In:
Starch - Stärke, Wiley, Vol. 59, No. 8 ( 2007-08), p. 357-365
Abstract:
Iodine‐based colorimetry remains the most widespread method for the determination of amylose content of starch. There are, however, many variants of this method, differing in solvent, temperature and method for converting absorbance to amylose content. Therefore, in thisstudy some of these methods were compared in order to identify which, if any, was most reliable. Australian commercial samples of wheat, rice, rye and oat were used. Flour was ground and starch was extracted. Half of the samples of flour and starch were defatted with n ‐propanol. Defatted and full‐fat flours and starches were dissolved by six procedures: DMSO, urea‐DMSO, CaCl 2 ‐DMSO, hot NaOH, cold NaOH and HCl. The solutions were diluted, coloured with iodine and the absorbances determined at 535 and 620 nm. Amylose content was determined by reference to standards using 620 nm as the single wavelength or by two calculations based on the ratio between the two absorbances. Reliability was tested by repeating all tests on three non‐consecutive days with three replicates on each day. Defatted starch provided more consistent results than flour or non‐defatted starch. The most reliable dissolution procedure, with both the lowest standard error and least day‐to‐day variation, was cold NaOH. One of the ratio‐based calculations provided adequate correction for the non‐starch content of flour of wheat and rice, but not of the other two cereals, and the other ratio‐based calculation seldom provided realistic results. It is concluded that a cold NaOH dissolution procedure is suitable for reliable amylose determination on defatted starch of a range of cereals from a single wavelength and that it is also suitable for use on defatted flour of some species.
Type of Medium:
Online Resource
ISSN:
0038-9056
,
1521-379X
DOI:
10.1002/star.200700612
Language:
English
Publisher:
Wiley
Publication Date:
2007
detail.hit.zdb_id:
1481133-9
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