Fabrication and Characterization of Native and Oxidized Potato Starch Biodegradable Films

The need to replace conventional polymers due to environmental pollution caused by them has led to increased production of biodegradable polymers such as starch. Thus, the application possibilities of starch have increased. In this study, we produced and characterized biodegradable films derived from native and oxidized potato starch. The film-forming solution was prepared with different concentrations of extracted starch (native or oxidized) and a plasticizer (glycerol or sorbitol). Then, the mechanical, barrier, morphological, and structural properties of the films were characterized. The moisture content of the films varied from 15.35?±?1.31 to 21.78?±?0.49%. The elastic modulus of the films ranged from 219?±?14.97 to 2299?±?62.91 MPa. The film of oxidized starch plasticized with sorbitol in the lowest content was the most resistant and flexible; moreover, this film also presented lower water vapor permeability and low solubility in water. Fourier-transform infrared spectroscopic analysis of the biodegradable films indicated the presence of same functional groups as those of starch with bands in the same regions. The film thickness was lower for the films plasticized with glycerol whereas the color variation (Δ?) was lower for the ones plasticized with sorbitol. In case of both plasticizers, the increase in their content decreased the Δ? value. All the biodegradable films presented stability against water absorption owing to their low solubility in water. Morphological evaluation revealed the presence of partially gelatinized starch granules in the films. The roughness parameter (Rq) of the films varied from 3.39 to 10.9 nm, indicating that their surfaces are smooth. X-ray diffraction studies showed a B-type pattern for the starches, which is representative of tubers. Further, the films present higher relative crystallinity (RC) compared to the starches. The biodegradable starch films are uniform, transparent and with low solubility in water. The oxidation of starch and use of sorbitol as a plasticizer resulted in improved properties of the starch films, which is suitable for application.     

Processing and characterization of porous structures from chitosan and starch for tissue engineering scaffolds

Natural biodegradable polymers were processed by different techniques for the production of porous structures for tissue engineering scaffolds. Potato, corn, and sweet potato starches and chitosan, as well as blends of these, were characterized and used in the experiments. The techniques used to produce the porous structures included a novel solvent-exchange phase separation technique and the well-established thermally induced phase separation method. Characterization of the open pore structures was performed by measuring pore size distribution, density, and porosity of the samples. A wide range of pore structures ranging from 1 to 400 microm were obtained. The mechanisms of pore formation are discussed for starch and chitosan scaffolds. Pore morphology in starch scaffolds seemed to be determined by the initial freezing temperature/freezing rate, whereas in chitosan scaffolds the shape and size of pores may have been determined by the processing route used. The mechanical properties of the scaffolds were assessed by indentation tests, showing that the indentation collapse strength depends on the pore geometry and the material type. Bioactivity and degradation of the potential scaffolds were assessed by immersion in simulated body fluid.     

Preparation and characterization of biodegradable poly-3-hydroxybutyrate-starch blend films

Bacterial polyesters have attracted much attention as biodegradable biocompatible polymers. Poly-3-hydroxybutyrate, a microbially produced thermoplastic, has similar material properties to polypropylene. Its potential application as biodegradable and biocompatible plastics is well documented. However, due to high cost it is used mainly in biomaterials for medical applications. Materials with useful properties may result from blending bacterial polyhydroxybutyrate (PHB) with other polymers. In this paper, the compatibility of PHB with starch for improved properties and cost reduction is discussed. The thermal and mechanical properties of the blended films were studied by means of thermogravimetry, differential scanning calorimetry and an automated material testing system. The results revealed that blend films had a single glass transition temperature for all the proportions of PHB:starch tested. The nature of all combinations was found to be crystalline. The tensile strength was optimum for the PHB:starch ratio of 0.7:0.3 (wt/wt). The variation in tensile strength, Young's modulus, extension needed to break, thermal stability, glass transition temperature, melting temperature, for the different proportions of PHB:starch are discussed.     

In vitro digestibility of edible films from various starch sources

Banana, maize, potato and sagu starches were boiled in the presence or absence of plasticizer (glycerol), producing edible films. In vitro digestibility features, amylose content and amylopectin gel filtration behavior of films and parent starches were evaluated. Available starch contents were lower in glycerol-containing films, due to dilution by the plasticizer. Total resistant starch increased in the maize starch-based film but decreased markedly in those prepared from the other starches. Amylose content of banana starch (40%) was about double those of the other starches. Nonetheless, all starch films exhibited similar retrograded resistant starch content. Although film production led to increased -amylolysis rates, these were further augmented by additional film heating, thereby indicating that film-manufacture did not promote complete starch gelatinization. Gel filtration chromatography suggested amylopectin depolymerization after film-making, which may also increase digestion kinetics. The presence of glycerol in the films slowed down starch digestion, a feature of potential dietetic use.     

Extrusion of pectin/starch blends plasticized with glycerol

The microstructural and thermal dynamic mechanical properties of extruded pectin/starch/glycerol (PSG) edible and biodegradable films were measured by scanning electron microscopy (SEM) and thermal dynamic mechanical analysis (TDMA). SEM revealed that the temperature profile (TP) in the extruder and the amount of water present during extrusion could be used to control the degree to which the starch was gelatinized. TDMA revealed that moisture and TP during extrusion and by inference the amount of starch gelatinization had little effect on the mechanical properties of PSG films. Furthermore, TDMA revealed that PSG films underwent a glass transition commencing at about −50°C and two other thermal transitions above room temperature. Finally, it was concluded that the properties of extruded PSG films were comparable to those cast from solution.     

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.     

Influence of thickness on the mechanical properties for starch films

The aim of the present study was to investigate some mechanical properties of starch films. Starch is a natural common polymer in nature and the use of natural materials is increasing in the industries. In this study, the mechanical properties of starch plasticized with 30 parts by weight, of glycerol, are investigated. For the mechanical testing films of different thickness were used, the thickness varied between 0.5 and 2.5 mm. T_g was measured with a differential scanning calorimeter and with a dynamical mechanical analysis. The starch films were tested in tension and characterised in terms of stiffness, strength and failure strain. Fracture toughness was measured by single edge notch tests. Both stiffness and strength showed a strong dependence on film thickness, stronger then expected from linear fracture mechanics. This can be due to the different molecule orientation in the films, and due to the crystallinity of the films.     

Solid-state and mechanical properties of aqueous chitosan-amylose starch films plasticized with polyols

The film-forming ability of chitosan and binary mixtures of chitosan and native amylose corn starch (Hylon VII) was evaluated with free films prepared by a casting/solvent evaporation method. Unplasticized and plasticized free chitosan films in aqueous acetic acid and respective films containing a mixture of chitosan and native amylose starch in acetic acid were prepared. Glycerol, sorbitol, and i-erythritol were used as plasticizers. Solid-state and mechanical properties of the films were studied by powder x-ray diffractometry (XPRD), differential scanning calorimetry (DSC), and a materials testing machine. The films composed of a mixture of chitosan and native amylose starch in acetic acid were clear and colorless. A plasticizer concentration of 20% wt/wt (of the polymer weight) ws sufficient to obtain flexible films with all samples tested. X-ray diffraction patterns and DSC thermograms indicated an amorphous state of the films independent of the type of plasticizer used. In conclusion, incorporation of native amylose com starch into chitosan films improves the consistency and the mechanical properties of the films.     

Effect of amylose content on physical and mechanical properties of potato-starch-based edible films

The present study investigated the amylose content and the gelatinization properties of various potato starches extracted from different potato cultivars. These potato starches were used to prepare edible films. Physical and mechanical properties of the films were investigated. The crystallinity of selected native starches and edible films made of the same starches were determined by X-ray diffraction. The amylose content of potato starches varied between 11.9 and 20.1%. Gelatinization of potato starches in excess water occurred at temperatures ranging from 58 to 69 degrees C independently of the amylose content. The relative crystallinity was found to be around 10-13% in selected native potato starches with low, medium, and high amylose content. Instead, films prepared from the same potato starches were found to be practically amorphous having the relative crystallinity of 0-4%. The mechanical properties and the water vapor permeability of the films were found to be independent of the amylose content.     

Origins of B-type crystallinity in glycerol-plasticised, compression-moulded potato starches

The amount of B-type crystallinity in compression-moulded, glycerol-plasticised potato starches was strongly dependent on both the properties of the potato starch used and the applied processing conditions. The presence of amylose and the morphology of the potato starch used, but also processing parameters such as moulding temperature and water content during moulding affected the amount of B-type crystallinity in the materials and thus the ultimate mechanical properties of the plasticised starches. This indicated that the direct relation between composition and physical properties of processed starches is not always valid; processing parameters are important tools for controlling the physical properties of processed starches as they influence the amount of B-type crystallinity in the material. It was shown that the total amount of B-type crystallinity in the glycerol-plasticised potato starches should be considered as a summation of residual amylopectin crystallinity and recrystallisation of both amylose and amylopectin, being strongly dependent on the applied processing conditions. In order to explain the observed amount of B-type crystallinity in these starches, partial (co-)crystallisation of both amylose and amylopectin should occur at high moulding temperatures. The measured mechanical properties of the plasticised potato starches correlated well with the amount of B-type crystallinity observed in the materials.     

'Green' crosslinking of native starches with malonic acid and their properties

Starch is a highly hydrophilic biomaterial with weak mechanical properties rendering it useless for commercial applications. A fully 'green' water based process is presented to crosslink corn (cereal) and potato (tuber) starch to enhance mechanical properties as well as lower hydrophilicity. In addition, malonic acid, a green, plant based water soluble and relatively inexpensive polycarboxylic acid, was used as the crosslinker. The reactivity of potato starch toward esterification and crosslinking was found to be higher than that of corn starch owing to the inherent differences in the granule morphology and internal structure of the two starches. It was observed that potato starch granules had a higher degree of substitution (DS) of 0.19 than corn starch granules (DS=0.1) under similar reaction conditions. Chemical, thermal and mechanical test results confirmed the crosslinking as well as reduced moisture sensitivity.     

The effects of different starch sources and plasticizers on film blowing of thermoplastic starch: Correlation among process,elongational properties and macromolecular structure

The material compositions and the technological procedures to prepare biodegradable films with the film blowing technology based on thermoplastic starch were studied in this work. The activities were focused on the analysis of the effects of starch source (maize, potato and wheat), supplier (Roquette, Cerestar and Cameo) and the type of plasticizers (glycerol, urea and formamide) and their content on the physical–chemical and mechanical properties. Moreover, in order to develop a film blowing technology, material composition as well as processing condition were optimized. Among 10 varieties of thermoplastic starch prepared, the combination of urea and formamide as plasticizer restrained retrogradation and improved mechanical properties. Extensional rheological properties of the thermoplastic starch films were also investigated: the results showed that the occurrence of strain-hardening behaviour in some of the investigated compositions lead to a positive effect on the film blowing process. In this study we found that the combination of high-amylose (>51%) starch and urea/formamide mixtures as plasticizer produced an homogenous film of a 50 μm thickness and a robust film blowing process due to the good elongational viscosity, high deformability of the melt and strain-hardening behaviour.     

Biodegradation of polyurethane acrylate with acrylated epoxidized soybean oil blend elastomers by Chaetomium globosum

This paper studies the biodegradation features of a novel blend of polyurethane acrylate-acrylated epoxidized soybean oil-based cross-linked polyurethane elastomers in the presence of the soft-rot fungus Chaetomium globosum. After the specimens were incubated at 28 °C for 90 and 130 days, the degree of fungal damage was measured by analysis of weight loss and mechanical properties. The biodegradation of the films was also evidenced by SEM and FTIR spectroscopic studies. After fungal attack, the FTIR spectra indicate a degradation of urethane and ester groups of the polyurethane and especially of the ester groups from the modified soybean oil part. The polyurethane blend films exposed to fungal attack suffered a loss in strength of up to 55% and a loss in elongation of up to 80%, depending on the content of acrylated epoxidized soybean oil. The biodegradation of the blends was also confirmed by SEM analyses. The biodegradation results show that samples with a high content of acrylated epoxidized soybean oil are more biodegradable than mere polyurethane acrylate. These biodegradable polymer blends present an optimum balance of physical properties and biodegradable properties with the potential for application as eco-friendly biomaterials.     

Properties and Antioxidant Action of Actives Cassava Starch Films Incorporated with Green Tea and Palm Oil Extracts

There is an interest in the development of an antioxidant packaging fully biodegradable to increase the shelf life of food products. An active film from cassava starch bio-based, incorporated with aqueous green tea extract and oil palm colorant was developed packaging. The effects of additives on the film properties were determined by measuring mechanical, barrier and thermal properties using a response surface methodology design experiment. The bio-based films were used to pack butter (maintained for 45 days) under accelerated oxidation conditions. The antioxidant action of the active films was evaluated by analyzing the peroxide index, total carotenoids, and total polyphenol. The same analysis also evaluated unpacked butter, packed in films without additives and butter packed in LDPE films, as controls. The results suggested that incorporation of the antioxidants extracts tensile strength and water vapor barrier properties (15 times lower) compared to control without additives. A lower peroxide index (231.57%), which was significantly different from that of the control (p<0.05), was detected in products packed in film formulations containing average concentration of green tea extracts and high concentration of colorant. However, it was found that the high content of polyphenols in green tea extract can be acted as a pro-oxidant agent, which suggests that the use of high concentration should be avoided as additives for films. These results support the applicability of a green tea extract and oil palm carotenoics colorant in starch films totally biodegradable and the use of these materials in active packaging of the fatty products.     

Use of xylan,an agricultural by-product,in wheat gluten based biodegradable films: mechanical,solubility and water vapor transfer rate properties

The possibility of using xylan, as an agricultural by-product, for production of composite films in combinations with wheat gluten was investigated. Different levels of xylan (0-40% w/w) were incorporated into wheat gluten to form biodegradable composite films. Films were prepared at pH 4 and 11, and dried at either uncontrolled or controlled conditions. The mechanical properties, solubilities and water vapour transfer rate (WVTR) of the composite films were studied. Films were obtained with added xylan without decreasing film-forming quality. Xylan can be used as an additive, as much as 40% (w/w), in wheat gluten films. Changing pH, wheat gluten/xylan ratio, xylan type and drying conditions affected mechanical and solubility properties, however, WVTR was not affected by xylan additions. Wheat gluten/xylan composite films having different characteristics can be produced depending on xylan type, composition and process conditions.     

Recrystallisation behaviour of native and processed waxy maize starch in relation to the molecular characteristics

Molecular characteristics were determined for native waxy maize starch and maize starch modified in different way (by mechanical treatment or/and acid hydrolysis). Recrystallisation behaviour was studied. Methods used in this study were MALLS, HPAEC-PAD, NMR, DSC, SEM, light microscopy.

Five starch materials were subjected to storage under the same conditions in the presence of water (70 w/w%). Molecular weight, radius of gyration, initial crystallinity, and degree of polymerisation, degree of branching, chain length distribution profiles, were related to nucleation rate during the recrystallisation process, rate of recrystallisation, thermal stability and amount of obtained crystallinity. This allowed the following connections between the molecular characteristics and kinetic of recrystallisation to be proposed: Amylopectin molecular weight appeared to affect the number of starch crystallites formed and amount of crystallinity but not the stability of the rebuilt crystallites. The stability of rebuilt crystallites can be controlled by degree of polymerization, degree of branching and unit chain length distribution, characteristics which were similar for the starches.

A mixture of two starches, with and without crystalline structure in initial state but with molecular weight in same range, were stored and scanned in order to understand possible cocrystallisation effects.     

Engineering starch for increased quantity and quality

The characterization and production of starch variants from mutation studies and transgene technology has been invaluable for our understanding of the synthesis of the starch granule. The knowledge gained has allowed for genetic manipulation of the starch biosynthetic pathway in plants. This in vivo approach can be used to generate novel starches and diminishes the need for post-harvest chemically and enzymatically treated starches. Thus, the modification of the starch biosynthetic pathway is a plausible means by which starches with novel properties and applications can be created.     

Understanding and influencing starch biochemistry

Starch is one of the most important products synthesized by plants that is used in industrial processes. If it were possible to increase production or modify starches in vivo, using combinations or either genetically altered or mutant plants, it may make them cheaper for use by industry, or open up new markets for the modified starches. The conversion of sucrose to starch in storage organs is, therefore, discussed. In particular the roles of the different enzymes directly involved in synthesizing the starch molecules on altering starch structure are reviewed, as well as the different models for the production of the fine structure of amylopectin. In addition, the process of starch phosphorylation, which is also important in determining the physical properties of starches, is reviewed. It is hoped that detailed knowledge of these processes will lead to the rational design of tailored starches. Starch degradation is also an important process, for example, in the cold-sweetening of potato tubers, but outside of cereal endosperm little is known about the processes involved. The enzymes thought to be involved and the evidence for this are discussed.     

Characterization of cellulose acetate-reinforced aliphatic-aromatic copolyester composites

The biodegradability, morphology, mechanical, and thermal properties of composite materials composed of maleic anhydride-grafted poly(butylene adipate-co-terephthalate) (PBAT) and cellulose acetate (CA) were evaluated. Composites containing maleic anhydride-grafted PBAT (PBAT-g-MA/CA) exhibited noticeably superior mechanical properties due to greater compatibility between the two components. The dispersion of CA in the PBAT-g-MA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules between the anhydride carboxyl groups of PBAT-g-MA and hydroxyl groups in CA. Each composite was buried in soil and monitored to assess biodegradability. Both the PBAT and the PBAT-g-MA/CA composite films were eventually completely degraded, and severe disruption of film structure was observed after 60-100 days of incubation. Although the degree of weight loss after burial indicated that both materials were biodegradable, even with high levels of CA, the higher water resistance of PBAT-g-MA/CA films indicated that they were more biodegradable than those made of PBAT.     

Preparation of clear noodles with mixtures of tapioca and high-amylose starches

Ways to simulate the making of clear noodles from mung bran starch were investigated by studying the molecular structures of mung bean and tapioca starches. Scanning electron micrographs showed that tapioca starch granules were smaller than those of mung bean starch. X-ray diffraction patterns of mung bean and tapioca starch were A- and C_A-patterns, respectively. Iodine affinity studies indicated that mung bean starch contained 37% of apparent amylose and tapioca starch contained 24%. Gel permeation chromatograms showed that mung bean amylopectin had longer peak chain-length of long-branch chains (DP 40) than that of tapioca starch (DP 35) but shorter peak chain-length of short-branch chains (DP 16) than that of tapioca starch (DP 21). P-31 n.m.r. spectroscopy showed that both starches contained phosphate monoesters, but only mung bean starch contained phospholipids. Physical properties, including pasting viscosity, gel strength, and thermal properties (gelatinization), were determined. The results of the molecular structure study and physical properties were used to develop acceptable products using mixtures of cross-linked tapioca and high-amylose maize starches. Tapioca starch was cross-linked by sodium trimetaphosphate (STMP) with various reaction times, pH values, and temperatures. The correlation between those parameters and the pasting viscosity were studied using a visco/amylograph. Starches, cross-linked with 0.1% STMP, pH 11.0, 3.5 h reaction time at 25, 35, and 45°C (reaction temperature), were used for making noodles. High-amylose maize starch (70% amylose) was mixed at varying ratios (9, 13, 17, 28, 37, and 44%) with the cross-linked tapioca starches. Analysis of the noodles included: tensile strength, water absorption, and soluble loss. Noodle sensory properties were evaluated using trained panelists. Noodles made from a mixture of cross-linked tapioca starch and 17% of a high-amylose starch were comparable to the clear noodles made from mung bean starch.