Thursday, July 18, 2024

Traditional Storage of Roots and Tubers

In the real sense, storage of foodstuffs including roots and tubers begins immediately the crop is detached or harvested from the parent plant. Normal storage is defined as the keeping of foodstuffs open to the atmosphere subject to room temperature and humidity.

The decomposition caused by fungi, bacteria and nematodes starts in the field and continues during the cause of storage.

Food self-insufficiency depends on increase production, reduced postharvest losses, improved processing methods and improved product distribution. But how can increase in food production, improved processing methods, and improve product distribution be effective or possible if postharvest losses are not to be studied and improved upon when the need arises.

1. Traditional Yam Storage

The food storage in the developing world is so severe, especially in the rural areas, that any means to increase agricultural production and limit losses is welcome.

Traditional yam storage methods are designed within the framework of a self-sufficient economy and have ensured the subsistence of populations for generation.

These traditional storage methods are based especially on the capacity of various yam varieties to resist rot. In this respect, the best species are D.alataand D. dumetorum.

According to the survey carried out in Benin on post- harvest technology, almost 85% of the rural population consumes yams that they produce themselves.

Taking into account these new data, and observations, efforts which should be maintained and developed, are being made to reduce post- harvest losses.

Yams are stored in many different ways depending upon the customs and practices of the various tribes which grow them. Two of the main precautions followed in storing yams are keep them dry and away from the soil, and also protect them from rays of the sun.

After the yams have been harvested, all the soil clinging to the tubers is removed, as it encourages the yams to grow, they also may harbor diseases. The yams are then removed to the yam store.

In some districts, it consist of a rough shed supported on strong corner posts and with the floor raised 2 or more feet above the ground and composed of rachis of palm-leaves, often referred to as branches.

Traditional Storage of Roots and Tubers

The wall of the shed are often made of the same material, and the roof is generally, consist of grass or palm-leaves or other form of thatch. The yams are piled on the floor and air is able to circulate freely through the gaps in the form and walls, which is great advantage in helping the yams to withstand deterioration.

The main disadvantage of this system is that yams in storage is often begin to rot. Rotting is caused by fungi and is spread by contact so that the rot or mould quickly spreads from one yam to another as they piled close together in heaps.

Also, each yam does not have equal conditions of drying and the yams at the bottom of the heap generally, have too much heat and hot air, and they contain more moisture, disease spreads more rapidly and through them.

Moreover, they tend to sprout earlier and this is a distinct disadvantage when yams are kept for eating.

In the Calabar district, yams are harvested in September or October and hung up to dry for three months. The seed yams are then put into a sheltered place, such as a shed, and are covered with a layer of plantain or other leaves.

The upper portion of the yams are placed facing upwards and in January sprouts generally appear. This system is specially adopted to help the yams to sprout, after which they are planted out at the end of January or February.

Probably, one of the best ways of storing yams is that followed by the Fantes, Northern Ashatis, and also by the Ibo tribes in the eastern.

A large frame work of poles is first erected, living posts being used for the vertical upright supports which are arranged in rows very close placed in position and tied to the erect poles with bush fire. The space left between each pair of erect poles with bush fire. The space left between each pair of erect poles is roughly 2 to 4 feet and 1 to 2 feet between the horizontal poles.

As the yams are brought in from the farm they are carefully, cleaned and all the soil removed, and they are then tied one by one to the erect poles beginning at the bottom. Long pieces of fibe are used, and they are looped round each yam and pulled tight so that each yam rests against the upright pole and often against the horizontal pole as well.

The yams are generally, stung up on both sides of the upright pole in such a way that they are kept slightly apart. The great advantage of this system is that each tuber has practically the same amount of air and the same temperature, so that conditions of storage are much more even and satisfactory.

The double rows of poles are placed generally 5 or 6 feet apart so that a farmer with many yams store covering a considerable area, with rows or ranks of yams which he can walk between and inspect with the greatest of ease.

Yams of the same variety are generally stored in the same part of the yam store so that one farmer may have five or six varieties of yams in separate groups in different parts of his store.

Another advantage of these stores is that the living poles quickly produce shoots at their upper ends and a mass of leaves soon completely shade the yams stored beneath, and the poles are not attacked by termites or boring insect.

The shade from the sun also prevents the tubers from cracking, as easily happens when they are fully exposed to the sun‘s rays. Even in wet weather the yams easily dry up afterwards because of the diffused sunlight and the wind circulating freely through the cracks.

These yams stores are sometimes made near the farm or on the outskirts of the village, and are often surrounded by fence which is entered through special door. The stores are often constructed in the compound itself so that the yams can easily be reached and removed one by one, beginning from the top, and used as food.

In Ibo districts, yams produced are kept in different parts of the compound, the men‘s yam being the larger.

After the yams have been stored for some weeks, and especially in damp weather, they begin to sprout. When stored in heaps, the yams at the bottom may have produced sprouts 2 to 3 feet long before they are discovered. In yam racks, however the sprouts can easily be seen, and the farmer goes round his store every few days, breaking off the sprouts with his fingers, or removing them with a knife.

Read Also: Agricultural Product Storage Complete Guide

2. Traditional Cassava Storage Methods

Cassava tubers are extremely perishable. They can be kept in the ground prior to harvesting for up to about 2 years, but once they have been harvested they begin to deteriorate within 40 to 48 hours. The deterioration is caused by physiological changes and subsequently, by rot decay.

Mechanical damage during the harvesting and handling stages also renders the crop unsuited to long term storage.

Deterioration of cassava has an adverse effect on the product, and thus the crop must be stored properly. Traditional and modern methods of storage have been devised to combat post-harvest losses.

In most areas where cassava is grown under subsistence farming conditions, the problem of storage is overcome by leaving the mature cassava crop in the ground until needed. The disadvantage of this method are that:

Large area of land are use as storehouse for the already matured crop and therefore cannot be used for further crop and therefore cannot used for further crop, this increases the economic output of the land and increases preserve on the land (there is already a considerable amount of pressure on the land in many countries in Africa because of high population growth rates).

Susceptibility to loss is increased because the tubers are vulnerable to attack by rodents, insects and nematodes.

Tubers become more fibrous, lignifications occurs, and consequently the crops starch content and its suitability for many food preparations decline.

Other traditional methods, based on the principle of prevention moisture loss from the tubers include:

Storing harvested tubers in pits involves buying them in pits lined with straw or some other vegetative materials.

Pilling them into heaps and watering them daily to keep them fresh.

Coating them with paste of mud.

Storing them under water.

These methods prolong the shelf life of cassava by only a few days and are not widely used.

3. Traditional Cocoyam Storage Methods

Cocoyam is usually harvested when the leaves begin to senesce (8-12 months after planting). In the regions where the rains do not immediately follow crop maturity, corms can be left in the soil and harvested as needed. Otherwise, the crop is completely harvested and any excess is stored.

Cocoyam intended for storage are harvested carefully to avoid injuring the corms and cormels which are exposed to sunlight for 2 to 3 days to encourage suberization. Tubers are stored in a dry, cool place either covered with dry leaves or in a hole lined with dry banana or plantain leaves.

In some cases, wood ash is sprinkled over the tubers (probably to serve as a fumigant or pesticide). The heap is covered with dry soil to form a mound about 50cm above ground level. Under such conditions Cocoyam can keep up to 4 months. The major problem encountered during storage are rotting and sprouting.

In the middle-belt of Nigeria for instance, fresh cocoyam when harvested are stored inside baskets for a while before they begin to rot. Fresh cocoyam are not usually palatable to insects or rodents, therefore, animals are not a major problem to fresh cocoyam storage.

Cocoyam unlike yam and cassava have less value as staple food and so not much is done to store them.

Read Also: Guideline to Proper Animal Feed Storage and Methods

4. Traditional Storage of Sweet Potato

Of the four major root crops commonly grown, sweet potatoes are not given the best based on cultural reasons. In some parts of the country, sweet potato was considered as dog food and used only for feeding animals and most people do not like the taste (that is the sugar content).

An increased awareness of the nutritional value of this crop has changed and situation, however, and sweet potato cultivation human consumption is expanding. The major obstacles to sweet potato storage are pests and sprouting.

Traditionally, after harvest only sound tubers are stored. The tubers are exposed to sunlight for 2 to 3 days to suberize, they are then put in a dry place or in a basket that is kept in a dry place and covered with banana leaves or grasses. Tubers may also be put in a hole lined with dry leaves in a dry place.

Wood ash is sprinkled on top of the tubers and the heap is covered with dry leaves or dry grass. In rare cases, a mound of dry earth is built on top of the heap. Under these conditions, the tubers keep up to 3 months, when the stored tubers are inspected, sprouted tubers are removed for consumptions and rotten tubers are discarded.

During transportation of the tuber from the field to the market, it is stored in a sack and the mouth is covered by the leaves of the potato or grasses. This way it stays fresh for a longer time. At times, the soil clinging to the stain of the sweet potato is allowed to stay on it as the tubers go bad when the soils are removed from them.

5. Traditional storage of Irish Potato

This is the least produced tuber in the country. This is because of the special environmental conditions required for its cultivation. It requires a cool dry weather to thrive well. The best place where the highest yield has been attained so far is in Jos the capital of Plateau state.

The tuber has a delicate peel that can peel off especially during transportation to other parts of the country. So far, its storage has been difficult but farmers normally allow the tubers in the air to dry up, that is enough ventilation to reduce moisture content to the barest minimum.

After this, they are packed into jute bags for transportation to distant places like the south and west. The tubers can also be stored by pouring ash on them and at the same time allowing air to move freely to touch each other as it generates heat and where there are not one, can easily be transferred to the next.

The tubers are checked frequently to pick out the bad ones. The tubers are also stored in baskets covered with dry leaves. The basket will allow air into it and the temperature of the tubers reduced, thereby reducing the rate of respiration and its ability to store better.

Problems Associated with Indigenous Traditional Storage of Roots and Tubers

Losses appear at all stages from the field to the consumer‘s table. There are losses during harvest, transportation to the markets, and processing. At all these stages, losses are caused by various factors.

They may be due to external agents (insects and other predators) or physical factors (handling, transportation and storage conditions) or they may have physical origins. All these are the problems of storage. The problems of traditional storage are described below:

1. Disease and Pest

Disease and pest greatly reduce yields of roots and tubers thus aiding deterioration in storage, for example, cassava has been adversely affected by some pests, e.g. the cassava mealy bug (Phenacclocus manihoti) and green spider mite (Mononychellus species).

Yams suffer from nematode, yam beetle, leaf spot and viral diseases. Similarly, Cocoyams are subject to attack by blight and the sweet potato yield declines under attack by viruses, root knot nematodes and the sweet weevil.

2. Labour Shortage

The shortage of labour is often accentuated by the seasonality of operations and division of labour is high coupled with a few that are available.

3. Post–Harvest Technology

Roots and tubers, in addition to problems of harvesting are too bulky to transport and handle. Because of their perishability, they also have problems of storage.

They have low protein content and must be processed, enhance their use in composite flours. The methods and equipment to ensure their availability in urban areas throughout the year.

4. Socio-economic Constraints

Roots and tubers suffer bias in research, extension, resource allocation, and even consumption and utilization because they are regarded as poor people‘s crops and of a lower status than cereal staples. For this reason, there are often shifts among higher income or urban classes toward cereals.

In addition to such shifts, the availability of cereals in forms that are easier to store and handle enhances the demand for them and their products. Roots and tubers are only slightly involved in international and inter-regional trade and, therefore there is a limit to move them from surplus areas to areas of scarcity.

5. Prices

Problems of marketing include those of collection and handling of bulky small quantities of irregularly supplied produce of high water content and perishability passing through long marketing chain involving several intermediaries and varying periodic markets.

The absence of an adequate marketing organization for roots and tubers makes farmers accept any price that is offered the farm gate or local market by middle men, who are able to process and transport goods to urban centers.

Consequently, farmers receive only a small fraction of the final price. In many countries, there are policy constraints for producers of roots and tubers that result in prizes for cereals but not for roots and tubers, this happens because of the poor traditional ways of storing these crops.

Improved Storage Methods of Roots and Tubers

Among the improved storage methods for fresh cassava are those based on techniques involving freezing, gamma irradiation, control of storage environment (relative humidity and temperature) and waxing. However, none of these techniques has been sufficiently tested.

Three improved storage methods which have undergone sufficient testing include:

Dipping fresh tubers in fungicide and packing them in polyethylene bags.

Storing in specially prepared trenches.

Storing them in moist saw dust.

Although these three methods are not yet widely used, they are useful for small and medium- scale cassava production.

1. Storage in Polyethylene Bags

This method appears to be the simplest way of storing tubers. If properly conducted, it ensures a shelf-life of two weeks or more. The method is based on the principle of curing‖. The capacity of tuber to form a new layer of cells over damaged tissues.

Freshly, harvested roots are treated with 0.4% solution of mertect, a thiabendazole based fungicide. They are then packed in polyethylene bags and sealed. Inside the bags, the tubers create the necessary temperature/humidity environment (temperature should range between 30 and 400C and RH should exceed 80%. The fungicide treatment prevents the growth of microorganism in humid environment.

2. Storage in Trenches

These low-cost method, developed by the stored products Research Institute keeps cassava fresh for at least 6 to 8 weeks and be implemented easily by farmers and processors.

A trench is dug in the ground at a site which has a low water table, thus protecting the tubers from seepage of underground water. The trench should be 2m long, 1.5m wide and 1m deep.

Depending on the size of the tubers, a trench of this size can store from s to 0.7 tons of cassava. .

Agents and Causes of Deterioration of Stored Foods

Stored foods are affected by a number of biological agents which cause deterioration. These include:-

  • Micro- organisms (fungi, bacteria and yeasts)
  • Arthropods (insects and mites)
  • Rodents (rats and mice)

Those organisms can cause considerable damage to stored produce improvement in storage methods reduces losses of stored produce. However, storage pests may still gain access to stored commodities and cause economic damage, especially in the tropics where the storage structures are inadequate. The rate of spoilage of duce may be aggravated by other factors such as climatic, technical or economic consideration.

Many species of insects and mites are found in stored produce but a few actually cause economic damage and loss. Some of them may even be beneficial (e.g. predators and parasitoids) because they attack other arthropod pests.

The two major insects pests groups are beetles and moths both of which are halometabolaus (i.e. they undergo complete metamorphosis in which the larval forms differ remarkably from the adult forms.

The non-biological causes of deterioration of stored commodities include:

Physical factors – temperature, humidity, water (moisture) and gas which influence the physiological activities of storage arthropod pests.

These are the conditions, methods and duration of storage, state of the product (whether broken or laden with impurities, residues etc.)

Physical Properties of Commodities

These include; free moisture, specific heat and thermal conductivity of grains and seeds which determine their storability.

Water Content

Water contained in grains and seeds exists in two forms, the water of composition which is the water contained within plant cells and free water on the surface of the cells part of which is adsorbed superficially by those cells.

Read Also : Principles of Crop Storage and Methods of Storage of Crops

The free moisture content determines the ability of the grains and seeds to store. For examples; most cereals and grain legumes will not keep well if their MC exceeds 13% and 15% respectively.

Maximum moisture content for long term storage of grains:

Paddy rice14%

Thermal Conductivity

Food grains have low specific heat and low thermal conductivity. The implication of these granular properties is that a mass of grains heats up quickly and once heated up, it losses the heat very slowly.

If for any reason, there is heating in the mass of grains or seeds, the natural movement of the air between the grains will be inadequate to evacuate the heat produced. This will inturn increase arthropod pest activity as well as encourage the growth of mould. This increase rapid deterioration by the commodity.

In summary, although traditional techniques give products that meet the organoleptic quality demands of the consumers, they are limited in terms of their utilization conditions, their low yield, and the sanitary quality of their products, the rather inadequate contribution that they make toward reducing losses, and the small quantities that they can handle.

Industrial technologies would have a clearly positive impact on reducing losses if their adoption was not limited by serious socioeconomic handicaps.

The various indigenous storage of crops in the country are indeed what we should be proud of as these methods are those that are effective and will be perfect if only agriculturist are willing to improve on what is already on ground. This is because personally, I do not buy the idea of using chemicals.

Taking into account the level of industrial development of some developing countries and their level of production (small, moderately unproductive family farms and wide geographical distribution), it seems that, at present, post-harvest technologies used at the cottage-industry level are the most effective and suitable solution to the problems involved in processing roots and tubers in rural environment.

The proper introduction of cottage-industry technologies based on improved traditional technologies would allow root and tubers to play greater role in achieving self-sufficiency in food production. Also, definite measures should be taken to ensure the linkage of research, training, and extension in root and tuber crops production, storage, processing, and utilization.

Specific action programs should be launched to facilitate rapid and widespread adoption of improved production, storage and processing technologies for these crops.

Attention should be given to handling, drying, transportation, and storage, processing and packaging of products based on the study of traditional food preparations and utilization, consumer preference in different regions and how to satisfy them with improved varieties and food procession.

Read Also: Sanitation and Waste Management Guide

Do you have any question, suggestion or other contributions? kindly use the comment box provided below for all your contributions. You are also encouraged to please kindly share this article with others you feel can benefit from this information if found useful enough as we may not be able to reach everyone at the same time. Thank you so much for sharing!


Benadine Nonye is an agricultural consultant and a writer with several years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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