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Introduction to Thermoplastic Composites
Published in R. Alagirusamy, Flexible Towpregs and Their Thermoplastic Composites, 2022
Starch is a biodegradable and biocompatible polysaccharide derived from renewable resources. It mainly consists of two dissimilar macromolecules named amylose and amylopectin. The amylose is a straight-chain polymer while amylopectin is a branch polymer. Figure 1.11 shows the chemical structure of amylose and amylopectin. Starch is obtained from various plant resources such as wheat, maize, rice, potatoes, peas etc. where its composition, i.e. the amylose and amylopectin content, varied from one source to another. The decomposition temperature of native starch is below its melting point. Hence on heating, the native starch tends to degrade thermally before melting. However, native starch can be transformed into a thermoplastic starch by adding a suitable plasticizer. A plasticizer enhances the mobility of the starch molecules and brings down the melting temperature of the starch below its degradation temperature. Glycerol, glycol, sorbitol, sugar and ethanolamine are some examples of plasticizers which are generally mixed with native starch to produce thermoplastic starch (Wang, Yang, and Wang 2003).
Biosynthesis of Starch
Published in Jean-Luc Wertz, Bénédicte Goffin, Starch in the Bioeconomy, 2020
Jean-Luc Wertz, Bénédicte Goffin
It is likely that GBSS synthesizes amylose within the granular matrix formed by amylopectin.6 Monitoring the distribution of amylose over time in potato lines, in which GBSS expression and amylose contents were repressed to low levels, suggested that amylose was more apparent toward the center of the starch granule and that this amylose-containing core grows together with the granule. It is important to realize that the granule is hydrated and small molecules such as ADPglucose can be used by granule-bound proteins. GBSS acts in a processive manner. The enzyme may synthesize amylose by elongating individual glucan chains in the environment surrounding crystalline or crystallizing amylopectin. Its product probably is well protected from the branching activity, explaining why it is largely linear. The nature of the primer used for amylose synthesis is not fully resolved.
Biopolymer Structures and Behaviors with Comparisons to Synthetic Polymers
Published in Alan Tonelli, Jialong Shen, Conformations, 2020
Polysaccharides, such as the starch polymers and cellulose illustrated in Figure 7.1, are the most abundant biopolymers found in Nature. Among these, cellulose is the most abundant organic compound on earth. Think about this the next time you hike through a dense forest or drive by what appears to be an almost endless field of wheat, corn, soybeans, cotton, or some other farm crop. Cellulose serves as a structural element in the cell walls of plants like wood and cotton. Amylose starch, on the other hand, serves as the principal food reserve in plants and is the major source of carbohydrates in the diets of animals, including humans, and is generally obtained from wheat, rice, corn, and potatoes. Humans possess amylase enzymes which can randomly cut the backbone bonds in the linear component of starch (amylose) and convert it to sugar (D-glucose) with its associated energy in the form of calories. No such cellulase enzymes exist in humans for digesting cellulose, but are present in other organisms, such as termites, which can literally “eat you out of house and home” if yours is constructed from wood.
Effects of drying treatment-induced changes in the physicochemical properties of starch on the textural characteristics of Ginkgo seed crisps
Published in Drying Technology, 2023
Chunju Liu, Yue Li, Yayuan Xu, Zhuqing Dai, Lei Feng, Da-jing Li, Ya-dong Xiao, Wen-qian Pang, Han-ci Ren, Min Zhang
Ginkgo seeds are rich in starch and contain amylose and amylopectin. Amylose is a linear, long-chain molecule with D-glucose monomers connectedr by α-(1,4) glycosidic bonds. Furthermore, amylose is readily soluble in water, has a high gelatinization temperature, and is adequate to film formation and strength.[8] On the contrary, amylopectin is a water insoluble polysaccharide with a branched dendritic structure and higher adhesion and stability than amylose.[9] Previous studies have found that food processing can change starch’s physical and chemical properties. Thus, for example, cooking pretreatment can change the physical properties of starch without causing molecular changes.[10] Similarly, drying temperature increases the temperature for gelatinization of starch granules, while freeze-drying reduces the order of short- and long-range molecular weights of yam starch, whereas hot-air drying promotes the formation of an ordered structure of starch granules.[11]
A Review on the Application of Starch as Depressant in Iron Ore Flotation
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Swagat S. Rath, Hrushikesh Sahoo
Starch is an energetic vegetative reserve photosynthesized by plants and stored in the cereals, fruits, roots tubers, and legumes in the range of 25–90% (De Ojogbo, Blanchard and Mekonnen 2018; Sousa et al. 2017). It is a natural semicrystalline polymer under the class of homopolysaccharides. Its simple chemical representation is (C6H10O5)n, where “n” represents the units of aldo-hexose, a monosaccharide. Starch is composed of two types of α-D-glucan chains, namely amylose and amylopectin. The other minor components are proteins, fatty acids, phosphorus, and some inorganic contaminants. Amylose is a linear glucose chain attached by α-1,4 glucosidase bond, whereas amylopectin is a branched glucose chain with branching at α-1,6 position (De Sousa et al. 2017). The polymerization index “n,” and hence, the molecular weight of starch and the ratio between the number of amylopectin and amylose species vary in a wide range. Figure 1 presents the structures of amylopectin and amylose chains.
Natural fibre filament for Fused Deposition Modelling (FDM): a review
Published in International Journal of Sustainable Engineering, 2021
H. J. Aida, R. Nadlene, M.T. Mastura, L. Yusriah, D. Sivakumar, R. A. Ilyas
According to Osorio-Dı́az et al. (2002), amylose, also referred to as a linear polysaccharide, is formed by 5–600 glucose units that are linked by α-(1,4) glycoside bonds. The linear structure of amylose contributes to the strength and flexible structure of starch granules. The structure of helix with six glucose units takes place in the core of granules and is soluble in water, as shown in Figure 21. Meanwhile, amylopectin is a branched molecule α-(1,6) produced by thousands of glucose units which prevent the formation of a helix structure. Therefore, a semi-crystalline structure is the arrangement of amylose and amylopectin forming a matrix of starch granules with alternating crystalline and amorphous, known as the growth ring in superior plant starch (Jenkins, Cameron, and Donald 1993).