Physicochemical Characterization of Natural and Acetylated Thermoplastic Cassava Starch (original) (raw)
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Thermoplastic starch composites have attracted significant attention due to the rise of environmental pollutions induced by the use of synthetic petroleum-based polymer materials. The degradation of traditional plastics requires an unusually long time, which may lead to high cost and secondary pollution. To solve these difficulties, more petroleum-based plastics should be substituted with sustainable bio-based plastics. Renewable and natural materials that are abundant in nature are potential candidates for a wide range of polymers, which can be used to replace their synthetic counterparts. This paper focuses on some aspects of biopolymers and their classes, providing a description of starch as a main component of biopolymers, composites, and potential applications of thermoplastics starch-based in packaging application. Currently, biopolymer composites blended with other components have exhibited several enhanced qualities. The same behavior is also observed when natural fibre is i...
Macromolecular Symposia, 2005
Thermoplastic starches (TPS) based on cassava starch have been produced by extrusion at 120 8C, using glycerol as plasticizer. Three forms of cassava starch were employed, viz: cassava root (CR), cassava bagasse (CB) and purified cassava starch (PCS). The main differences between these are the presence of sugars and a few fibres in CR and high fibre concentration in CB. Conditions of processing and characteristics such as amylose and fibre content, crystallinity, water absorption and mechanical behaviour in the tension x deformation test were evaluated. The results demonstrated that the PCS and CR had amylose contents consistent with literature values (14-18%) and that CB is a material constituted mainly by amylopectin. It was found that fibres in high proportions (as in the bagasse) can confer reinforcement properties and are thus able to generate natural composites of TPS with cellulose fibre. The sugars naturally found in the root reduce the elongation of the TPS under tension. The PCS and CR TPS were stable with respect to indices of crystallinity after processing; and during a period of 90 d in a relative humidity of 53%, while the CB TPS tended to vary its crystallinity, probably because its amylose chain had low degree of polymerization.
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Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 • C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T m ). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.
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Effect of some common chemical modifications such as acetylation, hydroxypropylation and cross-linking on the physico-chemical, morphological, thermal and rheological properties of starches from different botanical sources have been reviewed. The distinguishing factors that affect the efficiency of modification are the starch source, amylose to amylopectin ratio, granule morphology, and type and concentration of the modifying reagent. The extent of alteration in the starch properties reflects the resistance or the susceptibility of a starch towards different chemical modifications. Modified starches with desirable properties and degree of substitution can be prepared by critically selecting a suitable modifying agent and a native starch source.
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Starch is a naturally occurring glucose homo-polysaccharide of nutritional, pharmaceutical, and industrial importance. The complex polymeric structure and poor solubility of native starch in water limits their importance at pharmaceutical and industrial level. The structure, reactivity, and functionality of the native starch can be modified by physical, chemical, enzymatic, and biotechnological methods. Various physical modifications techniques, including the thermal, radio-thermal, freezing and thawing, annealing, high-pressure, ultrasonic, and pulsed electric field treatment, and chemical modifications, including oxidation, etherification, esterification, cationization, cross-linking, and graft polymerization, have been found to change the surface properties, polarity and linearity of the molecular chains, the degree of substitution, the polymeric, granular, and crystalline structure, amylose to amylopectin ratio, solubility, viscosity, pasting, gelatinization, swelling, water absorption, and emulsifying properties of starch. The structural changes have resulted in the improvement of thermal and freeze-thaw stability, viscosity, solubility, water binding capacity, swelling power, gelling ability, and enzymatic digestibility of starch. The exposure of reactive functional groups after physical or chemical modification modifies the reactivity of starch toward water, oil, acids, enzymes, and other chemical species. These modification techniques have led to some revolutionary changes in reactivity, functionality, and application of starch in various fields.
Synthesis and Characterization of Acetylated Cassava Starch with Different Degrees of Substitution
Brazilian Archives of Biology and Technology, 2020
Acetylated cassava starch with low and medium degrees of substitution (DS) were synthesized. Also, the effect of DS on swelling power, solubility, morphological properties, gelatinization temperature, paste clarity and moisture sorption were studied. Swelling power and solubility in water between 50ºC and 90°C were determined. Acetylated cassava starches with low DS showed an increased in both parameters, while at higher DS values a reduction of them was observed. Maximum swelling power values were measured in acetylated starch with DS of 0.2 and maximum solubility was registered at DS of 0.72. Equilibrium moisture content values from sorption isotherms presented a good fit using the GAB model (R2>0.96). SEM micrographs showed that as acetyl groups are incorporated the granules suffer surface changes and eventually lose their structure at DS of 1.5. Clarity of acetylated starch pastes with low DS was lighter than native starch paste. In addition, the increase in DS produced a reduction in gelatinization temperature.
Eduvest - Journal of Universal Studies
Starch is a carbohydrate or polysaccharide consisting of a large number of glucose units linked through glycosidic bonds and containing different amounts of amylose and amylopectin as macromolecules. Starch modification can be done physically, chemically, and enzymatically. The process of chemical modification of starch aims to separate the long glucose chains from the polymer molecules in order to reduce the high viscosity of the unmodified starch solution and thus maximize the possible amount of starch in technical applications This modification involves exploiting the many hydroxyl groups present in starch granules to introduce functional groups, resulting in changes in physicochemical and functional properties such as gelatinization, paste, and retrogradation properties of starch. Esterification and oxidation are types of chemical modification processes that can be applied to improve starch characteristics. However, the chemical modification process did not affect the morphology...
Carbohydrate Polymers, 2019
In this work, the effects of the multiphase transitions of starch, the screw configuration, and the conditions of reactive extrusion (REX) on the in situ thermoplasticization/succination of cassava starch were studied. Spectroscopic analyses indicated successful esterification during the REX with the appearance of characteristic bands of carbonyl ester groups. After the REX, the starch developed Band V-type structures, with the OSA starches showing an additional peak at 7.1°. As the degree of substitution increased, a greater number of partially gelatinized granules were embedded in the starch matrix; an additional degradation temperature of 364.5°C and a lower weight loss at the degradation temperature of the starch were observed. The incorporation of OS groups via REX imparts better thermal stability. The processing conditions helped prepare a thermoplastic-succinate starch in a single step through an environmentally friendly process.