Starch esters, commercial

Nitric acid esters of starch are the oldest known starch derivatives and are the only starch esters commercially produced on a large scale. Like cellulose nitrates, the starch nitrates are excellent explosives. They are used extensively in blasting compositions, for quarrying and for certain types of mining. Tapioca starch was used mainly for commercial nitrations in the United States until the advent of World War II and the disruption of supplies made it necessary to nitrate com starch. This transition has been accomplished with little difficulty, although the exact process used is a trade secret. 

Starch Esters. As with the starch ethers, a large number of starch esters have been prepared and patented, but only a few are manufactured and used commercially. Both inorganic and organic acid esters can, and have been, made. The latter are prepared by the same general procedure used to make starch ethers. 

Swinkels29 collected published characterization data for tapioca starch and compared it to that for other starches of commercial significance (Table 12.4). Tapioca starch is differentiated from other starches by its low level of residual materials (fat, protein, ash), lower amylose content than for other amylose-containing starches, and high molecular weights of amylose and amylopectin. The small amount of phosphorus in tapioca starch is partially removable30 and, therefore, not bound as the phosphate ester as in potato starch. It is also common to find protein and lipid values of zero, as reported by Hicks.31 The very low protein and lipid content is an important factor which differentiates tapioca starch from the cereal starches. 

Information on many parts of the starch ester field is decidedly inadequate. It is hoped that future investigations will extend and round out the knowledge of starch esters, not only from the theoretical aspect but also from the view of the commercial utilization of these potentially low-cost products. 

Starch esters represent an important class of starch derivates and have been recently reviewed by Tessler and Billmers [63]. Starch esters can be produced by an aqueous process, at low alkalinity, under controlled pH, and low temperature reactions usually reaching a fairly low degree of substitution (DS<0,2) [64]. Starch acetates with a DS of 2.4 or higher are not biodegradable, like cellulose, while intermediate DS acetate would be easily biodegradable [63,31,32]. Most commercially used starch derivates have a DS less than 0.2 [60]. Pure amylose starch is considered the most desirable precursor for starch-ester based thermoplastics since amylopectin has an adverse impact on mechanical and physical properties of these derivatives [64]. 

Starch can react with organic anhydride in water to yield starch esters, such as starch acetate that have been produced commercially by this process. Esters have also been prepared by aqueous reaction with vinyl esters, the byproduct acetaldehyde can be used to cross-link the starch by lowering the pH once esterification has been completed. 

Another class of carboxylic acid-derived surfactant is the sodium or calcium salts of fatty acid esters. Commercial examples include metal salts of stearic acid esterified with a dimer of lactic acid (sodium stearoyl lactylate) or maleic anhydride (sodium stearoyl fumarate), which are used as emulsifiers in bread making and in bread preservation due to their properties of preventing starch crystallization and dispersing fats [12, 13]. 

Commercially available cationic starches for wet end application are quaternary and tertiary products. These products have been available since about the mid 1950 s and no new basic chemistry has been developed since that time. The development in the late 1940 s and early 1950 s of starch ethers and esters made in the original granule form led to a torrent of starch derivatives for industrial use. Very few of these became commercial. This is possibly because the functions that were required by the industrial and food markets were far... 

In unmodified cellulose the hydroxyl groups give a large amount of hydrogen bonding which leads to insolubility in most solvents. On the other hand if these arc changed by chemical reactions to ether or ester groups a much more tractable material results. Cellulose acetate, butyrate and nitrate methyl and ethyl ether and carboxy methyl ether are widely used modified celluloses. Starches also are modified, but much less commercial success has been had with them. 

Both monostarch and distarch phosphate esters are commercial starch derivatives [90,102]. 

Several types of enzymes have found uses in LADD compositions [4,48], Most common are proteases, amylases, and lipases, which attack proteinaceous, starchy, and fatty soils, respectively. Proteases work by hydrolyzing peptide bonds in proteins. Proteases differ in their specificity toward peptide bonds. The typical protease used in LADD formulations, bacterial alkaline protease (subtilisin), is very nonspecific. That is, it will attack all types of peptide bonds in proteins. In contrast to proteases, amylases catalyze the hydrolysis of starch. They attack the internal ether bonds between glucose units, yielding shorter, water-soluble chains called dextrins. Lipases work by hydrolyzing the ester bonds in fats and oils. Often, combinations are used because of the specificity of each kind to one type of soil. The commercially available enzymes are listed in Table 9.6. 

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