Hibiscus Sabdariffa L. Extract as a Natural Additive in Food Packaging Biodegradable Films to Improve Antioxidant, Antimicrobial, and Physicochemical Properties.

In this study, biodegradable active films were prepared from potato starch and polyvinyl alcohol at different proportions, mixed with acetone extract of Hibiscus sabdariffa L. (HS) and using glycerol as a plasticizer. Functional properties, antimicrobial, and antioxidant capacity were evaluated. Potato starch films with a proportion of polyvinyl alcohol up to 50% and HS extract had significant antioxidant capacity and antibacterial effect against most of the analyzed strains. Adding polyvinyl alcohol (PVOH) and HS extract improved the mechanical performance and reduced water vapor permeability of the materials. The active biobased films with HS extract presented good physicochemical, antimicrobial, and antioxidant properties. These materials are considered as suitable for food packaging, and the active compounds in the roselle extract are a natural antibacterial option for the food area. The materials based entirely on biodegradable products are an excellent alternative when developing and marketing biobased materials, minimizing the environmental impact of food packaging.

Transformation of agricultural wastes into functional oligosaccharides using enzymes and emerging technologies.

INTRODUCTION: Pectin-oligosaccharides (POS) serve diverse purposes as a food ingredient, antimicrobial and biostimulant in plants, and their functionality is linked to the degree of esterification. Grape and broccoli wastes emerge as environmentally friendly alternatives to obtaining pectin, serving as a sustainable source to producing POS. For example, microwaves have proven to be an effective and sustainable method to extract polysaccharides from plant matrices. OBJECTIVE: This work aims to use grape and broccoli wastes as alternative sources for obtaining pectin by microwave-assisted extraction and biotransformation into POS, which possess biological properties. MATERIAL AND METHODS: The extraction conditions were identified at a power of 400 W, 300 s for the extraction of pectin from grape pomace and broccoli waste. Biotransformation of pectins into POS, using commercial enzyme preparations (Viscozyme L and Pectinase). Characterisation was carried out by Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. RESULTS: Physicochemical analysis indicated grape pomace and broccoli waste pectins had galacturonic acid content of 63.81 ± 1.67 and 40.83 ± 2.85 mg 100 mg-1, low degree of esterification of 34.89% and 16.22%, respectively. Biotransformation of pectins into POS resulted in a 20% hydrolysis rate. The main enzymatic activity was polygalacturonase for the degradation of the main structure of the pectin. CONCLUSION: Production of POS from agro-industrial wastes by emerging technologies, such as the combined use of microwave-assisted extraction and enzymatic processes, represents an alternative method for the generation of bioactive compounds with distinctive properties suitable for different applications of interest.

Improvements of thermal and mechanical properties of achira starch/chitosan/clay nanocomposite films.

Thermoplastic biofilms were developed from achira starch, chitosan and nanoclays using the solvent-casting method. To obtain the filmogenic solutions, different sonication times (0, 10, 20 and 30 min) were considered in order to evaluate the incidence of this parameter on the chemical and physico-mechanical properties of the bionanocomposite films. The chemical analysis using FTIR spectroscopy showed strong intermolecular interactions between the components with increasing sonication times. The results for tensile strength and elongation were satisfactory for films with 20 min of sonication with increases of 154% and 161%, respectively. Morphological analysis showed greater homogeneity, while thermal analysis showed that sonication favoured the plasticization process and thus, the production of homogeneous materials. The water absorption and wettability tests showed less hydrophilic materials allowing these new materials to be considered for use as coatings or packaging for the food sector.

Miscibility study of thermoplastic starch/polylactic acid blends: Thermal and superficial properties.

In this work, the miscibility of blends of thermoplastic Achira Starch (AS) and polylactic acid (PLA) was evaluated, assisted by Pluronic® F127 an amphiphilic triblock copolymer that acts as a surfactant and promotes the reduction of surface tension among AS and PLA in solution by emulsion stabilization. Different formulations of AS/PLA blends were obtained at 75:25, 50:50, and 25:75 containing 0 %, 4 %, and 8 % of Pluronic® F127, and glycerol was used as a plasticizer. Solvent casting was the method used to obtain blended polymeric films, which were characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC) and wettability by contact angle measurements. The results demonstrate that miscibility of PLA in AS or vice versa was achieved. The stability of emulsion and posterior drying of the different formulations allows the production of films for packaging, pharmaceutical, or biomedical applications.

Evaluation of the Antimicrobial, Thermal, Mechanical, and Barrier Properties of Corn Starch-Chitosan Biodegradable Films Reinforced with Cellulose Nanocrystals.

Packaging materials play an essential role in the preservation and marketing of food and other products. To improve their conservation capacity, antimicrobial agents that inhibit bacterial growth are used. Biopolymers such as starch and chitosan are a sustainable alternative for the generation of films for packaging that can also serve as a support for preservatives and antimicrobial agents. These substances can replace packaging of synthetic origin and maintain good functional properties to ensure the quality of food products. Films based on a mixture of corn starch and chitosan were developed by the casting method and the effect of incorporating cellulose nanocrystals (CNC) at different concentrations (0 to 10% w/w) was studied. The effect of the incorporation of CNC on the rheological, mechanical, thermal and barrier properties, as well as the antimicrobial activity of nanocomposite films, was evaluated. A significant modification of the functional and antimicrobial properties of the starch-chitosan films was observed with an increase in the concentration of nanomaterials. The films with CNC in a range of 0.5 to 5% presented the best performance. In line with the physicochemical characteristics which are desired in antimicrobial materials, this study can serve as a guide for the development this type of packaging for food use.

Effect of Plasticizer Content on Mechanical and Water Vapor Permeability of Maize Starch/PVOH/Chitosan Composite Films.

Packaging materials based on biodegradable polymers are a viable alternative to replace conventional plastic packaging from fossil origin. The type of plasticizer used in these materials affects their functionality and performance. The effect of different plasticizers such as glycerol (GLY), sorbitol (SOR), and poly(ethylene glycol) (PEG) in concentrations of 5%, 10%, and 15% (w/w) on the structural features and functional properties of starch/PVOH/chitosan films was evaluated. The incorporation of a plasticizer increased the thickness of the biodegradable composite films. Furthermore, the material plasticized with 30% (w/w) sorbitol had the highest elongation at break, lowest water vapor permeability, and better thermal resistance. The results obtained in this study suggest that maize starch/PVOH/chitosan biodegradable composite films are a promising packaging material, and that sorbitol is the most suitable plasticizer for this formulation.

Preparation and Physicochemical Properties of Modified Corn Starch-Chitosan Biodegradable Films.

Starch is a biopolymer with enormous potential for generating new biodegradable packages due to its easy availability and low cost. However, due to its weak functional properties, limitation of its interaction with some hydroxyl groups and evaluation of blends with other polymers are necessary in order to improve its performance. Glycerol-plasticized acetylated corn starch films were developed using the casting method, and the impact of incorporating chitosan (TPS:CH) in various proportions (75:25, 50:50, and 25:75 v/v) was studied in the present research. The effect of chitosan ratios on the physical, mechanical, water-vapor barrier, and thermal properties of the film was studied. Chitosan-protonated amino groups promoted the formation of intermolecular bonds, improving tensile strength, thermal stability, hydrophobicity, water adsorption capacity, and the gas barrier of starch films. The results show that the film composed of TPS25-CH75 proved to be the best barrier to water vapor; thus, these composite films are excellent choices for developing biodegradable packaging for the food industry.

Effects of Poloxamer Content and Storage Time of Biodegradable Starch-Chitosan Films on Its Thermal, Structural, Mechanical, and Morphological Properties.

Biodegradable packaging prepared from starch is an alternative to fossil-based plastic packaging. However, the properties of starch packaging do not comply with the necessary physicochemical properties to preserve food. Hence, in a previous study, we reported the preparation of a composite polymer material based on starch-chitosan-pluronic F127 that was found to be an adequate alternative packaging material. In this study, we modified the physicochemical properties of this material by storing it for 16 months under ambient conditions. The results indicate that the incorporation of pluronic F127 in the blend polymer can help avoid the retrogradation of starch. Moreover, at higher concentrations of pluronic F127, wettability is reduced. Finally, after storage, the materials exhibited surface modification, which is related to a color change and an increase in solubility, as well as a slight increase in stiffness.

Preparation of a novel biodegradable packaging film based on corn starch-chitosan and poloxamers.

Starch is an excellent alternative to produce packaging materials, however, due to its high hydrophilicity, it is necessary to mix it with other polymers. Chitosan (CTS) is a polymer extracted from shrimp shells and crabs, which can be used to make biodegradable materials. The principal component of biodegradable was corn starch and chitosan, the copolymer pluronic F127 was incorporated in several concentrations and its effect on the water vapor barrier, morphological, thermal, and mechanical properties of the films was evaluated, because its incorporation in the formulation of biodegradable materials could increase its hydrophobicity. The surface of starch-chitosan composite films obtained was more homogeneous and smoother with the increase in the content of pluronic F127. The %S and WVP of the starch-chitosan films decreased from 42 to 3%, and 21 × 10-11 to 3 × 10-14 g. m-1s-1 Pa-1, respectively, with the incorporation of pluronic from 3%, which makes these materials a good alternative for product packaging.

Rheological, Thermal, Superficial, and Morphological Properties of Thermoplastic Achira Starch Modified with Lactic Acid and Oleic Acid.

The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes.

Modelling the effect of temperature on the water sorption isotherms of chitosan films

Abstract The interaction of the water molecules from the environment with foods and other materials can be evaluated using sorption isotherms. Films and biodegradable films are susceptible to changes in their functional characteristics due to adsorbed water. The amount of moisture that biodegradable films can adsorb depends on the temperature, relative humidity of the storage area and chemical composition. Several mathematical models can be used to describe the behavior of sorption isotherms in biodegradable films and some of them have been modified to include the temperature parameter into the equation. In this research, the original and modified BET, GAB, Halsey, Henderson and Oswin models were assessed to determine their suitability describing the behavior of moisture adsorption isotherms of chitosan films at 15, 20, 25 and 30 °C. The modified models of GAB, Oswin and Halsey gave the best fit to the experimental sorption data of the chitosan films, with R2 values higher than 0.97 demonstrating that those models describe better the sorption isotherms at the temperatures studied.

Effect of equilibrium moisture content on barrier, mechanical and thermal properties of chitosan films.

Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Most studies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out under one relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisture content on the thermal, mechanical and barrier properties of chitosan films under several RH conditions. Microclimates, obtained with saturated salt solutions were used for conditioning samples and the properties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% of moisture at the higher RH studied. The percentage of elongation and the water vapour permeability increased while tensile strength, Young's modulus and glass transition temperature decreased, when the moisture content increased. The results suggest that the water molecules plasticized the polymer matrix, changing the properties when the films were in contact with high RH environments.