Cereals processing technology

Biotechnology, cereal and cereal products quality 59
4.5.1 Cereal quality and process requirements: the potential role of
biotechnology
The processing of cereals involves a wide range of techniques with very
differing raw material requirements. Several of the major processes of cereal
processing will be described here in an attempt to identify the major
opportunities for biotechnology to be applied to improving cereal processing
quality.
Milling
The milling of cereals (Fig. 4.1) involves processes that are dependent
substantially on the anatomical structure of the grain. The potential for single
genes to be manipulated in ways that enhance milling quality may be limited
because of the large number of grain characteristics contributing to milling
performance. The shape of the grain and adherence of the various outer layers
are of great importance. Hardness is also a key attribute in milling. Grain
colour is a key quality attribute that is influenced by the milling process. The
levels of pigments and the size of particles generated in milling both influence
colour. The contamination of endosperm fractions with more highly coloured
outer layers such as bran are key determinants of colour (Ziegler and Greer
1971).
Baking
Many components of cereals such as wheat are important in baking quality and
are obvious candidates for the application of biotechnology. The requirements of
modern high-speed plant bakeries are for a very consistent quality. Characteristics
such as dough stickiness associated with some alien (non-wheat) sources
of disease resistance in wheat are serious problems in these high-capacity
facilities.
The major components of wheat all contribute to baking quality and are thus
targets for genetic improvement of baking quality. Proteins are essential for the
visco-elastic properties of wheat doughs. Starch and cell wall polysaccharides
(e.g., pentosans) also influence baking quality. The breakdown of starch by
amylases is a key process in baking. The pentosans of the cell wall also have a
significant influence on loaf quality (Pomeranz 1971).
Malting
Malting is the first step of processing grain for use in brewing and distillation.
The malting of cereals, most specifically barley, is a process of germination. The
rate of germination and the changes in the composition of the barley during
malting are potentially important targets for biotechnology. The breeding of
malting barley varieties focuses on several major quality characteristics
associated with the malting process.
Enzymes are involved in the breakdown of cell walls during malting. The -
glucanases expressed during germination are essential to ensure that the levels
of -glucan in the malt are low. High malt -glucan levels contribute to high