*2.4.8 Dioscorea villosa (wild yam)*

It is a perennial vine that grows in moist thickets and hedges [57]. It possesses a reddish-brown stem, having heart-shaped leaves with prominent veins and inconspicuous greenish yellow flowers that flourish from September to October. It is usually cultivated as food source and its roots are harvested in the fall. Its taste is usually bland and then acrid, but under special preparation herbalist use its fresh and dried roots for medicine [58]. Also, it is a common herbal remedy for pains associated with rheumatism and arthritis, colic and intestinal cramps, as well as a reliable antispasmodic and anti-inflammatory [59]. It is also applicable in contraceptive manufacture. High content of saponin in species of *Dioscorea villosa* made them useful for the preparation of steroids in the pharmaceutical industry [60, 61]. Studies also revealed that *Dioscorea villosa* had antioxidant activities [62] and the anti-inflammatory activity could be linked to the antiphlogistic effect of the steroidal saponins.

#### **2.5 Cereals**

Cereals are edible grains or seeds that belong to the grass family *Gramineae* (**Figure 1**). Grains are developed from flowers or florets and their structures vary from one to another with some typical features [64, 65]. They possess *embryo* (or germ) which is a thin-walled structure, containing the new plant. The embryo is separated by the *scutellum* (which is involved in mobilization of food reserves of the grain during germination) from the main part of the grain. The endosperm surrounded by thin-walled cells (*aleurone*), packed with starch grains [66, 67]. The *aleurone* layer present in grains consist of one or three cell layers (wheat, rye, oats,

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*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects*

to store and transported, and they do not deteriorate readily if kept dry.

(e.g. intact whole grains and partially milled grains).

elliptical, oval or ovate shape, and has short or long brush hairs.

than other grains. It possesses higher protein content than rice [64].

bread and some types of corn-flakes).

maize and sorghum have one; rice and barley have three). The pericap is the outer layers of the grain (derived from the ovary of the flower) that surround the *seed coat* (the testa), while the bran is formed from the outer thick-walled structures. They are staple foods both for direct human consumption and indirect through livestock feed [68]. Cereal based foods are good sources of energy, protein, B vitamins and minerals for the world population. Cereals are inexpensive to produce, they are easy

However, in cereal products, a proportion of this starch is not digested and absorbed in the small intestine. This is referred to as resistant starch and it appears to act in a similar way to dietary fiber. Four categories of resistance have been

• RS1 refers to starch that is physically inaccessible for digestion as it is 'trapped'

• RS2 refers to native resistance starch granules (e.g. found in high amylose

• RS3 refers to retrograded starch (e.g. found in cooked and cooled potatoes,

• RS4 refers to chemically modified starch (e.g. commercially manufactured

Wheat is ranked as a major cereal crop in many parts of the world and belongs to the *Triticum* family of which there are many thousands of species [65, 67]. Among the known species, *T. aestivum* subspecies *vulgare* and the hard wheat *T. durum* are the most commercially viable [65, 70]. Wheat is grown in both winter and spring but their cultivation in winter or spring is dependent on the species, varieties and their adaptability. However, wheat is grown in many countries around the world, but the most prominent great wheat-producing countries are USA, China and Russia. Wheat grains are also present extensively in India, Pakistan, the European Union (EU), Canada, Argentina and Australia. Estimation showed that 556.4 million tons of wheat might have been produced in 2003; resulting to 30% of the world's cereal production [71]. The wheat grain is sandwiched between the lemma and the palea of each spikelet, possessing an

Rice is an important staple food crop for many of the world's population, especially those living in Asia. Rice is cultivated mainly for human consumption and this include utilization as breakfast cereals, and its use in Japan as brew saké [65, 67]. There are a lot of rice varieties but only a few are grown widely (*e.g.* varieties of the improved semi-dwarf plant type with erect leaves). The rice grain possesses an outer protective coating which is referred to as the hull or husk and the edible rice caryopsis. Also, the brown rice contains an outer layer called pericarp (which contains pigment), seed coat, the embryo and the endosperm. The endosperm comprises of the aleurone layer which encloses the embryo, sub aleurone layer and the starchy or inner endosperm. However, wild rice is less common and it is the grain of a North American plant, *Zizania aquatic*. It is difficult to harvest and it is more expensive

*DOI: http://dx.doi.org/10.5772/intechopen.95020*

defined [65, 69].

maize starch).

starches).

*2.5.1 Wheat*

*2.5.2 Rice*

**Figure 1.**

*Taxonomy of the Graminae family. Source: Shewry* et al*. [63].*

#### *Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects DOI: http://dx.doi.org/10.5772/intechopen.95020*

maize and sorghum have one; rice and barley have three). The pericap is the outer layers of the grain (derived from the ovary of the flower) that surround the *seed coat* (the testa), while the bran is formed from the outer thick-walled structures. They are staple foods both for direct human consumption and indirect through livestock feed [68]. Cereal based foods are good sources of energy, protein, B vitamins and minerals for the world population. Cereals are inexpensive to produce, they are easy to store and transported, and they do not deteriorate readily if kept dry.

However, in cereal products, a proportion of this starch is not digested and absorbed in the small intestine. This is referred to as resistant starch and it appears to act in a similar way to dietary fiber. Four categories of resistance have been defined [65, 69].

