Development and characterization of agar-based edible films reinforced with nano-bacterial cellulose

Development and characterization of dual-modified yam (Dioscorea rotundata) starch-based films

The current consumer demand for fresh food and the interest in caring for the environment have driven the development of biodegradable film packaging to replace synthetic films to preserve the integrity of food. The objective of this work was to evaluate the effects of starch modifications (oxidized, cross-linked, and dual: oxidized/cross-linked), starch concentration (1 and 2%), and glycerol concentration (5 and 15%) on water vapor permeability (WVP), mechanical properties (tensile strength and elongation), optical, and structural properties of films based on “hawthorn” yam starch. The WVP of the films was 4.4 × 10⁻¹⁰ to 1.5 × 10⁻⁹ g/m∗s∗Pa, where the films with oxidized yam starch showed a 58.04% reduction concerning the native starch. The tensile strength of oxidized yam starch films showed a decrease of 17.51% with an increase in glycerol concentration. For the 1% starch concentration, elongation increased by 17.03% when the glycerol concentration was increased from 5 to 15%. Modification of starch, starch concentration, and glycerol have a significant effect on the barrier, mechanical, physical, and structural properties of films made with yam starch, where films made with oxidized yam starches at a concentration of 1% starch and 5% glycerol showed the best responses of the properties evaluated.

Characterization of a novel konjac glucomannan film incorporated with Pickering emulsions: Effect of the emulsion particle sizes

In order to understand the effects of emulsion particle sizes on the properties of novel konjac glucomannan (KGM)-based emulsion films, four types of Pickering emulsions with different oil phase (10%, 30%, 50% and 70%, v/v) were prepared by the same stabilizers (2% BCNs/SPI colloidal particles dispersions) and added into the film-forming solutions to keep the same final oil content (0.2%, w/v) in all KGM-based emulsion films. The results showed that the average particle sizes of the prepared Pickering emulsion increased with the increase of the oil phase in emulsion system. The microstructure analyses indicated that the KGM-based emulsion films became smoother as the emulsion particle sizes increased. Moreover, the contact angle values of KGM-based emulsion films slightly increased with the increase of the emulsion particle sizes, while the thermal stability of KGM-based films was not significantly affected by the particle sizes. Furthermore, the KGM-based emulsion films formed mainly through the hydrogen bond interactions as analyzed by FTIR. In addition, with the increase of the emulsion particle sizes, physical and mechanical properties of KGM-based emulsion films were significantly affected. Taken together, these results suggested that the particle sizes of Pickering emulsions had remarkable effects on the properties of KGM-based emulsion films.

Development of gum arabic-based nanocomposite films reinforced with cellulose nanocrystals for strawberry preservation

The present study aimed to develop a new bio-nanocomposite film based on gum arabic (GA) reinforced with cellulose nanocrystals (CNC). CNC was successfully fabricated and its microstructure was characterized. Subsequently, the effects of CNC on the rheological, physicochemical and functional properties of GA-based films were systematically evaluated. Results showed that the tensile strength (2.21 MPa) and elongation at break (62.79%) of film incorporated with 4% (w/w) CNC were effectively increased compared with the GA film (1.08 MPa and 42.50%). Additionally, 4% CNC reduced the water vapor and oxygen permeability by 10.61% and 25.30% respectively, while improved the ultraviolet light barrier and thermal stability of film. The well dispersion and filling effect of nanofiller contributed to form a compact and homogeneous film structure. Furthermore, the film containing 4% CNC decreased the weight loss of strawberries by 23.80% compared with the control group, thus delaying the deterioration of strawberry quality during storage.

Preparation of nanobiocomposite film based on lemon waste containing cellulose nanofiber and savory essential oil: A new biodegradable active packaging system

Lemon waste after industrial juice extraction encompasses of valuable bio-components that stimulated the development of novel and biodegradable films. Lemon waste powder (LWP) based nanobiocomposite films were prepared by incorporating different concentrations of cellulose nanofiber (CNF) (3 and 6% w/w) and savory essential oil (SEO) (1.5 and 3% w/w) in order to modify physical, mechanical and antimicrobial properties of the films. The fabricated film samples were characterized in terms of FTIR, XRD, FE-SEM and DSC analyses as well as mechanical, water vapor permeability and antimicrobial properties. FTIR and FE-SEM results indicated a good compatibility between LWP matrix and incorporated CNF and SEO. Physical and thermal analysis showed a significant effect of incorporating SEO and CNF on enhancing glass transition temperature, tensile strength and water barrier properties of the film samples. SEM analysis revealed non-uniform dispersion of CNF at higher concentration, while SEO incorporation improved the structure of the films. In addition, the LWP based films significantly showed antimicrobial properties against five food borne pathogens and this effect improved considerably by elevating the SEO loading concentration. In conclusion, LWP based nanobiocomposite films containing 3% CNF and 3% SEO could be introduced as a good candidate for development of active food packaging.

Improving the performance of edible food packaging films by using nanocellulose as an additive

Due to the environmental pollution problems caused by plastic-based packaging, the development of edible food packaging films is imminent. However, the performance of most edible packaging films is insufficient to meet practical applications, so recent studies have focused on the research of various fillers to improve film properties. This article reviews recent applications of cellulose nanocrystals (CNC) and cellulose nanofiber (CNF) in edible food packaging films including the effect on thickness, optical properties, barrier properties, water sensitivity, mechanical properties, antioxidant and antimicrobial properties. The main conclusion of this review is that the incorporation of CNC and CNF could significantly improve the performance of edible food packaging films. Particular finding is that although CNC and CNF can be used as excellent addition to improve the performance of edible food packaging films, there is a key "optimum" concentration. In addition, we also found that CNC and CNF as excellent controlled release agents and stabilizers significantly increased the antioxidant and antibacterial properties of edible food packaging films.

Preparation and characterization of a new edible film based on Persian gum with glycerol plasticizer

A new type of biodegradable film was formulated and characterized when based on the water-soluble-phase of Persian gum (SPG). The edible film was formulated optimally by using different concentrations of SPG (2.0, 2.5, 3.0, 3.5 and 4%) and glycerol as plasticizer (25, 35, and 35% based on dried SPG). Further examinations involved evaluating the manufactured films in terms of the barrier and physical properties, mechanical qualities, optical indices, microstructural properties and Fourier transform. The results showed that the increase in SPG and plasticizer content caused increases in thickness, moisture uptake, water vapor permeability and density of films (p < 0.05). Water solubility increased in response to higher concentrations of glycerol but decreased by higher amounts of dry matter (p < 0.05). The highest levels of the tensile strength (59.95%) and elongation at break (40.3 MPa) were obtained by SPG (3.5%) + 35% glycerol treatment. The L*, a* and opacity values decreased, while there was an increase in the b* value, as a result of increasing the plasticizer content (p < 0.05). A reduction occurred in the L* value of films, while the a* and b* values increased when using higher amounts of dry matter (p < 0.05). By analyzing the samples with field emission scanning electron microscopy, no cracks were observed on films when the contents of glycerol and dry matter were higher than 30% and 2.5%, respectively. The findings demonstrated that creating edible films from SPG can be an effective approach to the production of edible films.

Synthesis and Adsorption Properties of Novel Bacterial Cellulose/Graphene Oxide/Attapulgite Materials for Cu and Pb Ions in Aqueous Solutions

Removing heavy metal ions from industrial wastewater is one of the most important and difficult areas of the water treatment industry. In this study, Bacterial Cellulose/Polyvinyl Alcohol/Graphene Oxide/Attapulgite (BC/PVA/GO/APT) composites were successfully prepared via a repeated freeze-thaw method using bacterial cellulose, polyvinyl alcohol as the skeleton, and graphene oxide, attapulgite as fillers. The capacities of adsorbing Cu²⁺ and Pb²⁺ ions in solution were investigated. FTIR, XRD, SEM, BET, and TG-DSC analyses showed that the BC/PVA/GO/APT hydrogel has a better hydrophilicity, a larger specific surface area and a better thermal stability than traditional materials. We found that the adsorption of Cu²⁺ and Pb²⁺ ions can be accurately predicted by the Freundlich kinetic model, and the optimal adsorption capacities of these ions were found to be 150.79 mg/g and 217.8 mg/g respectively. Thermodynamic results showed that the adsorption process is spontaneous and exothermic. BC/PVA/GO/APT composites are suggested to be an ideal adsorption material for removing heavy metal ions from industrial wastewater.

Agar-based edible films for food packaging applications - A review

Agar is a biopolymer extracted from certain red algae. The continuous and transparent film made from agar gum is becoming a common and renewable alternative for plastic-based food packaging materials. However, plain agar film suffers from brittleness, high moisture permeability, and poor thermal stability. Considerable researches have been devoted to improving the properties of agar films to extend their applications. These include reinforcements by nanomaterials, blending with other biopolymers, and incorporating plasticizers, hydrophobic components, or antimicrobial agents into their structure. This article comprehensively reviews the functional properties and defects of edible films made from agar gum. Also, it describes various strategies and components used to make an agar film with desirable properties. Moreover, the applications of agar-based edible films with improved functionality for food packaging are discussed.

Bacterial cellulose in food industry: Current research and future prospects

Bacterial cellulose, a pure exocellular polysaccharide produced by microorganisms, has many excellent properties as compared with plant-derived cellulose, including high water holding capability, high surface area, rheological properties, biocompatibility. Due to its suspending, thickening, water holding, stabilizing, bulking and fluid properties, BC has been demonstrated as a promising low calorie bulking ingredient for the development of novel rich functional foods of different forms such as powder gelatinous or shred foams, which facilitate its application in food industry. In this review, the recent reports on the biosynthesis, structure and general application of bacterial cellulose in food industry have been summarized and discussed. The main application of bacterial cellulose in current food industry includes raw food materials, additive ingredients, packing materials, delivery system, enzyme and cell immobilizers. In addition, we also propose the potential challenges and explore the solution of expanding the application of BC in various fields.

Development and characterization of a novel edible film based on Althaea rosea flower gum: Investigating the reinforcing effects of bacterial nanocrystalline cellulose

Althaea rosea flowers were used to procure the gum (ARG) needed for film preparation. Pretest studies suggested 1.5% ARG + 50% glycerol as optimum for film preparation. The reinforcement impact of 3, 5, and 8 wt% bacterial nanocrystalline cellulose (BNC) incorporation (based on the dry weight of ARG) was investigated on the structural, mechanical, physical, thermal, optical, morphological, and barrier properties of films. The Results suggested that increasing the BNC concentration until a certain level (5 wt% BNC) could improve the latter properties. However, at higher concentration (8 wt% BNC), cellulose nanoparticles tended to agglomerate, which led to the impairment of some of those properties, especially barrier properties. According to AFM and SEM results, BNC addition increased surface roughness and coarseness. All BNC-loaded films showed better functions compared to control sample (0 wt% BNC) and the film containing 5 wt% BNC was suggested as the optimum film.

The Effect of Cross-Linking with Citric Acid on the Properties of Agar/Fish Gelatin Films

The aim of this work was to assess the effect of fish gelatin-citric acid nucleophilic substitution and agar-citric acid esterification reactions on the properties of agar/fish gelatin films. Since temperature is an important cross-linking parameter, films were treated at 90 °C and 105 °C and film properties were compared to those of non-cured films. It was observed that temperature favored the aforementioned reactions, which induced physical and morphological changes. In this regard, darker films with a rougher surface were obtained for the films with a higher cross-linking degree. While mechanical properties were slightly modified, the barrier properties were enhanced due to the reactions that occurred. Therefore, these agar/fish gelatin films cross-linked through two different reactions can be considered to be promising materials as active films for different purposes, such as active packaging or pharmaceutical applications.

Synthesis and characterization of quaternized agar in KOH/urea aqueous solution

Quaternized agar (QA) is synthesized in KOH/urea aqueous solution and shows low melting and gelling temperatures and antibacterial properties.

Development and characterization of elephant foot yam starch-hydrocolloids based edible packaging film: physical, optical, thermal and barrier properties

The study aimed at the development of elephant foot yam starch (EFYS) based edible film through blending of Xanthan (XG) and agar-agar (AA). Film thickness and density increased with increase in concentration of hydrocolloids and the respective highest value 0.199 mm and 2.02 g/cm³ were found for the film possessing 2% AA. The film barrier properties varied with hydrocolloids and the lowest value of water vapour transmission rate (1494.54 g/m²) and oxygen transmission rate (0.020 cm³/m²) was observed for the film with 1% XG and 1.5% AA, respectively. Mechanical and thermal properties also improved upon addition of hydrocolloid. Highest tensile strength (20.14 MPa) and glass transition temperature (150.6 °C) was observed for film containing 2% AA. Fourier transform infrared spectroscopy demonstrated the presence of -OH, C-H, and C=O groups. The change in crystallinity was observed through peak in X-ray diffraction analysis, which increased with increase in the hydrocolloids' concentration.

Drying kinetics, antioxidants, and physicochemical properties of litchi fruits by ultrasound-assisted hot air-drying

To obtain better qualities of litchi fruits, fruit pulps were subjected to ultrasonic treatment (UT) followed by drying. Samples were subjected to UT at 3 W/g for 10 min with distilled or ice water and compared with non-UT dried samples. After drying, vitamin C, total phenolic content, color, texture, nutrition, microbial load, drying kinetics, and shelf life were assessed. Results suggest that shear stress plus increasing heat reduced drying time by about 50%, and retained 70% vitamin C and 60% total phenolic content. UT led to about 75% of vitamin C and 70% total phenolic content through inhibition of ultrasonic heat. No significant differences were found in redness, yellowness, and hardness. Inhibition of ultrasound heat resulted in about 27% glucose, 22% fructose, 17% sucrose, and prolonged storage time. Inhibition of increasing ultrasound heat allows low drying cost and high product quality of litchi fruit in air-drying. PRACTICAL APPLICATIONS: UT promotes drying efficiency and preserves product quality. However, this treatment triggers the loss of antioxidants and sugars of litchi fruits when water temperature arises in the treatment. Additional use of ice crystals can offset the thermal effect of the UT; this mechanism reduces the diffusion and loss of nutrients from the material to the solution. This strategy is simple and feasible to improve the drying rate and to retain the content of antioxidants, and further improve the flavor and storage quality of dried litchi fruits.

Formulation and Characterization of Edible Films Based on Organic Mucilage from Mexican Opuntia ficus-indica

The consumption of organic products has increased in recent years. One of the most important products in Mexico is nopal. Nopal’s content and properties make the formulation of edible films possible. In this study, we aimed to develop and characterize biodegradable edible films containing mucilage from Opuntia ficus-indica. The mucilage extraction yield, thickness, color, water vapor permeability, light transmission rate, film transparency, solubility, stability of dispersion, and puncture strength were measured. The use of mucilage from different cultivars affected the water vapor permeability (8.40 × 10−11 g·m−1·s−1·Pa−1 for cultivar Villanueva, 3.48 × 10−11 g·m−1·s−1·Pa−1 for Jalpa, and 1.63 × 10−11 g·m−1·s−1·Pa−1 for Copena F1). Jalpa provided the most soluble mucilage with the highest thickness (0.105 mm). Copena F1 provided the clearest film with the greatest transparency (3.81), the best yellowness index, and the highest resistance (4.44 N·mm−1). Furthermore, this film had the best light transmission rate (48.93%). The Copena F1 showed the best film formation solution viscosity. These results indicate that mucilage mixed with pectin is a potential source for the formulation of edible films.

Characterization of bacterial cellulose films combined with chitosan and polyvinyl alcohol: Evaluation of mechanical and barrier properties

Bacterial cellulose (BC) produced by Komagataeibacter xylinus is a biomaterial with a unique three-dimensional structure. To improve the mechanical properties and reinforce the BC films, they were immersed in polyvinyl alcohol (0-4%) and chitosan (0-1%) baths. Moisture content, mechanical properties and water vapour permeability were measured to assess the effect of polyvinyl alcohol and chitosan. The morphology, optical, structural and thermal properties were evaluated by scanning electron microscopy, spectral analysis, thermogravimetry and differential scanning calorimetry. Results showed that moisture content was significantly affected by the chitosan presence. Tensile strength values in the 20.76-41.65 MPa range were similar to those of synthetic polymer films. Percentage of elongation ranged from 2.28 to 21.82% and Young's modulus ranged from 1043.88 to 2247.82 MPa. The water vapour permeability (1.47 × 10^-11-3.40 × 10^-11 g/m s Pa) decreased with the addition of polyvinyl alcohol. The developed films own UV light barrier properties and optimal visual appearance.