Cereal structure and composition

Abstract

Cereals are cultivated grasses that are grown throughout the world. As well as providing food for man, they, or fractions derived from processing them, make an important contribution to the diets of farm stock. Cereal grains have a long storage life under favourable conditions because they are harvested at a relatively low moisture content and comprise stable components. The principal energy sources within the grains are protected from infestation by outer coverings that are difficult to penetrate and in some cases unpalatable components in the coverings discourage predation by wild populations. The largest morphological component of all grains is the starchy endosperm, and approximately 80% of this is starch, occurring as microscopical granules with forms characteristic of the species. Also characteristic of the species are the storage proteins, which make the next largest contribution to endosperm dry weight. Proteins are important both as nutrients and by virtue of the fact that the class includes enzymes which, although making a small contribution to grain weight, can have a marked effect on grain quality and hence price. Other chemical components present as minor contributors, but with potential for exerting significant nutritional influence, are phytates and tannins, and current knowledge of these is briefly discussed. The walls of endosperm cells comprise a complex mixture of polysaccharides including cellulose, arabinoxylans, and β-glucans, as well as proteins and esterified phenolic acids. Attention is drawn to the difficulty in defining ‘fibre’ as it is method- or function-dependent and includes contributions from the endosperm cell wall components as well as the lignified walls of cells in the outer protective pericarp and the contents and cuticle of the testa.

Molecular basis of barley quality

“…The large granules, designated A type, are round in shape and contain 70-80% amylose. The small, spherical, B type granules, contain 40-80% amylose (May and Buttrose 1959;Evers et al 1999).…”

“…Oliveira et al (1994) related the effect of starch properties, namely granule volume and size, to hot water extract. Recently, the gelatinisation properties of starch were reviewed by Evers et al (1999). For barley, gelatinisation temperature plays an important role in the quality of malt and hot water extract.…”

“…In 'waxy' barley, the amount of amylopectin increases to >90% (Evers et al 1999). However, waxy barleys generally have lower hot water extract values, and higher β-glucan content and cell wall modification levels (Ullrich et al 1986;Swanston 1996).…”

Pre-maturity α-amylase and incipient sprouting in UK winter wheat, with special reference to the variety Rialto

“…Of the many grist products, breadmaking and noodle flour are particularly sensitive to high enzyme levels because processing conditions are favourable to enzyme catalysed product degradation (Evers et al, 1999). The major effect of α-amylase comes about through the production of high molecular weight starch degradation products (Gold & Duffus, 1996).…”

Effect of γ‐radiation and microwave heating of wheat grain on some starch properties in irradiated grain as well as in grain of the next generation crops

“…Cereal grain has a long storage life under favourable conditions because it is harvested at a relatively low moisture content and comprises stable components [1]. Postharvest food losses are estimated in the range from 9% in the United States up to 50% in other parts of the world [2].…”