9. Development of the cassava-processing industry and its future

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Particularly in countries where the science of agriculture is not yet developed, continuous guidance under some type of development scheme is necessary in order to make the best use of cassava for local consumption and for export. Such a scheme may be operated through a government organization or through a private organization advised and in some cases supervised by the government.

The method chosen will depend on local conditions' and it must be realized that changing existing methods of production and processing will take time in most areas because of the retarding influence of local customs and beliefs as well as economic conditions. The scheme outlined below is only a suggestion and obviously must be adapted to the existing organizational pattern of the government, its extension services and the extent to which the industry itself is organized.


The initial approach to farmers and merchants should be through practical field demonstrations at the lowest levels of village production.

In many producing countries, the cassava industry suffers from such disadvantages as an insufficient and irregular supply of roots to the factories in addition to the high cost of roots. These countries should encourage research work with the object of obtaining a maximum yield of roots per hectare and a maximum starch content in the roots. Experiments should be conducted in various regions for the improvement of agricultural practices and the breeding of new varieties with continuous testing and selection for high yields and suitability to local conditions.

The formation of an organization of cassava growers in each region will encourage production, make possible financial and technical assistance, and help coordinate the supply of roots to the factories.

Processing and marketing

During the initial stages a competition sponsored by local officials or merchants with a prize for the best will foster interest in the scheme.

The most propitious occasion on which to inaugurate such a competition would be one of the many marketing and festival days celebrated in the villages. It may continue for several months and be open to participants from a number of villages in cassava-producing areas.

The next step could be the setting up of small cooperative processing units in areas which are ready for such development, whereby improved machinery and accessories could be brought into use to obtain a better product. A pilot plant may be established in each cassava-growing region as a centre for research and development of the industry, for demonstration of modern processing equipment and for the training of personnel.

Obviously, under such a development scheme a certain number of officers will be necessary to guide the programme - at least some instructors and an inspection officer stationed in the cassava-processing areas.

The instructors should be patient and tactful, as they must remain on good terms with the workers, and must be capable of good systematic instruction by practical demonstration.

The duties of an inspector call for an agricultural engineer specialized in processing with a good general education and practical background and with administrative experience. He should be senior to and supervisor of the district instructors.

As cassava is generally grown in rural areas and processed in small factories, the promotion and guidance of village farmers' cooperatives, not only for processing but also for grading and marketing, is an important part of the duties of the officers. Such cooperative societies should be able, in later stages, to deal with products for export.

Once a start has been made, the establishment of a cassava board composed of government officers, representatives of farmers' cooperatives and individual factory owners as well as representatives of merchants and related industries should be considered. The board should meet regularly to ensure a continuation of useful contacts and act in an advisory capacity to the government. It can handle problems of production and marketing of cassava products, open new markets and regulate prices of various products, provide financial assistance to processors and traders, maintain quality standards, promote research and the development of new products and so on.

Future of the cassava industry


Because starch-derived products are used in almost every industry, the starch industry itself is vulnerable to competition from more specialized synthetic products.

In the textile, foundry and paper-coating industries, synthetic polymers present a serious threat to starch products, but they are still expensive. Much work is therefore being carried out to form products combining starch and synthetic polymers with the best qualities of both materials. The future of starch utilization in such industries may be promising if technical efforts continue to make use of the new synthetic materials rather than compete with them or oppose them. There is no doubt, however, about the secure future of starch-based products in the food industry.

The new improved methods of producing glucose syrup and dextrose by enzymes and by direct conversion from raw materials are going to give sucrose stiff competition. Furthermore, it has recently been claimed that sucrose consumption has certain injurious effects on health while starch, starch products and glucose do not. The utilization of glucose syrup and dextrose is rapidly increasing in the food industry, and consequently their production from various starches is continuously expanding.

At present yellow maize is the most important raw material used for starch production. New waxy maizes have been developed with higher amylose content than and different properties from normal maize. The market position of cassava starch is believed to depend on the possibility of world industry, particularly in the United States, developing domestic substitutes from the waxy varieties of grains (maize and sorghum) and from roots and tubers such as sweet potatoes and white potatoes at lower cost than that of imported cassava starches.

Growing populations in the cassava-producing countries will continue to provide a home market for cassava roots and products. Many countries are entering production, and the international market for many products has become more competitive. Thus it seems unlikely that European markets will attract a large volume of exports. However, eassava could make a much more important contribution to national economies and provide a more stable base for food industries, both for local consumption and for export, if cassava starch could compete with other starches by improving the quality of its products and lowering the cost of production.


Bread consumption is constantly increasing in many developing countries, which still depend mostly on imported wheat or wheat flour while they grow various staples such as starchy tubers like cassava or cereals other than wheat. Recent experiments show the possibility of partial replacement of wheat flour in bread-making by other flours (e.g., cassava and soya).

It seems quite logical that the utilization of cassava flour in bread-making will increase considerably in most developing countries.


As the standard of living rises. the demand for meat and dairy products is also increasing, especially for quality products. Livestock breeding is progressing rapidly and significant increases in meat production are foreseen in many countries as shown in Table 19.

The use of well-balanced compound feedstuffs has proved to be the most efficient way to meet the shortage of home-grown natural fodder and to increase efficiency in the raising of milk cows, beef cattle, broilers and laying hens, and pigs. Many feeding experiments show that cassava provides a goodquality carbohydrate which may be substituted for maize or barley; however, cassava must be supplemented by other feeds that are rich in protein and vitamins.


Country Base year 1969-71 Projection 1975

Thousand tons

France 1 640 2 071
Germany, F.R 1296 1502
The Netherlands 302 335
United Kingdom 818 1185
Japan 270 305
Total 4 326 5 398

SOURCE: FAO, Agricultural commodities projections 1970-1980, revised 1975.

The consumption of cassava products such as dried roots, chips and pellets by the compound feedstuff industry is expected to increase considerably in the future: therefore, it is vitally important that producing countries encourage belter processing and quality control. Furthermore, it is hoped that more attractive markets for animal feed containing cassava will open up in the producing countries.


Methods and specifications for determining the quality of cassava flours

(Tapioca Institute of America, October 1943)



United States standard sieves, 140, 80 and 60 mesh.


Fifty grams of flour are screened through the appropriate sieve acnording to grade. While more accurate results can be obtained by making the test with a Ro-tap machine (a mechanical shaker of special design) or other type of mechanical shaker, satisfactory results can be obtained by hand shaking.


Grade Percent required to pass Mesh sieve to be passed
A 99 140
B 99 80
C 95 60



A sufficient sample of flour is taken to make a rectangle approximately 2.55 cm (I to 2 inches) on a side and 1.6-3.5 mm (1/16 to 1/8 inch) high. The flour is placed on a white paper pad, laid out to these measurements with a spatula and one side evened off. Adjoining this side, a similar pile is made with a standard flour. A clean smooth piece of paper is laid over both piles and pressed gently with the spatula to make a smooth upper surface. The two piles are compared by eye in a neutral light (i.e., by daylight) free from shadows and direct glare.


Grade Colour Black specks
A Near standard None
B Near standard Very few
C Near standard Few



Crystallizing dish 100 mm in diameter and 50 mm deep.


Twenty-five grams of the sample are thoroughly dispersed in 150 ml of distilled water in the crystallizing dish and allowed to settle for two hours. The sample is compared against a standard sample for dirt and foreign particles seen from the underside of the dish and in the floating liquid.


Grade Colour Dirt, foreign particles
A Near standard None
B Near standard Very few
C Near standard Few



United States standard sieve, 140 mesh

Graduated cylinder, 100 ml


Fifty grams of sample are put on the sieve and washed with water until the washings show substantially no starch particles. The residue is transferred to a 100-ml graduated cylinder and water added to the 100 ml mark. The pulp is allowed to settle for two hours. The pulp is measured as the number of millilitres of residue.


Grade Pulp (max. in ml)
A 0.5
B 2.5
C 12.0



Boiling water bath

Short-form pyrex beakers, 250-ml capacity

Glass rods 1 cm (3/8 inch) in diameter and 20 cm (8 inches) long Thermometers


By the proper amount of flour is meant the following:

As a standard for comparison, the standard for grade A is always cooked with 10 g of flour per 150 g of distilled water. If the sample which is to be graded is thought to be approximately grade A, then it should be cooked with 11 g of starch per 150 g of water. If the unknown flour is thought to be grade B. then 17 g should be used. If the flour is supposed to be grade C, then 20 g should be used. In this way, if the unknown flour has a higher viscosity than the standard when cooked with 10 g of flour to 150 g of water, then the unknown flour would be grade A, B or C, according to the amount of flour used in the viscosity test.

If a more accurate measure of the viscosity is desired, then additional "cookups" should be made in the same manner as above, with the exception that one should endeavour to find out how much flour is required when cooked with 150 g of water, in order to obtain the same viscosity as the standard grade A flour when cooked with 10 g of flour per 150 g of water.

This amount of flour required by the unknown flour would be the measure for viscosity. For example, if the unknown flour required 13 g per 150 g of water to give the same viscosity as grade A when cooked with 10 g per 150 g of water, then the flour in question would be grade B. having a viscosity of 13.

The proper amount of flour is mixed with 150 g of distilled water in a 250 ml beaker. A rod and a glass thermometer are inserted and the tare is taken. The beaker is placed in a boiling water bath and the contents stirred with the rod and thermometer until the temperature reaches 80C. The beaker is covered with a watch glass and is left in the bath for ten minutes without further stirring. At the end of this time the beaker and contents are removed from the bath and the loss in moisture by evaporation is adjusted with hot distilled water. It is then cooled in running water with a minimum of stirring until the starch solution reaches 25C. The thermometer is then removed and viscosity comparisons are made by stirring by hand at the rate of approximately two turns per second, with a roughly circular motion. By observing the resistance offered to the rod by the starch solution and comparing that resistance to the standard "cook-up," one can estimate the viscosity of a given sample.


Grade Max- g/ml water
A 11/150
B 17/150
C 20/ 150

6. ASH


Shallow, relatively broad ashing dish

Muffle furnace


Approximately 5 g of flour are weighed into the ashing dish, which has previously been ignited, cooled and weighed. A sample is inserted in the furnace at about 500C (dull red) until a light gray ash results, or to constant weight. The sample is then cooled in a desiccator and weighed.


Grade Max. ash (percent)
A 0.15
B 0.25
C 0.50



Metal dish, 55 ml in diameter, 15 ml in height, provided with inverted slipin cover fitting tightly on the inside.

Ventilated oven regulated to 130C 5C.


Approximately 5 g of flour are weighed into a dish which has previously been dried in the oven, cooled, and weighed. The dish is uncovered, and dish, cover and contents are dried in the oven at 130C 5C for four hours. The dish is covered while still in the oven and then transferred to the desiccator and weighed when cool. The moisture is calculated and the loss of weight expressed as a percentage of the original sample.


Grade Max. moisture (percent, factory packed)
A 12.5
B 12.5
C 14.0



Electrometric pH meter


Twenty-five g of flour are dispersed in 50 ml of distilled water. The initial pH is determined. N/ 10 hydrochloric acid or sulfuric acid is then added to the suspension until pH 3.0 is reached. The titration is run at room temperature.


Grade Initial pH Max. ml N/10 acid to reach pH 3.0
A 4.5-6.5 2.5
B 4.5-6.5 6.0
C 4.5-6.5 No titration required

Specifications for dextrin

(issued by the United States Government Printing Office)

The dextrin shall have been converted from starch derived from the cassava root. It shall be a high-quality dextrin adapted for use in gumming operations, free from grit or other foreign matter.

Detailed specifications

Dextrin by polarization 83.0
Reducing substance, as dextrose 3.0
Volatile at 105C 6.5
Ash content 0.2
Material insoluble in cold water 0.3
Fat content 0.4
Polariscope reading, Ventzke, 10 g of dextrin in 100 ml of solution 90.6
Refractive index at 25C, 250 g of dextrin plus 125 g of water 1.4555

Physical properties

The dextrin shall be in powdered form. After being applied to and dried on the paper, it must be light in colour, flexible, transparent, and of superior adhesive qualities. The dextrin must be neutral or have only a slightly acid reaction. It must have an unobjectionable odour and taste.

The viscosity Engler at 20C of a solution made by dissolving 120 g of dextrin (including moisture) in 250 g of water shall fall within the range 200250 seconds when measured after standing for 3, 24 and 48 hours.

General requirements

The dextrin shall be packed in tight paper-lined bags containing approximately 200 lb [about 90 kg].

Specifications for starch

(developed by a large food corporation)

1. Appearance and uniformity: Samples of about one teaspoonful from each bag are examined under a glass plate and compared for colour and specks. The colour should be uniform, white and free from pigments. The lot is considered nonuniform if over 10 percent of the samples are darker or have more specks than the rest.

2. Mesh size: 99 percent of the starch granules must pass through a 100-mesh screen or 95 percent pass through a 140-mesh screen.

3. Odour: The cooked flour must have a fresh odour, free from any musty or rancid odour.

4. Moisture content: Not more than 10-13 percent. Moisture content of less than 10 percent indicates severe drying conditions and a possible explosion hazard during storage. More than 13 percent indicates danger of mould contamination.

5. Ash content: Not more than 0.2 percent.

6. Protein content: Not more than 0.4 percent.

7. pH value: 4.5-5.5.

8. Viscosity: Must be suitable for both cold flour slurry and cooked starch paste.

Standards for cassava chips and manioc meal in thailand

(Notifications of the Ministry of Economic Affairs)

Re: Dried tapioca standards

By virtue of the power conferred in Section 4 of the Export Standards Act B.E. 2503, the Minister of Economic Affairs gives notice as follows:

1. Dried tapioca is declared standard goods.

2. Standards for dried tapioca shall be as specified in the annex hereto.

3. Persons taking or exporting dried tapioca from the Kingdom through the Bangkok Customs Station, Tah Chalaeb Customs Station, Changvad Chandaburi or the Klong Yai Customs Station, Changvad Trad, shall produce a good standard certificate.

4. Standards verification service charges for dried tapioca are prescribed as follows:

(1) for not more than 50 metric tons, not more than 250 baht;
(2) for amounts in excess of 50 metric tons, not more than 4 baht per metric ton.

In the event a sample is analysed, there shall be an additional charge of not more than 300 baht for verification of its standard.

5. Service charges for the issuance of standard certificates are prescribed as follows:

(1) for not more than 50 metric tons, not more than 20 baht;
(2) for amounts in excess of 50 metric tons, not more than 0.40 baht per metric ton.

Effective from the 1st of September 2506.

Notice given the 30th May 2506 (1962)

Minister of Economic Affairs

Dried tapioca standards

1. Definitions:

(1) "Dried tapioca" means tapioca root (Manihot utilissima Pohl) dried but not ground.
(2) "Fibre" means that part of the tapioca root which is not tapioca.
(3) "Foreign matter" means matter which is not dried tapioca, fibre or sand.

2. Dried tapioca must be light in colour, without admixture of foreign matter and free of unusual odour.

3. Dried tapioca shall be divided into two grades, the standard for each being prescribed as follows:

(a) Special grade, having a starch, including water-soluble carbohydrate, content of not less than 72 percent by weight and a moisture content of not more than 13 percent by weight. If there is sand or fibre it must not exceed the following rates:

(i) sand not more than 2 percent by weight;
(ii) fibre not more than 4 percent by weight.

(b) First grade, having a starch, including water-soluble carbohydrate, content of not less than 70 percent by weight and a moisture content of not more than 14 percent by weight. If there is sand or fibre it must not exceed the following rates:

(i) sand not more than 2 percent by weight;
(ii) fibre not more than 4 percent by weight.

4. In case of any argument, problem or dispute concerning the colour, the latest samples established at the Goods Standards Office shall be deemed the standard.

5. In the event of sale of dried tapioca in accordance with a sample, the standard of such dried tapioca must not be lower than that of the sample agreed to by the purchaser and the moisture content must not be higher than 14 percent by weight. Approval of the Goods Standards Office must be obtained.

6. Packing materials for dried tapioca must be gunny bags in good condition, suitable for export, free from tears, leaks and bad odour, the mouth sewn with a doubled hemp cord for sewing gunny bags, at least eleven stitches each way forward and back.

Re: Manioc meal standards

By virtue of the power conferred in Section 4 of the Export Standards Act B.E. 2503, the Minister of Economic Affairs issues a notice as follows:

1. Manioc meal standards prescribed in the schedule annexed to the Notification of the Ministry of Economic Affairs dated the 28th March 2505 Re: Manioc meal standards are cancelled.

2. Manioc meal standards are as prescribed in the schedule annexed hereto.

Effective from the 1st April 2506.

Published on the 16th January 2506 (1962)

Minister of Economic Affairs

Manioc meal standards

1. Definitions

(a) "Manioc meal" means the product derived from grinding the root of the cassava plant (Manihot utilissima Pohl) but shall not include manioc flour.

(b) "Fibre" means that part of the cassava root other than the manioc.

(c) "Foreign matter" means substances other than manioc meal, fibre, sand and moisture.

2. Manioc meal shall be divided into two grades, the standards for maniac meal of each grade being as follows:

(a) Special grade: a soluble flour including carbohydrate content of not less than 72 percent by weight and

(i) sand not more than 2 percent by weight;
(ii) fibre not more than 4 percent by weight;
(iii) moisture not more than 13 percent by weight.

(b) First grade: a soluble flour including carbohydrate content of not less than 70 percent by weight and

(i) sand not more than 3 percent by weight;
(ii) fibre not more than 5 percent by weight;
(iii) moisture not more than 14 percent by weight.

3. Both grades of manioc meal must be of light colour, have no foreign matter mixed in and no unusual or bad odour.

4. In the event of differences or a dispute over colour, the latest samples of the Goods Standards Office shall be taken as the standard.

5. In the event a sale of manioc meal is by sample, the governing standards shall not be lower than the standard of the sample agreed to by the purchaser and approved by the Goods Standards Office.

6. Packing materials for manioc meal must be gunny sacks in good condition suitable for export, free from tears, leaks and bad odour, and the mouth must be sewn with a double hemp cord for sewing gunny bags, forward and backward, at least eleven stitches each way.

List of processing equipment for a cassava starch factory producing 24 tons per day

Cleaning of fresh roots

3 belt conveyors with suitable gear motors and supports for transporting the roots
1 rotating root washer with gear motor
1 root breaker with motor for chopping washed roots
1 bucket conveyor with gear motor
1 pre-grater with motor
1 pump with stainless steel rotor and motor

Extraction of starch

3 sets of extractors with sieves and motors or a set of DSM screens for the separation of starch from fibres
2 screw conveyors with gear motors for grated material
4 pumps with stainless steel rotor and motor

Purification of starch

3 centrifugal separators or continuous channel separators with motors or Dorr Cloves
3 stainless steel stirrers with gear motors for the agitation of starch milk in basins
3 pumps with stainless steel rotors and motors

Dewatering and drying of starch

1 rotary vacuum filter with vacuum pump and motors or basket centrifuge
1 flesh drier complete with steam heating, pneumatic cooking system, ventilation, insulation, supports and motors
3 screw conveyors with gear motors
2 bucket-type elevators with gear motors
1 warm blending machine with conical mixer and gear motor
1 sifter and motor
1 sack-filling screw with two sack-filling sockets equipped with motors

Sulfurous acid plant

1 air compressor with motor
1 sulfur burning furnace with filler cap and water cooling
1 absorption tower (wood or ceramics)
1 storage tank (wood or concrete)
1 stainless steel pump with motor

Waler supply and piping

Drilling of two artesian wells
2 centrifugal pumps for well water
Piping inside factory (includes valves, fittings and condenser line for boiler)

Material handling equipment

2 storage tanks for fuel oil
2 platform scales for roots and starch fork-lift truck and handcarts


Packaged boiler to supply steam for drying starch
Power generation (stand-by unit)
Electrical installation, including switch gear, power distribution, transformer
Outside lines for water, power and sewage
Maintenance shop equipment
Quality control laboratory equipment
Trucks for transporting roots and starch

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