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| Fig. 68: Modern instrumental methods of cereal analysis |
1. Introduction
For many years the cereal industry has been making efforts to predict
processing quality as early, quickly and reliably as possible on the basis of
commercial samples. Over the past few decades, analytical values obtained by
indirect methods have been used more and more to complement or even replace the
results of baking trials. Fig. 68 gives an overview of the most commonly used
testing methods for characterizing wheat and rye for bread baking.
The purpose of this chapter is to give an insight into the routine
methods in general use at the present time. The tests are carried out on
cleaned sample material and fall into the categories of physical, chemical and
rheological methods and standard and basic baking trials. Standard baking
trials are those whose procedure and evaluation have been specified by
established national or international organizations, i.e. they are
standardized.
By basic baking trials we mean procedures that are not standardized
but whose performance in the published manner is especially recommended so that
they can be taken as a basis for further tests of one's own (Brümmer and
Neumann, 2002).
Physical methods such as sifting and weighing determine sizes and masses.
Drying and conductivity mainly give information on the moisture content, while
ashing reveals mineral concentrations. In some countries these methods are used
to determine levels in whole grains and also in milled products. Washing and
swelling methods serve mainly to determine the (wet) gluten content and also
the quality of the protein by means of the sedimentation value after Zeleny.
Great progress has been made with the introduction of near-infrared techniques. In
these methods, calibration of the instruments is extremely important for
precision and comparability. In Germany this is offered as an on-line service
by the Association of Cereal Research (AGF) in Detmold.
Chemical methods are used chiefly to determine the overall protein
content. Other methods are either no longer usual (maltose determination) or
have not yet been introduced (pentosan content).
Rheological methods play a major role (See Rheology ), and the more recent methods
described here also complement mainly the rheological testing sector. This is a
clear indication of the significance of rheological methods in the context of
cereal analysis. The chapter does not deal with sensory methods. Their
importance is still not fully recognized, although they involve very little
work and the results they produce are very valuable and far-reaching.
As far as the indirect routine methods are concerned, their
limitations and restricted ability to predict such aspects as baking properties
have often been emphasized, and in fact correlation coefficients of r = 0.5 to
0.6 usually have to suffice in practice.
Modern Cereal Analysis by New Rheological Methods:
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