Depolymerized starch

Partially depolymerized starch provides decreased fluid losses at much lower viscosities than the corresponding starch derivatives that have not been partially depolymerized [498]. 

Ultrasound has proven effective in promoting a few heterogeneous nonmetallic reactions. As early as 1933 Moriguchi noted that the reaction of calcium carbonate and sulfuric acid was faster in the presence of ultrasound(4). In the same year Szalay reported that ultrasonic waves depolymerized starch, gum arabic and gelatin(50). Examples of synthetically useful applications are fewer than metallic systems but activity in this arena is increasing. 

Depolymerizing modification of starch usually involves the use of enzymes, acid- (and less frequently base-) catalyzed hydrolysis, and thermolysis alone and thermolysis combined with acid-catalyzed hydrolysis (see a recent survey in this Series2). Despite several studies, the physical treatment of starch has not yet resulted in major practical applications. The aim of this Chapter is to review physical methods as tools for the treatment of starch which deliver amounts of energy suitable for depolymerizing starch to target products. It should be noted that the duration of such processes does not need to exceed that for conventional, namely enzymic, chemical, and thermal modifications. Moreover, a potential advantage of nonconventional physical treatments is the fact that they generate no waste products. 

Converted starches, also called thin-boiling starches, are produced by degradation of the starch chains into small segments. They can be cooked in water at higher concentrations than native starches. Low-viscosity starches are needed in applications where a high solid starch paste with a pumpable and workable viscosity is required. There are four classes of commercial converted starches dextrins (hydrolysis in solid-state) acid-modified starches (hydrolysis in a slurry) oxidized starches and enzymically depolymerized starches. 

Retrogradation is the reassociation of solubilized starch polymers in their native state or those in dextrins or in low-DE hydrolyzates resulting in an insoluble precipitate. Dextrins are depolymerized starches produced by heating a starch moistened with dilute hydrochloric acid or heating a moist starch in the presence of gaseous hydrogen chloride until a cold-water-soluble product is formed. 

The concept biochemical processing of vegetable gums is exemplified by the use of alpha amylase to depolymerize starch and by the Bacillus macerans transglycosylase in the formation of cycloamylose. Most biochemical processes are presently not... 

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). 

The use of alpha amylase on starch produces a depolymerized starch. The enzyme, cycloamylose gluconotransferase, is responsible for production of cycloamyloses. Biological modification is advantageous as enzyme reactions are often very specific, recognizing subtle variations in the polymer such as a particular monomer linkage or an or conformation. 

Starch can be hydrolyzed efiiciendy by acid treatment or by the use of enzymes yielding depolymerized starches with increased water solubility compared to the native starch. 

Degradation of starches with malt diastatic enzymes (which contain a-and )S-amylase) depolymerize starch to give soluble starch . "Thin-boiling starches are produced by mild acid hydrolysis of starch. D-Glucose is produced commercially by the total acidic hydrolysis of starch. 

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