Water resistance, mechanical properties and biodegradability of methylated-cornstarch/poly(vinyl alcohol) blend film

The main shortcomings of biodegradable starch/poly(vinyl alcohol) (PVA) film are hydrophilicity and poor mechanical properties. With an aim to overcome these disadvantages, cornstarch was methylated and blend films were prepared by mixing methylated-cornstarch (MCS) with PVA. The mechanical properties, water resistance and biodegradability of the MCS/PVA film were investigated. It was found that MCS/PVA film had higher water resistance than the native starch/PVA film. However, the water resistance of MCS/PVA films did not have significant difference with the increase in the degree of substitution (DS) of the methylated starch from 0.096 to 0.864. Enzymatic, microbiological and soil burial biodegradation results indicated that the biodegradability of the MCS/PVA film strongly depended on the starch proportion in the film matrix. The degradation rate of starch in the starch/PVA film was hindered by blending starch with PVA. Both tensile strength and percent elongation at break of the MCS/PVA film were improved as DS of the methylated starch increased. Conversely, increasing the methylated starch proportion in film matrix deteriorated both tensile strength and percent elongation at break of the film.     

Preparation of LDPE-acetylated/butyrylated starch blend blow films and characterization

Development of modified plastics has been studied through the LDPE-acylated starch blend films to examine the effect of different acyl groups and degrees of substitution(DS) on properties of films.Corn starch was modified with acetyl and butyryl groups and films were prepared by blending acylated starch with low density polyethylene(LDPE).Systematic studies were done to observe the effect of acyl groups,DS and starch concentration on the properties and biodegradability of the blend films.It was observed that blend films containing 5% acetylated and butyrylated starches of high DS(2.5,1.7) maintained 75% and 83% of tensile strength of LDPE films.Thermal analysis results indicated that acetylated and butyrylated starch blend films decomposed at 370 °C and 389 °C which were higher than the decomposition temperature of native starch film(349 °C).Scanning electron micrographs of blend films containing high DS acylated starch showed well dispersed starch particles due to improvement in dispersion between starch and LDPE.Water absorption capacity of high DS acetylated and butyrylated starch blend films(4.18% and 3.76%,respectively) was lower than that of native starch films(5%).This study has an advantage because of blown films prepared can be integrated with the present manufacturing systems without any other requirement.     

Studies on the properties and characteristics of starch-LDPE blend films using cross-linked, glycerol modified, cross-linked and glycerol modified starch

Corn starch was modified by cross-linking with epichlorohydrin and plasticizer glycerol. X-ray diffraction studies showed that relative crystallinity of the native and cross-linked starch were similar and were not affected by cross-linking. Different films were prepared by blending corn starch, cross-linked starch or glycerol modified starch in LDPE. The mechanical properties of the films were studied for tensile strength, elongation, melt flow index, and burst strength. The properties of the blend films were compared with LDPE films. It was observed that with the blending of 7.5% native starch, there was a decrease in tensile strength, elongation and melt flow index but burst strength increased. The tensile strength, elongation and melt flow index of the films containing cross-linked starch was considerably higher than those containing native starch but the burst strength showed a reverse trend. For native starch and cross-linked starch modified with glycerol, the elongation and melt flow index of the films increased but burst strength decreased. Surface scanning of the blend films were done by scanning electron microscope. Film containing cross-linked starch/glycerol modified starch in the blend was observed to be smoother than the native starch blend films.     

High Substitution Synthesis of Carboxymethyl Chitosan for Properties Improvement of Carboxymethyl Chitosan Films Depending on Particle Sizes

This study investigated the effect of chitosan particle sizes on the properties of carboxymethyl chitosan (CMCh) powders and films. Chitosan powders with different particle sizes (75, 125, 250, 450 and 850 µm) were used to synthesize the CMCh powders. The yield, degree of substitution (DS), and water solubility of the CMCh powders were then determined. The CMCh films prepared with CMCh based on chitosan with different particle sizes were fabricated by a solution casting technique. The water solubility, mechanical properties, and water vapor transmission rate (WVTR) of the CMCh films were measured. As the chitosan particle size decreased, the yield, DS, and water solubility of the synthesized CMCh powders increased. The increase in water solubility was due to an increase in the polarity of the CMCh powder, from a higher conversion of chitosan into CMCh. In addition, the higher conversion of chitosan was also related to a higher surface area in the substitution reaction provided by chitosan powder with a smaller particle size. As the particle size of chitosan decreased, the tensile strength, elongation at break, and WVTR of the CMCh films increased. This study demonstrated that a greater improvement in water solubility of the CMCh powders and films can be achieved by using chitosan powder with a smaller size.     

醋酸淀粉/聚乳酸的制备及性能的影响研究

采用自设计的双螺杆结构挤出制备聚乳酸(PLA)/醋酸淀粉(AS)的全生物降解材料,考察材料的AS的含量和取代度对复合材料动态流变性能、机械性能的影响。研究结果表明,AS含量明显影响复合材料的力学性能、复合黏度和储能模量:当AS含量从45%增加到70%,材料的拉伸强度下降,复数黏度和储能模量则提高。随着AS取代度由1.0上升为3.0,复合材料的复数黏度和储能模量下降,拉伸强度由12.0MPa上升为15.5MPa。对复合材料进行电镜扫描分析发现,AS以海岛结构形式分散在PLA的连续相中,取代度2.0的AS与PLA相容性最好,当其质量含量达到70%,材料的拉伸强度仍然不低于10.0MPa,具有较好的机械强度。     

Synthesis,Characterization, and Optimization Studies of Starch/Chicken Gelatin Composites for Food-Packaging Applications

The indiscriminate use of plastic in food packaging contributes significantly to environmental pollution, promoting the search for more eco-friendly alternatives for the food industry. This work studied five formulations (T1–T5) of biodegradable cassava starch/gelatin films. The results showed the presence of the starch/gelatin functional groups by FT-IR spectroscopy. Differential scanning calorimetry (DSC) showed a thermal reinforcement after increasing the amount of gelatin in the formulations, which increased the crystallization temperature (Tc) from 190 °C for the starch-only film (T1) to 206 °C for the film with 50/50 starch/gelatin (T3). It also exhibited a homogeneous surface morphology, as evidenced by scanning electron microscopy (SEM). However, an excess of gelatin showed low compatibility with starch in the 25/75 starch/gelatin film (T4), evidenced by the low Tc definition and very rough and fractured surface morphology. Increasing gelatin ratio also significantly increased the strain (from 2.9 ± 0.5% for T1 to 285.1 ± 10.0% for T5) while decreasing the tensile strength (from 14.6 ± 0.5 MPa for T1 to 1.5 ± 0.3 MPa for T5). Water vapor permeability (WVP) increased, and water solubility (WS) also decreased with gelatin mass rising in the composites. On the other hand, opacity did not vary significantly due to the films’ cassava starch and gelatin ratio. Finally, optimizing the mechanical and water barrier properties resulted in a mass ratio of 53/47 cassava starch/gelatin as the most appropriate for their application in food packaging, indicating their usefulness in the food-packaging industry.     

Development of Ginkgo (Ginkgo biloba) Nut Starch Films Containing Cinnamon (Cinnamomum zeylanicum) Leaf Essential Oil

There have been many studies on the development biodegradable films using starch isolated from various food sources as a substitute for synthetic plastic packaging films. In this study, starch was extracted from ginkgo (Ginkgo biloba) nuts, which were mainly discarded and considered an environment hazard. The prepared starch (GBS) was then used for the preparation of antioxidant films by incorporating various amounts of cinnamon (Cinnamomum zeylanicum) essential oil (CZEO), which provides antioxidant activity. The prepared GBS films with CZEO were characterized by measuring physical, optical, and thermal properties, along with antioxidant activity (ABTS, DPPH, and FRAP) measurements. With the increasing amount of CZEO, the flexibility and antioxidant activities of the GBS films increased proportionally, whereas the tensile strength of the films decreased. The added CZEO also increased the water vapor permeability of the GBS films, and the microstructure of the GBS films was homogeneous overall. Therefore, the obtained results indicate that the developed GBS films containing CZEO are applicable as antioxidant food packaging.     

Cold water fish gelatin films: Effects of cross-linking on thermal, mechanical, barrier, and biodegradation properties

Gelatin was extracted from Alaska pollock (Theragra chalcogramma) and Alaska pink salmon (Oncorhynchus gorbuscha) skins and cast into films. The fish gelatin films’ tensile, thermal, water vapor permeability, oxygen permeability, and biodegradation properties were compared to those of bovine and porcine gelatin films. In addition, fish gelatin films were cross-linked with glutaraldehyde. Pollock and salmon gelatin films had comparable tensile properties, but had lower tensile strength and percent elongation than mammalian gelatin films. The lower strength and elongation might have been due to lower structural gelatin levels present in fish gelatin films. The addition of cross-linkers had little effect on tensile properties and melting temperatures of fish gelatin films. Pollock gelatin films had the lowest water vapor and oxygen permeability values, whereas mammalian gelatin films had the highest permeability values. Cross-linking resulted in lower water vapor permeability for salmon gelatin films and higher oxygen permeability for pollock gelatin films. However, all fish gelatin films had better water vapor and oxygen barrier properties than mammalian gelatin films. Also, fish gelatin films degraded faster than mammalian gelatin films.     

Preparation,Characterization and Antibacterial Property Analysis of Cellulose Nanocrystals (CNC) and Chitosan Nanoparticles Fine-Tuned Starch Film

To improve the mechanical and antibacterial properties of traditional starch-based film, herein, cellulose nanocrystals (CNCs) and chitosan nanoparticles (CS NPs) were introduced to potato starch (PS, film-forming matrix) for the preparation of nanocomposite film without incorporation of additional antibacterial agents. CNCs with varied concentrations were added to PS and CS NPs composite system to evaluate the optimal film performance. The results showed that tensile strength (TS) of nanocomposite film with 0, 0.01, 0.05, and 0.1% (w/w) CNCs incorporation were 41, 46, 47 and 41 MPa, respectively. The elongation at break (EAB) reached 12.5, 10.2, 7.1 and 13.3%, respectively. Due to the reinforcing effect of CNCs, surface morphology and structural properties of nanocomposite film were altered. TGA analysis confirmed the existence of hydrogen bondings and electrostatic attractions between components in the film-forming matrix. The prepared nanocomposite films showed good antibacterial properties against both E. coli and S. aureus. The nanocomposite film, consist of three most abundant biodegradable polymers, could potentially serve as antibacterial packaging films with strong mechanical properties for food and allied industries.     

Response surface methodology (RSM) of chicken skin gelatin based composite films with rice starch and curcumin incorporation

This study aims to optimize the formulation of composite films based on chicken skin gelatin with incorporation of rice starch (10–20%, w/w) and curcumin (0.03–0.10%, w/v). The effect of their interaction on film's tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP) and antioxidant properties (DPPH%) were investigated using a response surface methodology-central composite design (RSM-CCD). The optimized film formulation was further validated to indicate the validity of the prediction model. The optimum conditions of the film were selected with incorporation of rice starch at 20% (w/w) and curcumin at 0.03% (w/v). The optimized film formulation has revealed better mechanical properties with low WVP value and good antioxidant activity. The results showed that optimized composite films formulation based on chicken skin gelatin with the incorporation of rice starch and curcumin has proving good validation of model prediction and can be effectively utilized in food packaging industry.     

Surface chemical modification of microfibrillated cellulose: improvement of barrier properties for packaging applications

Heterogeneous acetylation of microfibrillated cellulose (MFC) was carried out to modify its physical properties and at the same time to preserve the morphology of cellulose fibrils. The overall reaction success was assessed by FTIR together with the degree of substitution (DS) defined by titration and the degree of surface substitution (DSS) evaluated by means of XPS. Dynamic contact angle measurements confirmed the hydrophobicity improvement relative to non-modified samples. The increase of contact angle upon reaching a certain reaction time and some decrease following the further acetylation was confirmed. Mechanical properties of MFC films made from chemically modified material were evaluated using tensile strength tests which showed no significant reduction of tensile strength. According to SEM images, dimension analysis and tensile strength data, the acetylation seemed not to affect the morphology of cellulose fibrils.     

A comparative study of the characteristics of cross-linked, oxidized and dual-modified rice starches

Rice starch was cross-linked with epichlorohydrin (0.3%, w/w, on a dry starch basis) and oxidized with sodium hypochlorite (2.5% w/w), respectively. Two dual-modified rice starch samples (oxidized cross-linked rice starch and cross-linked oxidized rice starch) were obtained by the oxidation of cross-linked rice starch and the cross-linking of oxidized rice starch at the same level of reagents. The physicochemical properties of native rice starch, cross-linked rice starch and oxidized rice starch were also studied parallel with those of the two dual-modified rice starch samples using rapid visco analysis (RVA), differential scanning calorimetry (DSC), dynamic rheometry and scanning electron microscopy (SEM). It was found that the levels of cross-linking and oxidation used in this study did not cause any significant changes in the morphology of rice starch granules. Cross-linked oxidized starch showed lower swelling power (SP) and solubility, and higher paste clarity in comparison with native starch. Cross-linked oxidized rice starch also had the lowest tendency of retrogradation and highest ability to resistant to shear compared with native, cross-linked, oxidized and oxidized cross-linked rice starches. These results suggest that the undesirable properties in native, cross-linked and oxidized rice starch samples could be overcome through dual-modification.     

脂肪族水性聚氨酯的力学性能研究

考察了软段的种类、分子量大小、混合软段的组成对产物力学性能的影响作用。同时还研究了二羟甲基丙酸(DMPA)用量以及中和剂的影响作用．实验结果表明。软段结构对脂肪族水性聚氨酯成膜的力学性能影响很大，聚酯型产物具有较高的模量和拉伸强度。聚醚型产物则具有较高的伸长率．混合软段对产物力学性能的影响较为复杂，随着软段中聚醚含量的升高，产物的硬度和模量均大幅度下降，但拉伸强度和伸长率的变化并不是一个线性关系．产物的模量随软段分子量的提高而降低，但伸长率和拉伸强度却有所提高．当DMPA用量较高时。产物的模量和拉伸强度均较高：当DMPA用量较低时，产物则具有较高的伸长率．中和剂的种类对产物力学性能的影响明显，当以NaOH为中和剂时，产物具有较高的硬度、模量、拉伸强度：以三乙胺为中和剂时，产物具有较高的伸长率．     

Monomer and Radiation-Mediated Sago Starch Blend Film: Mechanical and Thermal Property Optimization

Bio-blend films were prepared with sago starch and N-vinyl-2-pyrrolidone (NVP) by the casting method, varying the concentrations of sago starch (100 to 93%) and NVP (0 to 7%). The formulations were designated as F1 (starch 100%), F2 (starch 97%), F3 (starch 95%), and F4 (starch 97%). The highest tensile strength (TS), tensile modulus (TM), and elongation at break (Eb%) were found correspondingly to be 30.47 MPa, 407.74 MPa, and 8.25% for the F3 formulation. Gamma radiation was applied to films to modify their performance through grafting and cross-linking. The highest TS, TM, and Eb% were found at 500 krad dose and they were 38.12 MPa, 481.00 MPa, and 9.78%, respectively for F3 formulation. The water uptake nature and thermal properties of the treated and untreated films were also investigated.     

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

Chitosan–starch blend films (thickness 0.2 mm) 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.     

Effect of Cactus (Opuntia ficus-indica) and Acacia (Acacia seyal) Gums on the Pasting,Thermal, Textural,and Rheological Properties of Corn,Sweet Potato,and Turkish Bean Starches

This study was planned to explore the locally available natural sources of gum hydrocolloids as a natural modifier of different starch properties. Corn (CS), sweet potato (SPS), and Turkish bean (TBS) starches were mixed with locally extracted native or acetylated cactus (CG) and acacia (AG) gums at 2 and 5% replacement levels. The binary mixtures (starch–gums) were prepared in water, freeze dried, ground to powder, and stored airtight. A rapid viscoanalyzer (RVA), differential scanning calorimeter (DSC), texture analyzer, and dynamic rheometer were used to explore their pasting, thermal, textural, and rheological properties. The presence of acetylated AG or CG increased the final viscosity (FV) in all three starches when compared to starch pastes containing native gums. Plain SPS dispersion had a higher pasting temperature (PT) than CS and TBS. The addition of AG or CG increased the PT of CS, SPS, and TBS. The thermograms revealed the overall enthalpy change of the starch and gum blends: TBS > SPS > CS. The peak temperature (T_p) of starches increased with increasing gum concentration from 2 to 5% for both AG and CG native and modified gums. When compared to the control gels, the addition of 2% CG, either native or modified, reduced the syneresis of starch gels. However, further addition (5% CG) increased the gels’ syneresis. Furthermore, the syneresis for the first cycle on the fourth day was higher than the second cycle on the eighth day for all starches. The addition of native and acetylated CG reduced the hardness of starch gels at all concentrations tested. All of the starch dispersions had higher G′ than G″ values, indicating that they were more elastic and less viscous with or without the gums. The apparent viscosity of all starch gels decreased as shear was increased, with profiles indicating time-dependent thixotropic behavior. All of the starch gels, with or without gums, showed a non-Newtonian shear thinning trend in the shear stress vs. shear rate graphs. The addition of acetylated CG gum to CS resulted in a higher activation energy (Ea) than the native counterparts and the control. More specifically, starch gels with a higher gum concentration (5%) provided greater Ea than their native counterparts.     

Sisal cellulose and its acetates: generation of films and reinforcement in a one-pot process

This study was undertaken to evaluate both the properties of cellulose acetate films as a function of their degree of substitution (DS) and the possibility of generating reinforcements during film preparation. Sisal was selected for the entire study, among other reasons, because it is a rapidly growing source of cellulose. Cellulose acetates with various DS values were prepared in a homogeneous medium (dimethylacetamide/lithium chloride as the solvent system) and characterized. In DMAc/LiCl, cellulose and cellulose acetate films (mixed or not mixed with sisal cellulose) were successfully prepared and characterized. The films with high DS values exhibited lower hygroscopicity, a distinct morphology (scanning electron microscopy images), and lower tensile strength. In some cases, the films prepared from acetates/cellulose exhibited higher tensile strength and/or storage modulus than the acetate films. This result suggested a reinforcing action of the auto-organized cellulose chains that enabled the generation of both a film and reinforcement in a one-pot process.     

海藻酸钠/羧甲基淀粉共混膜

用溶液共混法成功制备出海藻酸钠／羧甲基淀粉共混膜，IR、XRD、SEM结构表征以及力学性能、吸水性和水蒸汽透过率测定结果表明：共混膜中海藻酸钠和羧甲基淀粉间存在强烈的分子间氢键等相互作用及良好的相容性；随羧甲基淀粉含量的增加，共混膜的吸水率显著降低；当羧甲基淀粉含量(wCMS)=0．20时，共混膜的抗张强度和断裂伸长率分别为53．1MPa和5．3％，比海藻酸钠膜分别提高了97．4％和60．6％，水蒸汽透过率达最小值，是一种具有潜在应用前景的可食性包装膜材料。     

Extraction of Hemicelluloses from Corn Pericarp by the NaOH-Urea Solvent System

The NaOH-urea solvent system was applied for solubilization of hemicelluloses in corn pericarp (CP), an industrial waste of corn starch production, and the mechanical properties of films prepared from the isolated hemicelluloses were analyzed. CP was soaked in 0-8 wt% NaOH solutions containing 0-8 M urea, and the mixtures were frozen at -20 °C and thawed. By a simple recovery of the thawed solutions by filtration hemicelluloses were found to be solubilized efficiently above 2 wt% NaOH. The results of sugar compositional analysis indicate that the extracted materials were mixtures of hemicelluloses composed of arabinoxylan and β-(1,3;1,4)-glucan having arabinose/xylose ratios of 0.84-0.72. The present results indicated that NaOH solutions containing urea, with concentrations not enough to solubilize cellulose were adequate for extraction of hemicelluloses in CP. The hemicellulose extracted with 2 wt% NaOH-6 M urea could form transparent films whose mechanical properties were 56.2 MPa, 3.5% and 3.09 GPa for breaking stress (σmax), maximum strain (ɛmax) and elastic modulus (E), respectively, as evaluated by tensile tests. These values were 1.2-, 1.3- and 0.94-fold higher than those obtained by the film of arabinoxylan alone. Results suggest that β-glucan gives mechanical strength and flexibility to the stiff arabinoxylan films.     

Effects of NaOH treatment of cereal starch granules on the extent of granular starch hydrolysis

Effect of NaOH treatment on granular hydrolysis of cereal starches was studied and granular starch hydrolyzing enzyme is used to hydrolyze native and NaOH-treated starch for 24?h. The dextrose equivalent value of NaOH-treated starch increased significantly compared to native starch, i.e., 28–38?% for corn, 7–37?% for rice, but no significant increase for corn starch. Scanning electron microscopy micrographs showed that NaOH treatment caused an enlargement of pores and degrades the surface of starch granules. Hydrolyzed-treated starch exhibited rougher surface and more porous granules compared to native starch. The swelling power and pasting properties of NaOH-treated starches were markedly altered after hydrolysis. X-ray pattern of all starches showed no changes and the amylose content decrease significantly after hydrolysis, which could due to extensive degradation of amorphous region. Evidently, NaOH treatment below gelatinization temperature was effective in enhancing the degree of granular starch hydrolysis.