Many of the properties of cereal starches that determine their
suitability for particular end-uses are dependent upon their amylose/
amylopectin ratios. These properties include gelatinisation and
gelation characteristics, solubility, the formation of resistant starch,
and, for rice, the cooking and textural characteristics of whole
grains.1-5 Thus, the measurement of the amylose content of starches
is an important quality parameter for starch processing.
Amylose is most commonly determined in cereal starches by the
potentiometric, amperometric or colourimetric measurement of the
iodine binding capacity of the amylose with the resultant formation of
amylose-iodine inclusion complexes.6-10 However, these methods are
subject to uncertainties. Amylopectin-iodine complexes also form,
and these reduce the concentration of free iodine measured by the
non-colourimetric methods and may absorb at similar wavelengths
to amylose-iodine complexes in colourimetric methods. These
complexes lead to an over-estimation of the amylose, requiring
corrections to be applied. Many of the other problems experienced
in the use of these methods are detailed by Gibson et al.
11
The specific formation of amylopectin complexes with the lectin
concanavalin A (Con A) offers an alternative approach to amylose
measurement in starches that is not subject to these uncertainties.12,13
Under defined conditions of pH, temperature and ionic strength,
Con A specifically complexes branched polysaccharides based on
α-D-glucopyranosyl or α-D-mannopyranosyl units at multiple nonreducing
end-groups with the formation of a precipitate. Thus, Con
A effectively complexes the amylopectin component of starch but not
the primarily linear amylose component.
The procedure described in this booklet13 is a modification of a
Con A method developed by Yun and Matheson (1990).13 It uses
an ethanol pre-treatment step to remove lipids prior to analysis
Many of the properties of cereal starches that determine theirsuitability for particular end-uses are dependent upon their amylose/amylopectin ratios. These properties include gelatinisation andgelation characteristics, solubility, the formation of resistant starch,and, for rice, the cooking and textural characteristics of wholegrains.1-5 Thus, the measurement of the amylose content of starchesis an important quality parameter for starch processing.Amylose is most commonly determined in cereal starches by thepotentiometric, amperometric or colourimetric measurement of theiodine binding capacity of the amylose with the resultant formation ofamylose-iodine inclusion complexes.6-10 However, these methods aresubject to uncertainties. Amylopectin-iodine complexes also form,and these reduce the concentration of free iodine measured by thenon-colourimetric methods and may absorb at similar wavelengthsto amylose-iodine complexes in colourimetric methods. Thesecomplexes lead to an over-estimation of the amylose, requiringcorrections to be applied. Many of the other problems experiencedin the use of these methods are detailed by Gibson et al.11The specific formation of amylopectin complexes with the lectinconcanavalin A (Con A) offers an alternative approach to amylosemeasurement in starches that is not subject to these uncertainties.12,13Under defined conditions of pH, temperature and ionic strength,Con A specifically complexes branched polysaccharides based on
α-D-glucopyranosyl or α-D-mannopyranosyl units at multiple nonreducing
end-groups with the formation of a precipitate. Thus, Con
A effectively complexes the amylopectin component of starch but not
the primarily linear amylose component.
The procedure described in this booklet13 is a modification of a
Con A method developed by Yun and Matheson (1990).13 It uses
an ethanol pre-treatment step to remove lipids prior to analysis
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