Improved mechanical and thermal properties of gelatin films using a nano inorganic filler

Trends and challenges of biopolymer-based nanocomposites in food packaging

The ultimate goal of new food packaging technologies, in addition to maintaining the quality and safety of food for the consumer, is to consider environmental concerns and reduce its impacts. In this regard, one of the solutions is to use eco-friendly biopolymers instead of conventional petroleum-based polymers. However, the challenges of using biopolymers in the food packaging industry should be carefully evaluated, and techniques to eliminate or minimize their disadvantages should be investigated. Many studies have been conducted to improve the properties of biopolymer-based packaging materials to produce a favorable product for the food industry. This article reviews the structure of biopolymer-based materials and discusses the trends and challenges of using these materials in food packaging technologies with the focus on nanotechnology and based on recent studies.

Approaches in Animal Proteins and Natural Polysaccharides Application for Food Packaging: Edible Film Production and Quality Estimation

Natural biopolymers are an interesting resource for edible films production, as they are environmentally friendly packaging materials. The possibilities of the application of main animal proteins and natural polysaccharides are considered in the review, including the sources, structure, and limitations of usage. The main ways for overcoming the limitations caused by the physico-chemical properties of biopolymers are also discussed, including composites approaches, plasticizers, and the addition of crosslinking agents. Approaches for the production of biopolymer-based films and coatings are classified according to wet and dried processes and considered depending on biopolymer types. The methods for mechanical, physico-chemical, hydration, and uniformity estimation of edible films are reviewed.

Incorporation of Poly(Itaconic Acid) with Quaternized Thiazole Groups on Gelatin-Based Films for Antimicrobial-Active Food Packaging

Poly(itaconic acid) (PIA) was synthesized via conventional radical polymerization. Then, functionalization of PIA was carried out by an esterification reaction with the heterocyclic groups of 1,3-thiazole and posterior quaternization by N-alkylation reaction with iodomethane. The modifications were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR), as well as ζ-potential measurements. Their antimicrobial activity was tested against different Gram-negative and Gram-positive bacteria. After characterization, the resulting polymers were incorporated into gelatin with oxidized starch and glycerol as film adjuvants, and dopamine as crosslinking agent, to develop antimicrobial-active films. The addition of quaternized polymers not only improved the mechanical properties of gelatin formulations, but also decreased the solution absorption capacity during the swelling process. However, the incorporation of synthesized polymers increased the deformation at break values and the water vapor permeability of films. The antioxidant capacity of films was confirmed by radical scavenging ability and, additionally, those films exhibited antimicrobial activity. Therefore, these films can be considered as good candidates for active packaging, ensuring a constant concentration of the active compound on the surface of the food, increasing products' shelf-life and reducing the environmental impact generated by plastics of petrochemical origin.

Effects of bovine gelatin viscosity on gelatin-based edible film mechanical, physical and morphological properties

This study was conducted to determine the effect of gelatin reology on mechanical, physical and morphological properties of gelatin-based edible films. The aim of this study was to better understand the variation of viscosity on the structural behaviour of gelatin-based films in the presence of glycerol and sorbitol plasticizers. Gelatin-based films were casted by using gelatins of different viscosities as 2.5, 3.0 and 3.5 centipoise with plasticisers as glycerol and sorbitol. Finally, the physical, mechanical and morphological properties of the films were investigated via pH, thickness, tensile strength and elongation, fourier transform infrared spectroscopy and scanning electron microscopy. As a result of the study, it was observed that a durable film structure could be obtained with gelatin viscosity at 3 centipoise. Furthermore 5.5% gelatin, 0.1% glycerol and 0.4% sorbitol concentration were found as the most suitable formulation for gelatin based film structure with Tukey Test. The results suggest that gelatin-plastisizer combinations can be an excellent source of biobased packaging material with further investigations.

Nanohydroxyapatite-, Gelatin-, and Acrylic Acid-Based Novel Dental Restorative Material

The aim of this study was to prepare a novel dental restorative material (NDRM) and to understand its cell viability behavior. The hydroxyapatite (HA) nanopowder was synthesized using a wet chemical precipitation method using calcium hydroxide and orthophosphoric acid as precursors. The as-prepared HA nanopowder was annealed at different temperatures to get a pure compound with a Ca/P ratio close to 1.67. The optimal temperature was found to be 600 °C, whereas at a higher temperature, HA starts decomposing into CaO. The preparation of NDRM was conducted in two steps. The first step comprises the preparation of HA nanopowder- and gelatin (G)-based film using microwave heating. In the second step, the homogenized mixture of the HA-G film was mixed with different amounts of acrylic acid to form a self-flowable NDRM paste. Further, both these materials (HA nanopowder and NDRM) were characterized using FTIR, XRD, and SEM-EDX analyses. The FTIR and XRD results show the peaks corresponding to natural bone apatite and therefore confirm the formation of HA. EDX results showed the presence of Ca and P in HA nanopowder and NDRM with Ca/P ratios of 1.79 and 1.63, respectively. Synthesized NDRM was also analyzed for its in vitro cytotoxic and reproductive viability potential against normal cells using MTT and clonogenic assay. The analysis showed significantly higher cellular viability on the treatment with NDRM when compared to HA nanopowder as well as no colony suppression by both materials was observed on the normal cell line (fR2) even after exposure for 24 h, indicating its nontoxicity. The synthesized NDRM therefore can be considered as a promising candidate for dental caries restoration applications.

Physico-Mechanical and Antibacterial Properties of PLA/TiO2 Composite Materials Synthesized via Electrospinning and Solution Casting Processes

In this study, PLA/TiO2 composites materials were prepared via electrospinning and solution casting processes. By testing the mechanical properties, water contact angle, water vapor permeability, and solubility of the composite nanofibers and films, the comprehensive performances of the two types of nanocomposites were analyzed. The results show that maximum tensile strengths of 2.71 ± 0.11 MPa and 14.49 ± 0.13 MPa were achieved for the nanofibers and films at a TiO2 content of 0.75 wt.%. Moreover, the addition of TiO2 significantly cut down the water vapor transmittance rate of the nanofibers and films while significantly improving the water solubility. Further, the antibacterial activity increased under UV-A irradiation for a TiO2 nanoparticle content of 0.75 wt.%, and the nanofiber and films exhibited inhibition zones of 4.86 ± 0.50 and 3.69 ± 0.40 mm for E. coli, and 5.98 ± 0.77 and 4.63 ± 0.45 mm for S. aureus, respectively. Overall, the performance of the nanofiber was better than that of the film. Nevertheless, both the nanocomposite membranes satisfied the requirements of food packaging materials.

Improved mechanical properties and thermal-stability of collagen fiber based film by crosslinking with casein, keratin or SPI: Effect of crosslinking process and concentrations of proteins

This study utilized three different thermo-stable proteins of casein, keratin and soy protein isolate (SPI) to improve the thermal stabilities and mechanical properties of collagen fiber films using transglutaminase (TGase) crosslinking. The crosslinking greatly enhanced the thermal- stability of collagen fiber films, especially that of the collagen fiber crosslinking with 50% casein composite films, judged from thermogravimetric analysis (TGA). Furthermore, the TGase treatment improved the mechanical properties of the collagen fiber films interms of tensile strength (TS) and elongation at break (EAB). Importantly, a prominent improvement in EAB at wet and heated state was noted when collagen fiber crosslinked with 50% keratin or 50% casein, respectively. Moreover, different addition patterns of proteins in the collagen fiber films offered altered morphology as observed by scanning electron microscopy (SEM). Meanwhile, the conformational changes of the films revealed by fourier transform infrared spectroscopy (FTIR) confirmed a greater stabilization of film in the group of collagen fiber crosslinking with other proteins. In conclusion, the crosslinking action induced by TGase between collagen fiber and higher thermo-stable proteins promoted heat-resistance and mechanical properties of collagen fiber based film.