Native Starch Films Research Articles

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.

MODIFIED ARRACACHA STARCH FILMS CHARACTERIZATION AND ITS POTENTIAL UTILIZATION AS FOOD PACKAGING

Background: The use of petroleum-based plastics has increased in recent years. These materials are resistant and economically competitive. However, the environmental pollution caused by these is very high. For this reason, some research has focused on the alleviation of this environmental problem, mainly through the development and use of biodegradable polymers. The food industry as an economic dynamic sector is looking for new environmental and secure alternatives for the consumer welfare. In packaging sector, materials should be renewable and final products must be recyclable, innovative and economically competitive. New starch sources could be an adequate alternative. Objetive: The main objective in this research project was to evaluate the chemical modification of arracacha starch, testing different plasticizer concentrations, as a raw material for food biodegradable packaging production. Methods: The arracacha native starch was acetylated or oxidized to produce biodegradable films. The starches were characterized by infrared spectroscopy, scanning electron microscopy, x-ray diffraction and volumetric techniques. Results: Films made with acetylated starch presented more transparency. Native starch films had lower water solubility and greater stability in acid and alkaline conditions. The effect of alkaline conditions was higher than the acid conditions for the three types of films in all treatments. Conclusion: Physicochemical properties of the films were directly influenced by the amount of plasticizer used and by the starch modification type. The physicochemical and microbiological tests of the meat show the possible use of starch films for packaging.

Structural and mechanical characteristics of film using modified corn starch by the same two chemical processes used in different sequences

Structure of dual modified starches, cross-linked esterified corn starch (CES) and esterified cross-linked corn starch (ECS), and product films (CEF and ECF) were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). The peak 1730cm−1 of IR spectra confirmed the formation of ester carbonyl groups in starch matrix. The sequence of modification procedure had an impact on the final modification degree, resulting in structural differences of modified starches and starch films. Compared to native starch film (NF), CEF and ECF showed improved transparence (77.59% and 74.39% respectively) with compact structure, lower crystallinity (6.5% and 7.4% respectively). Results of mechanical test indicated that structure of ECF was more flexible than CEF, whereas tensile strength was higher in CEF. Accordingly, complex modification could be an effective method to adequate properties of starch films for specific processing requirements.

Starch-Chitosan Blend Films Prepared by Glutaraldehyde Cross-Linking

The present study evaluated the properties of the polymeric blend films obtained from chitosan and corn starch using glutaraldehyde as crosslinking agent and glycerol as plasticizer by the casting/solvent evaporation method. Fourier transform infrared (FTIR) analyses confirmed that the groups interactions of starch and chitosan in starch-chitosan blend films were present especially when using glutaraldehyde as crosslinking agent. Differential scanning calorimetry (DSC) studies revealed an endothermic peak of starch film at 98 oC corresponding to water evaporation. DSC also indicated that the endothermic peak of blend films moved to higher temperature with adding chitosan and glutaraldehyde compared with native corn starch film. The tensile strength of the blend films increased with the increasing content of glutaraldehyde. The starch-chitosan blend films exhibited the highest tensile strength of 11 MPa when the content of starch was 9% (w/v in water), glutaraldehyde content was 1.0 mL, chitosan ratio is 0.35 (wchitosan/wstarch), glycerol ratio was 0.35 (wglycerol /wstarch).

Development of oxidised and heat–moisture treated potato starch film

This study investigated the effects of sodium hypochlorite oxidation and a heat–moisture treatment of potato starch on the physicochemical, pasting and textural properties of potato starches in addition to the water vapour permeability (WVP) and mechanical properties of potato starch films produced from these starches. The carbonyl contents, carboxyl contents, swelling power, solubility, pasting properties and gel texture of the native, oxidised and heat–moisture treated (HMT) starches were evaluated. The films made of native, oxidised and HMT starches were characterised by thickness, water solubility, colour, opacity, mechanical properties and WVP. The oxidised and HMT starches had lower viscosity and swelling power compared to the native starch. The films produced from oxidised potato starch had decreased solubility, elongation and WVP values in addition to increased tensile strength compared to the native starch films. The HMT starch increased the tensile strength and WVP of the starch films compared to the native starch.

Biodegradable packages development from starch based heat sealable films

Heat sealing capacity of native and acetylated corn starch based films was evaluated to develop biodegradable packages, such as bags. Thermo-mechanical properties were analyzed since they condition their handling and applications. Acetylated starch addition reinforced 80% sealing resistance of starch films. Unplasticized heat-sealed films presented adhesive failures while those containing glycerol showed a rupture near the zip. Unplasticized films exhibited a single relaxation (at around 60 °C), detected by DMA and conventional DSC, which was not affected by the acetylated starch content. DMA curves of plasticized films showed two relaxations, one close to −50 °C associated to the glass transition of the plasticizer-rich phase, and other around 60 °C, attributed to the starch-rich phase. This last transition was also observed using MTDSC. Glycerol addition decreased the relaxation temperature of the starch-rich phase being this effect more marked in native starch films, about 28%. A relation between film composition, microstructure, mechanical behavior, and dynamic mechanical thermal analysis was established.

Characterization of Chemically Modified Potato Starch Films Through Enzymatic Degradation

The present investigation was undertaken to characterize the biodegradation pattern of chemically modified starch films. Chemically modified starch films obtained by esterification of the hydroxyl groups of the polysaccharide have shown lower water sorption than native starch films, being therefore more attractive for a number of processing applications. However, no systematic study characterizing their biodegradation behavior and comparing it with the degradation pattern of native starch films has still been published. In the current contribution we characterized the enzymatic degradation pattern of three derivatized starch films by use of a commercial α-amylase from Bacillus licheniformis. Optimum degradation conditions were chosen upon assaying the effect of enzyme load and temperature on the reaction course of native starch films. Under the conditions selected, comparison of different derivatization procedures revealed that the starch film modified with octanoyl chloride was enzymatically hydrolyzed at a much higher rate than native starch film. Maleated starch films also showed higher susceptibility to α-amylolytic hydrolysis than native starch, whereas acetylated starch showed a hydrolysis pattern similar to that of native starch. Differences in degradation rates of chemically modified films were explained in terms of their amylose content which promotes dense networks that hinder the access of starch-degrading enzymes.

Modulating rheo-kinetics of native starch films towards improved wet-strength

Starch directly functionalised in the plant by modulation of its biosynthesis by mutagenesis and transgene technology was exploited for its extended functionality beyond the normal variation. In this study we investigated the rheological and mechanical properties of films from such structurally highly different starch types derived from potato and cereal sources of normal and mutant and transgenic backgrounds. A new improved technique was developed to permit the dynamic mechanical analysis of films in the presence of water. It was found that the amylose content was decisive for the mechanical properties of the films – an increase in the amylose content resulted in both a higher stress and strain at break. Interestingly, there was no correlation between the speed of hydration and mechanical water resistance of the films. Generally, the films were clear and transparent, even after wetting. Transgenic potato starch with a low content of phosphate displayed an extraordinary combination of high robustness, transparency, mechanical strength and extensibility even in a wet condition. The combination of optimal phosphate and amylose concentrations in this sample probably favoured hydration and amorphisation without compromising the inter-chain interactions of the polysaccharide network.

Influence of the oxidation and acetylation of banana starch on the mechanical and water barrier properties of modified starch and modified starch/chitosan blend films

AbstractBanana starch was oxidized at three different levels and afterwards acetylated. The double‐modified starch was used for film preparation with the addition of chitosan. The physical, mechanical, and barrier properties were tested. The oxidation level increased the moisture content of the film, but the acetylation and the addition of chitosan decreased this characteristic. The oxidation level increased the whiteness of the film, but the second modification (acetylation) and the addition of chitosan to the blend did not affect this parameter. The solubility increased with the temperature and the oxidation level but decreased with the storage time of the film. The oxidation increased and the acetylation reduced the solubility with respect to the native starch film. The dual modification produced a solubility value less than that of its oxidized counterpart, and the addition of chitosan produced the highest solubility value. The addition of chitosan increased the tensile strength of the film, and the effect was higher with the oxidation level and longest storage time. The addition of chitosan produced a higher elongation value than that of its double‐modified film, but at the longest storage time, this parameter decreased. The water vapor permeability increased with the oxidation level because of the hydrophilic character, but the acetylation reduced this parameter because the acetylation increased the hydrophobic character of the starch due to the ester group. Films prepared with the double‐modified banana starch and the addition of chitosan had some improved physical, mechanical, and barrier properties, and they may be used in specific applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Water vapour permeability and mechanical properties of mixed starch-monoglyceride films and effect of film forming conditions

The effect on water vapour permeability (WVP) and mechanical properties of an addition of various amounts of an acetylated monoglyceride (Acetem) to native potato starch (NPS) films was studied. Phase separation was also evaluated by drying the films at different temperatures, since phase separation between starch and Acetem is affected by temperature. Films were gel-cast from a heated solution of NPS (3%). Five different concentrations (0–10%) of Acetem based on NPS were added to the solution and the films were dried at three different temperatures (23, 35 and 50 °C). The film properties were evaluated by measuring thickness, moisture content (MC), WVP and mechanical properties and the results were then evaluated with multivariate analysis. The MC was slightly reduced in the films dried in higher temperatures, despite reconditioned samples, and the film thickness increased with an increasing amount of Acetem. The WVP of a pure NPS film was decreased by 27 and 37% with addition of 10% Acetem or high drying temperature, respectively. The mechanical properties were affected mainly by changes in Acetem concentration. A greater amount of Acetem decreased Young's modulus, stress at break and strain at break. Micrographs showed extensive phase separation in the films, but pure bilayer films were not formed.

Preparation and characterization of modified starch‐based plastic film reinforced with short pulp fiber. II. Mechanical properties

AbstractNative corn starch‐ and hydroxypropylated starch (HPS‐) based plastic films were prepared using the short pulp fiber as the reinforcement and the glycerol as the plasticizer. The results of tensile test showed that the strain and stress at break and elastic modulus increased with pulp content. With glycerol content, the strain at break increased considerably, but the breaking stress and elastic modulus decreased. And the stress–strain curves showed that the brittleness problem of films was overcome by the pulp, glycerol, and water content. The hydroxypropyl starch films showed results similar to those of the native starch films. The results of the three‐point bending test showed that maximum deflection, flexural strength, and specific work increased with pulp content, but the flexural modulus was the highest at a pulp content of 20%. And with the glycerol content, the maximum deflection and specific work of rupture increased, but the bending elastic modulus decreased. The hydroxypropyl starch films showed results similar to those of native starch films as far as the maximum deflection and flexural strength were concerned, but the bending elastic modulus and specific work of the hydroxypropyl starch films were considerably lower than those of starch films. So it was concluded that the flexibility of films was improved by the hydroxypropylation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2108–2117, 2003

Characteristics of crosslinked potato starch and starch-filled linear low-density polyethylene films

Potato starch was crosslinked with 0.1, 0.5, 1.0 and 2.0g epichlorohydrin per 100g of starch and some physicochemical characteristics of the starch were determined. Starch-filled linear low-density polyethylene cast films were prepared to contain 5 or 10% crosslinked starch. Mechanical properties of these films were measured and compared to those of the films containing native potato starch. Molar degree of crosslinking of the crosslinked starch increased proportionally as epichlorohydrin concentration increased. X-ray diffraction pattern and scanning electron microscopy showed that crosslinking of starch did not affect the crystallinity or granular shape of the starch. The tensile strength, percent elongation and strain energy of the films containing crosslinked starch were generally higher than those of the films containing native starch. Films containing crosslinked starch were whiter in color than native starch films.

Structure-Property Relationships of Extruded Starch, 2 Extrusion Products from Native Starch

The supermolecular structure and morphology of extruded flat films from several native starch materials of A- and B-crystal type were investigated by wide-angle X-ray scattering and scanning electron microscopy. The degree of crystallinity and crystallite dimensions of both the different starting materials and the extruded films were determined and a scheme of the lattice transformations resulting from extrusion was established. The conditions of structure formation of the extruded starch films were varied in relation to plasticizer composition and extruder zone temperatures. The mechanical properties and biodegradability of the films were also measured. The extruded starches crystallized in the VH polymorph with crystallinities between 33 and 41% and crystallite sizes of up to 35 nm. An increase in crystallite size was found for all starches (sometimes a doubling) with increasing extruder middle zone temperatures from 120 up to 210°C. For extruded potato and maize starches a steep rise in strength and modulus and a drop in elongation was observed above 190°C. Purified amylopectin from maize showed after extrusion the crystalline A-type and small amounts of B polymorph with small crystallites (up to 3 nm) and the best mechanical performance with strengths and moduli of about 20 MPa and 1 500 MPa, respectively, for the present extrusion conditions. Native starch films that include 20 to 30% plasticizer biodegrade rapidly in 25 d consuming 90% of the oxygen needed for complete degradation, as analyzed by the Sapromat test.

Investigations on High Amylose Corn Starch Films. Part 3: Stress Strain Behaviour

AbstractBy autoclaving a watery high amylose corn starch suspension, homogenous and isotrope films were obtained with different processing parameters. The films were used for investigations on the stress strain behavior. A systematical dependence on the water content and the relationship between native lipids and the starch chains was observed. Especially for films obtained from defatted corn starch, a clear transition was obtained, depending on the water content, from a brittle behavior far below the glass transition temperature TG with a very high Youngsmodulus to a ductile failure behavior above TG. The results led to a microscopical model for the native high amylose corn starch films, which in addition outlines the very interesting possibility of controlling in detail changes of the macroscopic stress strain behavior through variations on a molecular scale.