Derivatized starch

Com and rice starches have been oxidized and subsequently cyanoethylated (97). As molecular size decreases due to degradation during oxidation, the degree of cyanoethylation increases. The derivatized starch shows pseudoplastic flow in water dispersion at higher levels of cyanoethylation the flow is thixotropic. Com and rice starches have been oxidized and subsequently carboxymethylated (98). Such derivatives are superior in the production of textile sizes. Potato starch has been oxidized with neutral aqueous bromine and fully chemically (99) and physically (100) characterized. Amylose is more sensitive to bromine oxidation than amylopectin and oxidation causes a decrease in both gelatinization temperature range and gelatinization enthalpy. 

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. 

Lighdy derivatized starch acetates are employed in food because of the clarity of their gels and their stabiHty. AppHcations include frozen fmit pies and gravies, baked goods, instant puddings, and pie fillings. Starch acetates are used in textiles as warp sizes and in paper to improve printabiHty, surface strength, and solvent resistance. 

The GBR resin works well for nonionic and certain ionic polymers such as various native and derivatized starches, including sodium carboxymethylcel-lulose, methylcellulose, dextrans, carrageenans, hydroxypropyl methylcellu-lose, cellulose sulfate, and pullulans. GBR columns can be used in virtually any solvent or mixture of solvents from hexane to 1 M NaOH as long as they are miscible. Using sulfonated PDVB gels, mixtures of methanol and 0.1 M Na acetate will run many polar ionic-type polymers such as poly-2-acrylamido-2-methyl-l-propanesulfonic acid, polystyrene sulfonic acids, and poly aniline/ polystyrene sulfonic acid. Sulfonated columns can also be used with water glacial acetic acid mixtures, typically 90/10 (v/v). Polyacrylic acids run well on sulfonated gels in 0.2 M NaAc, pH 7.75. 

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

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. 

In the following years, nanostructural differences in the particle morphology and thus differing gas diffusivity was identified as the cause of a different oxidative stability of microencapsulated nutritional oils. When using a octenylsuccinate-derivatized starch with a high proportion of low molecular weight disaccharides, a significant inhibition of autoxidation compared to a carrier... 

Derivatized starches are obtained by reaction with a-chloroacids, epoxy derivatives or anhydrides in alkaline conditions. In general, they have lower gelatinization temperature, better film-forming properties and tend to give softer gels. Typical products used in oil drilling fluids, adhesives and paper applications are carboxymethylated starches, hydroxypropylated starches, cationized starches and acetylated starches. 

Derivatized Starch - This term refers to starch molecules where chemical substitutions are made at the hydroxyls. 

Hydroxypropylstarehes are derivatized starches from waxy maize, eom, potato, or tapioca starch. They are often crosslinked to change texture, as well as to improve temperature and pH resistanee (14,19). Hydroxypropylstarehes are used for viscosity stabilization for both water and milk based products. They improve freeze-thaw and water holding eharaeteristics of produets. 

Figure 15]. The reaction optimally is run at approximately I70°C and 120 psig and produces a derivatized starch with five to eight percent acetylation, aDS of approximately 0.25 (19). 

High DS starch acetates are used to create brittle films and molded products. These have had little application, due to the economic superiority of cellulose acetates. In general, specific gravity and melting temperature both decrease with an increase in acetylation (45). Highly acetylated starches above 15% acetyl content (DS approximately 0.7) are soluble in water at 50° to 100°C and insoluble in organic solvents. When the acetyl content reaches 40% (DS approximately 2.5), the derivatized starch is soluble in aromatic hydrocarbons, ketones, and glycol ethers. 

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 ... 

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). 

Degree of substitution (DS) is the average number of substitutions per monomer, while molar substitution (MS) is the average moles of sustituent per monomer. While the exact structure of any derivatized starch is not known, in simple substitution, the DS is closely related to the MS, as no more than three molecules of substituent can attach to one monomer. With graft substitutions, such as polyhydroxyethylstarch, this assumption cannot be made as multiple molecules can be substituted at one hydroxyl. 

Heller, J., S.H. Pangburn and K.V. Roskos, Development of enzymratically degradable protective coatings for use in triggered drug delivery systems. II. Derivatized starch hydrogels, Biomaierials, 11 (1990)... 

Water molecules are so small and cellulose and so hydrophilic that this solution usually affords only temporary protection. Formaldehyde, glyoxal, polyethylen-imine, and, more recently, derivatized starch (50) and derivatized cationic polyacrylamide resins (51) have been used to provide temporary wet strength. The first two materials must be applied to the formed paper, but the other materials are substantive to the fiber and may be used as wet-end additives. Carboxymethylcellulose-calcium chloride and locust-bean gum-borax are examples of two-component systems applied separately to paper that were used to a limited extent before the advent of the amino resins. Today three major types of wet-strength resins are used in papermaking polyamide-polyamine resins cross-linked with epichlorohydrin (52) are used in neutral to alkaline papers cationic polyacrylamide resins cross-linked with glyoxal are used for acid to neutral papers and melamine-formaldehyde resins are used for acid papers. 

The specific activities of purified preparations of human parotid and pancreatic amylases towards Amylose Azure, Remazol Brilliant Blue starch, phosphate-derivatized starch, and cross-linked starch have been measured. The activities varied with the physical state of the substrate the parotid enzyme exhibited a higher specific activity towards all soluble starches, whereas the pancreatic amylase was more active towards insoluble chromogenic starches. Variations in the enzyme-substrate interactions support the view that there is a configurational difference between the amylases this may be useful in determining the proportions of these amylases in normal and pathological body fluids. 

A dyed derivative of starch (Remazol Brilliant Blue starch), phosphate-derivatized starch, and cross-linked starch have been compared as substrates for a-amylases. The different susceptibilities of the substrates to hydrolysis was used to ascertain the configurational requirements of the enzymes. 

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). 

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