functions to cellulose paper through successive chemical grafting of 3-aminopropyltriethoxysilane (APS) and cinnamaldehyde (CA). The results revealed that cellulose paper not only showed long-term antibacterial effect on different bacteria, but also inhibited a wide range of fungi. Encouragingly, the modified paper, which is fluorine-free, displays a high contact angle of 119.7°. Thus, even in the wet state, the modified paper can still maintain good mechanical strength. Meanwhile, the multifunctional composite papers have excellent biocompatibility and biodegradability. Compared with ordinary cellulose paper, multifunctional composite paper can effectively prolong the shelf life of strawberries. Therefore, the multifunctional composite paper represents good application potential as a fruit packaging material.

Development of innovative active packaging films using gelatin/pullulan-based composites incorporated with cinnamon essential oil-loaded metal-organic frameworks for meat preservation

This study aimed to investigate the effect of cinnamon essential oil (CEO)-loaded metal-organic frameworks (CEO@MOF) on the properties of gelatin/pullulan (Gel/Pull)-based composite films (Gel/Pull-based films). The incorporation of CEO@MOF into Gel/Pull-based films demonstrated significant antimicrobial activity against S. aureus, S. enterica, E. coli, and L. monocytogenes. Additionally, CEO@MOF integrated film exhibited a 98.16 % ABTS radical scavenging, with no significant change in the mechanical properties of the neat Gel/Pull film. The UV blocking efficiency of the composite films increased significantly from 81.38 to 99.56 % at 280 nm with the addition of 3 wt% CEO@MOF. Additionally, Gel/Pull/CEO@MOF films effectively extended the shelf life of meat preserved at 4 °C by reducing moisture loss by 3.35 %, maintaining the pH within the threshold limit (6.2), and inhibiting bacterial growth by 99.9 %. These results propose that CEO@MOF has significant potential as an effective additive in active packaging to improve shelf life and food safety.

Food applications of bioactive biomaterials based on gelatin and chitosan

Food packaging must guarantee the products' quality during the different operations including packing and maintenance throughout transportation and storage until to consumption. Thus, it should satisfy, both, food freshness and quality preservation and consumers health safety. Natural bio-sourced polymers have been explored as safe edible materials for several packaging applications, being interestingly carrier of bioactive substances, once added to improve films' properties. Gelatin and chitosan are among the most studied biomaterials for the preparation of edible packaging films due to their excellent characteristics including biodegradability, compatibility and film-forming property. These polymers could be used alone or in combination with other polymers to produce composite films with the desired physicochemical and mechanical properties. When incorporated with bioactive substances (natural extracts, polyphenolic compounds, essential oils), chitosan/gelatin-based films acquired various biological properties, including antioxidant and antimicrobial activities. The emerging bioactive composite films with excellent physical attributes represent excellent packaging alternative to preserve different types of foodstuffs (fruits, meat, fish, dairy products, …) and have shown great achievements. This chapter provides the main techniques used to prepare gelatin- and chitosan- based films, showing some examples of bioactive compounds incorporated into the films' matrix. Also, it illustrates the outstanding advantages given by these biomaterials for food preservation, when used as coating and wrapping agents.

Fabrication of multifunctional ethyl cellulose/gelatin-based composite nanofilm for the pork preservation and freshness monitoring

In this study, an active and intelligent nanofilm for monitoring and maintaining the freshness of pork was developed using ethyl cellulose/gelatin matrix through electrospinning, with the addition of natural purple sweet potato anthocyanin. The nanofilm exhibited discernible color variations in response to pH changes, and it demonstrated a higher sensitivity towards volatile ammonia compared with casting film. Notably, the experimental findings regarding the wettability and pH response performance indicated that the water contact angle between 70° and 85° was more favorable for the smart response of pH sensitivity. Furthermore, the film exhibited desirable antioxidant activities, water vapor barrier properties and also good antimicrobial activities with the incorporation of ε-polylysine, suggesting the potential as a food packaging film. Furthermore, the application preservation outcomes revealed that the pork packed with the nanofilm can prolong shelf life to 6 days, more importantly, a distinct color change aligned closely with the points indicating the deterioration of the pork was observed, changing from light pink (indicating freshness) to light brown (indicating secondary freshness) and then to brownish green (indicating spoilage). Hence, the application of this multifunctional film in intelligent packaging holds great potential for both real-time indication and efficient preservation of the freshness of animal-derived food items.

Design of triple-layer films with blackseed protein as dispersion or emulsion

The aim of study was to produce the blackseed protein for applications as a protein dispersion alone or an emulsifier to design of multi-layer film based on furcellaran and chitosan. The protein extraction of blackseed by-product resulted in a blackseed by-product protein isolate (BBPI) with a yield of 73% protein. The obtained BBPI resulted in a high polyphenols content (1543 mg/ml), antioxidant property (DPPH, 67%) and emulsification properties (encapsulation up to 96%), leading to a stable emulsions at pH 10 and 12. For the first time, innovative, active triple-layer films have been developed in the 1st furcellaran layer with BBPI stabilised emulsion or BBPI aqueous extract alone, followed by a 2nd layer of furcellaran and citric acid matrix, and a 3rd layer of chitosan and gelatin matrix. Compared to the control, the tested films showed improved the water behaviour, UV-Vis barrier and increased antioxidant activity for the DPPH parameter (>70%).

Nanocomposites and their application in antimicrobial packaging

The advances in nanocomposites incorporating bioactive substances have the potential to transform the food packaging sector. Different nanofillers have been incorporated into polymeric matrixes to develop nanocomposite materials with improved mechanical, thermal, optical and barrier properties. Nanoclays, nanosilica, carbon nanotubes, nanocellulose, and chitosan/chitin nanoparticles have been successfully included into polymeric films, resulting in packaging materials with advanced characteristics. Nanostructured antimicrobial films have promising applications as active packaging in the food industry. Nanocomposite films containing antimicrobial substances such as essential oils, bacteriocins, antimicrobial enzymes, or metallic nanoparticles have been developed. These active nanocomposites are useful packaging materials to enhance food safety. Nanocomposites are promising materials for use in food packaging applications as practical and safe substitutes to the traditional packaging plastics.

Cinnamaldehyde-enriched Pickering emulsions stabilized by modified cellulose I and II nanocrystals recycled from maple leaves for shrimp preservation

The utilization of biomass waste has attracted much interest, but such attention hasn't been paid to the abundant fallen maple leaves in Canada. Herein, we aim to obtain cellulose nanocrystals (CNCs) from maple leaves and explore their potential applications as sustainable stabilizers of Pickering emulsions for the preservation of food products with complicated structures. The results reveal that two types of CNCs were extracted from maple leaves at different alkaline conditions. Octenyl succinic anhydride was selected to modify rod-like CNCs, and the CNC-stabilized oil-in-water Pickering emulsions showed excellent stability. Cinnamaldehyde, a model antibacterial compound, was incorporated in the Pickering emulsions, which exhibited the improved storage stability and sustained antibacterial capacity towards both Gram-positive and Gram-negative bacteria. Shrimp was chosen as an example that has complicated surface structure and is hard to disinfect, and the CNC-stabilized Pickering emulsions could be easily sprayed on the surface of shrimp to inhibit the proliferation of bacteria and inactivate the psychrophilic bacteria responsible for shrimp spoilage at refrigerated condition, so as to preserve the quality of shrimp. Therefore, the current work suggests the possibility to utilize fallen maple leaves as a promising source of CNCs and the applications of CNC-stabilized Pickering emulsions in seafood preservation.

Bacterial cellulose/gelatin-based pH-responsive functional film for food freshness monitoring

Food safety is related to public health and environmental safety. Therefore, it is necessary to develop accurate and effective detection methods to assess food quality and safety. In this study, a pH-responsive functional film (BC/GA/FITC/PCA) was generated for the real-time and visual monitoring of shrimp freshness. Bacterial cellulose /Gelatin (BC/GA) was used as a film-forming matrix, and fluorescein isothiocyanate (FITC) and red cabbage (PCA) were used as the response signals. The addition of FITC and PCA increased the shading capacity (< 30 %) and antioxidant properties (22.8 %) of the films. WCA (82.73 ± 0.95°), WVP (1.48 × 10-11 g·cm/cm2·s·Pa) and OTR (2.42 × 10-15 cm3·cm/cm2·s·Pa) indicated that the film possessed water resistance and oxygen barrier properties. When exposed to daylight, the film underwent a color transition from purple to green as the ammonia concentration increased. In addition, the blue-green fluorescence of the films gradually increased and the detection limit was low (170 ppb). In particular, the change in film color caused by shrimp spoilage corresponded to the TVBN value. This study work provides a new strategy for controlling and monitoring food safety and has a wide range of applications in the fields of food-active packaging and smart packaging.

Nanoemulsion-integrated gelatin/bacterial cellulose nanofibril-based multifunctional film: Fabrication, characterization, and application

The current requirements of food safety regulations and the environmental impact stemming from plastic packaging can only be addressed by developing suitable bio-nanocomposite films. Therefore, this study is dedicated to the fabrication of multifunctional film composed of gelatin, bacterial cellulose nanofibrils (BCNF), and black pepper essential oil nanoemulsion (BPEONE) and application for duck meat preservation. BCNF was prepared through ultrasonication of cellulose derived from Komagataeibacter xylinus. BPEONE observed spherical morphology with a diameter ranging from 83.7 to 118 nm. A film matrix containing a higher gelatin proportion than BCNF was more effective in trapping BPEONE. However, increasing the BPEONE fraction showed more surface abrasion and voids in the film morphology. A flexible film with good interaction, crystallinity, and greater thermal stability (421 °C) was developed. Nevertheless, film hydrophobicity (118.89°) declined, resulting in a notable effect on water solubility, swelling, and water vapor permeability. Moreover, the film had improved antibacterial and antioxidant activities, coupled with controlled release characteristics. Consequently, the developed film effectively retarded the lipid oxidation, inhibited microbial growth, and extended the shelf life of duck meat at refrigeration (4 °C) by 3 days, and made the film a promising alternative in the realm of bio-active packaging technology.

Bacterial cellulose nanofibers used as nanofillers improved the fresh-keeping performance of gelatin-based edible coating for fresh-cut apples

In this study, bacterial cellulose nanofibers (BCNs) (0%, 1%, 2%, and 3%) were used as nanofillers to prepare gelatin-based edible films, and their physical properties and fresh-keeping performance were investigated. The microstructure observation showed that the BCNs were well dispersed in the gelatin-based edible films and the surface roughness of the films increased with the increase of BCNs content. X-ray diffraction and thermogravimetric analysis showed that the crystallinity and thermal stability of the film were significantly increased with the increase of BCNs. Fourier-transform infrared spectroscopy analysis suggested that hydrogen bond interactions occurred between BCNs and gelatin polymers, leading to improved mechanical properties with the increase of BCNs content. Furthermore, the barrier performance was also improved with the increase of BCNs content, where gelatin-based edible films with 2% BCNs showed the best mechanical property. Meanwhile, the gelatin-based film-forming solutions (FFSs) containing different BCNs were coated on the fresh-cut apples and the corresponding fresh-keeping performance was investigated. The results showed that the fresh-keeping parameters of fresh-cut apples coated with FFSs containing BCNs were better as compared with those of pure gelatin FFSs. Moreover, the fresh-keeping parameters were improved with the increase of BCNs, especially the FFSs containing 2% BCNs that showed the best fresh-keeping parameters. Therefore, BCNs, used as nanofillers, are an excellent enhancer to improve the fresh-keeping performance of the gelatin-based edible coating, showing a promising potential application in the food preservation field.

Carbon dots, cellulose nanofiber, and essential oil from Torreya grandis aril added to fish scale gelatin film for tomato preservation

In this study, carbon dots (CDs), cellulose nanofibers (CNF) and essential oil nanoemulsion (EON) were extracted from the aril waste of Torreya grandis following nuts production. These three nanomaterials were formulated for the preparation of a composite film to be employed for postharvest tomato storage. Visual, microscopical and physicochemical properties of the prepared nanocomposite films were analyzed at different levels of CDs and CNF for optimization purposes. The UV absorption and antioxidant capacity of gelatin film with 10 % CDs (G/10CD) were enhanced compared with gelatin (G) film, concurrent with a reduction in water barrier capacity, water contact angle (WCA) and tensile strength (TS). Compared with G/10CD film, the WCA of gelatin film after incorporation of 10 % CDs and 3 % CNF (G/10CD/3CNF) was significantly increased by 14.5°at 55 s. In contrast, TS increased by 1.26 MPa, as well as the significant enhancement in water barrier capacity. The above composite film mixed with NEO (G/10CD/3CNF/EON) exerted further antimicrobial effects against Escherichia coli. G/10CD/3CNF/EON coating effectively extended tomato shift life compared with the control group. Therefore, this new eco-friendly film presents several advantages of biodegradability, sustainability as well as multifunctional properties posing it as potential packaging material for food applications.

Original nanostructured bacterial cellulose/pyrite composite: Photocatalytic application in advanced oxidation processes

The development of an original catalytic composite of bacterial cellulose (BC) and pyrite (FeS₂) for environmental application was the objective of this study. Nanoparticles of the FeS₂ were synthesized from the hydrothermal method and immobilized on the BC structure using ex situ methodology. In the BC, the FTIR and XRD analyzes showed the absorption band associated with the Fe-S bond and crystalline peaks attributed to the pyrite. Thus, the immobilization of the iron particles on the biopolymer was proven, producing the composite BC/FeS₂. The use of the SEM technique also ratifies the composite production by identifying the fibrillar structure morphology of the cellulose covered by FeS₂ particles. The total iron concentration was 54.76 ± 1.69 mg L^-1, determined by flame atomic absorption analysis. TG analysis and degradation tests showed respectively the thermal stability of the new material and its high catalytic potential. A multi-component solution of textile dyes was used as the matrix to be treated via advanced oxidative processes. The composite acted as the catalyst for the Fenton and photo-Fenton processes, with degradations of 52.87 and 96.82%, respectively. The material proved stability by showing low iron leaching (2.02 ± 0.09 and 2.11 ± 0.11 mg L^-1 for the respective processes). Thus, its high potential for reuse is presumed, given the remaining concentration of this metal in the BC. The results showed that the BC/FeS₂ composite is suitable to solve the problems associated with using catalysts in suspension form.

Insights into electrospun pullulan-carboxymethyl chitosan/PEO core-shell nanofibers loaded with nanogels for food antibacterial packaging

Nisin, a natural substance from Lactococcus lactis, displays a promising antibacterial ability against the gram-positive bacteria. However, it is susceptible to the external environment, i.e. temperature, pH, and food composition. In this study, a dual stabilization method, coaxial electrospinning, was applied to protect nisin in food packaging materials and the effect of nisin concentration on the properties of the nanofibers was investigated. The core-shell nanofibers with pullulan as a core layer and carboxymethyl chitosan (CMCS)/polyethylene oxide (PEO) as shell layer were prepared, and then the prepared CMCS-nisin nanogels (CNNGs) using a self-assembly method were loaded into the core layer of the nanofibers as antibacterial agents. The result revealed that the smooth surface can be observed on the nanofibers by microstructure characterization. The CNNGs-loaded nanofibers exhibited enhanced thermal stability and mechanical strength, as well as excellent antibacterial activity. Importantly, the as-formed nanofibers were applied to preserve bass fish and found that the shelf life of bass fish packed by CNNGSs with nisin at a concentration of 8 mg/mL was effectively extended from 9 days to 15 days. Taken together, the CNNGs can be well stabilized with the core-shell nanofibers, thus exerting significantly improved antimicrobial stability and bioactivity. This special structure exerts a great potential for application as food packaging materials to preserve aquatic products.

Gelatin and Chitosan as Meat By-Products and Their Recent Applications

Meat by-products such as bones, skin, horns, hooves, feet, skull, etc., are produced from slaughtered mammals. Innovative solutions are very important to achieving sustainability and obtaining the added value of meat by-products with the least impact on the environment. Gelatin, which is obtained from products high in collagen, such as dried skin and bones, is used in food processing, and pharmaceuticals. Chitosan is derived from chitin and is well recognized as an edible polymer. It is a natural product that is non-toxic and environmentally friendly. Recently, chitosan has attracted researchers' interests due to its biological activities, including antimicrobial, antitumor, and antioxidant properties. In this review, article, we highlighted the recent available information on the application of gelatin and chitosan as antioxidants, antimicrobials, food edible coating, enzyme immobilization, biologically active compound encapsulation, water treatment, and cancer diagnosis.

Study of antimicrobial activity and mechanism of vapor-phase cinnamaldehyde for killing Escherichia coli based on fumigation method

The vapor-phase antibacterial activity of essential oils makes them suitable for applications in air disinfection and other fields. At present, vapor-phase antibacterial activity of plant-based essential oils has rarely been reported. Herein, we report a new approach to investigate the antimicrobial activity and mechanism of vapor-phase cinnamaldehyde using Escherichia coli (E. coli) and three other pathogenic bacteria (Pseudomonas aeruginosa, Salmonella, Staphylococcus aureus) as model bacteria. Plate fumigation and agar block transfer techniques were used to determine the antimicrobial activities of vapor-phase cinnamaldehyde fumigation on the four types of bacteria, and the mechanism of action was determined by electrical conductivity (EC), OD260nm measurement, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and fluorescence spectroscopy. Cinnamaldehyde had good vapor-phase antibacterial activity against the four types of bacteria. The TEM, EC, and OD260nm measurements showed that after fumigation with cinnamaldehyde, the ultrastructures of the cells were damaged, and plasmolysis, cell collapse, and leakage of intracellular substances were observed. The FTIR and fluorescence spectroscopy analyses showed that the secondary and tertiary structures of bacterial membrane proteins were altered. These findings indicate that the cell membrane is an important target for plant-based essential oils to exert their vapor-phase antimicrobial effects. The results showed that plant-based essential oils can be developed as volatile broad-spectrum disinfection products and vapor-phase antiseptics.

Chitosan-Coated Bacterial Cellulose (BC)/Hydrolyzed Collagen Films and Their Ascorbic Acid Loading/Releasing Performance: A Utilization of BC Waste from Kombucha Tea Fermentation

SCOBY bacterial cellulose (BC) is a biological macromolecule (considered as a by-product) that grows at the liquid-air interface during kombucha tea fermentation. In this study, BC:HC (hydrolyzed collagen) blend films coated with 1 wt% chitosan (CS) were loaded with ascorbic acid to study loading/releasing performance. At first, the mechanical properties of the blend films were found to be dependent on HC ratio. After chitosan coating, the coated films were stronger due to intermolecular hydrogen bonding interaction and the miscibility of two matrixes at the interface. The antibacterial activity test according to the AATCC Test Method revealed that chitosan-coated BC/HC films exhibited excellent antimicrobial activity against S.aureus growth from the underneath and the above film when compared to BC and BC:HC films. Moreover, chitosan was attractive to ascorbic acid during drug loading. Consequently, its releasing performance was very poor. For BC:HC blend films, ascorbic acid loading/releasing performance was balanced by water swellability, which was controlled using blending formulation and coating. Another advantage of BC films and BC:HC blend films was that they were able to maintain active ascorbic acid for a long period of time, probably due to the presence of plenty of BC hemiacetal reducing ends (protective group).

Emerging Food Packaging Applications of Cellulose Nanocomposites: A Review

Cellulose is the most abundant biopolymer on Earth, which is synthesized by plants, bacteria, and animals, with source-dependent properties. Cellulose containing β-1,4-linked D-glucoses further assembles into hierarchical structures in microfibrils, which can be processed to nanocellulose with length or width in the nanoscale after a variety of pretreatments including enzymatic hydrolysis, TEMPO-oxidation, and carboxymethylation. Nanocellulose can be mainly categorized into cellulose nanocrystal (CNC) produced by acid hydrolysis, cellulose nanofibrils (CNF) prepared by refining, homogenization, microfluidization, sonification, ball milling, and the aqueous counter collision (ACC) method, and bacterial cellulose (BC) biosynthesized by the Acetobacter species. Due to nontoxicity, good biodegradability and biocompatibility, high aspect ratio, low thermal expansion coefficient, excellent mechanical strength, and unique optical properties, nanocellulose is utilized to develop various cellulose nanocomposites through solution casting, Layer-by-Layer (LBL) assembly, extrusion, coating, gel-forming, spray drying, electrostatic spinning, adsorption, nanoemulsion, and other techniques, and has been widely used as food packaging material with excellent barrier and mechanical properties, antibacterial activity, and stimuli-responsive performance to improve the food quality and shelf life. Under the driving force of the increasing green food packaging market, nanocellulose production has gradually developed from lab-scale to pilot- or even industrial-scale, mainly in Europe, Africa, and Asia, though developing cost-effective preparation techniques and precisely tuning the physicochemical properties are key to the commercialization. We expect this review to summarise the recent literature in the nanocellulose-based food packaging field and provide the readers with the state-of-the-art of this research area.

A comprehensive review of food gels: formation mechanisms, functions, applications, and challenges

Gels refer to the soft and flexible macromolecular polymeric materials retaining a large amount of water or biofluids in their three-dimensional network structure. Gels have attracted increasing interest in the food discipline, especially proteins and polysaccharides, due to their good biocompatibility, biodegradability, nutritional properties, and edibility. With the advancement of living standards, people's demand for nutritious, safe, reliable, and functionally diverse food and even personalized food has increased. As a result, gels exhibiting unique advantages in food application will be of great significance. However, a comprehensive review of functional hydrogels as food gels is still lacking. Here, we comprehensively review the gel-forming mechanisms of food gels and systematically classify them. Moreover, the potential of hydrogels as functional foods in different types of food areas is summarized, with a special focus on their applications in food packaging, satiating gels, nutrient delivery systems, food coloring adsorption, and food safety monitoring. Additionally, the key scientific issues for future food gel research, with specific reference to future novel food designs, mechanisms between food components and matrices, food gel-human interactions, and food gel safety, are discussed. Finally, the future directions of hydrogels for food science and technology are summarized.

Characterization and Application in Packaging Grease of Gelatin-Sodium Alginate Edible Films Cross-Linked by Pullulan

Gelatin–sodium alginate-based edible films cross-linked with pullulan were prepared using the solution casting method. FTIR spectroscopy demonstrated the existence of hydrogen bonding interactions between the components, and scanning electron microscopy observed the component of the films, revealing electrostatic interactions and thus explaining the differences in the properties of the blend films. The best mechanical properties and oxygen barrier occurred at a 1:1 percentage of pullulan to gelatin (GP11) with sodium alginate dosing for modification. Furthermore, GP11 demonstrated the best thermodynamic properties by DSC analysis, the highest UV barrier (94.13%) and the best oxidation resistance in DPPH tests. The results of storage experiments using modified edible films encapsulated in fresh fish liver oil showed that GP11 retarded grease oxidation by inhibiting the rise in peroxide and anisidine values, while inappropriate amounts of pullulan had a pro-oxidative effect on grease. The correlation between oil oxidation and material properties was investigated, and water solubility and apparent color characteristics were also assessed.

The Influence of Copper Content on the Elastic Modulus and Antibacterial Properties of Ti-13Nb-13Zr-xCu Alloy

Device-related infection or inflammatory and stress shield are still the main problems faced by titanium alloy implants for long-term implantation application; therefore, it is of great significance to design an alloy with low elastic modulus and good antibacterial properties as well as good biocompatibility. In this paper, Ti-13Nb-13Zr-xCu(x = 3, 7 wt.%) alloys were designed and prepared to reveal the influence of Cu content on the elastic modulus and antibacterial property. X-ray diffractometer, metallographic microscope, scanning electron microscope, and transmission electron microscope were used to study the phase transformation, microstructure, mechanical properties, antibacterial properties, and cytotoxicity of the alloys. The experimental results have demonstrated that the antibacterial performance and the elastic modulus were significantly improved but the corrosion resistance deteriorated with the increase of the copper content. Ti-13Nb-13Zr-3Cu with a low modulus of 73 GPa and an antibacterial rate of over 90% against Staphylococcus aureus (S. aureus) exhibited great potential as a candidate for implant titanium in the future.

Fabrication of Antioxidant and Antimicrobial Pullulan/Gelatin Films Integrated with Grape Seed Extract and Sulfur Nanoparticles

Biopolymer-based functional blend films were prepared using pullulan and gelatin with functional fillers of sulfur nanoparticles (SNPs) and grape seed extract (GSE). A mixture of pullulan/gelatin (1:1) produced a compatible but slightly translucent free-standing film. SNPs capped with enoki mushroom extract and GSE were added as functional fillers to improve the properties (physical and functional) of the pullulan/gelatin-based film. The addition of SNP and GSE significantly (p < 0.05) boosted the UV-light barrier, water vapor barrier, and oxygen barrier properties of the pullulan/gelatin films. The mechanical performance of the pullulan/gelatin-based films was slightly decreased (∼10%), whereas the addition of fillers did not significantly affect the hydrophobicity and thermal stability. The addition of SNP provided the antimicrobial function against foodborne pathogenic bacteria, L. monocytogenes and E. coli, while GSE provided a powerful antioxidant activity to the pullulan/gelatin-based film. Therefore, pullulan/gelatin-based composite films with better UV, water vapor, and oxygen barrier properties and enhanced antioxidant and antibacterial properties are expected to have high utility in active food packaging applications.

Foaming with scCO2 and Impregnation with Cinnamaldehyde of PLA Nanocomposites for Food Packaging

Microcellular nanocomposite foams functionalized with cinnamaldehyde (Ci) were obtained through two-step supercritical foaming and impregnation processing. PLA nanocomposite foams with different C30B concentrations (1, 2, and 3 wt.%) were obtained by foaming with scCO2 at 25 MPa and 135 °C and impregnated with Ci at 12 MPa and 40 °C. The effect of the C30B content and Ci incorporation on the morphological, structural, thermal, and release properties of the developed foams were investigated. The incorporation of Ci was not influenced by C30B’s addition. The presence of C30B and Ci incorporation reduced the average pore diameter slightly and the crystallinity degree of the foams extensively. Simultaneously, the experimental and theoretical characterization of the Ci release from the PLA nanocomposite foams in EtOH 50% was analyzed. The mechanism of Ci release from the foams was defined as a quasi-Fickian diffusion process that could be successfully described using the Korsmeyer–Peppas model. The active PLA foams presented a higher potential of migration and faster release when compared with that reported in commonly used PLA films, showing that biopolymeric foams could be potentially used as active food packaging to improve the migration of active compounds with low migration potentials in order to improve their biological activity in foods.