Food Biochemistry and Food Processing (2 edition)

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606 Part 5: Fruits, Vegetables, and Cereals

food-making equipment, and the producers themselves, repre-

sent the initial fermentation flora. Malted flour is also an im-

portant source of microorganisms. The changes that take place

during the fermentation are due to both the metabolism of the mi-

croorganisms present and the activity of enzymes in the cereal,

and these are in turn affected by the great variety of technolo-

gies that are used. The technology may be simple, involving

little more than a mixing of flour with water and allowing it

to ferment, or it may be extremely complex and involve many

steps with obscure roles. Indigenous fermented foods are usu-

ally based upon raw materials that have a sustainable production

in their country of origin and are therefore attracting increasing

interest from researchers—both within pure and applied food

science and also in anthropology. These ancient technologies

often have deep roots in the culture of a country, and there

is increasing awareness of the importance of preserving these

traditional foods. Many products are not yet described in the

literature, and knowledge of them is in danger of disappearing.

It is therefore necessary to document the technologies used and

to identify the fermenting organisms and the metabolic changes

that are essential for the characteristics of the product. It is, how-

ever, often difficult to describe the sensory attributes of a product

that is inherently variable.

In Africa, as much as 77% of the total caloric consump-

tion is provided by cereals, of which rice, maize, sorghum, and

millet are most important. Cereals are also significant sources

of protein. Most of the cereal foods consumed in Africa are

traditional fermented products and are very important both as

weaning foods and as staple foods and beverages for adults. In

Asia, many products are based on rice, and maize is most widely

utilized in Latin America (FAO 1999).

Indigenous fermented cereals can be classified according to

raw material, type of fermentation, technology used, product

usage, or geographical location. They can range from quite solid

products such as baked flat breads to sour, sometimes mildly

alcoholic, refreshing beverages.

Many factors have an influence on the characteristics of an

indigenous product (Fig. 31.6). The choice of raw material may

be primarily influenced by price and availability rather than by

preference.

For instance Togwa, a Tanzanian fermented beverage, may

be made from maize in the inland areas of Morogoro and

Iringa, but from sorghum in the coastal areas of Dar es Salaam

and Zanzibar (Mugula 2001). Similarly, the Ethiopian prod-

uct borde may be made from several different grains accord-

ing to availability—sorghum, maize, millet, barley and also the

Ethiopian cereal tef (Abegaz et al. 2002). The use of different

grains obviously affects the sensory characteristics of a product,

and yet it may have the same name throughout the country. Some

fermented cereal products also contain other ingredients. Idli is

a leavened steamed cake made primarily from rice to which

black gram dahl is added. This not only improves the nutritional

quality, but in addition, the black gram imparts a viscosity, ap-

parently specific for this legume, which may aid air entrapment

during fermentation and thereby lighten the texture of the prod-

uct (Soni and Sandu 1990). However, on a broader basis, the

addition of legumes such as soybean flour to fermented cereals

Figure 31.6.Important factors determining the characteristics of

spontaneously fermented cereal products.

has been suggested as an economically feasible way to generally

improve the nutritional quality of cereal foods.

Some fermented cereal products are made using unmalted

grain, with no extra addition of amylase, but they tend to ei-

ther be very thick or of low nutritional density. Malted flour

is added to many indigenous fermented cereals, a traditional

technology that has far-reaching effects on several product char-

acteristics. The addition of malt provides amylases (in particular,

α-amylase) that hydrolyze the starch, sweeten the product, and

also cause a considerable decrease in viscosity of the product af-

ter heat treatment. The malting process, the germination of grain

following steeping in water, is associated with colossal micro-

biological proliferation, and the organisms that develop during

malting are a source of fermenting organisms. Many Asian prod-

ucts, for example koji, a Japanese fermented cereal or soybean

product, are first inoculated with a fungus, as a source of amy-

lase, in order to liberate fermentable sugars from the cereal starch

(Lotong 1998).

Many fermented cereals are multipurpose. A single product

may be prepared in varying thicknesses and used as a fermented

gruel for both adults and children, or it may be watered down

and used as a fermented thirst-quenching beverage. As Wood

(1994) remarked, the latter type of product makes a meaningful

contribution to nutrition; the potential of their replacement by

cola-type beverages would result in a serious negative impact on

the nutrition of people in developing countries.

The use of fermented cereals as weaning foods in develop-

ing countries raises several important issues. Unfermented gru-

els deteriorate very rapidly in unhygienic conditions, especially

if refrigeration is not available. They then represent a signif-

icant source of foodborne infections that annually claim the

lives of millions of young children (Adams 1998). Fermented

malted cereal gruels have been shown on the whole to contain

low numbers of pathogenic organisms since these are inhibited

and killed by the low pH that rapidly develops in the product.