Starch-chitosan Films Research Articles

Physical and Antimicrobial Properties of Compression-Molded Cassava Starch-Chitosan Films for Meat Preservation

The authors acknowledge the financial support provided by the Spanish Ministerio de Economia y Competividad (Projects AGL2013-42989-R and AGL2016-76699-R). Author Cristina Valencia-Sullca thanks the Peruvian Grant National Program (PRONABEC Grant).

Chitosan-Starch Films with Natural Extracts: Physical, Chemical, Morphological and Thermal Properties.

The aim of this study is to analyze the properties of a series of polysaccharide composite films, such as apparent density, color, the presence of functional groups, morphology, and thermal stability, as well as the correlation between them and their antimicrobial and optical properties. Natural antioxidants such as anthocyanins (from cranberry; blueberry and pomegranate); betalains (from beetroot and pitaya); resveratrol (from grape); and thymol and carvacrol (from oregano) were added to the films. Few changes in the position and intensity of the FTIR spectra bands were observed despite the low content of extract added to the films. Due to this fact, the antioxidants were extracted and identified by spectroscopic analysis; and they were also quantified using the Folin-Denis method and a gallic acid calibration curve, which confirmed the presence of natural antioxidants in the films. According to the SEM analysis, the presence of natural antioxidants has no influence on the film morphology because the stretch marks and white points that were observed were related to starch presence. On the other hand, the TGA analysis showed that the type of extract influences the total weight loss. The overall interpretation of the results suggests that the use of natural antioxidants as additives for chitosan-starch film preparation has a prominent impact on most of the critical properties that are decisive in making them suitable for food-packing applications.

Chitosan–Starch–Keratin Composites: Improving Thermo-Mechanical and Degradation Properties Through Chemical Modification

Chitosan–starch polymers are reinforced with different keratin materials obtained from chicken feather. Keratin materials are treated with sodium hydroxide; the modified surfaces are rougher in comparison with untreated surfaces, observed by Scanning Electron Microscopy. The results obtained by Differential Scanning Calorimetry show an increase in the endothermic peak related to water evaporation of the films from 92 °C (matrix) up to 102–114 °C (reinforced composites). Glass transition temperature increases from 126 °C in the polymer matrix up to 170–200 °C for the composites. Additionally, the storage modulus in the composites is enhanced up to 1614% for the composites with modified ground quill, 2522% for composites with modified long fiber and 3206% for the composites with modified short fiber. The lysozyme test shows an improved in the degradability rate, the weight loss of the films at 21 days is reduced from 73% for chitosan-starch matrix up to 16% for the composites with 5 wt% of quill; but all films show a biodegradable character depending on keratin type and chemical modification. The outstanding properties related to the addition of treated keratin materials show that these natural composites are a remarkable alternative to potentiating chitosan–starch films with sustainable features.

Thermoplastic cassava starch-chitosan bilayer films containing essential oils

Starch-chitosan bilayer films, containing or not essential oils in the casted chitosan layer were obtained by thermo-compression. Bilayer films exhibited a good interfacial adhesion and better mechanical resistance than starch monolayers, although they were less stretchable and less transparent. Starch-chitosan films were effective at controlling the bacterial growth in pork meat, but the thermal treatment applied to obtain the bilayers reduced their antimicrobial properties as compared to chitosan monolayers. The addition of essential oils did not promote any antimicrobial action in chitosan mono and bilayer films applied to pork meat. The final amount of essential oils in the films was very limited probably due to the losses occurred during film processing method. Other strategies to incorporate the essential oils into chitosan-based films should be used to improve their final retention in the film matrix and their effective release into the coated food.

Antimicrobial, Optical and Mechanical Properties of Chitosan-Starch Films with Natural Extracts.

Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan–starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV–VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications.

Modification of Physico-Mechanical Properties of Chitosan-Tapioca Starch Blend Films Using Nano Graphene

Biodegradable blend films from chitosan-tapioca starch were prepared by the casting method. To improve the properties of chitosan–starch blend films, nano graphene was used. The influences of the loading of graphene on the physico-mechanical properties in terms of water vapor transmission rate (WVTR), thermal stability, and tensile strength of the blend films were investigated. Scanning electron microscopy (SEM) and FTIR were used to investigate the surface morphology and molecular interaction of the blend films, respectively. After the incorporation of nano graphene, the blend film from chitosan-starch showed an increase in tensile strength and thermal stability, and a decrease in WVTR and elongation at the break. These results showed that the combination of a tiny amount of graphene presents a promising method for improving the mechanical and barrier properties of chitosan-starch biocomposite films. The SEM observations indicated that a high amount (3 wt.%) of graphene was easily agglomerated. This caused the mechanical properties of the composite films to be reduced. Among the various compositions studied, chitosan-starch film filled with 0.8 wt.% graphene showed superior properties. The structural properties investigated by FTIR showed a clear interaction between chitosan and starch, forming a new material with enhanced mechanical properties.

Chitosan–starch film reinforced with magnetite-decorated carbon nanotubes

Carbon nanotubes and magnetite nanoparticles are materials with unique and extraordinary properties having a wider range of applications in diverse areas of science and engineering. In addition, this kind of nanomaterial can be linked to a polymeric matrix resulting in a multifunctional composite material with enhanced properties. We present here the synthesis of chitosan–starch (CH–S) films reinforced with magnetite-decorated carbon nanotubes and their properties were studied. In order to synthesize the nanocomposite material, multi-walled carbon nanotubes (MWCNTs) were first decorated with magnetite nanoparticles (MNPs) of 13.4±3.7nm using MWCNT/MNPs ratios of 0.2 and 2. Chitosan chains were used as bonding agent, and in the next step, MWCNT/MNPs was incorporated into a polymeric matrix of 70% of chitosan and 30% of starch. Concentrations of magnetite decorated MWCNT in the films were 0.1%, 0.25%, and 0.5%, respectively. Thermogravimetric and dynamic mechanical analyses were performed. The lowest concentration polymeric film showed homogeneous particle distribution, and this homogeneity was lost due to the formation of large agglomerates (≈192nm) at higher concentration. This behavior affected the physical properties of nanocomposites. Storage modulus of the film decreased as the concentration of decorated MWCNT increased indicating dependence of storage modulus on agglomerates size. The storage modulus increased in the temperature range of 150–250°C. This behavior was more pronounced at 1:3 ratios of MWCNT/MNPs due to the stronger interfacial adhesion between nanoparticles and the polymeric matrix. The magnetic behavior and electrical conductivity of the nanocomposites were also studied.

Characterization and antimicrobial properties of water chestnut starch-chitosan edible films

The characterization and antimicrobial properties of water chestnut starch-chitosan (WSC) films containing Cornus officinalis fruit extract (COE 1% w/w), glycerol monolaurate (GML 1% w/w), nisin (10,000IU/g), pine needle essential oil (PNEO 0.35% v/v), and their combinations were evaluated. Incorporation of COE decreased pH value of the film-forming solution, the moisture content and the water absorption expansion ability (WAEA). GML-incorporated film had lower WAEA, tensile strength, elongation and puncture strength. However, films with nisin displayed good mechanical properties. All the treated films were less transparent and higher in water vapour permeability values. For film microstructure, the presence of PNEO caused discontinuities with lipid droplets or holes embedded in a continuous network and the incorporation of GML led to abaisse-like structures. The COE, GML, nisin, PNEO and their combinations incorporated in the WSC films are effective in inhibiting the growth of Escherichia coli O157:H7, Staphylococcus aureus and Listeria monocytogenes at different levels. The results showed that WSC films containing COE and GML, GML and nisin, COE and nisin were able to reduce the number of E. coli O157:H7, S. aureus and L. monocytogenes. This research has potential applications to the extension of the shelf life of food products.

Effect of the incorporation of antioxidants on physicochemical and antioxidant properties of wheat starch–chitosan films

Blend edible films were prepared from wheat starch (WS) and chitosan (CH) with glycerol as plasticizer. Four active ingredients (antioxidants) were added, namely basil essential oil, thyme essential oil, citric acid and α-tocopherol. The starch:antioxidant mass ratio was 1:0.1. Prior to characterisation, the films were conditioned at 25°C–53%RH as to their structural, mechanical, optical and barrier properties. The antioxidant capacity of the active ingredients was determined by means of a spectrophotometric method. The incorporation of antioxidants led to a heterogeneous film microstructure, mainly in those containing α-tocopherol, which affected the surface roughness. Yellowness was induced in films when α-tocopherol was added and no notable colour changes were observed in the other cases, although all the antioxidants increased the transparency of the films. Despite of the fact that the mechanical properties were barely affected by the incorporation of antioxidants, citric acid promoted an increase in the elastic modulus but a decrease in film stretchability. The water vapour barrier properties of the films were only slightly improved when citric acid and α-tocopherol were added, whereas the oxygen barrier properties were significantly improved in all cases. The greatest antioxidant capacity of the films was reported for films containing α-tocopherol, which exhibited the highest antioxidant power.

Characterization of edible starch–chitosan film and its application in the storage of Mongolian cheese

The physicochemical, mechanical, optical and structural properties based on different amylose content starch–chitosan films with the addition of hydrophilic glycerol and hydrophobic perilla oil were investigated, and the effects of the starch–chitosan coating on the physicochemical and microbial properties of Mongolian cheese were evaluated. The films were formed by casting method. Results showed that the incorporation of perilla oil resulted in a decrease in moisture content, solubility and mechanical properties and an increase in total color difference (ΔE*). High water vapor permeability (WVP), good transparency and low solubility were observed with the addition of glycerol. Meanwhile, the film based on mung bean starch–chitosan (MSC) exhibited higher moisture content, WVP values, ΔE* and less transparency than that based on water chestnut starch–chitosan (WSC). The morphology of films was also different based on MSC/WSC. The shelf life extension of Mongolian cheese was evaluated at 8°C. The results showed that the cheese coated by WSC film containing perilla oil presented better treatment performance in terms of microbial growth delay, weight loss and shelf life length.

Preparation and characterization of glycerol plasticized (high-amylose) starch–chitosan films

The chitosan–starch (high amylose) blend film (1;1), via microfluidization, was prepared by casting with different glycerol concentration (0%, 2.5%, 5% and 10%). The films were characterized for their mechanical, thermal and morphological properties. The addition of glycerol at 5% (w/w) and higher concentrations resulted in decrease in tensile strength, increase in elongation at break due to plasticization. The well-known antiplasticization was observed in the polymer films with 2.5% of glycerol. The addition of glycerol promoted the interactions among chitosan, starch and glycerol through hydrogen bonding as reflected on the shifting of main peaks of the glycerol-free film to higher wavenumbers as shown by FTIR spectra. The decrease in intensity of glycerol-related peaks in starch–chitosan–glycerol films in both 1H NMR and 13C NMR spectra proved the strong interactions (decrease in glycerol mobility) occurring among starch, chitosan and glycerol in glycerol-plasticized films.

Modification of mechanical and thermal property of chitosan–starch blend films

Chitosan–starch blend films (thickness 0.2mm) of different composition were prepared by casting and their mechanical properties were studied. To improve the properties of chitosan–starch films, glycerol and mustard oil of different composition were used. Chitosan–starch films, incorporated with glycerol and mustard oil, were further modified with monomer 2-hydroxyethyl methacrylate (HEMA) using gamma radiation. The modified films showed improvement in both tensile strength and elongation at break than the pure chitosan–starch films. Water uptake of the films reduced significantly than the pure chitosan–starch film. Thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the modified films experience less thermal degradation than the pure films. Scanning electron microscopy (SEM) and FTIR were used to investigate the morphology and molecular interaction of the blend film, respectively.

Mechanical Properties of Chitosan-Starch Composite Filled Hydroxyapatite Micro- and Nanopowders

Hydroxyapatite is a biocompatible ceramic and reinforcing material for bone implantations. In this study, Starch-chitosan hydrogel was produced using the oxidation of starch solution and subsequently cross-linked with chitosan via reductive alkylation method (weight ratio (starch/chitosan): 0.38). The hydroxyapatite micropowders and nanopowders synthesized by sol-gel method (10, 20, 30, 40 %W) were composited to hydrogels and were investigated by mechanical analysis. The results of SEM images and Zetasizer experiments for synthesized nanopowders showed an average size of 100 nm. The nanoparticles distributed as uniform in the chitosan-starch film. The tensile modulus increased for composites containing hydroxyapatite nano-(size particle: 100 nanometer) powders than composites containing micro-(size particle: 100 micrometer) powders. The swelling percentage decreased for samples containing hydroxyapatite nanopowder than the micropowders. These nanocomposites could be applied for hard-tissue engineering.

Antimicrobial, Mechanical, and Barrier Properties of Cassava Starch−Chitosan Films Incorporated with Oregano Essential Oil

The physicochemical and antimicrobial properties of starch-chitosan films incorporated with oregano essential oil (OEO) have been investigated. The antimicrobial effects of starch-chitosan-OEO films against Bacillus cereus, Escherichia coli, Salmonella enteritidis, and Staphylococcus aureus were determined by the disk inhibition zone method. The film mechanical properties, water vapor permeability (WVP), Fourier transform infrared spectra (FTIR), and thermograms (TGA) were also determined. Films added with OEO effectively inhibited the four microorganisms tested and demonstrated improved barrier properties. The presence of OEO in starch-chitosan films led to the formation of more flexible films. Chitosan was not effective against the tested organisms, but it decreased film rigidity and WVP. TGA analysis demonstrated that the addition of chitosan and OEO did not affect the thermal stability of the films.

Mechanical Property and Biodegradability of Cast Films Prepared from Blends of Oppositely Charged Biopolymers

Biodegradable cast films of about 50 μm thickness were fabricated by blending oppositely charged biopolymers such as anionic starch–chitosan, and cationic starch–pectin. The tensile strength and elongation at break (%) of films were evaluated as well as their capacity to degrade in compost. Films recovered from soil every 48 h showed consistent degradation (weight loss), diminution of the polymer’s characteristic peak absorbance in the carbohydrate fingerprint region of the FTIR, and changes in the surface morphology via scanning electron microscopy (SEM). Anionic starch–chitosan films had much superior tensile strength and elongation compared to cationic starch–pectin, suggesting that the ionic bonds formed between anionic-starch and positively charged groups in chitosan polymer were much more stable and stronger. Initially, both films lost about 36% weight within 96 h, which also correlated well with the loss in the characteristic absorption peaks in the region of the infrared spectrum typical of biopolymers. The total mineralization of films by microorganisms in compost soil was also measured using respirometric techniques. Though the rate of mineralization differed for two formulations, total mineralization (extent) for both films were achieved within 45 days.