Robust construction of konjac glucomannan/polylactic acid nanofibrous films incorporated with carvacrol via microfluidic blow spinning for food packaging.

In recent years, the application of biopolymer-based nanofibers prepared via microfluidic blow spinning (MBS) for food packaging has continuously increased due to their advantages of biocompatibility, biodegradability, and safety. However, the poor spinnability, undesirable water barrier capacity, and loss of antibacterial and antioxidant properties of biopolymer-based nanofibers strictly restrict their real-world applications. In this work, carvacrol (CV) incorporated konjac glucomannan (KGM)/polylactic acid (PLA) nanofibrous films (KP-CV) were produced by MBS. The FTIR spectra and XRD analysis revealed the hydrogen bonding interactions among CV, PLA, and KGM, thus significantly improving the TS of KP-CV nanofibrous films from 0.23 to 1.27 MPa with increased content of CV from 0 % to 5 %. Besides, KP-CV nanofibrous films showed improved thermal stability, excellent hydrophobicity (WCA: 128.19°, WVP: 1.02 g mm/m2 h kPa), and sustained release of CV combined with good antioxidant activities (DPPH radical scavenging activity: 77.51 ± 1.57 %), and antibacterial properties against S. aureus (inhibition zone: 26.33 mm) and E. coli (inhibition zone: 22.67 mm). Therefore, as prepared KP-CV nanofibrous films can be potentially applied as packaging materials for the extended shelf life of cherry tomatoes.

Pullulan nanofibrous films incorporated with W/O emulsions via microfluidic solution blow spinning technology.

In this work, pullulan (PUL) nanofibrous films incorporated with water-in-oil emulsions (PE) were prepared by microfluidic blowing spinning (MBS). The microstructures of nanofibers were characterized by scanning electron microscopy (SEM), fourier transform infrared (FT-IR), and X-ray diffraction (XRD). With the addition of W/O emulsions, the thermal stability, mechanical, and water barrier properties of PUL nanofibers were improved. Increases in emulsion content significantly affected the antioxidant and antimicrobial properties of nanofibrous films. ABTS and DPPH free radical scavenging rates increased from 10.26 % and 8.57 % to 60.66 % and 57.54 %, respectively. The inhibition zone of PE nanofibers against E. coli and S. aureus increased from 11.00 to 20.00 and from 15.67 to 21.17 mm, respectively. In addition, we investigated the freshness effectiveness of PE nanofibrous films on fresh-cut apples. PE nanofibrous films significantly maintained the firmness, and reduced the weight loss and browning index of the fresh-cut apple, throughout the 4 days of storage. Thus, the PE nanofibrous films exhibited good potential to prolong the shelf life of fresh-cut fruit and promote the development of active food packaging.

Electrospun Konjac Glucomannan/Polyvinyl Alcohol Long Polymeric Filaments Incorporated with Tea Polyphenols for Food Preservations.

In this study, nanofiber films were prepared by electrospinning technology with polyvinyl alcohol (PVA) and konjac glucomannan (KGM) as raw materials. Tea polyphenols (TPs) were incorporated in the above matrix, which increased physicochemical (thermal and mechanical characteristics) and antibacterial properties of the nanofiber films. The release behavior of phenolic compounds from PVA/KGM-TPs nanofiber films was determined in different food simulants; antioxidant and antibacterial activity of the films were also evaluated. The results showed that the addition of KGM increased the physical and chemical properties of the films. The tensile strength (TS) and elongation at break (EB) increased from 5.40 ± 0.33 to 10.62 ± 0.34 and from 7.24 ± 0.32 to 18.10 ± 0.91, respectively. PVA/KGM-TPs nanofiber films performed controlled release of TPs, with final release of 49.17% in 3% acetic acid, 43.6% in 10% ethanol, and 59.42% in 95% ethanol. The nanofiber films showed good antioxidation properties, with the free radical scavenging rate increasing from 1.33% to 25.61%, and good antibacterial properties with inhibition zones against E. coli and S. aureus of 24.33 ± 0.47 mm and 34.33 ± 0.94 mm, respectively. In addition, the as-prepared films showed significant preservation performance for raw bananas at 25 °C.

Highly Hydrophobic Gelatin Nanocomposite Film Assisted by Nano-ZnO/(3-Aminopropyl) Triethoxysilane/Stearic Acid Coating for Liquid Food Packaging.

Biodegradable gelatin (G) food packaging films are in increasing demand as the substitution of petroleum-based preservative materials. However, G packaging films universally suffer from weak hydrophobicity in practical applications. Constructing a hydrophobic micro/nanocoating with low surface energy is an effective countermeasure. However, the poor compatibility with the hydrophilic G substrate often leads to the weak interfacial adhesion and poor durability of the hydrophobic coating. To overcome this obstacle, we used (3-aminopropyl) triethoxysilane (APS) as an interfacial bridging agent to prepare a highly hydrophobic, versatile G nanocomposite film. Specifically, tannic acid (TA)-modified nanohydroxyapatite (n-HA) particles (THA) were introduced in G matrix (G-THA) to improve the mechanical properties. Micro/nanostructure with low surface energy composed of nanozinc oxide (Nano-ZnO)/APS/stearic acid (SA) (NAS) was constructed on the surface of G-THA film (G-THA/NAS) through one-step spray treatment. Consequently, as-prepared G-THA/NAS film presented excellent mechanics (tensile strength: 7.6 MPa, elongation at break: 292.7%), water resistance ability (water contact angle: 150.4°), high UV-shielding (0% transmittance at 200 nm), degradability (100% degradation rate after buried in the natural soil for 15 days), antioxidant (78.8% of 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity), and antimicrobial (inhibition zone against Escherichia coli: 15.0 mm and Staphylococcus aureus: 16.5 mm) properties. It should be emphasized that the bridging function of APS significantly improves the interfacial adhesion ability of the NAS coating with more than 95% remaining area after the cross-cut adhesion test. Meanwhile, the G-THA/NAS film could maintain stable and long-lasting hydrophobic surfaces against UV radiation, high temperature, and abrasion. Based on these multifunctional properties, the G-THA/NAS film was successfully applied as a liquid packaging material. To sum up, we provide a feasible and effective method to prepare high-performance green packaging films.

Konjac glucomannan/carboxymethyl chitosan film embedding gliadin/casein nanoparticles for grape preservation.

Constructing biopolymer-based packaging films with fantastic water resistance and mechanical properties for food preservation is highly desirable and challenging. In this work, Gliadin/Casein nanoparticles (GCNPs) were prepared by pH-driven method and embedded into konjac glucomannan/carboxymethyl chitosan (KC) film matrix to improve the water resistance and mechanical properties of KC film. Gliadin and Casein showed good compatibility and co-assembled to form compact GCNPs clusters through hydrogen bonding and hydrophobic interaction verified by FT-IR spectroscopy, and fluorescence spectroscopy. The particle size and zeta potential of GCNPs was 269.7 nm and -7.6 mV, respectively. The effect of GCNPs on the mechanics, water barrier, thermal stability, and UV-shielding of KC-GCNPs film was investigated. SEM images revealed that GCNPs uniformly distributed into KC film matrix and significantly improved the mechanics (tensile strength: 75.6 MPa, elongation at breaking: 36.7 %), water barrier ability (water contact angle: 91.3°, water vapor permeability: 0.994 g mm/m2 day kPa, water solubility: 52.0 %), thermal stability and UV blocking property of KC-GCNPs film. Furthermore, KC-GCNPs film could also be applied to extend the shelf life of grapes. This paper demonstrated the great potential of GCNPs as functional nanofillers in enhancing the physicochemical properties of KC film.

Multi-functional konjac glucomannan/chitosan bilayer films reinforced with oregano essential oil loaded ß-cyclodextrin and anthocyanins for cheese preservation.

In this work, a multifunctional bilayer film was prepared by solvent casting method. Elderberry anthocyanins (EA) were incorporated into konjac glucomannan (KGM) film as the inner indicator layer (KEA). ß-cyclodextrin (ß-CD) loaded with oregano essential oil (OEO) inclusion complexes (ß-CD@OEO) was prepared and incorporated into chitosan (CS) film as the outer hydrophobic and antibacterial layer (CS-ß-CD@OEO). The impacts of ß-CD@OEO on the morphological, mechanical, thermal, water vapor permeability and water resistance properties, pH sensitivity, antioxidant, and antibacterial activities of bilayer films were thoroughly evaluated. The incorporation of ß-CD@OEO into bilayer films can significantly improve the mechanical properties (tensile strength (TS): 65.71 MPa and elongation at break (EB): 16.81 %), thermal stability, and water resistance (Water contact angle (WCA): 88.15°, water vapor permeability (WVP): 3.53 g mm/m2 day kPa). In addition, the KEA/CS-ß-CD@OEO bilayer films showed color variations in acid-base environments, which could be used as pH-responsive indicators. The KEA/CS-ß-CD@OEO bilayer films also presented controlled release of OEO, good antioxidant, and antimicrobial activity, which exhibited good potential for the preservation of cheese. To sum up, KEA/CS-ß-CD@OEO bilayer films have potential applications in the field of food packaging industry.

Development of chitosan/konjac glucomannan/tragacanth gum tri-layer food packaging films incorporated with tannic acid and ε-polylysine based on mussel-inspired strategy.

Constructing biodegradable food packaging with good mechanics, gas barrier and antibacterial properties to maintain food quality is still challenge. In this work, mussel-inspired bio-interface emerged as a tool for constructing functional multilayer films. Konjac glucomannan (KGM) and tragacanth gum (TG) with physical entangled network are introduced in the core layer. Cationic polypeptide ε-polylysine (ε-PLL) and chitosan (CS) producing cationic-π interaction with adjacent aromatic residues in tannic acid (TA) are introduced in the two-sided outer layer. The triple-layer film mimics the mussel adhesive bio-interface, where cationic residues in outer layers interact with negatively charged TG in the core layer. Furthermore, a series of physical tests showed excellent performance of triple-layer film with great mechanical properties (tensile strength (TS): 21.4 MPa, elongation at break (EAB): 7.9 %), UV-shielding (almost 0 % UV transmittance), thermal stability, water, and oxygen barrier (oxygen permeability (OP): 1.14 × 10-3 g/m s Pa and water vapor permeability (WVP): 2.15 g mm/m2 day kPa). In addition, the triple-layer film demonstrated advanced degradability, antimicrobial functions, and presented good moisture-proof performance for crackers, which can be potentially applied as dry food packaging.

Robust microfluidic construction of polyvinyl pyrrolidone microfibers incorporated with W/O emulsions stabilized by amphiphilic konjac glucomannan.

In this work, we prepared polyvinyl pyrrolidone (PVP) microfibers incorporated water-in-oil (W/O) emulsions. The W/O emulsions were fabricated by hexadecyl konjac glucomannan (HKGM, emulsifier), corn oil (oil phase) and purple corn anthocyanins (PCAs, water phase). The structures and functions of emulsions and microfibers were characterized by confocal laser scanning (CLSM) and scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman and nuclear magnetic resonance (NMR) spectroscopy. The results showed that W/O emulsions exhibited good storage stability for 30 d. Microfibers presented ordered and uniform arrays. Compared with pure PVP microfiber films, the addition of W/O emulsions with PCAs improved the water resistance (WVP from 1.28 to 0.76 g mm/m2 day kPa), mechanical strength (Elongation at break from 18.35 % to 49.83 %), antioxidation (free radical scavenging rate from 2.58 % to 16.37 %), and antibacterial activity (inhibition zone against E. coli: 27.33 mm and inhibition zone against S. aureus: 28.33 mm) of microfiber films. Results showed that microfiber film exhibited controlled release of PCAs in W/O emulsions, and about 32 % of the PCAs were released from the microfiber film after 340 min. The as-prepared microfiber films exhibited potential applications for food packaging.

Biosynthesis of Quercetin-Loaded Melanin Nanoparticles for Improved Antioxidant Activity, Photothermal Antimicrobial, and NIR/pH Dual-Responsive Drug Release.

Quercetin (QCT) is a promising dose-dependent nutraceutical that usually suffers from poor water solubility and low bioavailability issues. In this work, a novel QCT-loaded nanoscale delivery system was constructed based on the oxidative self-polymerization of melanin (Q@MNPs). The FT-IR, XRD, and Zeta potential analyses confirmed that QCT was successfully absorbed on the melanin nanoparticles (MNPs) via Π-Π and hydrogen bonding interactions. The encapsulation efficiency and particle size of Q@MNPs were 43.78% and 26.68 nm, respectively. Q@MNPs improved the thermal stability of QCT and the antioxidant properties in comparison to MNPs. Meanwhile, Q@MNPs presented fantastic photothermal conversion capacity and stability triggered by the NIR laser, which significantly enhanced the antibacterial capability with a sterilization rate of more than 98% against E. coli and S. aureus. More importantly, Q@MNPs exhibited NIR/pH dual-responsive drug release behavior and good biocompatibility (at concentrations of < 100 µg/mL). Thus, Q@MNPs show promising prospects for flavonoid delivery.

Recent Trends of Microfluidics in Food Science and Technology: Fabrications and Applications.

The development of novel materials with microstructures is now a trend in food science and technology. These microscale materials may be applied across all steps in food manufacturing, from raw materials to the final food products, as well as in the packaging, transport, and storage processes. Microfluidics is an advanced technology for controlling fluids in a microscale channel (1~100 µm), which integrates engineering, physics, chemistry, nanotechnology, etc. This technology allows unit operations to occur in devices that are closer in size to the expected structural elements. Therefore, microfluidics is considered a promising technology to develop micro/nanostructures for delivery purposes to improve the quality and safety of foods. This review concentrates on the recent developments of microfluidic systems and their novel applications in food science and technology, including microfibers/films via microfluidic spinning technology for food packaging, droplet microfluidics for food micro-/nanoemulsifications and encapsulations, etc.

Development of pH-responsive konjac glucomannan/pullulan films incorporated with acai berry extract to monitor fish freshness.

In this work, konjac glucomannan (KGM)-based film reinforced with pullulan (PL) and acai berry extract (ABE) was developed by solvent casting method. The as-prepared films performed pH-sensitive properties, which can be potentially applied for fish freshness detection. Rheology, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) were used to characterize chemical structure and morphology of ABE-loaded KGM/PL (KP) films (KP-ABE). FT-IR spectrum indicated that hydrogen bond dominated the formation of KP-ABE films. Adding PL contributed to enhanced mechanical properties of KGM film with increased tensile strength (TS) from 21.25 to 50.27 MPa and elongation at break (EAB) from 10.64 to 19.19 %. Incorporating ABE upgraded flexibility, UV-shielding, thermostability, water barrier (decreased Water vapor permeability (WVP) from 2.07 to 1.67 g·mm/m2·day kPa), antioxidant, and antibacterial ability of KP films, but weakened TS. In addition, KP-ABE films can reflect fish freshness in real time through color variability. Therefore, KP-ABE films exhibited potential applications in intelligent food packaging materials.

Chitosan films with tunable droplet size of Pickering emulsions stabilized by amphiphilic konjac glucomannan network.

In this work, chitosan (CS) emulsion films were prepared with grapefruit essential oil (GEO) Pickering emulsions (OGEOs) stabilized by amphiphilic octenyl succinic anhydride (OSA) konjac glucomannan (OSA-KGM) network. The droplet size of emulsion was regulated by altering oil content in OGEOs (10 %, 20 %, 30 % and 40 %, w/w). The structural and physicochemical properties of CS films with tunable emulsion droplets (OGEOs) were investigated. The droplet size of OGEOs increased with the increasing content of GEO. FT-IR revealed that the formation of CS-OGEOs films was attributed to hydrogen bonding. CS-OGEOs films with large droplets presented smoother surface, enhanced water resistance, UV-shielding property, mechanical properties, but increased water vapor permeability (WVP) compared with CS-OGEOs films with small droplets. In addition, CS-OGEOs films with large droplets also presented compact film structure, controlled release of GEO, high efficiency of DPPH free radical scavenging and antibacterial activity. To sum up, incorporation of emulsion droplets was a good strategy for improving the structural and physicochemical properties of CS films.

Stable O/W emulsions and oleogels with amphiphilic konjac glucomannan network: preparation, characterization, and application.

BACKGROUND: The stabilization of oil-in-water (O/W) emulsions has long been explored. Assembly of polymer networks is an effective method for stabilizing O/W emulsions. Konjac glucomannan (KGM) is a plant polysaccharide and the network of KGM gel is a good candidate for stabilizing O/W emulsions based on its high viscosity and thickening properties. However, natural KGM has strong hydrophilicity and is not able to offer interfacial activity. Octenyl succinic anhydride (OSA) is a hydrophobic molecule, which is widely used as thickener and stabilizer in food emulsions. In this work, the amphiphilic biopolymer (OSA-KGM) was fabricated by modifying the KGM with OSA. Furthermore, OSA-KGM biopolymer was used to prepare O/W emulsions, which were then freeze-dried and used to prepare oleogels as fat substitute for bakery products. RESULTS: OSA-KGM had advanced hydrophobicity with water contact angle 81.13° and adsorption behavior at the oil-water interface, with interfacial tension decreasing from 18.52 to 13.57 mN m-1 within 1 h. The emulsification of OSA-KGM remarkably improved the stability of emulsions without phase separation during storage for 31 days. Oleogels with OSA-KGM showed good thixotropic and structure recovery properties (approximately 100%) and low oil loss (from 69.5% to 50.4%). Cakes made from oleogels had a softer texture than cakes made from peanut oil and margarine. CONCLUSION: Amphiphilic biopolymer OSA-KGM shows advanced interfacial activity and hydrophobicity. This paper provides an insight into preparing stable O/W emulsions with a new biopolymer and oleogels potentially applied as fat substitute in bakery products. © 2022 Society of Chemical Industry.

Construction of Konjac Glucomannan/Oxidized Hyaluronic Acid Hydrogels for Controlled Drug Release.

Konjac glucomannan (KGM) hydrogel has favorable gel-forming abilities, but its insufficient swelling capacity and poor control release characteristics limit its application. Therefore, in this study, oxidized hyaluronic acid (OHA) was used to improve the properties of KGM hydrogel. The influence of OHA on the structure and properties of KGM hydrogels was evaluated. The results show that the swelling capacity and rheological properties of the composite hydrogels increased with OHA concentration, which might be attributed to the hydrogen bond between the KGM and OHA, resulting in a compact three-dimensional gel network structure. Furthermore, epigallocatechin gallate (EGCG) was efficiently loaded into the KGM/OHA composite hydrogels and liberated in a sustained pattern. The cumulative EGCG release rate of the KGM/OHA hydrogels was enhanced by the increasing addition of OHA. The results show that the release rate of composite hydrogel can be controlled by the content of OHA. These results suggest that OHA has the potential to improve the properties and control release characteristics of KGM hydrogels.