Starch acetate optical rotation

Starch acetates may be characterized, in part, by (1) acetyl content, (2) solubility, (3) behavior in solution, (4) optical rotation, (5) fusion temperature, and (6) mechanical properties. 

Optical rotations of starch acetates have, as a rule, been measured by means of the sodium-D-lines with chloroform or, less frequently, pyridine as the solvent. Although individual specific rotations have ranged from + 128 to +276 , the values reported for triacetates prepared by mild treatments seem to lie relatively close together, as indicated in Table I. 

The starch content of a natural product or of a man-made product may be required. The latter products might contain modified starches, and a limited number are permitted for food purposes acetate, adipate, succinate, oxidized, hydroxypropyl. For nonfood applications cationic and carboxymethyl starches are in common use. Polarimetric methods, when applied to such modified starches, reveal that calcium chloride dissolution is better than the Ewers method. Even with cross-bonded starches, which are difficult to solubilize, complete dissolution is achieved within 30 min with calcium chloride solution. Recovery, based on a universal optical rotation of 203°, is over 95%. While this application of the method needs further verification, several laboratories in an ISO work group report similar findings. 

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