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

Konjac glucomannan-based composite materials: Construction, biomedical applications, and prospects

Konjac glucomannan (KGM) as an emerging natural polymer has attracted increasing interests owing to its film-forming properties, excellent gelation, non-toxic characteristics, strong adhesion, good biocompatibility, and easy biodegradability. Benefiting from these superior performances, KGM has been widely applied in the construction of multiple composite materials to further improve their intrinsic performances (e.g., mechanical strength and properties). Up to now, KGM-based composite materials have obtained widespread applications in diverse fields, especially in the field of biomedical. Therefore, a timely review of relevant research progresses is important for promoting the development of KGM-based composite materials. Innovatively, firstly, this review briefly introduced the structure properties and functions of KGMs based on the unique perspective of the biomedical field. Then, the latest advances on the preparation and properties of KGM-based composite materials (i.e., gels, microspheres, films, nanofibers, nanoparticles, etc.) were comprehensively summarized. Finally, the promising applications of KGM-based composite materials in the field of biomedical are comprehensively summarized and discussed, involving drug delivery, wound healing, tissue engineering, antibacterial, tumor treatment, etc. Impressively, the remaining challenges and opportunities in this promising field were put forward. This review can provide a reference for guiding and promoting the design and biomedical applications of KGM-based composites.

Electrospun gelatin/tea polyphenol@pullulan nanofibers for fast-dissolving antibacterial and antioxidant applications

Bio-based active food packaging materials have a high market demand. We use coaxial electrospinning technology to prepare core-shell structured nanofibers with sustained antibacterial and antioxidant properties. The fiber core layer was composed of gelatin and tea polyphenols, whereas tea polyphenols provide antibacterial and antioxidant properties; the fiber sheath was composed of pullulan polysaccharides with antioxidant properties. By using a scanning electron microscope, it can be seen that the diameter distribution of the prepared nanofibers was uniform and the surface is smooth; using a transmission electron microscope, it can be clearly seen that the nanofibers have a core-shell structure; Fourier Transform Infrared and X-ray diffraction analysis indicate that the nanofibers have an amorphous structure; the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging shows that nanofibers have higher antioxidant properties with the addition of tea polyphenols; antibacterial test showed that nanofibers had obvious inhibitory effect on the growth of Staphylococcus aureus and Escherichia coli; and the nanofiber film dissolution test shows that nanofibers can be used as fast soluble active packaging. Finally, core-sheath-structured nanofibers can serve as active packaging for instant food, possessing both rapid water solubility and excellent antibacterial and antioxidant activity, making water-soluble nanofibers interesting applications in the field of food packaging.

Enhancement of Mechanical Properties of Zein-Based Nanofibers by Incorporation of Millet Gliadin

In this work, a novel reinforcing filler, millet gliadin (MG), was used for the improvement of the mechanical properties of zein nanofibers. The structural and physicochemical properties of MG were compared with those of zein, and the influence of MG on the morphology, physical properties, and molecular structure of zein nanofibers was investigated. The results indicated that MG has an obviously smaller weight-average molecular weight (7623) in comparison to zein (13,330). Transmission electron microscopy showed that zein molecules more easily form aggregates with larger diameters than MG molecules in acetic acid. At a concentration of 30% (w/v), MG exhibited a significantly higher viscosity (0.66 ± 0.03 Pa·s) than zein (0.32 ± 0.01 Pa·s), indicating the stronger interactions of MG molecules. With the incorporation of MG, the tensile strength was significantly increased to 49.32 MPa (ZM-1/2), which is 2.08 times and 4.45 times higher than that of pure zein nanofibers (ZM-1/0) and MG nanofibers (ZM-0/1-1), respectively. Moreover, zein/MG composite nanofibers exhibited improved water stability. Fourier transform infrared spectra showed evidence of the hydrogen bonding interaction between zein and MG. Therefore, MG is a good candidate for use as a natural reinforcing filler in electrospun nanofibers made of biopolymers.

Electrospun Photodynamic Antibacterial Konjac Glucomannan/Polyvinylpyrrolidone Nanofibers Incorporated with Lignin-Zinc Oxide Nanoparticles and Curcumin for Food Packaging

Due to the growing concerns surrounding microbial contamination and food safety, there has been a surge of interest in fabricating novel food packaging with highly efficient antibacterial activity. Herein, we describe novel photodynamic antibacterial konjac glucomannan (KGM)/polyvinylpyrrolidone (PVP) nanofibers incorporated with lignin-zinc oxide composite nanoparticles (L-ZnONPs) and curcumin (Cur) via electrospinning technology. The resulting KGM/PVP/Cur/L-ZnONPs nanofibers exhibited favorable hydrophobic properties (water contact angle: 118.1°), thermal stability, and flexibility (elongation at break: 241.9%). Notably, the inclusion of L-ZnONPs and Cur endowed the nanofibers with remarkable antioxidant (ABTS radical scavenging activity: 98.1%) and photodynamic antimicrobial properties, demonstrating enhanced inhibitory effect against both Staphylococcus aureus (inhibition: 12.4 mm) and Escherichia coli (12.1 mm). As a proof-of-concept study, we evaluated the feasibility of applying nanofibers to fresh strawberries, and the findings demonstrated that our nanofibers could delay strawberry spoilage and inhibit microbial growth. This photodynamic antimicrobial approach holds promise for design of highly efficient antibacterial food packaging, thereby contributing to enhanced food safety and quality assurance.

Improvement in the Sustained-Release Performance of Electrospun Zein Nanofibers via Crosslinking Using Glutaraldehyde Vapors

Volatile active ingredients in biopolymer nanofibers are prone to burst and uncontrolled release. In this study, we used electrospinning and crosslinking to design a new sustained-release active packaging containing zein and eugenol (EU). Vapor-phase glutaraldehyde (GTA) was used as the crosslinker. Characterization of the crosslinked zein nanofibers was conducted via scanning electron microscopy (SEM), mechanical properties, water resistance, and Fourier transform infrared (FT-IR) spectroscopy. It was observed that crosslinked zein nanofibers did not lose their fiber shape, but the diameter of the fibers increased. By increasing the crosslink time, the mechanical properties and water resistance of the crosslinked zein nanofibers were greatly improved. The FT-IR results demonstrated the formation of chemical bonds between free amino groups in zein molecules and aldehyde groups in GTA molecules. EU was added to the zein nanofibers, and the corresponding release behavior in PBS was investigated using the dialysis membrane method. With an increase in crosslink time, the release rate of EU from crosslinked zein nanofibers decreased. This study demonstrates the potential of crosslinking by GTA vapors on the controlled release of the zein encapsulation structure containing EU. Such sustainable-release nanofibers have promising potential for the design of fortified foods or as active and smart food packaging.

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.