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The Cassava Chipping Machine: Saving labour, improving quality and increasing income

By goGreen | November 1, 2011
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Background

The importance of cassava as a staple food in Africa has continued to grow because it possesses certain properties, such as tolerance to drought, and poor soils and even neglect. It is grown in over 30 African countries. Nearly 200 million people rely on cassava as a staple food, each person consuming an average of over 100 kg of the crop per annum. In certain marginal areas and regions fraught by civil wars and other crises, cassava is often the only food crop which is readily available. Fresh cassava roots, however, cannot be stored for longer than three to four days without being processed in some way.

Cassava chips are an essential raw material for countless dishes based on cassava flour. This leaflet describes how cassava chips can be produced more quickly, more efficiently and more profitably using manually operated cassava chipping machines.

Constraints in Traditional Cassava Chip Production

Traditional cassava chips are a common commodity in Africa’s rural and urban markets. They vary from grey to brown in colour, and often have visible traces of mould and holes caused by insect attack. These characteristics often make them undesirable from a hygienic point of view. The production of traditional chips has a series of drawbacks that show up in subsequent steps of the post-harvest system:

Cutting

Cutting cassava manually produces rather large, irregularly shaped chips with poor drying properties (see below). Producing smaller chips with knives or machetes would require considerably more work. When large amounts of cassava roots are to be processed at a time, cutting can become quite a tedious task.

Drying

Manually cut cassava chips dry slowly and ununiformly because they are rather large and irregularly shaped. Depending on the climatic conditions during the drying period, the process may take 2 to 3several weeks. As a result, the chips often go mouldy, become soiled or are attacked by beetles. After drying, large cassava chips retain higher amounts of cyanide than small chips. Thus, the overall quality of traditional chips tends to be rather poor.

Storage and Transportation

Traditional cassava chips are bulky and not easy to package. This causes some constraints in storage and transportation: they require a lot of space, and larger quantities are difficult to handle.

Marketing

The ease with which traditional cassava chips may be marketed depends, among other factors, on their quality. Chips which are mouldy or have a lot of holes produced by beetles are difficult to sell and often have to be fed to farm animals because they are not accepted by humans. As a result, a considerable amount of chips may be lost for human consumption.

Detoxification

Depending on the variety, traditional cassava chips may contain high amounts of highly poisonous cyanide. Lengthy detoxification procedures, such as soaking in water for about 3 to 5 days, fermentation, boiling or roasting, are required during subsequent processing in order to avoid health hazards.

Objectives

Chips produced by a chipper are generally of a higher quality than chips produced in the traditional way and will therefore be easier to market; they may even be exported. Traditional cassava chips are often regarded as a food for poor people in times of shortage. Chips produced by machine have a high potential for becoming a quality food and fodder, mainly due firstly to their quality, qualities such as the attractive white colour, less insect attack during storage and secondly, as they are less bulky, to the ease with which they may be stored and transported. This leaflet aims is to promote high-quality cassava chips as one of Africa’s leading agricultural products in the future.

Women constitute an important target group. Initiatives in the area of R&T technology can reduce their workload and increase their income and social status. This leaflet will help facilitate the switch from a tedious manufacturing process to an efficient and profitable small-scale processing industry owned by women.

Target Groups

This leaflet primarily addresses agricultural extension workers who assist small-scale farmers. It may be used in participatory development programmes with families at the village level. The information contained here is designed to help develop solutions to specific problems in the post-harvest sector.

Women constitute an important target group. Initiatives in the area of R&T technology can reduce their workload and increase their income and social status. This leaflet will help facilitate the switch from a tedious manufacturing process to an efficient and profitable small-scale processing industry owned by women.

The task of extension workers is not limited to presenting and explaining innovations to the farmers. They should also act as an intermediaries between other stakeholders. They should, for example, be in touch with village craftsmen who are able to maintain and repair machines, such as the cassava chipper, and discuss with them the experiences of the users in order to introduce improvements.

They should also discuss their experiences with their superiors and raise the level of awareness of problems which must be solved by decision makers (see Section 5)..

The second main target group is policy and decision makers in the development process. The aim is to broaden their views on the economic potential of R&T commodities, which is often underrated.

2. Manually Operated Chipping Machines

Manually operated chipping machines have been developed by institutions dealing with applied technology, such as IITA in Ibadan, Nigeria or the Kwame Nkrumah University of Science and Technology (KNUST) in Kumasi, Ghana. Some improvements have been introduced by other development partners working with rural families at the grassroots level. The IITA model has been successfully promoted in several West African countries and has the following features:

The chipper consists of the following parts:

- – - a wooden frame with a seat, a table from which the hopper is fed and a basin to collect the chips

- – - a circular metal chipping plate, which is attached to a wooden wheel on which a crank handle is mounted. The plate has a diameter of 35 cm and a number of holes, 3 mm in diameter with sharp, raised edges, that cut the chips from the peeled cassava root fed through the feed tray

- – - a metal shaft resting on two bearings on which the wheel with the chipping plate rotates.

Uniform chips of about 5 cm in length and 3 mm in diameter are produced by turning the handle in a clockwise direction and pressing the cassava root against the chipping plate. The chipper has capacity of about 60 kg of cassava roots per hour.

The machine is simple and portable, and can be maintained by people without an engineering background.

Extension workers may address village craftsmen in order to discuss and introduce the technical improvements of the cassava chipper.

The design of the shaft and bolt could be modified in order to prevent rapid wear and to achieve a fixed and durable clearance between wheel and frame.

Experience with existing cassava chippers has shown that chipping plates made from ordinary iron corrode easily when they come in contact with the cassava roots. In order to avoid rusting, tempering of the chipping plates is recommended. The machine should be cleaned well after use. If the first chips that are produced show rust stains they may be fed to animals.

The frame of the chipper may be redesigned to make it adjustable in order to increase comfort and optimise the mechanical efficiency of the operator’s physical work input. Increasing the weight of the wheel would raise the angular momentum and facilitate turning.

The problem of chip spillage, especially at the higher working speeds preferred by many operators, should also be examined in order to avoid losses and soiling.

3. Benefits of Machine Chipping

Using manually operated chipping machines will bring about three major changes:

Improved Chip Quality

The chips obtained using the chipper are smaller and therefore dry quicker and better than traditional chips. They also contain less cyanide. As a result, the chips have a low moisture content that makes them easy to store, and they have an appetising whitish colour. During the short drying process, they stay cleaner and are less prone to mould and insect attack than traditional chips. Small chips are easier to store. Trials conducted in Ghana have shown that insect attack was reduced. Generally, chips are subsequently processed into flour, from which a wide range of dishes may be prepared. As the quality of the chips is higher, the flour derived from small chips is also much superior in quality.

Best results are obtained using varieties low in cyanide. Other varieties should be detoxified by fermentation before chipping (by soaking in water for about 3 to 5 days).

Reduced Workload

The drying time is considerably reduced. Experience in Northern Ghana, for example, has shown that chips produced by machine take only 3 to 4 days to dry (when placed in layers 2 to 3 cm deep),, compared to 2 to 3 weeks for chips produced in the traditional way. As a result, less handling is required in the drying stage.

Drying is most efficient on cemented surfaces or on dark foils. The chips must be stirred in order to achieve best results. When placed in layers 2 to 3 cm deep (as recommended), the chips need only be stirred up to three times a day. If possible, Ddrying should not be carried out on the roadside or in other dirty places. Animals must be kept away from the drying area.

To produce flour, traditional cassava chips must be pounded before being taken to the mill. Small chips obtained from the chipper can be milled directly to produce a very fine flour for immediate use. As, aso that second, or even a third, milling process is not necessary, the wwomen or children who generally have to do this job save a lot of time and energy.

Furthermore, small chipsthe cassava is are easier to store and handle, as one bag of small chips is equivalent to three bags of traditional chips.

Higher Incomes

IncomeOutputs can be increased and work made easier using a manually operated chipping machine, and the quality of the chips is higher then in traditional production. Operating a chipping machine as a small-scale enterprise that provides services to the farming community of the neighbourhood or village could provide a good source of income. Cassava chipping is generally a task carried out by women or children; the improvement in quality brought about by the use of machines will help to increase their income while decreasing their workload. (see section 5).

The production of high-quality flour from small chips may help to create more demand for all kinds of food based on cassava flour. This may raise the incomes of all those involved in processing and trading cassava.

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