Starch complexing

Treatment with chlorine gas converts amines to chloramines, whose active chlorine oxidizes iodide to iodine. This then forms the well-known, deep blue iodine-starch complex [13]. 

Iodine-starch inclusion compounds la 46 Iodine-starch complex lb 195 Iodine substitution under the influence of light la 47... 

Borated starch compositions are useful for controlling the rate of cross-linking of hydratable polymers in aqueous media for use in fracturing fluids. The borated starch compositions are prepared by reacting, in an aqueous medium, starch and a borate source to form a borated starch complex. This complex provides a source of borate ions, which cause crosslinking of hydratable polymers in aqueous media [1552]. Delayed crosslinking takes place at low temperatures. 

Condition/ Absorbance of the liberated iodine-starch complex for different durations... 

Although the dipolar and resonating nature of the interaction of amylose and iodine is well established, Schlamowitz173 regards the iodine in a starch complex as being in a predominantly non-polar form, and Meyer and Bern-feld174 refute the helix theory and consider that adsorption of iodine occurs on colloidal micelles in amylose solutions. Most of the experimental facts which Meyer presents can, however, be satisfactorily explained on the helical model. 

Drying out can be prevented in one of two ways, either by packaging or by lowering the water activity of the product. Starch retrograda-tion can be inhibited by using a starch complexing emulsifier with or without the addition of fat. Mould growth is inhibited by a low water activity. 

The problem of starch retrogradation is tackled by using a starch complexing emulsifier. When all these problems have been attended to the shelf life can be measured in months rather than days. 

Since the time of Schardinger, one of the most important reasons for studying the cyclodextrins was for the information they might yield on the structure of starch and of the well known blue iodine-starch complex. In fact, the similarity between the iodine-starch reaction and the iodine-alpha cyclodextrin reaction was first noted by Schardinger in 1911, in his final paper on the cyclodextrins. 

The investigations carried out by Professor French and his students were based on sound experimental approaches and on intuitive theoretical considerations. The latter often resulted in new experiments for testing a hypothesis. On the basis of theoretical considerations, Professor French proposed a model for the structure of the amylopectin molecule, and the distribution of the linear chains in this molecule. This model was tested by utilizing enzymes that selectively cleave the linear chains, and the results substantiated the theoretical deductions. He proposed a theory on the nature and types of reactions occurring in the formation of the enzyme - starch complex during the hydrolysis of starch by amylases. In this theory, the idea of multiple attack per single encounter of enzyme with substrate was advanced. The theory has been supported by results from several types of experiments on the hydrolysis of starch with human salivary and porcine pancreatic amylases. The rates of formation of products, and the nature of the products of the action of amylase on starch, were determined at reaction conditions of unfavorable pH, elevated temperatures, and increased viscosity. The nature of the products was found to be dramatically affected by the conditions utilized for the enzymic hydrolysis, and could be accounted for by the theory of the multiple attack per single encounter of substrate and enzyme. 

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... 

The approaches that were offered are illustrated in the patent literature of the time. Chiu et al.121 claim that starch heated after being adjusted to an alkaline pH value and then dried would behave as though it was crosslinked. In a patent awarded in 1999, Mahr and Trueck122 claim the use of amylose-containing starches complexed with lipid to enhance tolerance to thermal processing. Kettlitz and Coppin123 treated starch with activated chlorine to create a native product that was temperature-tolerant like a conventionally crosslinked starch. 

I2 + starch — iodine — starch complex (blackish-blue)... 

The formation of decanal - starch - complexes with time at different temperatures is presented in Figure 1. The reaction is completed in a matter of minutes, and a stable equilibrium is obtained. Isotherms of complex formation are shown in Figure 2. The complex formation starts at very low concentrations and comprises appreciable amounts of ligand. We are actually studying these reactions in some detail and are interested in the consequences of these interactions for taste and odor perception. As reported elsewhere, the complexed ligands, if present in dry state, have a remarkably increased chemical stability (25). 

Figure 1. Formation of decanal—starch complexes with time—starch (as glucose) 0.613mM decanal 5.31 M H20 10 mL pH 7.0 temperature 20, 35, 50°C...

Iodates, III, 138, 157, 178 Iodic acid, as oxidant, III, 178 Iodine, adsorption by starch, I, 256 colors of products formed from starch by amylases, V, 261 as oxidant, III, 151, 169 solubility of, III, 136 Iodine starch complex, dichroism of flow of, I, 266... 

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

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. 

The formation of starch complexes with metal salts of metal oxides is of practical interest in, for instance, textile finishing (see discussion by Hal-... 

The formation of a barium-starch complex is well known579-581 Stern582 determined its composition as (QHioOs BaO. Complexation of starch with barium is also used to precipitate starch from its solution. 

In some instances the carrier of the guest plays the role of emulsifier. For example, alcohols and lower fatty acids or their esters are used in the formation of fat-starch complexes.676 In this case, conditions for preparation of complexes resemble conditions for extraction, and unexpected results can accompany both processes. For example, it has been shown that extraction of lipids with 1-propanol from their surface complex with oat starch produced a helical lipid-starch complex that was absent prior to extraction.677... 

Starch complexes with aromas and flavoring agents are usually synthetic in origin. In nature, starch sometimes includes some aroma- and flavor-genic components that generate flavor and aroma on processing (see, for instance, ref. 678). Such agents include mainly aldehydes, ketones, and carboxylic esters however, hydrocarbons, alcohols, carboxylic acids, and haloalkanes have also been used. 

According to Hollo et al.,709 the low stability of starch-alcohol complexes (lower than that of the starch-iodine complex) is caused by the relatively small amount of space inside the amylose helix that is available for the hydrophobic moiety of the alcohol. The data in Table XXX appear to confirm this assumption and indicate iodine sorption amounts by starch complexes with subsequent members of the homologous series of alcohols. With the exception of ferf-butanol, the iodine uptake decreases as the alcohol inside of the helix becomes more bulky. 

Phenols readily form starch complexes, and they are also readily extract-able. As indicated in Table XXXII, the extraction of phenols from their complexes with amylopectin and amylose using diethyl ether generally proceeds more readily with amylopectin. 

Relationships between the structure and stability of phenol-starch complexes are not clearly understood. Apart from the complexes of phenols listed in Table XXXII, complexes of chlorocresols,712 three isomeric nitro-phenols,715 resorcinol, phloroglucinol, and rutin,716 have been reported. The formation of complexes with nitrophenols has been monitored by ultraviolet... 

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