Modified starches derivatized

Through genetic manipulation, com cultivars with altered starch compositions have been developed. Various modified and derivatized starches are... 

Because consumers have become more mindful of what is in their diet, and because in the European Economic Community chemically-modified starches must be labeled as such, there has developed an interest in starches that have only been heated to achieve the process tolerance and short texture of a lightly-crosslinked starch. Such developments in modifying the properties of starch without chemical derivatization are discussed in two chapters. 

In the past several years, between 100 and 150 million pounds of starches and dextrins have been used by the textile industry for weaving and finishing cloth, almost 85% of which is acid-modified and derivatized starches. Very little dextrin or unmodified starch is used in warp sizing. 

Starches are altered in several ways. Derivatized starches have greater water solubility and changed rheological characteristics. Crosslinked starches increase viscosity and promote granule stability in solution. Depolymeiized starches create solutions with lower viscosity. Combinations of crosslinkages, depolymerizations, and derivatizations are common. Dextiins, a special class of modified starches, constitute a variety of industrially important starches. Modified and derivatized starches are used in numerous industries as adhesives, thickeners, stabilizers, and emulsifiers. 

The potential combinations and applications of starches is almost limitless. For example, the esterification of an oxidized, crosslinked, thin boiling starch with a polycarboxylic acid anhydride forms a modified, derivatized starch often used as a warp size in the textile industry (19). This combination of modifications demonstrates the variety of changes that can be made to produce a unique gum. As new modifications and techniques are developed, the number of combinations continues to increase, and the potential of developing new, beneficial modified starches is assured. 

A food processing manufacturer cans a highly acidic fiuit filling for home pie preparation. Unfortunately, the product loses its viscosity upon heating. What type of modified or derivatized starch could be used as a thickening agent for this situation ... 

Chemical modifications may also include the derivatization of starch by reaction of its hydroxyl groups with alkylene oxides. Other suitable substances are such that form ether linkages, ester linkages, urethane linkages, carbamate linkages, or isocyanate linkages. The degree of substitution of the chemically modified starch varies from 0.05 to 0.2. 

Chemical or enz5miatic agents may also be used to destructur-ize, oxidize, or derivatize the starch. Modified starches have been used to make biodegradable plastics, wherein the modified starch is blended as an additive or the minor component with petroleum-based or synthetic pol5m ers. 

Starch derivatized by reaction with ethene oxide has been hydrolysed and silylated, and the distribution of the hydroxyethyl groups in the modified D-glucose units determined by gas chromatography. Six monosubstituted and twelve disubstituted forms were completely separated and identified from their mass spectra. 

The chemical substitution of hydroxyl groups with functional groups yields modified starches with unique functionalities and uses. Acetylated and hydroxypropylated starches are produced after treatment with anhydrous acetic and propylene oxide under an alkaline pH, respectively. After the reaction, the slurry is neutralized, filtered, and dried. These derivatized starches are less prone to retrogradation, produce weaker and clearer gels, and have improved water-holding capacity (Mauro et al. 2003, Thomas and Atwell 1999). 

A. behaves like starch or amylose in reactions such as ->hydrolysis, derivatization or physical treatment (modified starches). Application of debranching - enzymes (pullulanase and iso-amylase) opens the possibility of total splitting of the a-1,6-linkages, thus enhancing hydrolysis as well as producing short-chain amyloses fit>m a. on a commercial scale. 

In this chapter, we have presented a great deal of information on important physicochemical and functional characteristics of native potato starch in comparison with some cereal starches. In addition, we have also discussed various modification techniques being used to modify potato starch, with an emphasis on the post-modification changes (particularly after derivatization)... 

AVEBE, the starch producers cartel declined rapidly. Their companies were either closed or taken over by the farmers. In 1948, it was decided that AVEBE should increase its market base and derivatization of potato starch was started. Today, AVEBE modifies about 70% of the potato starch it produces. 

The major starch sources are corn, potato, waxy maize, wheat and tapioca. Refined starches are supplied in powder form or as slightly aggregated pearl starch.16 Unmodified (native) starch is rarely used in the paper industry, except as a binder for laminates and in the corrugating process. Most starches for use in papermaking are specialty products that have been modified by controlled hydrolysis, oxidation or derivatization.17... 

Many starch derivatives are prepared in a manner similar to cellulose modification. Both heat and alkali ate often used to prepare the starch for chemical addition. As with cellulose, the properties of the starch change with the degree of derivatization. The final characteiisties of the modified gums are controlled by factors which include (a) the amylose/amylopectin content, (b) the degree of modification, (c) the degree of derivatization, and (d) the type of derivatization. This range of factors can result in wide varieties of different gums. 

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). 

In contrast to - cellulose derivatives, which are modified to a greater extent to make them water-soluble, low - DS are sufficient in most of the s. to have the wanted effect on their functional properties. Derivatization reactions are mostly performed in heterogeneous aqueous phase at alkaline pH, keeping the s. in the granular state. After completing the reactions, the starch granules are washed free from reagent residues and other solubles, dewatered and dried. 

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