Title: Terminology and measurement
techniques of starch components
Morell, Harald Pasch,
Louise Slade, Takayuki
Visser, and Jurgen
The aims of this project are (1) to reach agreed definitions of
the three types of starches, and (2) to explore reliable and reproducible
means of measuring the relative amounts of each in a given sample.
At present, different laboratories report different results for
what ostensibly is the same quantity.
There are two well known types of starch in cereals, amylose, or
apparent amylose, and amylopectin; research indicates a third. All
are polymers of glucose. Amylose, or apparent amylose, is amorphous
and contributes to most, if not all, the cooking and processing
properties of cereals and tubers. Amylopectin is semi-crystalline
and branched and accounts for the greatest proportion of starch
in cereals and tubers. The third type is amorphous and branched
and its functionality is still unknown.
IUPAC has invested resources into the
nomenclature of starches, but there is still no agreed description
of amylose, and there is no agreed method to measure it. Thus measured
values for amylose content are inconsistent between laboratories.
Recent research has made significant progress in understanding the
structure of the starches. This proposal is designed to bring together
people from around the world who research starch structure, people
who need to understand the functionality of the starches, people,
including from industry, who need to measure the ratio of the different
starches, and people with knowledge of terminology.
The measurement techniques will be the
iodine method commonly accepted to give the relative amounts of
amylose and amylopectin, and both capillary electrophoresis and
multi-detector size-exclusion chromatography (with analysis by MALLS,
DRI, MALDI and NMR of the eluent) to provide molecular weight distribution
for both a given starch and the same starch which has been fully
debranched by debranching enzymes. These data, for a wide variety
of starches, either currently available, or which will be measured
for this purpose in the laboratories of the Task Group members,
will form the basis for agreed definitions of starch types in terms
of these quantitative distributions.
Two meetings are planned. The first will
be a preliminary meeting to define a 12 month action plan for describing
and measuring the starches, and will run in conjunction with an
IUPAC symposium on biopolymers in Mauritius in June 2005. The issues
and actions will be managed by electronic communication for the
next 12 months, and then a second meeting will be held at the International
Rice Research Institute in the Philippines to wrap up and to finalise