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close this bookTraditional Storage of Yams and Cassave and its Improvement (GTZ)
View the document(introduction...)
View the documentPreface
View the document1 Introduction
View the document2 Socio-cultural aspects involved in the production of roots and tubers
View the document3 Basic comments on the storage properties of roots and tubers
close this folder4 Yams
View the document(introduction...)
View the document4.1 The environmental requirements of yams
View the document4.2 The yam tuber
View the document4.3 Farm-economic aspects of yam production
View the document4.4 Yam harvesting
close this folder4.5 Causes of storage losses for yams
View the document(introduction...)
View the document4.5.1 Dormancy
View the document4.5.2 Transpiration
View the document4.5.3 Respiration
View the document4.5.4 Germination
View the document4.5.5 Rot due to mould and bacteriosis
View the document4.5.6 Nematodes
View the document4.5.7 Insects
View the document4.5.8 Mammals
close this folder4.6 Traditional storage systems for fresh yams
View the document(introduction...)
View the document4.6.1 Leaving the yam tubers in the ridges after maturity
View the document4.6.2 Storing the yam tubers in trench silos
View the document4.6.3 Storage of yam tubers in heaps on the ground
View the document4.6.4 Storage of yam tubers in clamp silos
View the document4.6.5 Storage of yam tubers under a conical protective roof made of maize or millet stalks
View the document4.6.6 storage of yam tubers in mud huts
View the document4.6.7 The storage of yam tubers in the yam barn.
close this folder4.7 Measures to improve traditional yam storage
View the document(introduction...)
View the document4.7.1 Care in harvesting transport and storage
View the document4.7.2 Curing
View the document4.7.3 Influencing dormancy
View the document4.7.4 Influencing the storage climate
View the document4.7.5 control of rot
View the document4.7.6 Control of nematodes
View the document4.7.7 Control of insects damaging stored produce
View the document4.7.8 Measures for protection from mammals
View the document4.7.9 The improved traditional yam barn
close this folder5 Cassava
View the document(introduction...)
View the document5.1 The environmental requirements of cassava
View the document5.2 The cassava root
View the document5.3 Economic aspects of cassava production
View the document5.4 Causes of limitations to storage for fresh cassava roots
close this folder5.5 Ways of and limits to. storing fresh cassava roots
View the document(introduction...)
View the document5.5.1 Storing cassava roots in the soil after maturity
View the document5.5.2 Traditional methods of storing fresh cassava roots
View the document5.5.3 Storage of fresh cassava roots in clamp silos
View the document5.5.4 Storing fresh cassava roots in crates
View the document5.5.5 Storing fresh cassava roots in a dip
View the document5.5.6 Storing fresh cassava roots in plastic bags
View the document5.5.7 Use of modern methods to store fresh cassava roots
View the document5.5.8 Measures to prepare fresh cassava roots for storage
View the document5.5.9 Suitability of storage systems for fresh cassava roots on a small farmholder level
close this folder5.6 The processing of cassava roots
View the document5.6.1 The purpose of processing
View the document5.6.2 Hydrogen cyanide and its release
View the document5.6.3 The production of cassava chips
View the document6 Summary
View the document7 Bibliography

6 Summary

As carriers of carbohydrates, tropical roots and tubers contribute greatly to securing the basic nutrition. This particularly applies to the countries of the humid tropics in Africa where this group of products often secures over 50% of the nutrients for local populations.

Judged by the area on which they are cultivated and the total yield, cassava and yams are the most significant roots and tubers in Africa. Therefore this work concentrates on these two crops.

Tropical roots and tubers have a high output per unit area and, with the exception of yams, have low demands on soil quality. They are marked by high resistance to drought and low susceptibility to mass pests.

These properties are the reason why roots and tubers have a firm place in small farm systems. Here, they contribute to reducing the risks involved in cultivation and frequently serve the purpose of providing nutrition during bottlenecks.

In contrast to specific advantages in production, roots and tubers have negative storage properties mainly resulting from the high water content of their storage organs. High losses are consequently a feature of their post-harvest behavioural pattern.

The bad storage properties have thus contributed to traditional societies searching more for measures to avoid storage than for measures to improve this. To avoid storage in a fresh state, the roots and tubers are frequently processed into dry products which will keep.

Traditional storage systems for fresh products have been developed for yams in particular whose tubers have a natural storage quality due to their dormancy. These systems are all very simple in design 'end have often remained unchanged over a long period.

Improvements to traditional storage systems for fresh yam tubers are possible. These must begin at the time of harvesting when tubers should be handled carefully so that uninjured tubers can be put into storage. Small technical improvements to keep away pests, to improve the climate in storage and to facilitate regular control of the stored produce can contribute substantially to reducing losses.

The lack of storage ability of fresh cassava roots is caused mainly by physiological processes leading to fast destruction of the root tissue. All experiments to substantially prolong the storage of fresh cassava roots so far have not been convincing.

The only possibility of storing fresh cassava roots consists of leaving them in the ground after the harvest. In this way, the roots can be "stored" for several months without showing any great losses. However, this blocks land for the cultivation of other crops.

The most simple method of overcoming the lack of storage ability in fresh cassava roots is to produce dried chips. This is a traditional process and is widespread in Africa. The storage of cassava chips can be improved particularly by reducing the process of drying which frequently takes several weeks. This can take place by preparing smaller chips and by making use of the energy from the wind and the sun for drying.

Storage of the dried chips with a remaining moisture content of 12% should be in insect-proof containers. The definition of suitable storage systems, of both traditional and modem design, and the measures of chemical storage protection, both require more detailed examination before recommendations can be made on applying these to cassava chips.