Cassava processing
Practical Action
roots out of the ground, then removing them from the base of the plant by hand. The
upper parts of the stems with the leaves are removed before harvesting the roots.
Care must be taken during harvesting to minimise damage to the roots, as this
greatly reduces shelf life. Mechanical harvesters have been developed that lift the
roots from the ground. One such design comes from the National Centre for
Agricultural Mechanization in Nigeria.
During the harvesting process, the cuttings for the next crop are selected. These
must be kept in a protected environment to prevent them from drying out.
Cassava storage
Cassava can stay in the ground for a long time but once harvested can rot very quickly. Post
harvest losses from rot, pests, rodents can be very high unless effective measures are taken.
Traditionally cassava has been stored by piling the roots into heaps that are kept watered to
prevent the tubers drying out. Sometimes cassava is stored in pits that are lined with straw or
other vegetable material and kept watered. Cassava can also be stored in containers with moist
sawdust that keep the tubers from touching. Other approaches to storing for short periods are to
keep the tubers under water or to coat the tubers in mud or ash to prevent moisture loss.
Modern storage methods have been adopted for commercial cassava production. One low-cost
method developed by the Nigerian Stored Products Research Institute is to store the tubers in
trenches. A layer of palm and raffia leaves is laid at the bottom of the trench and then a layer of
roots is placed on top. A new layer of leaves is added, then more roots until the trench has been
filled. The top of the trench is covered with earth and a roof is constructed above the trench.
Harvested roots are now frequently packed in plastic bags. The bags are airtight so limiting the
supply of oxygen, which helps prevent the crop from rotting, although fungicides are sometimes
applied before bagging the crop. The universal fungicide "Benomyl" restricts mould growth. The
crop can be stored in this fashion for more than 14 days reducing losses during transportation.
This has worked successfully in Columbia although it is not as well developed in African
countries.
Another element to consider is temperature - the optimum storage temperature for fresh root is
3°C. Once cassava has been packed into plastic bags it can also be frozen and this approach is
currently used in South America on a commercial basis. While the texture can be affected by
freezing, the flavour is not.
Other preservation methods such as coating the roots with a wax containing fungicide, and
dipping the cassava into cooled paraffin have been
tried to a lesser extent.
Processing
Good quality raw materials are required for
processing if the final product is to be of a good
quality. Cassava should be free from disease,
infestations and damage. The crop should be
processed within two days of harvest to maintain
product quality. Attention should be paid to the
proper application of hygienic practices to prevent
contamination. The cassava should be thoroughly
washed, in potable water, to avoid contamination
and waste material from the process should be
removed to prevent cross-contamination.
Peeling
Ideally the cassava roots are peeled immediately
after harvesting either with a traditional cutting
tools such as a machete or with a mechanical
peeling device. Typically one woman can peel
Figure 2: A cassava peeler
Illustration: Neil Noble/Practical Action
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