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Acetylated distarch adipate - Chemically modified crosslinked and stabilized food starch in which some of the hydroxyl groups on neighboring starch molecules have been chemically linked by adipate groups. Acetylation of some starch hydroxyl groups is also achieved when treated with a mixed adipic/acetic anhydride reagent.
Acetylated distarch phosphate - Chemically modified food starch, which has been cross-linked using either phosphorus oxychloride or sodium trimetaphosphate phosphate. In addition, some of the other hydroxyl groups are esterified with acetyl groups, by treatment with acetic anhydride.
Acetyl value - Acetyl value is the % of acetyl groups on a modified starch based on a dry weight basis. It is measured by hydrolysis of the acetyl groups and subsequent titration.
Acetylated starch - Starch in which some of the hydroxyl groups have been esterified with acetyl groups by treatment with acetic anhydride.
Acidity - Defined as the amount of alkali which is needed to neutralize the acids in a starch product under defined conditions.
Acid stability - The stability of a given key product property, usually viscosity, to an acidic (low pH) environment.
Acid-thinned starch - Acid-thinned starch is a term usually used for a starch suspension treated with dilute acid at a temperature below the gelatinization point. The granular form of the starch is maintained and the reaction is ended by neutralization, filtration and drying once the desired degree of conversion is reached. This results in a reduction in the average molecular size of the starch polymers. Acid-thinned starches tend to have a much lower hot viscosity than native starch and a strong tendency to gel when cooled.
Agglomerated starch – Cook up or instant starch which has been specially processed to give granular agglomerates to improve dispersibility in liquids or to modify flow properties or density. A second material such as maltodextrin may be present to serve as binder or inter-particle adhesive.
Alkali lability - Some chemical substituents on a modified starch may be easily removed by treatment with alkali. Ester groups such as acetate and adipate are sensitive to hydrolysis by alkali. Phosphate groups are more resistant but they too can be hydrolyzed under more severe conditions.
Alpha amylase - An enzyme which randomly fragments starch chains by rupture of 1,4-alpha-glucosidic bonds. It is also used to produce maltodextrins, syrups and dextrose. It naturally occurs in human saliva.
Amorphous - An amorphous material is non-crystalline. Within the starch granule there are both amorphous and crystalline regions. The amorphous areas are characterized by a high degree of molecular disorder with the chains having a random configuration. In the crystalline regions the linear sections of molecules, of amylose and amylopectin, are arranged in parallel crystalline bundles.
Amylose - The constituent of starch in which anhydroglucose units are linked by a-D-1,4 glucosidic bonds to form linear chains. The level of amylose and its molecular weight vary between different starch types. Amylose molecules are typically made from 200-2000 anhydroglucose units. Aqueous solutions of amylose are very unstable due to intermolecular attraction and association of neighboring amylose molecules. This leads to viscosity increase, retrogradation and, under specific conditions, precipitation of amylose particles. Amylose forms a helical complex with iodine giving a characteristic blue color.
Amylopectin - A constituent of starch having a polymeric, branched structure. In addition to 1,4 bonds which are present in amylose and the linear segments of amylopectin, the amylopectin molecule has a-D-1,6 bonds which occur every 20-30 anhydroglucose units. Aqueous solutions of amylopectin are characterized by high viscosity, clarity, stability, and resistance to gelling. The level of amylopectin varies between different starch types. Waxy starches are almost 100% amylopectin.
Analysis - Analytical methods are well established for determination of a wide range of physical and chemical properties of starch and its derivatives.
Angle of repose - When a sample of starch powder is allowed to fall onto a flat surface under specific conditions to form a pile, the angle of repose is the angle between the sloping surface of the pile and the horizontal. A highly flowable powder, forming a relatively flat pile has a low angle of repose. A poorly flowable powder with a relatively tall pile has a higher angle of repose.
Anhydroglucose unit - The unit constituent of the starch polymers amylose and amylopectin. It corresponds to a molecule of glucose minus the one molecule of water, which is eliminated from each glucose unit, as it condenses onto the growing chain during synthesis of the starch in nature.
Anionic starch - Modified starch containing groups imparting a negative charge on the molecule in aqueous conditions under suitable pH conditions. Examples include oxidized starch, carboxymethyl starch, and monophosphate starch.
Arrowroot starch - Starch isolated by wet milling of the tuberous roots of the genus Maranta linnaeus and Maranta arundinacea Linnaeus.
Ash - The inorganic mineral residue of a starch product after complete combustion under defined conditions.
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