| FOOD CHAIN No. 8 - March 1993 |
Ogi is an important weaning and adult food in Nigeria, eaten as a cake or porridge. I.A. Adeyemi describes the nutritional gains and recommends simple ways of fortifying the final product.
ON is traditionally produced by soaking cereal grains, mainly maize, sorghum or millet in water at ambient conditions for two to three days, then washing them. The steeped grains are them milled and sieved while wet and then soured (fermented). Finally the product is recovered in the form of a cake, and sold by women who are the commercial manufacturers and who still rely on the traditional process.
Two major products prepared from ogi are a porridge referred to as ogi by Yoruba people or akanmu by the Igbos of eastern Nigeria, and a cooked gel which normally contains 15-16 per cent of solid matter. To produce the gel, ogi stirred continuously while being cooked in water in clay pots and then wrapped in leaves. This gel is called eko and agidi respectively by the Yorubas and Igbos.
Nutrients are lost during the production process. Water-soluble nutrients are thrown away in the steeping and washing water, and fine bran, germ and some starch fractions are drained away in the water passing through the sieves after steeping. Between 20-50 per cent of nutrients available in the original grain is lost in this way; the actual loss depending on the grain type, variety, method of production and the fineness of the sieve. The lost material, known as overtails, is fed to livestock.
But traditional processing does have some nutritional advantages. For instance, wet milling has been shown to lead to a reduction in the level of anti-nutritional factors (substances that reduce the body's capability to use part of a food) such as physic acids and tannins. Furthermore, a significant reduction of 60-74 per cent in the level of aflatoxin B1 (a toxin produced by moulds that grow on damp grains) has been reported in infected grains which are wet-milled.
When cereals are fermented together with legumes, such as cowpea, the fermentation results in a reduction or an elimination of trypsin inhibitors (another anti-nutritional factor) as well as indigestable sugars such as raffinose and stachyose which cause flatulence. Recent investigations have also shown that the souring or fermentation stage improves protein digestibility when compared with an unfermented flour.
It is apparent therefore, that the traditional process should not be considered totally irrelevant but rather its unique advantages should- be identified and exploited.
Ogi porridge of desirable consistency is usually made up of 6-8 per cent solid content with 92-94 per cent of water. Mixing at solid ratios of less shall six per cent results in over-dilution which reduces the amount of nutrient in the final porridge. Feeding infants with over-diluted porridge is thought to en courage marasmus (a childhood disease caused by too little protein and calorie intake, which causes the infant to literally 'waste away'), which is still prevalent in many parts of the developing world. Some ogi porridge consumers prefer a highly soured product and they do add souring water, taken from previous fermentations in the preparation of the porridge. As the souring water contains some water-soluble proteins (amino acids) and vitamins, the nutritional value of the porridge is improved.
FORTIFYING THE PRODUCT
One way of increasing the use of ogi as a weaning food would be to fortify it with plant protein. Protein sources that have been exploited include soya beans, groundnuts, melon seeds and cowpea. The addition of up to 20 per cent by weighs of the flour of any of these protein rich materials has significantly improved the protein content of the final product. In our studies soya milk has been found more acceptable than soya flour as it has a less beany flavour and the product has better storage characteristics. We believe that fortification of ogi with any of these products would enhance its nutritional value and so reduce the incidence of kwashiokor (a serious disease caused by lack of protein and high calorie foods, the victims of which are under weight and suffer from oedema or swelling) amongst infants weaned solely on ogi porridge.
In order to introduce variety, fruits such as papaya and mango have been incorporated into ogi. The final product has higher levels of vitamin C and minerals such as calcium and phosphorus, and is very acceptable to consumers As fruits are so abundant in many tropical countries their incorporation into traditional foods could increase both their nutritional and aesthetic value
While the traditional method of preparing ogi is the most common, there is little doubt that nutritional values can be improved by adding plant materials. Larger scale production, using dry-milling and artificial drying could help reduce the incidence of malnutrition that accounts for such high infant mortality rates in many parts of the world.