Starch guest complexes

Variations of this method are possible in several ways. First of all, cyclodextrin which is available on a large scale by enzymatically catalyzed modification of starch can be tailored by chemical reactions. Furthermore, copolymerizations between different host-guest complexes are possible whereby in some cases the reactivity ratios differ from those reported in literature. 

Interest in biological mimics probably started in the late 1800s with the discovery of cyclodextrin (CD), obtained from the starch digest of a strain of Bacillus. The realization that CDs could form host-guest complexes with a variety of small molecules, and the myriad of uses implied therein, led to extensive study in both academics and industry. 

Starch-guest molecule compounds in inclusion complexes are usually nonstoichiometric species. On the other hand, in the case of amylose such compounds are stoichiometric, but their composition is not repeatable. Starch complexes may consist of partly physical mixtures, adsorbates, and true inclusion complexes formed by direct involvement of dipolar interactions, host-guest hydrogen bonds, and/or clathration-like interactions within the starch matrix. 

Conditions for the formation of potato starch-alcohol complexes do not follow predictable trends. For example, all complexes are formed more readily from air-dried starch rather than from oven-dried starch. Only the starch-methanol complex favors room temperature for its formation the other alcohols require elevated temperatures for effective complexations (see Table XXXI).659,681 682 In contrast, moisture inhibits the formation of the starch-(-)-menthol complex, which is characterized as an interchain complex.710 The Scatchard binding parameters show that (-)-menthol and 1-hexanol adsorb on starch by only one mode, whereas 1-octanol and 1-decanol adsorb in two modes.656 The results for the latter two alcohols indicate that the helices are not fully filled before the second mode of complexation starts. Temperatures of the formation of starch-alcohol complexes likewise do not follow any clear relationship.673,680 Bushuk and Winkler687 reported that the amount of guest molecules (HzO, MeOH,... 

Figure 4A.42 Cyclodextrin, (a) The helical structure of the starch yields mainly cyclodextrins with six to eight glucose units. fhttp //www.chemiedidaktik.uni-wuppertal.de/disido cy/cyen/info/01 manufacture cy.htmj (b) Chemical structure of the three main types of cyclodextrins, Stanisfaw Skowron, shape of single monomers. From work of Bartosz Marcin Kojak, for Wikimedia commons, GNU Free Documentation License, Version 1.2) c) Host-Guest complex of 3-cyclodextrin and phenolphthalein hydrogen bonds between the p-cyclodextrin molecule and the phenolphthalein dianion. fhttp //www.chemiedidaktik.uni-wuppertal.de/disido cy/cyde/exp/06 cy phenol.htm (aj 7ndfc,)ProfessorDr. Simone Krees, Westfdlische Wiihelms-University Munster, with kind permission)...

It should be noted that molecular complexes of the cyclodextrins may be isolated as crystalline solids for example, a crystalline complex is obtained with iodine (which resembles the well known blue complex between iodine and starch) as well as with a large number of other inorganic and organic guests. 

Among enzyme modified starch derivatives,cyclo dextrins behave as empty molecular capsules with the ability to entrap guest molecules of appropriate geometry and polarity.The included molecules are protected from surroundings light, heat,oxidation, etc. The flavor cyclodextrin com -plexes show the above advantageous properties while they are in the dry,solld state.On contact with water,cyclodextrin complexes release their flavor content. In Hungary,the spice flavor beta-cyclodextrin complexes have been on the market, since 1982. 

In starch chemistry and technology, extrusion is used for cooking as well as for preparation of starch complexes with such guest molecules as gluten6511 and lipids.651 Acylation of starch with cyclic anhydrides of dioic acids on extrusion has been demonstrated the reaction provides anionic starches.651... 

IV. Starch Complexes with Other Nonmetallic Guests.312... 

Inclusion complexes of amylose are rather well defined, and a consistent theory of such complexes is available that explains amylose complexes with iodine, fatty acids, alcohols, and other guest molecules.4,5 This subject is surveyed in this article because of the growing interest and importance of such complexes in pharmacology and in the food industry. It is probable that starch in its biological sources (tubers, granules) exists in the form of native complexes with proteins, lipids, mineral salts, and water. 

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