Storage of fresh cassava roots:
The rapid post-harvest deterioration of fresh cassava root
is due to physiological and microbial activities. Various amounts
of moist saw dust were evaluated as storage media. Complete preservation
with maintenance of storage root freshness was achieved by 0.6 kg
storage medium/kg of fresh roots during the test periods of 56 days.
Storage media of less than 0.4 kg/kg of storage roots resulted in
complete decay within 28 days of storage. Increased water loss influenced
the occurrence of physiological and microbial deterioration.
Improvement of traditional processing methods:
Cyanide intake from improperly processed cassava with high
cyanogenic potential (CNP) is a key factor in several diseases and
ailments. The potential toxicity in cassava is due to the presence
of cyanogenic glucosides, in plant cells. An investigation into
the effectiveness of three local processing techniques; water-soaking,
solid substrate heap fermentation and sun-drying, in the reducing
of cyanogens was carried out using the cultivar Karangwa with high
cyanogenic potential. Results revealed that cyanogenic glucoside
levels of thin and thick segments dropped from 400 and 800 to 56
and 150 mg CN eq./kg dry weight, respectively, within 4 days and
remained stable thereafter. Cyanohydrin levels increased to 25 and
50 mg CN eq./kg dry weight, respectively, and then lowered gradually
to marginal levels through drying. Moisture levels decreased from
approximately 65 to 10% in 8 days. All dried thin chips had higher
residual cyanogenic potential than the thicker storage root segments
because glucoside hydrolysis and linamarase activity cease below
20% moisture content. Sun-drying alone is not appropriate for cultivars
with high cyanogenic potential. Heap fermentation is more effective
than sun-drying in reducing cyanogen levels although it does not
guarantee complete cyanogen removal. Neurospora sitophila, Geotrichum
candidum and Rhizopus oryzae were the predominant fungi responsible
for fermentation and modification of flour viscosity without affecting
its quality.
Cyanogenic potential in storage roots, leaves and food products:
Equipment for CNP determination has been provided to Kenya, Uganda
and Madagascar. ESARC/EARRNET has developed the capacity to extract
linamarase from cassava thereby eliminating the need for importation
and providing NARS with easy access to the enzyme for quantitative
analyses.
Testing the quality of cassava genotypes is an ongoing activity
aimed at providing profiles for developing and evaluating germplasm
populations for target markets. Country reports indicate that over
60% of clones being evaluated have low to medium CNP and high dry
matter (DM). Genotypes MH95/0338 and NA95/361 have dry matter content
of 47 % while MH96/006, MH96/105, MH96/143, MH96/334 and MH96/420
have CNP score of 1.
Product development:
Major emphasis in product development was placed on cassava flour
fortified with beans, greengram, eggs and milk to prepare weaning
foods and snacks (crisps, chips, bhajia, and casserole, hot balls).
Composite flours were tested in the preparation of uji, ugali and
other products (cakes, biscuits, drop cones, muffin, pancakes, mandazi,
chapati, kaimati, doughnuts). Bread was found acceptable with a
cassava: wheat ratio of 20:80 while all others were prepared using
a 50:50 mixture of cassava and wheat flours. Genotype KME 1 was
identified as suitable for composite flour products. A pamphlet
on cassava recipes has been compiled for use in training of processors,
extension agents, NGOs and farmers.
Cassava in livestock feed:
Foliage production potential of TMS 30786 and Bukalasa 11
were evaluated to assess biomass production potential and protein
content in leaves as fodder for ruminants. Bukalasa 11 outyielded
TMS 30786 due to differences in vigor. Increased harvesting frequency
stimulated foliage regrowth. Optimum foliage biomass production
was obtained with a spacing of 50 x 50 cm. Initiation of defoliation
at 6 months after planting (MAP) did not significantly reduce root
yield. Crude protein content of the leaves did not vary with timing
and frequency of defoliation. Nutritional studies indicate that
5-10% maize bran is needed to prepare good silage from cassava foliage.
There is need to select for vigor, high leaf to stem ratio, leaf
retention and root yield in the development of fodder types of cassava.
Processing equipment: The IITA manual
grater/chipper has been modified by incorporating a new cutting
plate for chipping, grating or slicing. This adaptation has increased
the output from 40-50kg to 80-100kg per hour for chipping and has
reduced cost by 20% per unit. Improvements on the feed mechanism
of the power grater is being undertaken by an engineering workshop
in Uganda. Tests have shown that the new machine has higher thoroughput
and safer to operate. It is self-feeding with an output of 400-700kg
compared to 120kg per hour in the original model.
A hydraulic press which is cheaper and simpler to use compared to
screw press has been developed and being fabricated for testing
at proposed pilot resource centers in Kenya, Uganda, Rwanda and
Madagascar. A solar/wood fuelled drier has been developed and being
evaluated in Madagascar.
Utilisation/marketing potential of cassava:
The study was conducted to identify;
(a) market opportunities for cassava as ingredients for food products,
(b) utilisation pattern of major cassava-based products,
(c) import substitution potential of cassava for wheat and
(d) potential demand for cassava from new sources such as small
and large scale food, animal feed, textile and paper industries.
Survey data is being analysed.
The
Regional / National collaborative research:
Development of improved post-harvest technologies to expand cassava
utilization and markets
Objectives
Identify, develop and promote post-harvest technologies to increase
domestic and industrial utilization and expand cassava markets
Background information and methodology
The role of cassava in the cropping pattern and family diet of a
household is closely associated with its poverty level. This suggests
that millions of low income rural and urban consumers in the ECA
sub-region depend on cassava in providing dietary energy, protein,
vitamins and minerals through consumption of the storage root and
leaves. It is a reliable source of food under conditions of drought
and civil unrest and has great potential in food, feed and starch
industries. Development of cassava could thus contribute substantially
to food security, poverty alleviation and socio-economic growth
of the sub-region. Supporting and improving the status and performance
of cassava as food while expanding its potential commercial role
should therefore receive high priority. The demand-driven approach
to development of this commodity should systematically identify
opportunities and constraints starting from food security and nutritional
needs of subsistence farmers and low income consumers to actual
market requirements. Institutional and policy measures related to
crop harvesting, transportation, storage, processing and marketing
would have to be identified and linked to production issues ranging
from development of appropriate germplasm, protection and production
packages. Unfortunately developing local, national or regional processing
capacities have been unprofitable, due to inadequate supply of raw
material or access to markets at competitive prices. Inadequate
focus on tailoring of new varieties to suit end-user and market
requirements aggravate the problems.
Post-harvest handling of cassava is the largest constraint to increasing
cassava production in Africa. Processed cassava products must compete
in markets with grain products, so lowering costs of production
is essential to its survival as an industrial crop. Developing a
strategy that will contribute to food security and socio-economic
growth and development would entail the existence of a growing demand
(market) for cassava. This can occur when its unique characteristics
are exploited in a specific end use market or cassava becomes economically
more attractive for a particular use than do competing products.
An immediate concern would be to identify and analyze the current
uses and the potential markets for cassava and its products.
Data from COSCA and additional diagnostic studies will identify
the current situation of end-uses of traditional and market-oriented
products and provide an analysis of food, feed and industrial applications
(i.e. market shares by products, prices for different products,
future prospects for processing, manufacturing and consumption).
The review would also identify countries with potential markets
and demand in cassava and cassava products and provide recommendations
on which end uses would need further investigations. The major categories
of cassava products must be considered separately due to peculiar
strengths and weaknesses in their production/processing/marketing
continuum, which require different strategies to improve their performance
in the sub-sector. Cassava can be used for direct food, non-food
and animal feed formulations.
Fresh roots and leaves: Fresh storage roots and leaves are used
almost exclusively as human food with very high acceptance quality
requirements based on tradition, custom and familiarity with locally
available varieties, including root form, color of skin and flesh,
ease of peeling, cooking time, aroma and taste. Storage roots are
consumed or marketed close to the centers of production due to their
perishability. Preservation methods would be needed to prolong the
shelf life of fresh roots. Cassava leaves can be eaten as fresh
vegetable either ground fresh and frozen in plastic bags, or dried
and ground for sale in plastic bags. Leaves are more nutritionally
balanced than the roots and could help to prevent certain deficiency
diseases. Their cyanogenic potential may be high but can be reduced
to safe levels through grinding and evaporation during cooking.
Urbanization and rising incomes have reduced the market for fresh
roots. However, expansion of the market for this end-use would require
improvement in production, storage and processing technology, and
market infrastructure. Reducing pest and disease attack, cyanogenic
potential levels in roots and leaves, lowering costs of production
and processing are priority needs.
Home or village-level processing: Cassava is processed mostly by
women and children in small units at home or at village level into
toasted flour (farinha, gari) for human food. These toasted flours
have potential for growth in demand in commercial markets, be they
local, urban and international. Farinha and gari are considered
as convenience foods because they are easy to buy store and prepare
into a meal. Home and village-level processed products may be exported
to non-producing countries where an ethnic market might exist, or
a new group of consumers might be found. These possibilities would
be explored and products from such processing efforts would be identified
and improved.
Starch: African countries are still importing a very large proportion
of their starch needs while they could not only satisfy their domestic
needs but also export to the world market. Capitalizing on its special
features, viscosity, resistance to stress and freezing, and potential
for industrial and human uses, cassava starch can be used directly
in different ways or as a raw material for further processing. The
main classes of starch-based products may be classified as (1) unmodified
or native starch; (2) modified (physical, chemical, biological)
starches for industrial purposes; and (3) sweeteners, including
high fructose syrup, glucose (dextrin, monosodium glutamate, pharmaceuticals,
etc.). Using micro-organisms to meet specific market needs might
change unmodified starches. Native starches would be more competitive
if their inherent special traits set them apart from competing starches
(e.g. maize-derived, sweet potato-derived, etc.). It is important
to determine and capitalize on the special traits of cassava starch
that are not available in competing starches. Starch modification
usually adds value, so efforts would be made to identify and produce
modified starches and their derived products with market potential
within the ECA sub-region. Specialty markets are available for baby
foods, non-allergenic products, and food for displaced persons,
alcohol, butanol and acetone.
Flour: High quality cassava flour and chips can be produced and
fed into rural- and urban-based industries for use by the food processing
industry. Dry cassava chips can be utilized as raw material in industrial
production of ethanol. Flour has potential in ECA countries, where
there is a large consumption of bread made from 100 percent imported
wheat. Composite cassava: wheat flour may lead to different grades
of breads and prices for the consumer. Research will be needed to
evaluate different proportions of cassava/wheat flour, working in
partnership with the bakery industry. The success of these ventures
will depend on setting up cassava processing units on-farm or as
near the farm as possible to reduce transportation costs, and increase
the private sector involvement. Increasing the protein content in
cassava for human use can be done by (a) mixing with, e.g. 5% soybean
or groundnut resulting in 8-10% protein content, and (b) use of
microbial fermentation.
Animal feeds: African feed manufacturers still rely on cereals,
particularly maize whose production is highly dependent on rainfall
which has recently become erratic. The scarce supply of maize can
lead to competition between human and animal consumption. Increased
reliance on cassava would ease such competition. Animal feeds derived
from cassava, mostly meal and pellets, have been a major success
in Thailand. Potential exists to expand the utilization of cassava
in livestock feed rations. The foliage and other plant parts are
a source of protein, vitamins and minerals which could reduce the
cost of animal feed and increase the access of African consumers
to animal protein. The stability of cassava production in drought-prone
areas is prompting feed manufacturers to adopt cassava as the energy
source in feed formulations. Technical details for using dried cassava
in rations are well established, both in terms of milling and blending
and in animal nutrition. The main constraints for greater use for
animal feeds are lack of constancy of supply of cassava feeds throughout
the year, inconsistent quality, and price competitiveness with grains.
Because animal feeds derived from cassava compete with grain crops
in particular; lowering the costs of production is of great importance.
There is the need for research and development institutions to help
make cassava feeds competitive with grains in private sector markets.
This will involve cost reductions and targeting of specific markets.
Determination of the functional characteristics of importance to
the various applications will contribute to the development of cassava
varieties that meet specific market opportunities. The pasting properties
of cassava vary greatly. Some varieties are uniquely suited to be
used in alcohol production because of their low energy requirement
during liquefaction and saccharification steps in the process of
producing ethanol from cassava. On the other hand, high viscosity
cassava flour is recommended for use in the baking industry. Information
about variety characteristics of cassava that make varieties suitable
for specific applications need to be identified and incorporated
in cassava breeding programs so as to develop new varieties with
superior attributes for applications that are in high demand by
the market.
The COSCA study concluded that improvement in cassava processing
technology is urgently needed in the ECA sub-region. A processing
technology that reduces processing labor requirement and improves
product quality and thereby expands market demand for cassava products
will motivate small, medium and large-scale enterprises to adopt
available improved technologies. As farm production rises and more
farmers go commercial, demand for simple but efficient farm equipment
is likely to grow among the ECA nations. Private entrepreneurship
will develop to meet this need.
Appropriate equipment to carry out post harvest operations reduces
crop waste and enables more complete utilization of the food crops
grown. This is especially true for farmers who are stepping beyond
the subsistence stage to farming that can generate income. IITA
has devoted attention to designing and fabricating improved equipment
such as cassava graters, de-watering devices, sifters, stoves, chipping
machines, and grinders to minimize crop losses and improve labor
productivity and product quality which, in turn enhance the welfare
of rural women and children. On-farm testing and demonstration of
the equipment and training of manufacturers are being undertaken
to promote the use of improved equipment.
Preservation technologies will be evaluated for their ability to
keep cassava products over an extended period of time. Quality of
the product will be monitored at regular intervals. Processing equipment
and other technologies will be introduced and tested on pilot basis
and socio-economic factors affecting adoption will be studied. Demonstration
through group training at pilot resource centers will create awareness
of utilization potential. National post-harvest programs will be
encouraged to boost the variety development efforts in the determination
of cyanogenic potential, starch yield and quality, dry matter content,
cooking characteristics and suitability of varieties for dominant
food and product preparations within the region.
Sub-themes
¨ Identification, introduction, adaptation and promotion of
suitable traditional and improved post-harvest technologies (products,
equipment) to expand agro-based markets
¨ Quality analyses of cassava genotypes and products
¨ Storage management and integrated control of storage pests
and diseases.
Expected output
¨ Technical specification and drawings of new equipment available
¨ Improved technologies and products (recipes) available
¨ Non-food potential uses of cassava identified and developed
¨ Cassava based livestock feed available and commercialized
¨ Genotypes with specific end-use (products) characteristics
identified
¨ Cyanogenic potential of varieties and cyanogen levels in products
determined
¨ Regional capacity for quality analyses strengthened
¨ Pests and pathogens of stored cassava and resistant varieties
identified
¨ Optimum storage conditions developed
Indicators for monitoring progress and impact
· At least 6 pieces of processing equipment adapted, developed
and produced
· At least 5 new food products developed/adapted
· Number of improved processing technologies available
· At least 2 weaning foods developed and promoted
· At least 5 recipes per product developed
· Composition, nutritional value and safety of cassava products
known
· At least 2 non-food uses of cassava developed
· Number of entrepreneurs producing cassava based livestock
feed
· At least 10 genotypes for specific end-uses identified
· At least 4 analytical laboratories identified and facilitated
for regional analyses
· Number of catalogues on genotypes and products published
· Percentage of area covered by storage pests and pathogens
· At least 12 resistant varieties to storage pests and pathogens
identified
· Number and types of storage control methods recommended
and applied.
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