Amylose water insoluble

Figure 17-5. Amylose, cellulose. Amylose consists of a water-soluble portion, a linear polymer of glucose, the amylose and a water-insoluble portion, the amylopectin. The difference between amylose and cellulose is the way in which the glucose units are linked. In amylose, a-linkages are present, whereas in cellulose, p-linkages are present. Because of this difference, amylose is soluble in water and cellulose is not. Chemical modification allows cellulose to become water soluble.

Problem 22.44 Amylopectin, the water insoluble fraction of starch, behaves like amylose, except that more 2,3,4,6-tetra-O-methyl-D-glucose (5%), and an equal amount of 2.3-di-O-methyl-D-glucose, is formed. Deduce the structure of amylopectin. 

Cellulose, a fibrous, tough, water-insoluble substance, is found in the cell walls of plants, particularly in stalks, stems, trunks, and all the woody portions of the plant body. Cellulose constitutes much of the mass of wood, and cotton is almost pure cellulose. Like amylose and the main chains of amylopectin and glycogen, the cellulose molecule is a linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units. But there is a very important difference in cellulose the glucose residues have the /3 configuration (Fig. 7-16),... 

Plants use starch granules for storing energy. When the granules are dried and ground up, different types of starches can be separated by mixing them with hot water. About 20% of the starch is water-soluble amylose, and the remaining 80% is water-insoluble... 

Other Polymers. Other hydrophilic polymers also exhibit the shear stiffness anomaly when contacted with hydrogen bonding solvents. Films of amylose respond to water and dimethylsulfoxide as shown in Table III. When wet with water, there is a comparatively large increase in attenuation followed by a slow decline to a level plateau. We attribute this leveling out to the comparative water insolubility of retrograded amylose. Dimethyl sulfoxide is a much stronger solvent for amylose than is water and the increase in stiffness which is followed by a rapid decay to zero indicates complete film solution as was the case with water on PVA. The... 

The fractionation of starch has been the subject of many publications in the past as well as in the present. The literature of the last twenty years, especially, shows a rapid accumulation of articles on starch research this can be accounted for by at least three major influences. These are, first, K. H. Meyer s fundamental discovery that most native starches consist, to the extent of about 20 %, of an essentially linear polysaccharide, which he called amylose. Second, T. J. Schoch s equally important demonstration of the ability of amylose to form water-insoluble, complex compounds with minor proportions of higher alcohols. Third, the fast-growing interest which Industry takes in useful polymers. In view of the great successes of cellulose chemistry, amylose chemistry could at least be very promising. 

Neo-amylose is an unbranched water insoluble poly-l,4-a-D-glucan with a chain length of up to 35-100 glucose units (Fig. 14). It is analogous to amylose but... 

Many other amylose complexes are water-insoluble, and the complexes with methanol, 1-propanol, acetone, and butanone may be precipitated from solutions of amylose in methyl sulfoxide, as well as from aqueous solution. As amylose frequently forms crystalline complexes. X-ray diffraction patterns have been obtained for a number of them. Amylose-methyl sulfoxide complexes have a structure almost identical to those of amylose-ethylenediamine complexes, in which the complexing ratio is one ethylenediamine molecule per two n-glucose residues. The helix packing-diameter of the complexes, at least for complexes with linear aliphatic ketones, is dependent upon the chain-length of the molecule complexed, although other factors are also involved. ... 

Amylopectin a component of starch (the other is amylose). A. is a branched, water-insoluble polysaccharide (A/, 500,000-1,000,000) consisting of a main chain of a-l,4-linked D-glucose units with side chains (15-25 D-glucose units) attached a-1,6 to every 8th or 9th glucose. A. forms violet to red-violet inclusion compounds with iodine. It swells in water, and upon heating it forms a paste. 

Cyclodextrins, on the other hand, are used extensively in cosmetic and drug delivery applications (132-136). Cyclodextrins, as the name implies, are cyclic amyloses comprised of 6 (a-), 7 (P-), and 8 (y-), a-D-(l,4)-glucose monosaccharides (Fig. 30). Their small size classifies them as oligo- instead of polysaccharides, which places them somewhat outside the scope of this chapter. Nevertheless, cyclodextrins are important components in many cosmetic formulations where they function as hosts and solubilizing agents for water-sensitive or water-insoluble materials. 

It has also been demonstrated that the presence of the cationic hydrophobe may afford a unique blending synergy with amylose, the linear component of ordinary starch (Section Ill.C.l.a) (193). The combination of these two natural polymers imparts improved yield stress to solutions of PQ-24, which allows them to better suspend water-insoluble oils. It has been proposed that the polymer blend is a mixture in which the amylose, because of its ability to encase fatty alkyl groups, forms a three-dimensional network by tying hydrophobic groups of the PQ-24 together (Fig. 46). The ability of solutions of the blend... 

Starch is another polymer of glucose, like cellulose. But you know that starch is quite different from cellulose. Plant starch typically consists of two components water-soluble amylose and water-insoluble amylopectin. Amylose is a linear polymer of glucose, but its connection is different from that in cellulose. The structure of amylopectin is different from that of amylose. We discuss these issues later. 

Polysaccharides are compounds formed by linking many sugar molecules together. Two of the most common naturally occurring polysaccharides are amylose (an important component of starch) and cellulose. Both are formed by linking glucose molecules together. Starch, a water-soluhle compound, is found in many of the foods we eat— potatoes, rice, flour, beans, corn, and peas. Cellulose, a water-insoluble compound, is the major structural component of plants. Cotton, for example, is composed of about 90% cellulose and... 

The a-linkages cause amylose to form a helix and be water soluble the j8-linkages allow the molecules of cellulose to form linear arrays and be water insoluble. 

In its native state, starch is semi-crystalline (about 20-45%) and water insoluble. Native starch granules typically have dimensions ranging from 0.5 to 175 pm and appear in a variety of shapes. It is composed of linear (amylose) and branched (amylopectin) polymers of ot-D-glucose. Amylose has a molecular mass of about 10 -10 g moU while amylopectin has a molecular mass in the range 10 -10 g moU Starch rich in amylose is usually preferred for conversion to TPS as the linearity of amylose improves the processability of starch even though it is present as a minor component (between 20 and 30wt%). The ratio of amylose to amylopectin depends on the source and age of the starch, and can also be influenced by the extraction process. ... 

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