(FoDiS)Cassava Processing in Zambia
FoDiS Information Series
Cassava Processing in Zambia
-Primary Processing- |
Preamble
Cassava production has spread to non-traditional cassava producing areas such as Southern and Eastern provinces of Zambia. The government has recognized that cassava can be a powerful poverty fighter and can transform rural economies. However, cassava easily deteriorates once harvested and thus needs to be eaten or processed quickly within a short period of time to prevent streaking and loss of quality. Processing also requires removing a certain type of toxins (cynanogenic glucosides) that are contained in fresh cassava roots and known to aggravate iodine deficiency, malnutrition and in acute situations can cause paralysis in the lower limbs.
It is for this reason that this brochure has been published to specifically strengthen knowledge and skills of cassava processing among the farming community and processors. The brochure has included information on primary processing technologies utilized in Zambia.
Information and illustrations used in this brochure were mainly derived from “Cassava Production, Processing and Utilization in Zambia” (Maureen. M. Chitundu; Isabel L. Tembo), a booklet published by Programme Against Malnutrition (PAM). Special acknowledgement is expressed to PAM for a kind cooperation in agreeing on the use of information. |
Contents
I. Types of Processing Cassava Tubers
II. Steps in Cassava Processing
Step 1. Peeling
Step 2. Washing
Step 3. Soaking
Step 4. Slicing, Chipping, Grating
Step 5. Dewatering and fermentation
Step 6. Drying
Step 7. Pounding and milling
III. Traditional Processing of Cassava Primary Products
Method 1. Unfermented Cassava
Method 2. Fermented Cassava
Method 3. Fermented Cassava “Bwabi"
Method 4. Fermented Cassava “Kapesula” |
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I. Types of Processing Cassava Tubers
Straight Dried Products:
Straight dried products are produced by spreading peeled whole or chipped roots on rocks, mats or raised racks in direct sun light. The drying time required depends on the size of cassava being dried. Dried cassava is thereafter stored or milled to produce flour. |
Baked cassava with groundnuts |
Soak-Fermented Products:
Roots are placed in water to ferment. During fermentation, the roots soften producing a product with a distinct acid flavour. The roots are thereafter removed, squeezed by hand to remove excess water and are dried whole, split or mashed. Once dried, the products may be stored or milled to obtain flour. |
Soaked roots shown in the dish and woven baskets |
Fermented Products:
Fermented products are produced by grating or pounding peeled cassava roots and placing the mash in bags or baskets for a number of days depending on the desired acidic taste. The mash may then be roasted (gari) or sun dried and stored. Gari is a popular granular roasted product used to prepare eba, similar to nshima in West Africa. |
Packaged and labeled cassava products |
II. Steps in Cassava Processing
Cassava processing is often elaborate and involves a number of steps. The characteristics and quality of the final product depends on the sequence of steps used. These steps are important to understand and follow when processing cassava because they are essential in producing safe cassava chips or flour meant for home consumption and marketing. Poorly processed cassava can lead to goiter, malnutrition and in acute cases lameness.
Step 1. Peeling
Peel using stainless steel knives. Adequate peeling is necessary to avoid the presence of peel fragments in the final product. The peel is rich in protein and when dried is used as stock-feed. Much of the cyanogenic glucoside are contained in the peel, hence peeling is the first stage of hydrogen cyanide removal. Peeling is deemed the most time consuming by processors, but is essential to the quality of the final product.
Plate 1 Fresh cassava roots and peeling |
Plate 2 Peeling by stainless steel knives |
Step 2. Washing
Thoroughly wash in clean tap or borehole water to remove soil particles and dirt which could affect the quality of the final product. This is done using plastic drums or dishes to avoid the adverse effects of rust.
Plate 3 Washing in a plastic dish |
Plate 4 Cassava roots after washing |
Step 3. Soaking
Peeled roots can be placed in a drum, slow moving stream or pond to ferment. Fermentation is complete when roots soften. Soaking generally takes 3 – 4 days in the hot and 4 – 7 days in the cold season. Availability of adequate clean water and softening of roots is crucial to efficient processing.
Plate 5 Soaking in a plastic drum |
Plate 6 Soaking in a cement tank |
Step 4. Slicing, Chipping, Grating
The peeled root is chipped using a chipper or sliced using a knife. Chipping has the advantage of yielding a product with higher starch content but should not be used for cassava with high cyanogenic glucoside levels because these require grating to completely remove the hydrogen cyanide (refer to cassava varieties).
Plate 7 Chipping by household chippers |
Plate 8 Chips |
Peeled roots can be mashed using a grater. Grating disintegrates the cassava tissue and frees the moisture so that pressing is easily performed. Both “sweet” and “bitter” varieties can be grated.
Plate 9 Household grater |
Plate 10 Manual grater |
Step 5. Dewatering and fermentation
Water is removed by applying pressure on cassava mash. The mash is placed in sacks and pressure is applied using heavy rocks, hydraulic jack or screw press. When left to dewater for a few days, an acidic fermentation occurs and the longer the fermentation the greater the acidic taste. Dewatering reduces the drying or roasting time, but when producing flour, pressing time should be kept to a reasonably short time to avoid fermentation.
Plate 11 Dewatering cassava mash |
Step 6. Drying
Drying may be carried out using hot air mechanical dryers or sun/solar dryers. The cassava should be thinly spread on the drying surface to allow maximum air circulation. The lower the loading density the faster the drying process and better quality product. Completely dried cassava can be detected by lightness of color, “sharp snap” when broken, or a hollow sound when a piece is tapped.
Plate 12 Sundry cassava chips on a reed mat |
Plate 13 Drying chips on a iron sheet |
Plate 14 Sundry chips on a raised platform |
Plate 15 Improved sun-dryer |
Step 7. Pounding and milling
Pounding fresh cassava produces a mash similar to that produced by grating however; pounding is not as efficient as grating. Pounding dried cassava chips produces flour. Pestles and mortars are commonly used, but dried cassava can equally be taken to a hammer mill.
Plate 16 Pounding dried cassava |
Plate 17 Cassava hammer mill |
III. Traditional Processing of Cassava Primary Products
Traditional processing of cassava is still very common in cassava-based farming systems. The major traditional processing method practiced is the production of cassava chips and flour. The process used can follow any one of the routes given in Figure 1 below
Figure 1 Traditional processing methodologies
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| Method 1. Unfermented Cassava |
The traditional process for preparing unfermented cassava flour is as follow:
Peel cassava roots with a stainless steel knife.
Wash roots in clean water.
Cut roots into chunks or slices.
Dry cassava chunks on mats, rocks or roof tops (drying takes 3-5 days depending on the weather).
Store dried cassava chunks in sacks placed in the house before selling or milling for household consumption.
In this process, cassava is not grated or soaked, and since the slices are too big, hydrogen cyanide in the roots is not completely removed. Therefore, consumption of flour processed in this way is likely to lead to hydrogen cyanide exposure. This process is therefore only suitable for sweet cassava varieties with low hydrogen cyanide content. |
| Method 2. Fermented Cassava |
The traditional process for preparing fermented cassava flour is as follow:
Unpeeled roots are soaked in water for 5–7 days to ferment. When soft, the roots are peeled.
The soaked cassava is washed and mashed or dried whole on mats, roof tops, or rocks or black plastic sheets. Drying on black surface helps to kill pests and insects.
When completely dry, cassava is stored in sacks or dishes and is milled when required for household consumption or sale. Dry flour is light (not heavy) and flows freely in a bowl when tilted.
However, the resulting cassava flour by this method is usually dark which may not be appealing to customers not accustomed to eating cassava nshima. |
| Method 3. Fermented Cassava “Bwabi” |
Method 3 is the most common method of processing cassava in Zambia, which involves:
Peeling>>>Soaking for 3-6 days>>>Mashing or Dying whole roots
This method is used to produce dried cassava called “bwabi” which is good for roasting. The roasted dried chips called “ubwaushi” in Luapula province are eaten with roasted groundnuts, providing a nutritious snack rich in energy and protein for both old and young. |
| Method 4. Fermented Cassava “Kapesula” |
This method of processing cassava is very popular in Luapula province. The method involves
Peeling>>>Chipping>>>Drying for 3-4 days>>>Soaking for 3-4 days>>>Re-drying
The resulting chips are hard and are not easily attacked by insect pests. The chips can store for more than 6 months but are not suitable for roasting. The chips and flour obtained are good for the bakery and animal industries because of the high starch content. |
