Cereals processing technology

those of traditional resistance breeding. However, if the transgenic strategies
prove dramatically more effective they could seriously deplete populations of
plant pathogens and even lead to the extinction of highly specific pest
organisms. Evaluation of these risks is important in successful applications of
transgenic technology (Bergelson et al. 1999).
4.4 Improved nutritional properties
Biotechnology, cereal and cereal products quality 57
4.4.1 Cereals and human nutrition
Cereals are a very important part of human diets. The three major species,
wheat, maize and rice, account for a large proportion of the calories and
protein in human diets. The importance of cereals in the food chain is also
attributable to the extensive use of cereals in the diets of animals. The major
constituents of cereals are the carbohydrates and proteins. Other grain
components such as lipids and vitamins may be of great significance in human
nutrition because of the large contribution of cereals to the diet.
Biotechnology provides new options for manipulation of the nutritional
properties of cereal grains. The carbohydrates of cereals include the simple
sugars, the more complex oligosaccharides such as fructans, storage
polysaccharides of the grain (starch) and the cell wall polysaccharides, all
of which are of nutritional value. All of these carbohydrate components are
potential targets for manipulation in improvement of cereal quality. (For
example, sugar beet has been transformed to produce fructans (Sevenier et al.
1998).) Benefits that may result include reduced cariogenic bacteria (dental
health), lower energy value and stimulation of beneficial bacteria in the colon.
The sugar content may also influence the quality of the grain for various
products. Fructans may be considered to be important to human nutrition
because of their possible role as soluble fibre (Ninees 1999). Starch, as the
major component by weight of the grain, may have a great impact on
nutritional quality. Resistant starches (not digested in the gut) may be
considered critical in influencing the incidence of certain human diseases,
such as heart disease. The cell wall polysaccharides may also be important as
either soluble or insoluble fibre, depending on the composition of the
polysaccharides in the cereal product. Soluble fibres may reduce the risk of
heart disease while insoluble fibres contribute to reduced risk of colonic
cancers.
Cereal proteins are not well balanced in amino acids required in a
nutritionally balanced diet, and genetic engineering may provide opportunities
to improve the balance of essential amino acids in cereal-based diets. The lipids
in cereals are generally of limited importance in human nutrition but may be
important in animal diets. The manipulation of iron levels in cereals through the
introduction of haemoglobin illustrates the potential application of biotechnology
to enhancing the nutritional value of cereals.