Iodine affinity, dextrins

Using results of these kinds of studies, the characteristic structure of amylose can be differentiated from that of amylopectin. Amylose has a small number of branches and crystallizes and precipitates when complexed with 1 -butanol. The iodine affinity of amylose is much greater (i.a. 18.5 to 21.1) than that of amylopectin (i.a. 0.0 to 6.6),79,152-158,163,169-174 and the iodine affinity of amylose (3-limit dextrin is similar to that of the parent amylose. The average chain length of amylose (3-limit dextrins is much larger than that of the amylopectin (3-limit dextrin.160... 

The iodine affinity is due to the formation of colored complexes with amylose. The color of this complex depends on both the concentration of the iodine in the solution and the kind of starch. Amylose binds 20% (v/v) of iodine, to develop a blue color, whereas amylopectin binds only O.S to 1% (v/v) of iodine to give a red-violet eolor. Starch which does not contain any amylose gives a red color with iodine. Thus, evaluation of the degree of dextrinization based on the observations of Komm and Martin needs standardization of the method and approach, because ofthe variability in the origin of the starch. Table XVI shows that methods in use to date are not equivalent to one another. The color-development characteristics are again dependent on the origin of the starch. ... 

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