Amylose properties

Similar materials are available based on potato starch, eg, PaseUi SA2 which claims DE below 3 and has unique properties based on its amylose—amylopectin ratio pecuhar to potato starch. The product contains only 0.1% proteia and 0.06% fat which helps stabilize dried food mixes compounded with it. Another carbohydrate raw material is waxy-maize starch. Maltodextrias of differeat DE values of 6, 10, and 15, usiag waxy-maize starch, are available (Staley Co.). This product, called Stellar, is offered ia several physical forms such as agglomerates and hoUow spheres, and is prepared by acid modification (49). Maltodextrias based oa com starch are offered with DEs of 5, 10, 15, and 18 as powders or agglomerates (Grain Processing Corp.). 

Starch acetates may have low or high DS. The industrial importance of low DS acetates results from their abiUty to stabilize aqueous polymer sols. Low DS acetates inhibit association of amylose polymers and reduce the association of the longer outer chains of amylopectin. These properties are important in food appHcations. Highly derivatized starches (DS 2—3) are useful because of their solubiHty in organic solvents and abiHty to form films and fibers. 

The small change in stereochemistry between cellulose and amylose creates a large difference in their overall shape and in their properties. Some of this difference can be seen in the strorcture of a short portion of fflnylose in Figure 25.9. The presence of the a-glycosidic linkages imparts a twist to the fflnylose chain. Where the main chain is roughly linear- in cellulose, it is helical in anylose. Attractive forces between chains are weaker in fflnylose, and fflnylose does not form the same kind of strong fibers that cellulose does. 

Amylose is an instructive example, showing the relationships between different conformations and chemical properties (28). In the discussion of gelation mechanisms, the evaluation of the fine structure of the polysaccharides is a very important point. 

The linear arrangement of iodine atoms in the amylose inclusion compound has generated much interest right from the early days with respect to its spectroscopic and optical properties 138 -140). It has also been known for many years that polyvinyl alcohol (PVA) behaves similarly, and this was applied by Polaroid Corporation for the manufacture of polarising plastic using stretched sheets of iodine-stained polyvinyl alcohol170). 

Molecular Structure. Most starches consist of a mixture of two polysaccharide types amylose, an essentially linear polymer, and amylopectin, a highly branched polymer. The relative amounts of these starch fractions in a particular starch are a major factor in determining the properties of that starch. 

From measurements of the dichroism of flow of amylose-iodine solutions,161 and from studies of the optical properties of crystalline amylose platelets and iodine-stained platelets,163 it was shown, following the suggestion of Hanes, that a helical configuration of the amylose in this complex is probable. This was later confirmed by x-ray measurements (see p. 378) the iodine atoms were shown to be situated in the core of helically-oriented amylose molecules. 

Properties of Original Amylose and High-Polymer Residue213... 

Pea starch granules are oval, sometimes fissured, with a diameter of 20-40 ym (13). Molecular and structural characteristics of the two main components of field pea starch—amylose and amylopectin—are important in determining functional properties (25,26). Smooth field pea starch concentrate contains 97.2% starch of which 30.3-37.8% is amylose (9,23,25-27), and wrinkled pea starch concentrate contains 94.8% starch, which is 64% amylose (26). The gelatinization temperature of smooth pea starch is between 64 to 69 C, and that of wrinkled pea starch is greater than 99 C to 115 C. Gelatinization temperature depends on maturity of field pea seed and amylose content (26,27). 

Jane, J., Chen, Y. Y., Lee, L. F., McPherson, A. E., Wong, K. S., Radosavljevic, M., and Kasemsuwan, T. (1999). Effects of amylopectin branch chain length and amylose content on gelatinization and pasting properties of starch. Cereal Chem. 76, 629-637. 

Gelatinization of sweet potato, tania, and yam tuber starches. Starch/Starke. 47, 298-306. Varavinit, S., Shobsngob, S., Varanyanond, W., Chinachoti, P., and Naivikul, O. (2003). Effect of amylose content on gelatinization, retrogradation and pasting properties of flours from different cultivars of Thai rice. Starch/Starke 55,410-415. 

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