Starch solubilization

When a starch sol is allowed to stand, the A-fraction slowly retrogrades and precipitates from solution. Numerous attempts have been made to effect a fractionation by this means, usually on starches solubilized by hydrolytic action. Several investigators have reported the... 

Figure 1. High-performance size exclusion chromatographic profiles of common and dull horny maize starch solubilized by microwave energy O common, 4 dull horny.

Most manufacturing technologies consist of treating native starches in a reactor with temperature and agitation controls. Generally, a starch slurry with approximately 35% solids and adjusted to a certain pH is treated with chemicals to promote the desired reactions. In most instances, gelatinization and starch solubilization is avoided so as to prevent the disruption of the starch granule. 

Binders. Paper-coating biaders are either polymers derived from aatural sources or syathetic polymers. The largest volume, aaturally derived biader is starch (qv) (99). Starch is provided ia derivatized form or unmodified form pead com starch is used predomiaanfly for the latter. Unmodified starch is solubilized by thermal conversion or enzyme conversion. The most common derivatized products are acetylated [9045-28-7] oxidized, and hydroxyethylated starches. 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

Polymerization in P-cyclodextrin (CD) complexes with monomer offers a route to polymerization, as well as other organic reactions, in water without the need for organic solvents [Ritter and Tabatabai, 2002]. P-Cyclodextrins are toms-shaped, cyclic oligosaccharides obtained by degradation of starch. The hydroxyl groups of the glucose repeat unit of CD are located on the outer surface. This makes the outer surface hydrophilic, whereas the inner surface and cavity are hydrophobic. Water-insoluble monomers become solubilized in water when mixed with CD or CD derivatives because the monomers are absorbed into the cavity. This allows polymerization in aqueous, not organic media, with water-soluble initiators. 

Starch gelatinization is the disruption of molecular orderliness within the starch granule. It results in granular swelling, crystallite melting, loss of birefringence, viscosity development, and solubilization. 

Its toxicity is discussed by Curme Johnston (Ref 4, p 317). In skin absorption it is about l/l0th as toxic as formaldehyde The industrial utilization of glyoxal is largely based on the advantage which may be taken of its two aldehyde groups, its lack of volatility from aqueous solns, and its inoffensive color. Among its uses may be cited in-solubilizing of proteins, polyvinyl, alcohol, starch, etc (Ref 4, p 127) (See also Ref 5). 

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