Effect of sodium acetate and drying temperature on physicochemical and thermomechanical properties of gelatin films

Enhancing physical properties of konjac glucomannan/ethyl cellulose/zein blend films by optimizing molecular assembly with varying drying temperatures

Appropriate selection of the drying temperature is of great importance to achieve desirable film preparation. The present study investigated the impact of drying temperature (40-80 °C) on the physical properties and molecular assembly process of konjac glucomannan/ethyl cellulose/zein blend films through the casting method. Microstructural observations indicated that the drying temperature impacted the particle aggregation in the films, and at the drying temperature of 60 °C, a most even component distribution was suggested with the strongest hydrogen bond interaction according to the FTIR and micro-FTIR analysis. Moreover, at this drying temperature, the blend film reached optimum performance for most physical properties including mechanical properties, surface hydrophobicity, moisture barrier, and water resistance properties. To explain this phenomenon, the molecular assembly process during the KGM/EC/zein film formation was proposed. This contributed to a deepened understanding of the molecular assembly process of complex macromolecules under different drying conditions.

Mechanism of maltogenic α-amylase modification on barley granular starches spanning the full range of amylose

Amylopectin (AP)-only (APBS), normal (NBS), and amylose (AM) only (AOBS) barley starches were selected here to investigate catalysis pattern of maltogenic α-amylase (MA) on hydrolyzing AP and AM granular starches. MA shortened starch side chains with degree of polymerization (DP) 11-30. MA-treated APBS exhibited porous granular structures and dramatically increased degree of branching (DB, 17-20 %), and reduced ordered degrees, suggesting high hydrolysis and transglycosylation activities of MA. MA-treated NBS showed less pronounced porous structures and slightly increased DB (2-4 %), indicating high hydrolysis but low transglycosylation activities. AOBS displayed minimal changes in DB (0.2-0.3 %) and starch structures, implying low hydrolysis and transglycosylation activities. Therefore, MA preferred to attack the AP molecules with abundant glucan substrates with DP 11-30, while AM restricted MA activity likely by creating ineffective binding sites and undergoing rapid reorganization. These findings deepened the understanding of the mechanisms of MA in modifying granular starches with varying AM content.

Tailoring hydrophobicity and strength in spider silk-inspired coatings via thermal treatments

The advent of advanced coatings has transformed material functionalities, extending their roles from basic coverage and visual appeal to include unique properties such as self-healing, superior hydrophobicity, and antimicrobial action. However, the traditional dependency on petrochemical-derived materials for these coatings raises environmental concerns. This study proposes the use of renewable and alternative materials for coating development. We present the use of bioengineered spider silk-inspired protein (SSIP), produced through recombinant technology, as a viable, eco-friendly alternative due to their ease of processing under ambient pressure and the utilization of water as a solvent, alongside their exceptional physicochemical properties. Our research investigates the effects of different thermal treatments and protein concentrations on the mechanical strength and surface water repellency of coatings on silica bases. Our findings reveal a direct correlation between the temperature of heat treatment and the enhancements in surface hydrophobicity and mechanical strength, where elevated temperatures facilitate increased resistance to water and improved mechanical integrity. Consequently, we advocate SSIPs present a promising, sustainable choice for advanced coatings, providing a pathway to fine-tune coating recipes for better mechanical and hydrophobic properties with a reduced ecological footprint, finding potential uses in various fields such as electronics.

Preparation and properties of edible active films of gelatin/carboxymethyl cellulose loaded with resveratrol

Resveratrol (Res) powder was incorporated into gelatin (GEL)/carboxymethyl cellulose (CMC) film-forming solutions to create GEL/CMC-Res composite films (G/C-R) without the use of organic solvents. The study focused on how phase separation affected the properties of these films. The film formation mechanism of the G/C-R films was analyzed using infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The findings revealed that the Res powder was evenly distributed within the GEL/CMC film matrix, which enhanced the crystallinity and surface roughness of the films, contributing to improved surface hydrophobicity. Dynamic rheological analysis showed that the presence of Res increased both the modulus and viscosity of the film-forming solutions. Thermal analysis, including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA), indicated that Res elevated the phase transition temperature, decreased the rate of thermal degradation, and enhanced the thermal stability of the films. Additionally, Res reduced water vapor permeability (WVP) by 75 % and significantly boosted antioxidant activity from 15 % to 85 %. This study demonstrates that the dispersion of Res powder in G/C-R blend films markedly improves their water barrier and antioxidant properties, effectively inhibiting the oxidation of soybean oil, and highlighting their potential as active packaging for food.

Water state, thermal transition behavior and structure of hydrated gelatin films

The state of water, thermal transition behaviors, molecular interactions, crystalline structure, and mechanical performance of hydrated gelatin films were studied by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), X-ray diffraction, and universal testing instruments. The DSC results showed that with increase of the water content, two types of water, including unfreezable bound water and freezable water, appeared in turn. Below a critical water content of 30%, the glass transition temperature (Tg) of the hydrated gelatin films decreased notably with an increase in water content, which leveled off at water content higher than this threshold. This observation suggests that only the unfreezable water exhibits a plasticizing effect. In addition, the melting temperature (Tm) of hydrated gelatin films decreased continuously with an increase in water content, whereas the melting enthalpy showed a non-monotonic dependence on hydration level. Structural analysis showed that at medium hydration levels up to 13.4% water content, the unfreezable water facilitated the formation of additional triple helices, confirmed by DSC results. Spectral data revealed that the -OH groups of unfreezable water molecules interacted with the -NH groups of the protein via hydrogen bonds. Moreover, the mechanical properties of the hydrated gelatin films were sensitive to their hydration level, and the tensile strength was dominated by the helix content of the protein films. These results show the feasibility of using hydration to regulate the microstructure and properties of biopolymers.

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.

Synthesis and characterization of polysaccharide- and protein-based edible films and application as packaging materials for fresh fish fillets

The rising packaging industry together with global demand for sustainable production has increased the interest in developing biodegradable packaging materials. The aim of the study was to develop edible films based on pectin, gelatin, and hydroxypropyl methylcellulose and evaluate their applicability as biodegradable packaging materials for gilthead seabream fillets. Mechanical properties, water barriers, wettability of the films through contact angle measurement, optical, and UV-Vis barrier properties were evaluated for food packaging applications. The effective blend of polysaccharide and protein film-forming solutions was confirmed by the produced films with excellent optical properties, acceptable mechanical properties and adequate barriers to water vapor. The contact angle for pectin based and gelatin based films were higher than 90° indicating the hydrophobic films, while HPMC based films had contact angle lower than 90°. The produced films were tested as alternative and environmentally friendly packaging materials for gilthead seabream fillets during refrigerated storage. All tested packaging conditions resulted in similar shelf-life in packed gilthead seabream fillets (i.e. 7-8 days at 2 °C). The results showed that the developed films may reduce the use of conventional petroleum-based food packaging materials without affecting the shelf-life of fish.

High-Performance, Degradable, Self-Healing Bio-Based Nanocomposite Coatings with Antibacterial and Antioxidant Properties

The purpose of this study is to obtain a bio-based coating with good functional activity and self-healing ability, demonstrating its potential in food, materials, and other application fields. Plastic coatings can cause serious environmental pollution. It was a good solution to replace plastic coatings with degradable coatings. However, the development of degradable coatings in the fields of food and materials was limited due to their insufficient antibacterial ability and weak comprehensive properties. Therefore, chitosan nanoparticles (NPs) loaded with gallic acid (GA) were self-assembled with gelatin (GE) to prepare high-performance, degradable, self-healing bio-based nanocomposite coatings with antibacterial and antioxidant properties. The oxygen permeability of GE nanocomposite coatings decreased gradually with the addition of NPs, and the barrier properties increased significantly. At the same time, due to the excellent antioxidant and antibacterial ability of GA, the antioxidant effect of the nanocomposite coatings increased by 119%, and the antibacterial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) increased by 32% and 58%, respectively, compared with the pure GE coatings. In addition, the nanocomposite coatings can be repaired within 24 h after being scratched at room temperature. Finally, GA coated with chitosan nanoparticles can significantly delay the escape of GA, and the retardation of gallic acid release exceeded 89% in simulated solutions after 24 h immersion, extending the service life of the nanocomposite coatings.

Development of active and intelligent pH food packaging composite films incorporated with litchi shell extract as an indicator

The anthocyanin-rich litchi shell extract (LE) was mixed with the matrix to prepare active/intelligent food packaging composite films. The microstructure and properties of composite films were characterized. The results showed that the composite films incorporated with LE had texture-oriented layered, compact, uniform cross-sections. The composite films with LE showed different degrees of red. The composite films had similar water vapor transmission rates (1.62-1.65 × 10^-12 g·cm/cm²·Pa·s). However, gelatin/chitosan/polyvinyl alcohol/litchi shell extract (Gel/Csa/PVA/LE) film had better UV blocking rates (0-20 %), the best tensile strength (18.6 MPa) and elongation at break (116%). When the composite films monitored for fish freshness at 4 °C (10 d) and 25 °C (3 d), the Gel/Csa/PVA/LE film had the pH sensitivity to show an obvious color change at 25 °C, 1th day. The results suggested that the Gel/Csa/PVA/LE film could be applied to intelligent food packaging film to indicate the freshness of fish.

Novel Active Food Packaging Films Based on Gelatin-Sodium Alginate Containing Beetroot Peel Extract

Currently, the exploration of natural colorants from vegetal waste has gained particular attention. Furthermore, incorporation of these natural sources into biopolymers is an encouraging environmentally friendly approach to establishing active films with biological activities for food packaging. The present study developed bioactive antioxidant films based on gelatin-sodium alginate (NaAlg) incorporated with aqueous beetroot peel extract (BPE). Firstly, the effects of combining gelatin-NaAlg and BPE at 0.25, 0.5, and 1% on the mechanical, physical, antioxidant, and antibacterial properties of the films were analyzed. With increasing BPE, mechanico-physical properties and antioxidant and anti-foodborne pathogen capacities were enhanced. Likewise, when added to gelatin-NaAlg films, BPE remarkably increased the instrumental color properties. Moreover, during 14 days of storage at 4 °C, the impact of gelatin-NaAlg coating impregnated with BPE on microbial and chemical oxidation and on the sensory characteristics of beef meat samples was periodically assessed. Interestingly, by the end of the storage, BPE at 1% limited the microbial deterioration, enhanced the instrumental color, delayed chemical oxidation, and improved sensory traits. By practicing chemometrics tools (principal component analysis and heat maps), all data provided valuable information for categorizing all samples regarding microbiological and oxidative properties, sensory features, and instrumental color. Our findings revealed the ability of gelatin-NaAlg with BPE as an antioxidant to be employed as food packaging for meat preservation.

Assessing the compressive elasticity and multi-responsive property of gelatin-containing weakly anionic copolymer gels via semi-IPN strategy

A series of semi-interpenetrating polymer network (semi-IPN) hydrogels based on acrylamide (AAm) and itaconic acid (ITA) was prepared in the presence of different amounts of the natural polymer gelatin (GLN). The semi-IPNs were synthesized by simultaneous polymerization using N,N'-methylene bisacrylamide as a crosslinking agent. A pH-sensitive system was obtained by adding 2 mol% ITA as an anionic comonomer. The effect of GLN content by changing the amine/carboxyl functional groups and incorporating carboxyl groups of ITA in semi-IPN on the swelling, elasticity and physical properties of the hydrogels was investigated. The presence of GLN improved the thermal stability, and the GLN-containing semi-IPNs exhibited a higher degradation temperature compared to the GLN-free copolymers. The addition of a small amount of GLN could effectively increase the swelling of the semi-IPNs in water. By employing the GLN-containing semi-IPN as a model system, the solvent/matrix interactions were demonstrated to reveal the effect of solvent structure on the swelling-shrinkage response. The addition of GLN improved the pH-sensitivity of the semi-IPN gels, resulting in a clear response to pH change by action of NH₃⁺ and COOH of GLN and additional COOH groups from ITA. The mechanical performance of the copolymer network was improved by entangling PAAm/ITA chains with GLN, which acted as a reinforcement node. In terms of the effect of Hofmeister anions on the swelling behavior, the anion effect became more pronounced with salt concentration. The affinity of semi-IPNs towards the cationic dyes methylene blue and malachite green was tested and the dependence of the adsorption process on the initial dye concentration, contact time and GLN content was determined. This method presents a simple and efficient approach for the design of chemically crosslinked protein-based gels for drug delivery applications.

Gallic Acid Crosslinked Gelatin and Casein Based Composite Films for Food Packaging Applications

In the current work, we fabricated gelatin–casein-based edible films (GC-EFs) crosslinked with gallic acid (GA). We analyzed the physiochemical characteristics, crystallinity, thermal stability, and surface properties of the EFs using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). It was found that the edible films possessed a semi-crystalline structure. Addition of GA enhanced the thermal stability of the edible films as well as the surface properties of the films. It was found that a higher concentration of GA (4–5% w/v) significantly improved the surface properties, observed in the surface and cross-sectional examination of SEM micrographs. EFs containing higher amounts of GA showed more compact and denser structures with smoother and more homogeneous surfaces than the control samples. In addition, swelling degree (SD), thickness, water solubility (WS), moisture content (MC), and water vapor permeability (WVP) were found to be low in EFs containing more GA concentration. Mechanical parameters revealed that the Young modulus (Ym) and tensile strength (TS) increased with a rise in GA concentration, and elongation at break (EB) reduced with a rise in GA concentration. In transparency and color analysis, it was observed that GA positively affected the transparency of the edible films.

Low temperature extrusion blown ε-polylysine hydrochloride-loaded starch/gelatin edible antimicrobial films

Edible antimicrobial films made from starch/gelatin (S/G) incorporated with different ε-polylysine hydrochloride (ε-PL) contents were developed by low-temperature extrusion blowing process. ε-PL addition reduced the complex viscosity and storage modulus of blends, while promoted the formation of hydrogen bonding among film components. The control film had an A-type crystalline structure, while increasing the ε-PL content promoted its transformation to B-shaped structure. Without ε-PL and under the processing temperature used, the starch granules were not sufficiently gelatinized. However, ε-PL addition significantly enhanced the gelatinization degree. Increasing ε-PL content in S/G films increased film flexibility, water contact angle value, swelling degree, antimicrobial effect, and storage period of fresh bread, but decreased water vapor permeability and tensile strength. S/G film with 4 wt% ε-PL had the highest water contact angle (94°) and elongation at break (149%). This research demonstrates the plasticizing effects of ε-PL and potential of S/G films containing ε-PL for food preservation/packaging.

Graphene-Oxide Porous Biopolymer Hybrids Enhance In Vitro Osteogenic Differentiation and Promote Ectopic Osteogenesis In Vivo

Over the years, natural-based scaffolds have presented impressive results for bone tissue engineering (BTE) application. Further, outstanding interactions have been observed during the interaction of graphene oxide (GO)-reinforced biomaterials with both specific cell cultures and injured bone during in vivo experimental conditions. This research hereby addresses the potential of fish gelatin/chitosan (GCs) hybrids reinforced with GO to support in vitro osteogenic differentiation and, further, to investigate its behavior when implanted ectopically. Standard GCs formulation was referenced against genipin (Gp) crosslinked blend and 0.5 wt.% additivated GO composite (GCsGp/GO 0.5 wt.%). Pre-osteoblasts were put in contact with these composites and induced to differentiate in vitro towards mature osteoblasts for 28 days. Specific bone makers were investigated by qPCR and immunolabeling. Next, CD1 mice models were used to assess de novo osteogenic potential by ectopic implantation in the subcutaneous dorsum pocket of the animals. After 4 weeks, alkaline phosphate (ALP) and calcium deposits together with collagen synthesis were investigated by biochemical analysis and histology, respectively. Further, ex vivo materials were studied after surgery regarding biomineralization and morphological changes by means of qualitative and quantitative methods. Furthermore, X-ray diffraction and Fourier-transform infrared spectroscopy underlined the newly fashioned material structuration by virtue of mineralized extracellular matrix. Specific bone markers determination stressed the osteogenic phenotype of the cells populating the material in vitro and successfully differentiated towards mature bone cells. In vivo results of specific histological staining assays highlighted collagen formation and calcium deposits, which were further validated by micro-CT. It was observed that the addition of 0.5 wt.% GO had an overall significant positive effect on both in vitro differentiation and in vivo bone cell recruitment in the subcutaneous region. These data support the GO bioactivity in osteogenesis mechanisms as being self-sufficient to elevate osteoblast differentiation and bone formation in ectopic sites while lacking the most common osteoinductive agents.

Effect of lipids with different physical state on the physicochemical properties of starch/gelatin edible films prepared by extrusion blowing

The effects of various physical state lipids (rapeseed oil (RO), shortening (ST), beeswax (BW)), on the physicochemical properties of starch (S) (hydroxypropyl distarch phosphate (HP), oxidized hydroxypropyl starch (OS))/gelatin (G) blown films were studied. S/G-lipid blends showed decreased storage modulus and complex viscosity. The formation of hydrogen bonds was inhibited by the ST and BW, but facilitated by the RO. Compared with BW and ST, RO was more effective to promote the melted and fractured of starch. Lipids addition promoted the compatibility of starch and gelatin. The presence of the lipids significantly improved the surface hydrophobicity, mechanical, water vapor barrier and water resistance properties of S/G films. S/G-RO films exhibited the strongest surface hydrophobicity and tensile strength, while HP/G-BW film showed the strongest water resistance and water vapor barrier properties. These results revealed that the appropriate lipids could be used to produce S/G-lipid films with desirable physicochemical properties.

Improving gelatin-based emulsion films with cold plasma using different gases

In this research, the effects of cold plasma treatment on the properties of gelatin-based emulsion films (GEFs) using different gases were investigated. The gases used include O2, N2, air, Ar, and ethanol-argon (EtOH-Ar). Surface hydrophobicity, morphology, water vapor permeability (WVP), and mechanical, thermal, and antifungal properties after plasma application on the film were analyzed. The results revealed that surface hydrophilicity significantly increased after cold plasma, while the contact angle significantly decreased (p < .05). Furthermore, atomic force microscopy results showed that the argon gas plasma significantly increased roughness of the GEFs surface. Besides, plasma did not decrease WVP. Different gases had no significant effect on the mechanical properties of the GEFs (p > .05). Oxygen permeability after plasma application was significantly different from the control sample; consequently, the permeability after plasma application decreased and the lowest level 55.7 (cm3μm m-2 day-1 Pa-1) was seen for oxygen gas. Plasma treatment caused etching effects and lessened the surface moisture of the polymer film. Antimicrobial activity was observed in the cold plasma-treated samples, especially under air and nitrogen atmosphere. Cold plasma treatment is an effective method for surface modification, expanding the application of emulsion films in the packing industry with improved performance properties.

Graphene Oxide Reinforcing Genipin Crosslinked Chitosan-Gelatin Blend Films

This study was targeted towards the synthesis and characterization of new chitosan–gelatin biocomposite films reinforced with graphene oxide and crosslinked with genipin. The composites’ mode of structuration was characterized by Fourier Transform Infrared spectroscopy and X-ray diffraction, while morphology and topography were investigated by scanning electron microscopy, nano-computer tomography and profilometry. Eventually, thermal stability was evaluated through thermogravimetrical analysis, mechanical properties assessment was carried out to detect potential improvements as a result of graphene oxide (GO) addition and in vitro enzyme degradation was performed to discern the most promising formulations for the maturation of the study towards in vivo assays. In accordance with similar works, results indicated the possibility of using GO as an agent for adjusting films’ roughness, chemical stability and polymer structuration. The enzymatic stability of chitosan–gelatin (CHT-GEL) films was also improved by genipin (GEN) crosslinking and GO supplementation, with the best results being obtained for CHT-GEL-GEN and CHT-GEL-GEN-GO3 (crosslinked formulation with 3 wt.% GO). Yet, contrary to previous reports, no great enhancement of CHT-GEN-GEL-GO thermal performances was obtained by the incorporation of GO.

The modification of gelatin films: Based on various cross-linking mechanism of glutaraldehyde at acidic and alkaline conditions

In order to investigate the effect of glutaraldehyde (GTA) on the structure, mechanical properties and thermal stability of gelatin films, gelatin films modified by GTA at various pH (4.5, 6.5, and 11), were prepared. According to FTIR analysis, the reaction mechanism between GTA and gelatin was different at various pH. With the addition of GTA, the intermolecular forces (hydrogen bonds and ionic bonds) and triple helix structure of gelatin film were significantly disrupted. At pH 4.5, gelatin films modified by GTA showed the highest mechanical properties and thermal stability among all films, which tensile strength and residues in TGA up to 16.13 MPa and 15.05%, respectively. Therefore, an optimum pH was around 4.5 in gelatin films cross-linked by GTA.

Functional properties of amaranth, quinoa and chia proteins and the biological activities of their hydrolyzates

Amaranth, quinoa and chia are non-conventional sources of proteins whose interest has increased in recent years due to their excellent nutritional value. Vegetable proteins can be used as food ingredients to replace animal proteins in human diet. The present article provides a comprehensive analysis of amaranth, quinoa and chia proteins and focuses on their solubility, superficial, gelling and textural properties as well as on the biological activities of enzymatic hydrolyzates.

Physical properties and antioxidant activity of gelatin-sodium alginate edible films with tea polyphenols

Active edible films were prepared by incorporating tea polyphenols (TP) into gelatin and sodium alginate. The effects of 0.4%-2.0% TP (w/w, TP/gelatin) on physical, antioxidant, and morphological properties of gelatin-sodium alginate films were evaluated. Tensile strength (Ts), contact angle (CA), and cross-linking degree showed an enhanced trend as TP concentration in the film increased, whereas elongation at break (EAB) and water vapor permeability (WVP) possessed a decline trend. The light transmittance of the film was decreased by the incorporation of TP. Antioxidant capacity was improved by increasing TP content in the films. For DPPH and ABTS radical, the films with 2.0% TP possessed the highest values of 90.62 ± 2.48% and 53.36 ± 1.06 Trolox (mg Trolox equivalent/g film), respectively. Fourier transform infrared spectroscopy analyses (FTIR) indicated the interactions existed between gelatin‑sodium alginate and TP. Smooth and continuous surface and dense internal structure of the films with TP were observed by scanning electron microscopy (SEM). Thus, incorporating TP into gelatin and sodium alginate film solution was an effective method in order to improve physical properties and antioxidant activity of the films. Gelatin-sodium alginate films with TP could be used as an edible film for food packaging applications.