Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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sorted, based on size, into commercial and noncom-

mercial classes. For industrial processing, all roots are

collected.

Deterioration

0010 Freshly harvested cassava roots have the shortest

postharvest life of any of the major staple food

crops. Roots become inedible within 24–72 h after

harvest due to a rapid physiological deterioration

process. This deterioration is a major constraint for

industrial processing of the fresh roots and for

marketing them to distant urban centers. Deterior-

ation is due to the rapid, de novo, postharvest

synthesis of simple phenolic compounds (catechins,

coumarins, leucoanthocyanins) that polymerize to

form blue, brown, and black pigments (condensed

tannins). The accumulation of the coumarin, scopo-

letin, is especially rapid, reaching 80 mg hg

1

(dry

weight) in 24 h. Scopoletin has intense blue fluores-

cence in UV light and can be confused with aflatoxins

and B

which also have blue fluorescence and

similar R

values under some chromatographic

systems: many reports of aflatoxins in fresh and

processed cassava should therefore be treated with

caution. (See Mycotoxins: Occurrence and Determin-

ation; Phenolic Compounds.)

0011 Rapid physiological deterioration is an oxidative

process. Tissue dehydration, especially at sites of

root mechanical damage, encourages the rapid onset

of this phenomenon. Care at harvest to reduce mech-

anical damage is beneficial. Tissue discoloration is

initiated at damage sites and rapidly spreads through

the entire root, starting in the vascular system, but

later spreading to parenchymal cells. Within 3 days

after harvest, a ring of discolored tissues arranged

around the outer portion of the parenchyma (Figure 1)

typically appears. In advanced cases, dehydrated,

brown–white parenchyma tissues result. (See Oxida-

tion of Food Components.)

0012A secondary deterioration can follow physiological

or primary deterioration 5–7 days after harvest. This

is due to microbial infection of mechanically dam-

aged tissues, and results in the same tissue discol-

oration with vascular streaks spreading from the

infected tissues. Generalized rotting and fermentation

of tissues follow.

Storage

0013Conditions of high temperature (30



C) and high rela-

tive humidity (85%) favor the rapid wound healing of

mechanically damaged tissues (curing). Under these

conditions, the physiological processes described

above are localized in the vicinity of the wound itself.

The cured tissues represent a barrier to further

oxygen entry, thus preventing the oxidative reactions

that lead to the formation of condensed tannins.

Encouragement of this curing process is the basis

for several simple storage methods for fresh cassava.

0014Traditionally, cassava roots are preserved in the

fresh state by reburying them in soil or moist sand.

Field clamps, using straw and roots in layers below a

soil-covered mound, with adequate ventilation, were

developed in the 1970s. Packing roots in boxes with

moist sawdust, coconut fiber or other locally avail-

able materials has also been successful. Packing roots

in perforated polyethylene bags (with optional use of

a thiabendazole-based fungicide to protect against

microbial deterioration) is effective and has under-

gone commercial trials in South America and West

Africa. With all these storage methods, root quality is

maintained for 2–3 weeks. Beyond this time, starch

breakdown to free sugars gives roots an unacceptable

sweet taste. (See Fungicides; Storage Stability: Mech-

anisms of Degradation.)

0015For export markets, paraffin-coating of fresh roots

provides an artificial barrier to oxygen entry and

hence to deterioration. Costa Rica and the Domin-

ican Republic export paraffin-coated roots to the

USA and Europe. Peeled, frozen, or vacuum-packed

cassava pieces are also marketed widely in Latin

America and exported. No economically viable

method for fresh root storage at the plant level prior

to industrial processing is available. Fresh roots

fig0001 Figure 1 Transverse section through cassava root showing

symptoms of physiological deterioration, 3 days after harvest.

Reproduced from Cassava: The Nature of the Tuber, Encyclopae-

dia of Food Science, Food Technology and Nutrition, Macrae R,

Robinson RK and Sadler MJ (eds), 1993, Academic Press.

966 CASSAVA/The Nature of the Tuber

should be processed within 2 days of harvest to ensure

an acceptable quality and yield: starch extracted from

deteriorated roots is light brown in color and of a

poor functional quality, and the starch yield decreases

by 10% for each day beyond the initial 2 days of

storage. Excellent links between processing plant

and cassava producers are essential to avoid deliveries

of roots of unacceptable quality. The lack of a large-

scale storage method for fresh cassava limits process-

ing-plant operations to cassava harvest periods.

However, in many areas, cassava can be harvested

all year round, especially if irrigation is available. If

necessary, fresh roots can be chipped and sun-dried:

the dried chips can be used for starch extraction at a

later date, although starch yield and quality are lower.

Chemical Composition of the Cassava

Root

0016 The chemical composition of cassava roots is shown

in Tables 1 and 2. The composition of peel and par-

enchyma is different: the peel has more protein, fiber,

sugars, and cyanogens than the parenchyma, and less

dry matter and starch. A wide range of values is

reported in the literature for each root component.

Reports of whole-root dry-matter contents vary from

20% to 40%, and between 70% and 90% of dry

matter is composed of starch, with average values

between 80% and 85%. Total carbohydrates, includ-

ing starch, free sugars, and other cellulose or

hemicellulose components, together make up over

90% of parenchyma dry weight. The protein content

is uniformly low (below 2% on a fresh-weight basis),

as are fats and ash content. The fiber contents are

more variable, and increase with plant age. A great

variation in total cyanogen content is also found, with

parenchyma values of 30–100 mg kg

1

common for

low-cyanogenic cultivars destined for direct con-

sumption, compared with 1350 mg kg

1

in industrial

varieties used for processing. (See Carbohydrates:

Classification and Properties; Starch: Sources and

Processing.)

0017A variation in chemical composition is found be-

tween cassava varieties, and also within varieties at

different plant ages, and is due to changing environ-

mental and biotic stress factors. For example, paren-

chyma dry-matter content may decrease from 35% to

28% after a period of drought followed by the onset

of rainfall. Under these conditions, starch is rapidly

hydrolyzed to free sugars, especially sucrose, which

are used by the plant to initiate regrowth of foliage.

These large fluctuations in root quality over relatively

short periods must be taken into account in planning

harvesting times, both for direct consumption and for

processing. (See Starch: Modified Starches.)

Cyanide in Cassava Roots

0018All known Manihot species contain cyanogens. In

cassava, cyanide is synthesized in the leaf and trans-

ported to the roots, where it is partitioned between

peel and parenchyma. Some 85% of the cyanide

occurs as cyanoglucosides, mainly linamarin but

also lotaustralin. Linamarin is broken down by the

enzyme linamarase, also found in cassava tissues. In

intact roots, the compartmentalization of linamarase

in cell walls and linamarin in cell vacuoles prevents

the formation of free cyanide. On processing, the

disruption of tissues ensures that the enzyme comes

into contact with its substrate, resulting in rapid pro-

duction of free cyanide via an unstable cyanhydrin

intermediary.

0019Cassava varieties differ in their total cyanogen con-

tent, and although the variation in content is continu-

ous, two distinct types can be discerned in many

regions of the world: low- and high-cyanogen

varieties. Low-cyanogen varieties are often called

sweet, although confusion with elevated free sugar

contents in some conditions may occur. These are

grown for fresh consumption, or for simple process-

ing. High-cyanogen varieties are called bitter, al-

though the phenolic compounds involved in root

physiological deterioration can also produce a bitter

taste. These are invariably grown for processing,

especially for farinha in Brazil and gari in Africa. It

is interesting that low-cyanogen varieties are rarely

tbl0001 Table 1 Constituents of cassava root parenchyma and peel

Constituent Percentage of dry weight

Parenchyma Peel

Dry matter (%, fresh weight) 23–44 15–34

Starch 70–91 44–59

Total sugars 1.3–5.3 5.2– 7.1

Crude fiber 3.0–5.0 5.0–15.0

Ash 1.0–2.5 2.8–4.2

Protein 1.0–6.0 7.0–14.0

Fat 0.3–1.5 1.5–2.8

tbl0002 Table 2 Vitamin, mineral, and cyanide constituents of cassava

root parenchyma and peel

Constituent Milligrams per kilogram dry weight

Parenchyma Peel

Total cyanide 30–1350 60–50

Calcium 480–920

Phosphorus 770–150

Potassium 6000–10 000

Iron 5–25

Vitamin A 0–70

Vitamin C 380–900

CASSAVA/The Nature of the Tuber 967

used for processing: the reasons for a preference for

high-cyanogen varieties are unclear. Contrary to an-

ecdotal evidence, high-cyanogen varieties do not yield

more than low-cyanogenic varieties. There is some

evidence that cyanide may protect against rodent

pests and robbery, and also that there may be a link

between end-product quality (e.g., farinha texture)

and cyanogen content.

0020 Cyanide is concentrated in the root peel, especially

in low-cyanogen varieties where peel:root ratios of

40:1 are found. In high-cyanogen varieties, ratios

of 1.6:1 are common. The use of whole or peeled

roots for processing may therefore result in great

differences in end-product cyanogen content. In root

parenchyma tissues, free cyanide – hydrogen cyanide

(HCN) plus cyanhydrin – normally accounts for 15%

of total cyanide; the remainder is bound as linamarin

or lotaustralin. All cassava varieties characterized

to date contain these cyanogens. Projects involving

genetic manipulation are currently under way to

reduce the toxicity problems of cassava, through

regulation of cyanide synthesis and increasing the

activity of linamarase.

Starch

0021 Cassava starch has many food and industrial uses,

which are linked to its functional properties. Al-

though the basic properties of this starch are known,

much research is required to complete our knowl-

edge, especially as regards varietal differences in com-

position and functional properties. Cassava starch

granules are round with a truncated end and a well-

defined hilum. The granule size is between 5 and

35 mm. The starch has an A-type X-ray diffraction

pattern, usually characteristic of cereals, and not the

B type found in other root and tuber starches. The C-

type spectrum, intermediate between A and B types,

has also been reported. The nonglucosidic fraction of

cassava starch is very low: the protein and lipid con-

tent is below 0.2%. There is thus no formation of an

amylose complex with lipids in native starch. Amy-

lose contents of 8–28% have been reported, but most

values lie within the range of 16–18%. (See Starch:

Structure, Properties, and Determination.)

0022Figure 2 shows Brabender amylographs of starch

from four cassava varieties. Although a significant

varietal variation is present, all curves follow the

same general pattern and are similar to all high-

amylopectin starches. The starch gelatinizes at

relatively low temperatures. Initial and final gelatin-

ization occurs at 60



C and 80



C, respectively. The

peak viscosity is high and is reached rapidly, within

2 min. At high temperatures starch viscosity decreases

greatly. Viscosity increases again on cooling (set-

back), and then remains stable. Cassava starch has a

low retrogradation tendency (i.e., viscosity is stable

over time following the cooling episode) and pro-

duces a very stable and clear gel. The swelling

power of the starch is also very high: 100 g of dry

starch will absorb 120 g of water at 100



C. At this

temperature, over 50% of the starch is soluble. (See

Starch: Functional Properties.)

1200

1000

800

600

400

200

0 20 40 60 80 100 120

Heating from 25 to 90 ⬚C

(1.5 ⬚C min

−1

)

(1.5 ⬚C min

−1

)

Const.temp

(50 ⬚C)

Const.temp

(90 ⬚C)

for 20 min

Cooling to 50 ⬚C

Time (min)

Viscosity (Brabender Units)

fig0002 Figure 2 Brabender viscoamylograms of starch from four cassava varieties (4% w/v paste). —— CMC-40; —&— CM 523-7;

. . . . . . . . . MCol 8; —m— MCol 1684. Source: CIAT (International Centre for Tropical Agriculture), Cali, Columbia. Reproduced from

Cassava: The Nature of the Tuber, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson RK and Sadler MJ

(eds), 1993, Academic Press.

968 CASSAVA/The Nature of the Tuber

See also: Carbohydrates: Classification and Properties;

Fungicides; Mycotoxins: Occurrence and

Determination; Oxidation of Food Components;

Phenolic Compounds; Starch: Structure, Properties,

and Determination; Sources and Processing; Functional

Properties; Modified Starches; Storage Stability:

Mechanisms of Degradation

Further Reading

Bradbury JH and Holloway WD (1988) Chemistry of trop-

ical roots crops: significance for nutrition and agricul-

ture in the Pacific. Australian Center for International

Agricultural Research Monograph No. 6.

Cock JH (1985) Cassava: New Potential for a Neglected

Crop. Boulder, CO: Westview Press.

Cooke RD and Coursey DG (1981) Cassava: a major cyan-

ide containing food crop. In: Conn E, Knowles EJ, Ven-

nesland B, Westley E and Wissung F (eds) Cyanide in

Biology, p. 193. New York: Academic Press.

Kay DE (revised by Gooding EGB) (1987) Crop and

Product Digest No. 2 – Root Crops, 2nd edn. London:

Natural Resources Institute XV.

Richard JE and Coursey DG (1981) Cassava storage. Part 1:

storage of fresh cassava roots. Tropical Science 23: 1–32.

Wheatley CC and Best R (1991) How can traditional forms

of nutrition be maintained in urban centers: the case of

cassava. Entwicklung & Landlicher Raum 1: 13–16.

Uses as a Raw Material

C C Wheatley, Nelson, New Zealand

G Chuzel and N Zakhia, CIRAD-AMIS, Montpellier,

France

Background

0001 The fresh cassava root is an important staple in many

rural areas of the tropics, especially in sub-Saharan

Africa, where it is the principal carbohydrate source

for 40% of the population. More recently, the crop

has been used as a raw material for food and other

industries. This article briefly reviews the wide range

of products made from cassava roots and then focuses

on four of the most important products.

Use as a Staple Food

0002 The fresh, peeled root is commonly boiled for 15–

30 min, either alone or with other ingredients in a

soup. Raw or boiled root pieces can also be fried.

Boiled cassava should have a soft, floury texture,

but is sometimes hard and glassy, leading to rejection

by consumers. The causes of glassy texture are

unknown. The bitter taste is frequently due to re-

sidual cyanide remaining after boiling, although the

phenolic compounds involved in physiological deter-

ioration can also produce a bitter taste. Cultivars with

a low cyanogen content in the parenchyma are invari-

ably used for fresh consumption. Consumption per

capita of fresh cassava may reach very high levels

(e.g., 405 kg per year in Zaire, and over 200 kg per

year in rural areas of Paraguay). A variety of foods

made with grated or mashed, boiled cassava are pre-

pared at the household level. Examples of other staple

foods based on cassava are gari in Nigeria and farinha

in Brazil. These processed products will be considered

in the next section. (See Phenolic Compounds.)

0003Cassava leaves form an important part of the diet

in Zaire and other African countries, and are of minor

importance in South-east Asia. In Zaire, cassava

leaves comprise nearly 70% by weight of all vege-

tables consumed. They are normally chopped and

boiled, a process that greatly reduces the level of

residual cyanogens.

Cyanide Toxicity and Processing

0004Tissue disruption (chipping, grating or fermentation)

is effective in bringing linamarase into contact with

the linamarin substrate, thereby liberating hydrogen

cyanide (HCN). Processes such as sun-drying of large

root pieces or boiling are less effective. Toxicity prob-

lems may result when poorly processed cassava

products are consumed. Acute cyanide toxicity

appears when more than 30 mg is consumed over a

24 h period. The body’s natural thiocyanate detoxifi-

cation mechanism requires a good supply of sulfur-

containing amino acids: a protein-deficient diet in

combination with cyanide consumption can therefore

result in health problems. In addition, thiocyanate

interferes with iodine uptake by the thyroid gland,

leading to goiter and, in extreme cases, cretinism.

Epidemic spastic paraparesis has been reported on

several occasions in Africa since 1981, affecting a

total of 5000–10 000 people with leg paralysis. The

exact metabolic processes involved are unknown, but

each outbreak is clearly associated with famine-

induced consumption of poorly processed cassava

and a lack of protein in the diet. (See Iodine: Iodine-

deficiency Disorders.)

0005The toxicity of processed cassava products is due to

the residual linamarin and cyanhydrin remaining

after the action of linamarase ceases. Once consumed,

linamarin reaching the gut may be broken down by

microbial enzymes or by ingested linamarase. This

process is incomplete, since linamarin can also be

detected in the urine. The percentage of linamarin

CASSAVA/Uses as a Raw Material 969

that may be degraded in the gut has received little

research attention; however, individual sensitivity to

cyanide toxicity seems to vary with nutritional status.

Adequate cassava processing (grating, fermentation,

slow sundrying), combined with sufficient dietary

protein, is necessary for populations at risk in order

to take advantage of the food security offered by

cultivating high-cyanide cassava varieties. The use of

cassava varieties low in cyanogens also has potential.

Overview of Cassava Processing

0006 Processing of cassava has several objectives: to pro-

duce a more stable product, capable of being stored in

tropical environments for extended periods with no

decrease in quality or deterioration; to reduce the

content of cyanide to innocuous levels; to reduce

bulk and hence lower transport costs; to diversify

the food and other uses of cassava, leading to market

expansion; and to provide food and other industries

with a low-cost raw material for further processing.

0007 Cassava roots may be processed whole, after re-

moval of the peel, or after washing, a process that

also removes most of the outer barky layer. The roots

can then be grated, chipped, or sliced. Grated roots

may be pressed to remove excess water and then

toasted to produce the flour called farinha, or a flat

bread called cassabe. These are staple foods in several

Latin American and Caribbean countries. If a fermen-

tation stage is included, using peeled roots, the

product is gari, a staple in West Africa. Alternatively,

starch can be extracted from the grated roots, and can

be either dried directly or fermented to produce a

naturally modified starch (sour starch). Cassava

chips are usually sun-dried to produce a dried chip

(gaplek), which is used for human consumption in

Indonesia, and for animal consumption in Latin

America. Larger root pieces are sun-dried in Africa.

(See Starch: Sources and Processing.)

0008 A high-quality cassava flour can be produced from

washed or peeled roots, chipped and sun-dried on

trays, or artificially dried to avoid microbial contam-

ination. This flour can replace wheat and other

imported flours in tropical countries. In Africa, pieces

of cassava roots are fermented and dried to produce

a flour called lafun. In Indonesia, root pieces are

fermented using an innoculum of Amylomyces and

Endomycopsis, to produce a moist product called

tape. In Africa, whole roots are retted, grated,

and boiled to produce a fermented dough called

chickwangwe or fu-fu.

0009 A great diversity of products are prepared from

cassava roots in rustic, small-scale facilities, using

traditional methods. Over recent decades, medium-

scale processing of these traditional products has

developed on all continents. This had led to the design

of more efficient processing equipment, and to im-

provements and standardization of quality. In recent

years, large-scale operations for starch and farinha

have been developed to supply urban and export

markets, especially in Brazil, Thailand, and Indo-

nesia. (See Traditional Food Technology.)

Important Products

Gari

0010Gari, a fermented, cooked and dehydrated cassava

meal, is widely consumed in West Africa. It is a stable,

ready-to-use foodstuff, well-suited to urban markets.

Gari consumption is increasing, even in countries

where it is not a traditional food. Gari is principally

consumed in the main meal with vegetable sauces and

meat. It can also be eaten as a snack soaked in cold

water or milk, with roasted peanuts or coconut. Gari

contributes up to 60% of the total calorie intake in

West Africa, where an average of 150 g per person per

day is consumed. Gari is mainly produced on a small

scale and marketed by women; it provides an import-

ant source of income in many rural areas. Although

many process improvements have been designed,

diffusion of equipment has been patchy, especially

for the roasting stage, so today, most of the gari

consumed is still manufactured using the traditional

process.

0011In traditional preparation of gari (Figure 1), the

roots are hand-peeled, then grated into a pulp, often

using a roughly perforated iron sheet. This pulp or

mash is placed in hessian sacks, under heavy weights

(logs, rocks) to squeeze out excess water. The mash is

left to drain for 1–6 days, during which natural fer-

mentation occurs. The pressed cake is shredded by

hand and then rubbed through a woven palm-frond

sieve to remove fiber and large lumps. This sieved

mash is toasted (garified) in clay or iron vessels over

a wood fire until the starch gelatinizes, and the mois-

ture content is reduced to 10–15%. The mash must be

stirred constantly to avoid sticking or burning. Palm

oil may be added to facilitate this operation and

imparts a yellow color to the final product.

0012Great variability exists in consumer perception of

gari quality, and it is difficult to establish optimum

values for the different quality parameters. However,

in general, consumers prefer a crisp, fine-grained,

slightly sour product with good swelling power in

water, and a lightly toasted color. Although all the

processing steps are important in determining end-

product quality, some of them are only mechanical

(peeling, grating, sieving, dewatering), whereas others

involve some physical and chemical modifications that

970 CASSAVA/Uses as a Raw Material

improve the digestibility and reduce the cyanide tox-

icity (fermentation, garification). The fermentation

step is crucial to the development of the characteristic

aroma and sour flavor of gari, imparted mainly by

lactic acid bacteria, which produce lactic acid and vola-

tiles such as aldehydes, diacetyl esters, and ethanol.

Fermentation also helps to detoxify the mash, whereas

grating allows linamarase to come into contact with

cyanoglucoside substrates. During fermentation, free

HCN is released. The pH falls from 6.8 to 4.5 after

24 h of fermentation. Because the cyanohydrin inter-

mediary is quite stable in acidic conditions, and lina-

marase activity is also reduced, less free cyanide is

produced, and cyanhydrins accumulate in the fer-

mented mash. Cyanide detoxification of the mash

occurs in three ways: enzymic hydrolysis of cyanoglu-

cosides, solubilization of cyanide in the water lost

during dewatering, and volatilization of free cyanide

during garification, at temperatures over 26



C. The

combination of these is not enough to completely

remove all cyanide from the end product: total cyano-

gen contents of 15–33 mg kg

1

, with a free cyanide

content of 5–25 mg kg

1

, have been reported. (See

Lactic Acid Bacteria.)

0013The garification step is essential to obtain good-

quality gari, for which 60–80% of starch should be

gelatinized. This also improves starch digestibility.

The starch is not completely gelatinized during gari-

fication because of the low initial moisture content of

the dewatered mash (50–55%) and the temperatures

used (60–85



C). Gelatinization proceeds until the

moisture content is reduced to about 40%, after

which only drying occurs. The efficiency of manual

stirring during garification is an additional variable

affecting the final quality.

Farinha

0014Farinha de mandioca is a major dietary staple in

Brazil, especially in the northeast region of the coun-

try, where the per capita consumption is over 40 kg

per year or 1881 J (450 cal) per person per day. This

represents 25% of the total calories consumed – more

than rice and wheat combined. In Brazil as a whole,

farinha contributes an average of 752 J (180 cal) per

person per day to the diet. Farinha is a traditional

cassava product and is still the major source of diet-

ary energy for many of the indigenous peoples of the

Amazon basin; one study of the Colombian Vaupes

Washing/peeling

Grating

Dewatering

(no fermentation)

Crumbling/sifting

Roasting

200 kg230 kg

Roasting

(garification)

Crumbling/sifting

Fibre and

lumps

Dewatering

(fermentation)

Juice from

dewatering

Grating

Washing/peeling

Peels

1000 kg

Roots

Farinha de

mandioca

Gari

fig0001 Figure 1 Flow diagram of the traditional processes for production of gari (West Africa) and farinha de mandioca (Brazil).

Reproduced from Cassava: Uses as a Raw Material, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson

RK and Sadler MJ (eds), 1993, Academic Press.

CASSAVA/Uses as a Raw Material 971

region found that cassava provided over 80% of diet-

ary calories and that farinha was the major product

consumed.

0015 The process for the production of farinha is similar

to that of gari (Figure 1). It is probable that gari is an

adaptation of farinha to African tastes, which oc-

curred when cassava was introduced from Brazil to

Africa. Unlike gari, however, a typical farinha prepar-

ation does not include a fermentation step. The oper-

ation proceeds directly from grating through pressing

and sieving to toasting. Another difference is the use

of washed but unpeeled roots. The end product is thus

a cream/yellow-colored meal with no fermented taste.

The final moisture content is the same as in gari, but

the residual cyanogen content is lower (10 mg kg

1

Since no fermentation occurs, acid conditions do not

develop, and the cyanhydrin intermediate rapidly

breaks down to free cyanide.

0016 Farinha is an integral ingredient in many trad-

itional dishes. Mixed with beans, farinha provides a

thicker texture. Farinha is also consumed with meats.

Consumption decreased markedly between 1960 and

1980, as government subsidies on wheat reduced the

competitiveness of farinha. However, over the last

few years, elimination of wheat subsidies has resulted

in an increase in the attractiveness of farinha. As a

storable, rapidly prepared, and well-accepted food,

farinha integrates easily into urban food habits.

0017 Considerable applied research has resulted in the

design, testing, commercial construction and use of

efficient medium- and large-scale farinha production

facilities in Brazil. Plants with a capacity of 50–200

tonnes of cassava roots per day are in operation.

Alongside this, many thousands of small-scale trad-

itional ‘casas de farinha’ exist, especially in the north-

east, providing employment over vast areas of this

region, the poorest in Brazil. Over 460 000 such

plants exist, often run as communal operations at

the village level. The range of scales of operation

and the regional differences in cassava varieties and

the process itself result in large variations in end-

product quality. The variation in quality and its effect

on consumption patterns need to be studied further.

Research aimed at improving and standardizing

quality has yet to produce results.

Starch

0018 Although cassava is an efficient starch producer, only

5% of total starch traded worldwide is from cassava,

representing about 0.8–1.0 10

tonnes per year. The

main industrial-scale producers of cassava starch

are Thailand, Brazil, China, and Indonesia. Produc-

tion of cassava starch has increased dramatically in

Thailand: by 1994, 50% of the 19 10

tonnes of

cassava roots produced were processed into starch.

Exports, mainly to East Asia, totaled 1.15 10

tonnes, and domestic use comprised 0.9 10

tonnes.

In Thailand, starch is developing as a feedstock for

further processing: in 1994, 31% of starch was modi-

fied, 12% was used for sweeteners, and 12% was

used for MSG (monosodium glutamate). In addition

to large-scale industries, many small-scale starch ex-

traction plants operate in South and South-east Asia

and in Latin America. Here, cassava starch is used in

the local food industry to make a wide range of

traditional food products (tapioca or sago in India;

krupuk in Indonesia; chipa in Paraguay; maltose in

Vietnam). In Brazil and Colombia, moist starch is

fermented before drying, and a naturally modified

starch is obtained, which has functional properties

distinct from those of native cassava starch, namely

a spontaneous expansion capability during baking.

This starch is used in several traditional cheese breads

(pandebono, pandequeso, bizcocho) and, more re-

cently, in novel snack foods.

0019Cassava roots are washed and peeled; sometimes,

only the outer bark is removed and then grated to

release starch granules (Figure 2). The starch is ex-

tracted under running water and separated from the

fiber and other root components by screening. Solid

starch is separated from the starch/water slurry by

sedimentation or centrifugation. The resultant starch

is dried to a final moisture content of 12–14%. Sun-

drying in small-scale operations and flash-drying in

large-scale plants are typical. To obtain sour, fer-

mented starch, the sedimented starch is left in tanks

for 20–30 days before drying. Whereas a small-scale

extraction plant may process only 2–10 tonnes of

cassava per day, large-scale operations in Brazil and

Thailand can handle 200 tonnes per day. Starch

extraction rates are usually 18–22% for small-scale

plants and 20–25% in large operations, depending on

the process efficiency and initial root starch content.

In small-scale plants, operations are manual or par-

tially mechanized, resulting in less efficient starch

extraction: in Colombia, 45% of the starch contained

in the roots is lost in the waste water from the process,

or remains in the peel and fiber byproduct, which is

dried and used for animal feed. Waste water from

processing plants can present severe environmental

contamination problems, owing to significant con-

centrations of starch and cyanide. More efficient use

of water in the process, and simple water treatment

systems can reduce pollution. Regulatory pressure,

especially on large-scale factories, is increasing.

0020In India, Brazil, and Malaysia, partially dried

native cassava starch is used to make tapioca or

sago: the still moist starch is globulated on a vibrating

972 CASSAVA/Uses as a Raw Material

surface, and the resulting small spheres are then

steamed or baked to gelatinize the surface layers of

starch. The end product, tapioca pearls, is used to

make a variety of desserts. In Indonesia and Malaysia,

the native starch is mixed with water, fish, or prawn

flavoring and coloring. This dough is steamed, then

sun-dried to make krupuk, or prawn crackers. When

fried, these expand to several times their original size.

They are a major snack food in Java and elsewhere in

the region.

0021 Fermented or sour starch has excellent expansion

power; thus, the volume of a dough containing this

starch increases greatly during baking. Although

many factors affect the expansion power of sour

starch, including environmental conditions, cassava

variety and water quality, the major factors are

fermentation and sun drying. During fermentation,

amylolytic organisms produce reducing sugars,

which are immediately consumed by lactic acid bac-

teria to produce organic acids (lactic, propionic,

butyric, acetic, etc.) and carbon dioxide (CO

). The

high lactic acid content in sour starch correlates with

a good expansion power and a good-quality final

baked product. The action of the amylolytic enzymes

and the acidification of the fermentation medium (pH

3.2) result in a lower viscosity, improved ease of

baking, and reduced gelling ability of sour starch

compared with native cassava starch. During baking

of doughs containing sour starch, the moisture con-

tent loss (from 50% to 8–12%) together with volatil-

ization of lactic acid and CO

results in an increased

expansion power and reduced gelling ability, giving

the end product its characteristic texture. A simple

method for assessing the expansion power of sour

starch is now available and in use with processors in

Colombia.

Residue 'Afrecho'

Residue 'Mancha'

Waste water

Washing/peeling

1000 kg

Water

(3 −5 m

per t fresh

roots)

(8 −12 m

per t fresh

roots)

Grating

Sieving

Sun-drying Animal feed

80 kg

Waste water

Sedimentation

Fermentation

Sun-drying Sun-drying

200 kg 210 kg

Roots

Sour starch Starch

fig0002 Figure 2 Flow diagram of the process for production of fermented (sour) and nonfermented (sweet, native) cassava starch.

Reproduced from Cassava: Use as a Raw Material, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson

RK and Sadler MJ (eds), 1993, Academic Press.

CASSAVA/Uses as a Raw Material 973

Flour

0022 In several regions of Africa and in Indonesia, cassava

roots are chopped into pieces, sun-dried, and then

pounded into a coarse meal or flour. This flour serves

as a base for the production of many dishes at the

household level. More recently, in Thailand, sun-

dried cassava chips have been produced on a large

scale, over 6 10

tonnes per year, for export to

Europe as an animal feed. The chips are ground to a

meal, which is then converted under steam and pres-

sure to hard pellets. Dried cassava for animal feed

expanded in Latin America during the 1980s as an

alternative to imported grains for internal use. Glob-

alization and cheap imports of feed grains reduced the

feed use of cassava in the early to mid-1990s, but is

now becoming increasingly competitive again. Poten-

tial also exists to produce high-quality cassava flour

to replace imported wheat flour in bakery and other

products in many tropical countries. One such

program in Brazil was halted during the 1970s by

wheat flour subsidies, which made it impossible for

cassava flour to compete. The food industry use of

root crop flours depends largely on international

wheat grain prices: if these continue to decrease, the

potential for substitution will be limited to those uses

where cassava flour offers some specific functional

advantages, or in remote areas where the transport

costs for wheat flour are high (e.g., the Peruvian

Amazon, where cassava flour is currently a commer-

cial product).

0023 The process for the production of high-quality cas-

sava flour requires the use of cleaned roots with the

bark removed. Peel removal is optional. Roots are

chipped and sun-dried on trays or artificially dried

(60



C for 8–10 h) to obtain a hygienic product. The

dried chips, with 12% moisture content, can be re-

duced in size (premilled) sufficiently to enable them to

be used in standard wheat flour roller mills. Conver-

sion rates in excess of 90% can be obtained in this

way, compared with 72% for wheat grains. If roots

are not peeled before chipping and drying, the peel

and fiber fractions can be removed efficiently during

the milling and grading process. A conversion rate of

3:1 is possible with cassava flour, compared with 4.5–

5:1 for starch. The approximate composition of the

flour is as follows: moisture 12%; carbohydrate 75%;

protein 3%; fiber 5%; and lipids 2%. The total

cyanogen content should be below 50 mg kg

1

0024 Industry trials with cassava flour in Colombia have

demonstrated that some specific attributes of the

flour are especially suited to certain products. A 40–

50% substitution of cassava for wheat flour produces

biscuits with superior texture and color compared

with 100% wheat flour controls. In Indonesia, a

wide range of bakery products are being manufac-

tured from cassava flour, at the village level as well

as the food-industry level. (See Flour: Analysis of

Wheat Flours; Dietary Importance; Roller Milling

Operations.)

See also: Flour: Roller Milling Operations; Analysis of

Wheat Flours; Dietary Importance; Iodine: Iodine-

deficiency Disorders; Lactic Acid Bacteria; Phenolic

Compounds; Starch: Sources and Processing;

Traditional Food Technology