Traditional Methods of Food Processing in West African Agriculture

Simple, low-cost traditional food processing techniques form the foundation of small-scale food processing enterprises, which are crucial to rural development in West Africa.

These small-scale food industries generate employment opportunities in rural areas, thereby reducing rural-urban migration and its associated social problems.

They play a vital role in reducing post-harvest food losses and increasing food availability. However, rapid growth and development of small-scale food industries in West Africa are limited by the adoption of inefficient and inappropriate technologies, poor management, inadequate working capital, limited access to banks and other financial institutions, high interest rates, and low profit margins.

Despite these challenges, some progress has been achieved in upgrading traditional West African food processing technologies, including mechanization of gari (fermented cassava meal) processing, production of instant yam flour or flakes, production of soy-ogi (a protein-enriched complementary food), and industrial production of dadawa (a fermented condiment).

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Traditional Food Processing Technology and Its Impact on Food Security in West Africa

The capacity to preserve food depends on the level of technological development. The slow progress in upgrading traditional food processing and preservation techniques in West Africa contributes to food and nutrition insecurity in the sub-region.

Traditional food processing and preservation technologies date back thousands of years and, unlike modern electronic industries, preceded any scientific understanding of their nature and effects.

Traditional foods and processing techniques form part of the culture of the people. These activities represent a vital body of indigenous knowledge handed down over generations.

Unfortunately, this knowledge is often undervalued. Some traditional food products and processing practices have been lost over time, which diminishes the cultural and agricultural heritage of the sub-region.

Those retained have survived because they are appropriate to the technological level and socioeconomic conditions of West African countries.

Simple, low-cost traditional food processing techniques remain the foundation of small-scale food processing enterprises in West Africa, contributing significantly to the economy.

Objectives and Main Features of Traditional West African Food Processing Techniques

Technique/OperationObjectiveMain Features/Limitations1. Preliminary/Postharvest OperationsThreshingDetach grain kernels from the panicleDone by trampling or beating with sticks; labor-intensive, inefficient, low capacityWinnowingSeparate chaff from grainDone by throwing grain into the air; labor-intensive, low capacity, inefficientDehullingRemove grain from outer protective casingDone by pounding in mortar with pestle; labor-intensive, low capacity, excessive grain breakagePeelingSeparate peel or skin from edible pulpManual peeling with knives; labor-intensive, low capacity, loss of edible tissue2. Milling (e.g., corn)Dry millingSeparate bran and germ from endospermDone by pounding or grinding with stone; laborious, inefficient, limited capacityWet millingRecover mainly starch for fermented foods (e.g., ogi)Done by pounding or grinding after steeping; laborious, limited capacity, high protein losses, poor quality product3. Heat ProcessingRoastingImpart sensory qualities, enhance palatability, reduce antinutritional factorsPeanuts roasted by stirring in hot sand; laborious, limited capacityCooking (e.g., wara)Contract curd, facilitate whey expulsion, reduce microbial load, impart sensory qualitiesCurd cooked over wood fire; limited capacityParboiling (e.g., rice)Facilitate milling, enrich rice with B-vitamins and mineralsSteeping and steaming paddy rice; limited capacity, poor quality productBlanchingInactivate plant enzymes, minimize oxidative changesSlices heated in hot water; limited capacity, poor quality product4. DryingShallow layer sun dryingReduce moisture content, extend shelf lifeProduct spread thinly in open; labor-intensive, requires space, moisture often too high for long-term stability, poor qualitySmoke drying (e.g., banda)Impart sensory qualities, reduce moisture, extend shelf lifeMeat exposed to smoke in kiln or drum; limited capacity, poor quality5. FermentationExtend shelf life, inhibit spoilage and pathogens, improve sensory qualities and nutritional valueNatural fermentation with microbial flora selection; limited capacity, variable quality

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Traditional Fermentation: Key Role in West African Food Preservation

Fermentation is one of the oldest and most important traditional food processing and preservation methods. It involves microorganisms and enzymes to produce foods with quality attributes distinct from the original raw materials.

An example is the conversion of cassava (Manihot esculenta) into gari, a staple in Nigeria, Ghana, Ivory Coast, Sierra Leone, Liberia, Guinea, Senegal, and Cameroon.

Nigeria leads cassava production globally, with an annual output of 35-40 million metric tons. Cassava varieties exceed 40 types in Nigeria, accounting for over 20% of all food crops consumed. Cassava roots are rich in starch (20-30%) and are considered the highest carbohydrate producer among crops, next to sugar cane.

The main challenge with cassava utilization is the presence of two cyanogenic glucosides, linamarin and lotaustralin, which release toxic hydrogen cyanide (HCN) upon hydrolysis.

Cyanide levels in cassava vary by variety, with sweet varieties low in cyanogens and bitter varieties high, distributed throughout the root. Environmental factors like drought increase cyanide levels.

Chronic consumption of cyanide from cassava products can cause health issues such as goiter, cretinism, and neurological diseases.

The traditional West African process for detoxifying cassava roots involves peeling, washing, grating, fermenting, pressing, roasting, and sieving to produce gari.

Fermentation allows the enzyme linamarase to hydrolyze cyanogens, reducing cyanide content to safe levels below the WHO standard of 10 ppm. This process is more effective than other regional methods like heap fermentation and sun drying.

Besides gari, numerous traditional fermented foods exist in West Africa, including staples like fufu, lafun, and ogi; condiments like iru (dadawa), ogiri, and ugba; alcoholic beverages like burukutu, shekete, and agadagidi; and fermented milks and cheese.

Lactic acid bacteria and yeasts drive most fermentations, which are part of a vital indigenous knowledge system passed down through generations.

Dadawa (Iru) Fermentation: Nutritional and Economic Importance

Dadawa or iru is the most important fermented food condiment in Nigeria and many West and Central African countries.

It is made by fermenting African locust bean seeds, which are rich in fat (39-47%) and protein (31-40%). Dadawa significantly contributes to energy, protein, and vitamin intake, especially riboflavin, in the region.

Production involves boiling the seeds for 12-15 hours until tender, dehulling by pounding or rubbing, then boiling again with softening agents like 'kuru' (sunflower seed and trona or sodium sesquicarbonate).

The seed balls are wrapped in banana leaves or placed on raffia mats and fermented for 2-3 days under jute bags or spread hot on trays and fermented for about 36 hours.

The primary microorganisms involved are Bacillus subtilis and Bacillus licheniformis. Significant biochemical changes during fermentation include protein hydrolysis, breakdown of indigestible oligosaccharides, synthesis of B-vitamins (thiamin and riboflavin), and reduction of antinutritional factors like oxalate and phytate.

Importance of Fermentation

Fermentation offers several key benefits beyond detoxification and elimination of natural nutritional stress factors.

1. Reduction of mycotoxins such as aflatoxins occurs during the processing of traditional foods like ogi, making these foods safer.

2. Conversion of inedible plants into edible forms happens when fermentation hydrolyzes indigestible components in African locust bean and African oil bean, producing popular foods like iru and ugba.

3. Improvement of flavor and texture enhances raw agricultural products by adding desirable sourness and distinct flavors, as seen in gari and ogi.

4. Nutritional quality enhancement happens by increasing protein digestibility through protein hydrolysis, improving mineral bioavailability (calcium, phosphorus, zinc, iron) by breaking down phytates and oxalates, and raising B-vitamin levels via microbial synthesis.

Production of Complementary Foods

Breast milk sufficiently meets infants' nutritional needs up to about four to six months. Beyond this period, complementary or weaning foods become essential.

The weaning phase is critical for growth, disease resistance, intellectual development, and survival. However, traditional complementary foods in West Africa, mostly made from cereals, starchy roots, and tubers, are carbohydrate-rich but low in quality protein, which leads to protein-energy malnutrition in infants and preschool children.

Traditional cereal-based gruels like ogi have high viscosity and must be diluted, further lowering energy and nutrient density. While commercial complementary foods exist, they are often too costly for most families.

Therefore, simple, affordable, and community-level processing techniques are necessary to produce nutritious and safe complementary foods.

Complementary Foods from Cereal-Legume Blends

Cereals generally lack sufficient protein and are low in essential amino acids like lysine and tryptophan.

1. Supplementation with legumes, which are rich in protein and lysine but often low in sulfur amino acids, improves both the protein content and quality through amino acid complementation.

2. A cereal-legume ratio of 4:1 has been successful in producing high protein-energy weaning foods across many African countries. For example, Ghana’s 'Weanimix' was widely adopted in the 1980s, supported by UNICEF’s provision of grinding mills to rural women groups.

3. The choice of cereal and legume types and blending ratios is critical because higher legume concentration can improve protein quality only up to a limit before another amino acid becomes limiting.

Among legume supplements, soybean and winged bean blends with cereals offer the best protein quality, followed by cowpea and pigeon pea. Groundnut performs poorly due to inadequate amino acid complementation.

Production of Instant Yam Flour

Yam is a staple food in West Africa and a major economic crop, with white yam (Dioscorea rotundata) used mainly for fufu or pounded yam. Traditionally, pounded yam is labor-intensive, requiring boiling and pounding with mortar and pestle.

To ease preparation, instant yam flour products such as "poundo yam" were introduced in the 1970s. Instant yam flour, when mixed with hot water, forms a smooth dough similar to pounded yam and has become very popular locally and internationally, especially among African diaspora communities.

Instant yam flour is typically produced by sulfiting peeled yam pieces, then steaming, drying, milling, and packaging.

Alternatively, it can be made by drum-drying cooked, mashed yam followed by milling, a method similar to dehydrated mashed potato production.

Some Traditional Nigerian Fermented Foods

Fermented FoodRaw MaterialsMicroorganisms InvolvedUsesGariCassava pulpLeuconostoc spp., Lactobacillus spp., Streptococcus spp., Geotrichum candidumMain mealFufuWhole cassava rootsLactobacillus spp., Leuconostoc spp.Main mealLafunCassava chipsLeuconostoc spp., Lactobacillus spp., Corynebacterium spp., Candida tropicalisMain mealOgiMaize, sorghum, milletLactobacillus plantarum, Streptococcus lactis, Saccharomyces cerevisiae, Rodotorula spp., Candida mycoderma, Debaryomyces hanseniiBreakfast cereal, weaning foodIru (Dawadawa)African locust bean, soya beanBacillus subtilis, B. licheniformisCondimentOgiri (Ogili)Melon seed, fluted pumpkin, castor oil seedBacillus spp., Escherichia spp., Pediococcus spp.CondimentKpayeProsopsis africana (algarroba or mesquite)Bacillus subtilis, B. licheniformis, Bacillus pumilusCondimentUgba (Ukpaka)African oil beanBacillus licheniformis, Micrococcus spp., Staphylococcus spp.Delicacy (consumed with stock or dried fish)Palm winePalm sapSaccharomyces spp., Lactic acid bacteria, Acetic acid bacteriaAlcoholic drinkBurukutu/Pito/OtikaSorghum, millet, maizeSaccharomyces spp., Lactic acid bacteriaAlcoholic drinkSheketeMaizeSaccharomyces spp.Alcoholic drinkAgadagidiPlantainSaccharomyces spp.Alcoholic drink

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