Starch, amylose separation from

The variation between the starch from different plants is considerable. The percentage of amylose varies from 27% in maize starch through 22% in potato starch to 17% in tapioca starch. The waxy maizes are unusual in that they are almost pure amylopectin. This is extremely convenient because it avoids the need to separate amylopectin from amylose chemically. 

Starch from ae su kernels in a dent background consists of 51-60% amylose, as determined by the blue value procedure (Table 3.6), with the amylose percentage increasing with increasing kernel age.57 Yeh et al.,90 in contrast, reported that ae su reduced amylose concentration from 65% for su to 28% for ae su, based on SEC separation of starch polysaccharides isolated from kernels in a sweet com background. Three fractions were obtained (Table 3.7). The first two were loosely-branched, similar to the amylopectin fractions in ae. Amylose from the third peak fraction was similar in iodine staining to that from normal however, some short chain length amylose as... 

Potze J. Commercial Separation of Amylose and Amylopectin from Starch. In Radley JA, ed. Starch Production Technology. London, UK Applied Science Publishers 1976. 

Cyclodextrins are degradation products from starch by the bacterium Bacillus macerans. They are separated by precipitation with complexing agents and purified by recrystallization. They could probably be produced industrially by the tonne. The formation of cyclodextrins is interpreted as a trans glycosidation of amylose under enzymic control. The latter, in aqueous solution, adopts at least partially the shape of a helix with a period of six glucopyranose units. The bacterial enzyme catalyses the junction of two glucopyranose residues separated... 

Precipitation by a specific complexing agent is another general technique. Perhaps the most successful application is that resulting in the almost complete separation of an amylose complex from a starch solution on addition of a polar organic molecule. (In this connection, it should be... 

On treating with hot water, starch is separated into the soluble amylose and the insoluble amylopectin. Alternatively, the amylose can also be separated from amylopectin by precipitation from aqueous solution with butanol or by dissolution in liquid ammonia. Generally, starches contain... 

The /3-amylases in the absence of the a-amylases are incapable of degrading whole starches completely. The hydrolysis proceeds rapidly until about 50 to 55 % of the theoretical amount of maltose is produced and then very slowly until a limit of about 61 to 68% is reached (101), The solution is still viscous and the residue, called a /3-amylase limit dextrin, is unfer-mentable. The limit dextrin arises from the inability of /3-amylase to act beyond a branch point in the randomly branched amylopectin molecule and may be envisaged as a pruned amylopectin structure. In the case of potato starch, the /3-limit dextrin includes all the associated phosphate. The limit dextrin contains one end group for every 10 to 12 D-glucose residues (102), in contrast to one in every 25 or 30 residues for the original amylopectin. The initial attack of /3-amylase on amylopectin is about 20 times as fast as on amylose (103), Maltose in amounts of 53 to 62 % of the theoretical have been reported from the action of /3-amylases on amylopec-tins separated from various starches (104). When the /3-limit dextrin is cleaved by acid hydrolysis or by the action of a-amylase, the structure is opened and new chain ends are made available which can be further acted upon by i3-amylase. 

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