Amylopectin properties

Likewise, many of the adhesive properties can be explained by reference to the amylose and amylopectin properties of the starch used. Jelly gums are usually made from waxy starches (100% amylopectin) and are stable at room temperature for many months, as would be expected from the slow retrogradation rate of this starch. A corrugating formulation must set to form a bond and become water resistant in a short period of time. The low molecular weight portion of the amylose would be expected to come out of solution fairly rapidly to make a temporary bond, and the high molecular weight portion would more slowly tend to create water resistance. 

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. 

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. 

Retrogradation is another important property of starch. It is generally accepted that retrogradation is involved in the staling of baked products such as bread. In particular it appears that retrogradation is the recrystallisation of the amylopectin present. Notably, retrogradation is still a subject of research. The application of techniques such as 13C NMR allows insights that older techniques do not provide. 

Starches with modified properties can be obtained in several ways. One way is to use a source with starch that has different properties. Examples of this are waxy maize, which gives almost pure amylopectin, and tapioca. These are still starch in food law. 

Obtaining Different Properties in the Starch. One method of obtaining a starch with different properties is the biological method of using a different type of plant. The best example of this is waxy maize, which yields a starch that is nearly pure amylopectin. The other method is to chemically modify the starch. Chemically modified starch is normally declared as modified starch . A whole range of modified starches are available. There is of course no bar to chemically modifying a starch from a special source. 

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. 

The isomeric polysaccharides amylose (a component of starch) and cellulose also show the significance of stereoisomerism on polymer properties. Cellulose and amylose have the structures shown in Fig. 8-8. (Amylopectin, the other component of starch, has the same structure as amylose except that it is branched at carbon 6.) Both are polymers of glucose in which the... 

Amphoteric a substance that exhibits both acidic and basic properties Amylopectin branched glucose polymer component of starch... 

Potato starch, and tuberous starch in general, has some unique properties as compared to cereal starches. The most important ones include long amylopectin chains forming hydrated and ordered B-type crystallites and the presence of phosphate esters. The clusters of potato amylopectin are comparatively small, comprising 5-10 short chains. The internal part ofthe clusters is organized into branched building blocks mainly found in the amorphous lamellae of the... 

Aberle, T., Burchard, W., Vorwerg, W., Radosta, S. (1994). Conformational contributions of amylose and amylopectin to the structural properties of starches from various sources. Starch/Stdrke, 46, 329-335. 

Noda, T., Takigawa, S., Matsuura-Endo, C., Kim, S. -J., Hashimoto, N., Yamauchi, H., Hanashiro, I., Takeda, Y. (2005). Physicochemical properties and amylopectin structures of large, small, and extremely small potato starch granules. Carbohydr. Polym., 60,245-251. 

Yusuph, M., Tester, R. F., Ansell, R., Snape, C. E. (2003). Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chem., 82,283-289. Zhu, Q., Bertoft, E. (1996). Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydr. Res., 288, 155-174. 

Most potato starches are composed of a mixture of two polysaccharides, a linear fraction, amylose, and a highly branched fraction, amylopectin. The content of amylose is between 15 and 25% for most starches. The ratio of amylose to amylopectin varies from one starch to another. The two polysaccharides are homoglucans with only two types of chain linkage, a-(l 4) in the main chain and a-(l 6)-linked branch chains. Physicochemical properties of potato and its starch are believed to be influenced by amylose and amylopectin content, molecular weight, and molecular weight distribution, chain length and its distribution, and phosphorus content (Jane and Chen, 1992). 

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