Structural Starch Modifications

Modifications of the native starch form can be made by means of thermal and mechanical treatments where the amount of water has an essential role. Referring to Equation 8.1, when starch is heated at a water volume fraction above 0.9 a pure 

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Modification, which involves the alteration of the physical and chemical characteristics of the native potato starch to improve its fimctional characteristics, can be used to tailor it to specific food applications. The rate and efficacy of any starch modification process depend on the botanical origin of the starch and on the size and structure of its granules. This also includes the surface structure of the granules, which encompasses the outer and iimer surface depending on the pores and channels, which cause the development of the so-called specific surface (Juszczak, 2003). Potato starch modification can be achieved in three different ways physical, conversion, and chemical (derivatization) (Table 10.6). 

Jane J, Atichokudomchai N, Suh D-S. In Tomasik P, Yuryev VP, Bertoft E, eds. Starch Progress in Structural Studies, Modifications and Applications. Cracow Poland Polish Society of Food Technology 2004 147. 

As used in this chapter, a starch modification refers to starch molecules which have a general change in the polyglucan structure without the addition of a chemical sustituent. Examples include depolymerized starches and dextrins (including pyrodextrins and cycloamylases). Derivatized starches have had the addition of chemical groups at the hydroxyls. These include the starch ethers and esters. Oxidized starches can be both modified (when depolymerized) and derivatized (with carboxyl and carbonyl groups). 

Shogren R.L., Lawton J.W., Tiefenbacher K.F., Baked starch foams Starch modifications and additives improve process parameters, structure and properties, Ind. Crops. Prod., 16, 2002, 69-79. 

E Onofre, Y.-J. Wang and A. Mauromoustakos, Effects of structure and modification on sustained release properties of starches, Carbohydr.Polym., 76 (4) 541-547, 2009. 

There are five prime factors that determine the properties of starches 1. starch is a polymer of glucose (dextrose) 2. the starch polymer is of two types linear and branched 3 the linear polymeric molecules can associate with each other giving insolubility in water 4. the polymeric molecules are organized and packed into granules which are insoluble in water and 5 disruption of the granule structure is required to render the starch polymer dispersible in water. The modification of starch takes into account these factors. 

It appears that estimates of the dimensions of the unit cell for the B -modification of starch (or amylose) are reasonably in agreement, but that structural interpretations of these observations are at variance. 

Jacobs, H. and Delcour, J. A. (1998). Hydrothermal modifications of granular starch with retention of granular structure A review. J. Agric. Food Chem. 46, 2895-2905. 

This paper will also assume that the reader has basic starch and cellulose knowledge and that it is not necessary to review the structure of the molecules. It is, however, important to know that starch from native, non-genetically selected sources, is a mixture of two molecules and not simply one compound. Amylose is an essentially linear molecule and differs from amylopectin, which has about 4-6%oC-(l—>6) branches, even though both molecules are mainly o4 -(1—>4) linked D -glucose. The differences in these two molecules and their chemical modifications are the basis of application technology and the reason for the growing importance of specialty starches. 

Cyclodextrins, products of the degradation of starch by an amylase of Bacillus macerans(1), have been studied in terms of chemical modifications, mainly for the purpose of developing efficient enzyme mimics(2). Not only their unique cyclic structures, but also their ability to form Inclusion complexes with suitable organic molecules, led us to Investigate the total synthesis of this class of molecules(3) We describe here an approach to a total synthesis of alpha(l), gamma(2), and "iso-alpha" cyclodextrin (3). 

Hoover, R. and Sosulski, E. W. (1991). Composition, structure, functionality, and chemical modification of legume starches— A review. Can. ]. Physiol. Pharmacol. 69, 79-92. 

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