Characterization of films made with chayote tuber and potato starches blending with cellulose nanoparticles

The aim of this study was to characterize chayotextle starch films reinforced with cellulose (C) and cellulose nanoparticle (CN) (at concentrations of 0.3%, 0.5%, 0.8% and 1.2%), using thermal, mechanical, physicochemical, permeability, and water solubility tests. C was acid-treated to obtain CN. The films were prepared by casting; potato starch and C were used as the control. The solubility of the starch films decreased with the addition of C and CN compared with its respective film without C and CN. No statistical difference (α = 0.05) was found in the films added with different concentrations of C and CN. In general, the mechanical properties were improved with the addition of C and CN, and higher values of tensile strength and elastic modulus were determined in the films reinforced with CN. The melting temperature and enthalpy increased with the addition of C and CN, and the values of both thermal parameters were higher in the films with CN than with C; the enthalpy value of the film decreased when the concentration of C or CN increased in the composite. Low concentration of C and CN is better distributed in the matrix film. The addition of C and CN in the starch films improved some mechanical, barrier, and functional properties.     

Physical, chemical and mechanical properties of pehuen cellulosic husk and its pehuen-starch based composites

Pehuen cellulosic husk was characterized and employed as reinforcement for composite materials. In this research, thermoplastic pehuen starch (TPS) and TPS/poly(lactic acid) (PLA)/polyvinyl alcohol (PVA) composites, reinforced with 5 and 10% of pehuen husk, were prepared by melt-blending. Comparative samples of pehuen TPS and TPS/PLA/PVA blend were also studied. Physical, thermal, structural and mechanical properties of composites were evaluated. Pehuen husk mainly consists of cellulose (50wt%), hemicellulose (30wt%) and lignin (14wt%). In respect to lipids, this husk has only a 0.6wt%. Its surface is smooth and damage-free and it is decomposed above 325°C. The incorporation of pehuen husk improved considerably the thermal stability and mechanical properties of the studied composites, mainly in TPS composites. Their thermal stability enhances since biofiber hinders the "out-diffusion" of volatile molecules from the polymer matrix, while mechanical properties could raise due to the natural affinity between husk and starch in the pehuen seed.     

Properties of biodegradable citric acid-modified granular starch/thermoplastic pea starch composites

Pea starch-based composites reinforced with citric acid-modified pea starch (CAPS) and citric acid-modified rice starch (CARS), respectively, were prepared by screw extrusion. The effects of granular CAPS and CARS on the morphology, thermal stability, dynamic mechanical thermal analysis, the relationship between the mechanical properties and water content, as well as the water vapor permeability of the composite films were investigated. Scanning electron microscope and X-ray diffraction reveal that the reinforcing agents, the granules of CAPS and CARS, are not disrupted in the thermoplastic process, while the pea starch in the matrix is turned into a continuous TPS phase. Granular CAPS and CARS can improve the storage modulus, the glass transition temperature, the tensile strength and the water vapor barrier, but decrease thermal stability. CARS/TPS composites exhibit a better storage modulus, tensile strength, elongation at break and water vapor barrier than CAPS/TPS composites because of the smaller size of the CARS granules.     

Edible films made from natural resources; microcrystalline cellulose (MCC), methylcellulose (MC) and corn starch and polyols-Part 2

Aqueous blends of microcrystalline cellulose (MCC) or methyl cellulose (MC) and corn starch with or without polyols were extruded, hot pressed and studied, after their conditioning at different relative humidities, in terms of their thermal, mechanical and water and gas permeability properties. An increase in water or polyol content showed a considerable increase in percentage elongation but also a decrease in the tensile strength of films. The presence of high cellulose contents increased the tensile strength and decreased the water vapour transmission of films. The development of crystallinity with time resulted in a decrease of both gas and water permeability. Several semiempirical models for calculation of gas permeability and tensile strength and tensile and flexural moduli were applied. The obtained values were compared to those experimentally determined and with the ones reported in the literature. On several occasions, quite significant discrepancies were found which were attributed to differences in molecular weight, percentage crystallinity and polymorphism.     

Preparation and study of novel biodegradable blends based on gelatinized starch and 1,4-trans-polyisoprene (gutta percha) for food packaging or biomedical applications

The gas and water vapour permeability coefficients of novel biodegradable films based on 1,4-trans-polyisoprene and gelatinized starch were determined. The glass transitions, indirectly determined from gas permeability measurements, were compared to those obtained from thermal measurements (differential thermal analysis and dynamic mechanical thermal analysis). Incorporation of a low plasticizer amount in the blend was attempted in order to improve the mechanical properties of the blends. Some initial biodegradability experiments showed that these novel blends are biodegradable. This is primarily due to the presence of starch.     

Ionic liquid-based preparation of cellulose-dendrimer films as solid supports for enzyme immobilization

Surface-active cellulose films for covalent attachment of bioactive moieties were achieved by codissolution of cellulose with polyamidoamine (PAMAM) dendrimers in an ionic liquid followed by regeneration of the composite as a film. Different generations of PAMAM were used for the formation of cellulose-dendrimer composites, as well as films with the dendrimer covalently bonded to the cellulose by means of the linker 1,3-phenylene diisocyanate. Surface characterization, thermal stability, and utility for immobilization of laccase were determined. The presence of the dendrimer amino groups was confirmed by detailed characterization of the films' surfaces. These modified films exhibit acceptable thermal stability, comparable to that of other regenerated cellulose films, but the number of active functional groups on the surface is much smaller than the theoretical amount expected. Films made with 1,3-phenylene diisocyanate as linker for covalently bound cellulose and dendrimers exhibit a better performance for immobilization of laccase than those prepared by simple mixing of the cellulose and dendrimer. In general, a linear correspondence between the dendrimer generation within the films and the specific activity of immobilized laccase in such films was not observed.     

Transparent cellulose films with high gas barrier properties fabricated from aqueous alkali/urea solutions

Transparent and bendable regenerated cellulose films prepared from aqueous alkali (NaOH or LiOH)/urea (AU) solutions exhibit high oxygen barrier properties, which are superior to those of conventional cellophane, poly(vinylidene chloride), and poly(vinyl alcohol). Series of AU cellulose films are prepared from different cellulose sources (cotton linters, microcrystalline cellulose powder, and softwood bleached kraft pulp) for different dissolution and regeneration conditions. The oxygen permeabilities of these AU cellulose films vary widely from 0.003 to 0.03 mL μm m(-2) day(-1) kPa(-1) at 0% relative humidity depending on the conditions used to prepare the films. The lowest oxygen permeability is achieved for the AU film prepared from 6 wt % cellulose solution by regeneration with acetone at 0 °C. The oxygen permeabilities of the AU cellulose films are negatively correlated with their densities, and AU films prepared from solutions with high cellulose concentrations by regeneration in a solvent at low temperatures generally have low oxygen permeabilities. The AU cellulose films are, therefore, promising biobased packaging materials with high-oxygen barrier properties.     

Preparation of chitin/cellulose composite gels and films with ionic liquids

In this study, we performed preparation and characterizations of the chitin/cellulose composite gels and films using the two ionic liquids, 1-allyl-3-methylimidazolium bromide and 1-butyl-3-methylimidazolium chloride. First, chitin and cellulose were dissolved in each appropriate ionic liquid. Then, the two liquids were mixed in the desired ratios at 100 °C to give the homogeneous mixtures. The gels were obtained by standing the mixtures for 4 days. On the other hand, the films were obtained by casting the mixtures on glass plates, followed by soaking in water and drying. The obtained gels and films were characterized by XRD and TGA measurements. The mechanical properties of the gels and films were evaluated under compressive and tensile modes, respectively.     

Characterization of edible emulsified films with low affinity to water based on kefiran and oleic acid

New edible composite films based on kefiran and oleic acid (OA) at the ratio of 15, 25, and 35% (w/w) were prepared using emulsification with the aim of improving their water vapour barrier and mechanical properties. Film-forming solutions were characterized in terms of rheological properties and particle-size distribution. The impact of the incorporation of OA into the film matrix was studied by investigating the physical, mechanical, and thermal properties of the films. The water vapour permeability (WVP) of the emulsified films was reduced by approximately 33% by adding OA. The mechanical properties of kefiran films were also affected by adding OA: tensile strength was diminished, and elongation increased considerably. Differential scanning calorimetry showed that the glass transition temperature (T_g) of the kefiran film was −16 °C and was not considerably affected by adding OA. Therefore, OA could be incorporated into these films for some food-technology applications that need a low affinity toward water.     

Preparation of cellulose–starch composite gel and fibrous material from a mixture of the polysaccharides in ionic liquid

This paper reports the preparation of a cellulose–starch composite gel from an ionic liquid solution. The gel was obtained by keeping the homogeneous mixture of cellulose (10% w/w) and starch (5% w/w) in 1-butyl-3-methylimidazolium chloride (BMIMCl) for several days at room temperature and characterized by elemental analysis, X-ray diffraction, and thermal gravimetric analysis. Furthermore, the production of the fibrous material composed of cellulose and starch by reconstitution from the homogeneous mixture (10% w/w each) in BMIMCl is demonstrated.     

Bi-Functional Biobased Packing of the Cassava Starch,Glycerol, Licuri Nanocellulose and Red Propolis

The aim of this study was to characterize and determine the bi-functional efficacy of active packaging films produced with starch (4%) and glycerol (1.0%), reinforced with cellulose nanocrystals (0–1%) and activated with alcoholic extracts of red propolis (0.4 to 1.0%). The cellulose nanocrystals used in this study were extracted from licuri leaves. The films were characterized using moisture, water-activity analyses and water vapor-permeability tests and were tested regarding their total phenolic compounds and mechanical properties. The antimicrobial and antioxidant efficacy of the films were evaluated by monitoring the use of the active films for packaging cheese curds and butter, respectively. The cellulose nanocrystals increased the mechanical strength of the films and reduced the water permeability and water activity. The active film had an antimicrobial effect on coagulase-positive staphylococci in cheese curds and reduced the oxidation of butter during storage.     

Structure and properties of carboxymethyl cellulose/soy protein isolate blend edible films crosslinked by Maillard reactions

Edible films based on carboxymethyl cellulose (CMC) and soy protein isolate (SPI), compatibilized by glycerol, were prepared by solution casting. The effects of CMC content on blend structure, thermal stability, water solubility and water sorption, and mechanical properties were systematically investigated. Fourier transform infrared (FTIR) spectra showed that Maillard reactions occurred between CMC and SPI, and X-ray diffraction (XRD) scans indicated that the Maillard reactions greatly reduced the crystallinity of SPI. According to differential scanning calorimetry (DSC) analysis, CMC/SPI blends had a single glass transition temperature (T_g) between 75 and 100 °C, indicating that CMC and SPI form one phase blends. Increasing the CMC content improved the mechanical properties and reduced the water sensitivity of blend films. The results indicate that the structure and properties of SPI edible films were modified and improved by blending with CMC.     

Effects of extrusion and glycerol content on properties of oxidized and acetylated corn starch-based films

Oxidized and acetylated corn starch-based films were prepared by casting with glycerol as a plasticizer. The present study investigated the effects of extrusion prior to film-making and glycerol content on the properties of starch films. The films with extrusion exhibited lower tensile strength, higher elongation at break, higher water vapor permeability and higher oil permeability than those without extrusion. Extrusion reduced heat sealability of the films. With the increase of glycerol content, the films became more flexible with higher elongation at break and lower tensile strength. Water vapor permeability, oil permeability and the range between the onset temperature and the melt peak temperature rose as glycerol content increased. The thermograms indicated that plasticizers and biopolymers were compatible. These results suggested that extrusion did no good to starch films while glycerol content had apparent effect on the mechanical and barrier properties of the films.     

Biodegradability and mechanical properties of starch films from Andean crops

Different Andean crops were used to obtain starches not previously reported in literature as raw material for the production of biodegradable polymers. The twelve starches obtained were used to prepare biodegradable films by casting. Water and glycerol were used as plasticizers. The mechanical properties of the starch based films were assessed by means of tensile tests. Compost tests and FTIR tests were carried out to assess biodegradability of films. The results show that the mechanical properties (UTS, Young's modulus and elongation at break) of starch based films strongly depend on the starch source used for their production. We found that all the starch films prepared biodegrade following a three stage process and that the weight loss rate of all the starch based films tested was higher than the weight loss rate of the cellulose film used as control.     

Biodegradable films made from low density polyethylene (LDPE), wheat starch and soluble starch for food packaging applications. Part 2

Blends of LDPE and wheat or soluble starch were extruded, hot pressed and studied, after conditioning at various relative humidities, with regard to their mechanical properties and gas/water permeabilities before and after storage. Several theoretical and semiempirical calculations for mechanical properties and gas permeability are applied and possible interpretations are provided for occasionally observed deviations between the experimental and the theoretical values. Some of the semiempirical models predicted reasonably well the mechanical behaviour of the films. The presence of starch, at contents >30%, had an adverse effect on the mechanical properties of LDPE/starch blends. The degradability of several LDPE/starch blends and the accompanying changes in their mechanical properties are also assessed. Gas permeability and water vapour transmission rate increased proportionally with the starch content in the blend.     

Mechanical properties and water vapor transmission in some blends of cassava starch edible films

The continuous increase of consumer interest in quality, convenience and food quality has encouraged further research into edible films and coatings from natural polymers, such as polysaccharides. Ecoefficient products are the new generation of biobased products prepared with sustainable materials, that agree with ecological and economic requirements including environmentally acceptable disposal of post-user waste. The numerous potential applications of natural polymers such as polysaccharides stimulated the study with edible films based on cassava starch. Blends of glycerol (GLY) and polyethylene glycol (PEG) as plasticizers, and glutaraldehyde (GLU) as crosslinking agent were prepared in order to determine the mechanical properties and water vapor transmission of those films. A response surface methodology was applied on the results to identify the blend with the best mechanical properties and lowest water vapor transmission. The crosslinking effect of glutaraldehyde in the films can be observed. The plasticizing action of polyethylene glycol was restrained by more than 0.5 g of glutataraldehyde. The use of glycerol was less evident for this property even after 284 h of contact time with water vapor.     

Thermal, Mechanical and Microstructures Properties of Cellulose Derivatives Films: A Comparative Study

The proposal in this study was to evaluate the physical properties of different biopolymers films. The materials used were: pectin, carboxyl methylcellulose, methylcellulose, hydroxyl propylcellulose, hydroxypropyl-methylcellulose, and corn waxy starch; from these polysaccharides aqueous dispersions were prepared to 3% (w/v) for obtained films. In these biopolymer films, the thermal diffusivities (α) was evaluated by the Open Photoacoustic Cell method; also, their mechanical properties as tensile strength, elongation, and Young’s modulus were measured, their crystallinity percentage was evaluated by X-ray diffraction and microstructure through atomic force microscopy in contact mode. From the polysaccharide films, it was observed that most of them were flexible and transparent. In the case of the films, mechanical properties were found that the highest value of tensile strength and Young’s modulus corresponded to carboxyl methylcellulose with 69.17 and 1,912.20 MPa values, respectively. Also, Open Photoacoustic Cell method and X-ray diffraction measurements showed that there exist a correlation between the thermal diffusivity values and the crystallinity measured in the biopolymer films. It was also observed that α values of cellulose derived was affected by the substitution group in the molecule, reaching the highest α value, the films of carboxyl methylcellulose. Regarding the microstructural of the films, starch showed the highest roughness value (88.6 nm) whereas hydroxypropyl-methylcellulose resulted with the lowest roughness value (7.67 nm).     

Comparison of lignin derivatives as substrates for laccase-catalyzed scavenging of oxygen in coatings and films

Background

Lignin derivatives are phenylpropanoid biopolymers derived from pulping and biorefinery processes. The possibility to utilize lignin derivatives from different types of processes in advanced enzyme-catalyzed oxygen-scavenging systems intended for active packaging was explored. Laccase-catalyzed oxidation of alkali lignin (LA), hydrolytic lignin (LH), organosolv lignin (LO), and lignosulfonates (LS) was compared using oxygen-scavenging coatings and films in liquid and gas phase systems.

Results

When coatings containing lignin derivatives and laccase were immersed in a buffered aqueous solution, the oxygen-scavenging capability increased in the order LO?<?LH?<?LA?<?LS. Experiments with coatings containing laccase and LO, LH or LA incubated in oxygen-containing gas in air-tight chambers and at a relative humidity (RH) of 100% showed that paperboard coated with LO and laccase reduced the oxygen content from 1.0% to 0.4% during a four-day period, which was far better than the results obtained with LA or LH. LO-containing coatings incubated at 92% RH also displayed activity, with a decrease in oxygen from 1.0% to 0.7% during a four-day period. The oxygen scavenging was not related to the content of free phenolic hydroxyl groups, which increased in the order LO?<?LS?<?LH?<?LA. LO and LS were selected for further studies and films containing starch, clay, glycerol, laccase and LO or LS were characterized using gel permeation chromatograpy, dynamic mechanical analysis, and wet stability.

Conclusions

The investigation shows that different lignin derivatives exhibit widely different properties as a part of active coatings and films. Results indicate that LS and LO were most suitable for the application studied and differences between them were attributed to a higher degree of laccase-catalyzed cross-linking of LS than of LO. Inclusion in active-packaging systems offers a new way to utilize some types of lignin derivatives from biorefining processes.     

Lignin-based electrospun nanofibers reinforced with cellulose nanocrystals

Lignin-based fibers were produced by electrospinning aqueous dispersions of lignin, poly(vinyl alcohol) (PVA), and cellulose nanocrystals (CNCs). Defect-free nanofibers with up to 90 wt % lignin and 15% CNCs were achieved. The properties of the aqueous dispersions, including viscosity, electrical conductivity, and surface tension, were examined and correlated to the electrospinnability and resulting morphology of the composite fibers. A ternary lignin-PVA-water phase diagram was constructed as a tool to rationalize the effect of mixing ratios on the dispersion electrospinability and morphology of the resulting fibers. The influence of reinforcing CNCs on the thermal properties of the multicomponent fibers was investigated by using thermal gravimetric analysis and differential scanning calorimetry. The thermal stability of the system was observed to increase owing to a strong interaction of the lignin-PVA matrix with the dispersed CNCs, mainly via hydrogen bonding, as observed in Fourier transform infrared spectroscopy experiments.     

Chitosan and gelatin based edible films: state diagrams, mechanical and permeation properties

Films of chitosan and gelatin were prepared by casting their aqueous solutions (pH≈4.0) at 60°C and evaporating at 22 or 60°C (low- and high-temperature methods, respectively). The physical (thermal, mechanical and gas/water permeation) properties of these composite films, plasticized with water or polyols, were studied. An increase in the total plasticizer content resulted in a considerable decrease of elasticity modulus and tensile strength (up to 50% of the original values when 30% plasticizer was added), whereas the percentage elongation increased (up to 150% compared to the original values). The low-temperature preparation method led to the development of a higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two orders of magnitude, of CO₂ and O₂ permeability in the chitosan/gelatin blends. An increase in the total plasticizer content (water, polyols) of these blends was found to be proportional to an increase in their gas permeability.