In traditional food preparation, sweet cassava, cocoyam, sweet potato, and yam are often wasted. These are peeled and covered with cold water for boiling either alone or in combination. Seasonings are added to enhance palatability and flavor.
Fufu Processing from Boiled Roots and Tubers
Boiled roots and tubers are pounded in a shallow wooden mortar using a fufu stick or wooden pestle to produce a paste commonly called “fufu.”
For good quality fufu, the cut roots or tubers are cooked until “just done,” ensuring starch granules are partially gelatinized; overcooking causes excessive gelatinization, preventing proper fufu formation.
The pieces are crushed gradually with the fufu pestle to avoid lumps. Crushing continues until all pieces are completely crushed before pounding begins.
The mass is moistened with cold water and turned by hand between beatings. Beating breaks down starch granules, absorbing water and making the mass soft, sticky, and elastic.
At the desired softness and stickiness, the product is shaped and served with thin or thick soups. Fufu is made from one type of root or tuber, such as cassava, yam, or cocoyam, or a combination.
Sweet potato is not used for fufu, as it is too sweet and lacks stickiness or elasticity when pounded.
Preparation of Fried and Roasted Root and Tuber Snacks
Pared yam, cocoyam, and potatoes are cut, salted, and deep-fried to produce fried snacks sold as ready-to-eat or convenience foods.
The cut pieces can also be grilled or roasted on open fires. Cocoyam, Irish potato, and green plantain can be thinly sliced, fried in oil, salted, and packaged as crisps. Yams are usually avoided for crisps because they become bitter when fried to crispiness.
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Cassava Processing into Gari: Traditional and Commercial Practices
Both traditional and commercial cassava processing into gari follow basic principles. Fresh tubers are peeled, washed, and grated into pulp.
The pulp is collected and packed in a hessian bag, which is pressed mechanically or traditionally with stones or heavy materials for about 3 days.
During this process, moisture is lost, and some hydrogen cyanide (prussic acid) is eliminated. Fermentation also occurs, releasing more hydrogen cyanide.
Two fermentation stages occur in grated cassava mash. The first stage involves bacteria attacking starch granules, producing acids that react with poisonous compounds to form gases released within 24 hours of fermentation.
The second stage occurs after sufficient organic acids like lactic acid are produced, allowing yeast fermentation to create compounds responsible for the taste, flavor, and aroma of fermented cassava products such as gari.
The pulp is sifted to remove coarse fibers, leaving starch or gari, which is then heat-dried (“fried”) with constant stirring, destroying residual hydrogen cyanide.
Palm oil is added during frying to produce yellow gari. The finished gari swells about three times its weight when mixed with cold water and can be stored in dried form.
Processing of Fruits and Vegetables in Nigeria: Challenges and Opportunities
Nigeria is rich in indigenous fruits and vegetables essential for nutrition and body health. They also serve as raw materials for agro-allied industries.
However, inadequate nutrition education, limited utilization, seasonal variation, perishability, poor preservation methods, and consumption habits hinder their full potential. This results in underutilization and wastage across ecological zones.
Fruits are fleshy, edible products from woody or perennial plants closely linked with flowers (e.g., mango, pineapple, guava, banana, avocado, apple, grape, citrus, plantain, passion fruit, sweet sop).
Vegetables are shrubs or herbaceous annuals, which may include leaves, roots, flowers, seeds, fruits, or inflorescence.
Commonly used vegetables in Nigeria are leaves, seeds, fruits, and roots, consumed as supplementary foods, side dishes (raw), or in soups alongside staples (e.g., spinach, lettuce, cabbage, pumpkin, bitter leaf, amaranthus, onions, tomatoes, okra, pepper, melons, garlic, peas).
Fruits and vegetables are highly perishable and require processing for longer storage. Most household-level processing does not provide adequate shelf life for commercial exploitation.
Few large-scale processors like Lafia Canning Factory (Oyo State) and Vegetable and Fruit Processing Company Ltd (Borno State) specialize in fruit and vegetable processing.
Cottage industries such as Takog Food Processing Company and Tella Fruit Juice Industries (both in Ibadan) operate on a small scale. Vegru Company (Bauchi) processes fruits into juices and tomatoes into puree.
Major firms like Lever Brothers Nigeria Ltd and Nigeria Bottling Company Ltd produce fruit squashes mainly from imported concentrates.
Methods used in fruit and vegetable processing for extended storage include dehydration, canning, sugar processing, fermentation, and pickling.
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Dehydration Techniques for Fruit and Vegetable Preservation
Fruits and vegetables contain tissues with semi-permeable cellulose walls. Heating or freezing destroys these walls, allowing water to be lost while retaining nutrients.
Removing water from food before marketing is called dehydration, drying, or evaporation. If the end product remains liquid, this is evaporation; if solid, it is drying or dehydration.
The main goal of water removal is to reduce bulk for easier handling, transport, and distribution, and to improve shelf life by lowering moisture to prevent microbial attack.
Fruits and vegetables are heat-sensitive, so dehydration requires careful control to avoid flavor loss, nutrient degradation, and reduced product acceptability. Successful dehydration uses minimal heat and careful handling.
Proper drying preserves taste, concentrates flavors, and protects nutrients. It is energy-efficient and reduces storage space.
A combination of warmth, low relative humidity (RH), and moving air facilitates drying. Dry air absorbs moisture, which is carried away by airflow, continuing until equilibrium is reached.
Low temperature or high RH prolong drying and risk spoilage. High temperature with low humidity can cause case hardening, where the surface hardens and traps moisture inside, causing spoilage.
Preparing Fruits and Vegetables for Drying
Quality fruits and vegetables are thoroughly washed, preferably in cold water, to preserve freshness without soaking (which causes vitamin loss and moisture absorption).
Produce is trimmed, peeled if necessary, and cut into uniform shapes such as halves, cubes, slices, or strips. Thinner and smaller pieces dry faster and more evenly, preserving nutrients.
Mango Processing for Juice Production
Ripe mature mangoes are peeled manually and crushed into a fine blend. Water is added and mixed, then preheated to 15–20°C before juice extraction.
The juice is clarified to remove sediments, pasteurized, and filled into sterilized cans by automatic machines. Cans undergo sterilization by immersion in boiling water for 20–30 minutes, then precooled, cooled, and packed.
Plantain Processing for Flour and Snacks
Plantain is processed into flour to extend shelf life, used for baked goods like bread, cake, and biscuits. Other products include chips and dodo.
Flour production preserves plantain, stabilizes prices, and facilitates transport to areas where plantain is scarce.
Historically, plantain flour production has been small-scale, performed by households processing surplus fruits. Flour is produced by drying, milling, and sieving, similar to coffee beans, kola nuts, and tobacco leaves.
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