Why
cassava needs processing
Constraints
in the traditional processing of cassava
Traditional
methods for processing cassava
Processing
techniques and reduction of cyanide in cassava
Processed
products
Processing
equipment
Storage
of processed products
Cassava
leaves as vegetable
Utilization
of processed products
Modes
of consumption
Potentials
of cassava as animal feed
The
future of cassava
References
Cassava is one of the most important staple food crops grown
in tropical Africa. It plays a major role in efforts to alleviate the African
food crisis because of its efficient production of food energy, year-round
availability, tolerance to extreme stress conditions, and suitability to
present farming and food systems in Africa (Hahn and Keyser 1985, Hahn et al.
1987).
Traditionally, cassava roots are processed by various
methods into numerous products and utilized in various ways according to local
customs and preferences. In some countries, the leaves are consumed as
vegetables, and many traditional foods are processed from cassava roots and
leaves.
Improvement of cassava processing and utilization techniques
would greatly increase labor efficiency, incomes, and living standards of
cassava farmers and the urban poor, as well as enhance the-shelf life of
products, facilitate their transportation, increase marketing opportunities,
and help improve human and livestock nutrition. This paper presents a general
overview of traditional cassava processing and utilization methods now used by
small-scale farmers and processors in Africa, and examines the opportunities
for improving postharvest technologies.
Fresh cassava roots cannot be stored for long because they
rot within 3-4 days of harvest. They are bulky with about 70% moisture content,
and therefore transportation of the tubers to urban markets is difficult and
expensive. The roots and leaves contain varying amounts of cyanide which is
toxic to humans and animals, while the raw cassava roots and uncooked leaves
are not palatable. Therefore, cassava must be processed into various forms in
order to increase the shelf life of the products, facilitate transportation and
marketing, reduce cyanide content and improve palatability. The nutritional
status of cassava can also be improved through fortification with other
protein-rich crops. Processing reduces food losses and stabilizes seasonal
fluctuations in the supply of the crop.
Environmental factors
During the rainy season, sunshine and ambient temperatures
are relatively low for processing cassava, particularly in lowland humid areas
where cassava is mainly grown and utilized. In other localities, particularly
in savanna zones, water which is essential for processing cassava, is not
easily available. During the early rainy season, the dry matter content of
roots is usually lower than in the dry season, which can result in a lower
yield of products. In the dry season when the soil is hard, harvesting and
peeling tubers for processing are difficult and result in more losses.
Varietal factors
Cassava shape varies among cultivars. Roots with irregular
shapes are difficult to harvest and peel by hand, resulting in great losses of
usable root materials. Root size also varies with cultivars although it depends
more on environmental factors such as soil. Smaller roots require more labor
for peeling. Varietal differences in dry matter content, and in starch content
and quality influence the output and quality of the processed products. Cyanide
content varies with varieties, but is also affected by the crop growth
environment.
Agronomic factors
Time of planting and harvesting, and age of plant, from
planting to harvesting, all affect starch content, yield and quality of
products. Other agronomic practices such as intercropping, fertilizer
application and spacing can also affect yield and crop quality.
Socioeconomic factors
Harvesting and transporting of roots from farm to homestead
and subsequent processing are mainly done by women. Most of the steps in
processing are carried out manually using simple and inexpensive tools and
equipment that are available to small farmers. Cassava processing is labor
intensive and productivity is usually very low. Transport of products to
markets is made difficult by the poor condition of rural roads. The drudgery
associated with traditional processing is enormous and the products from traditional
processing methods are often contaminated with undesirable extraneous matter.
Some of the products are therefore not hygienic and so are of poor market
value. Better processing methods can improve the life-styles and health of
rural people through higher processing efficiency, labor saving and reduced
drudgery, all of which improve the quality of products.
Subsistence farmers harvest cassava when needed. Thus they
leave the cassava in the ground for long periods, believing that the cassava is
safer and would undergo less damage than when harvested. Although this system
has certain merits, a delay in harvest can result in root losses due to root
rots, damage by animals, and a decrease in the starch content in roots.
Furthermore, keeping cassava in the ground prevents the use of that land for
other purposes.
Traditional cassava processing methods in use in Africa
probably originated from tropical America, particularly northeastern Brazil and
may have been adapted from indigenous techniques for processing yams (Jones
1959). The processing methods include peeling, boiling, steaming, slicing,
grating, soaking or seeping, fermenting, pounding, roasting, pressing, drying,
and milling. These traditional methods give low product yields which are also
of low quality.
Rapid urbanization in tropical Africa increased mobility in
both rural and urban areas and the changing roles and status of women have
resulted in an unprecedented demand for convenience foods. Added to these
factors is the high cost of fuel for cooking in urban areas at a time when fuel
wood is not only inconvenient to use but is becoming increasingly scarce.
Therefore, cassava processing and utilization technologies for the future
should improve traditional methods and develop low cost equipment with low
energy demands. Improved processing and utilization technologies should address
issues related to farmers' (producers') and consumers' needs (particularly
urban needs in future), and also to economic factors and nutritional values.
Knowledge of the current traditional processing and utilization methods and of
present urban patterns of consumption and changing urban needs will guide
future strategies for cassava processing and utilization.
Improvement of nutritional values of processed products also
requires special attention from policymakers and researchers. Cassava is
frequently denigrated because its roots are low in protein. However, protein
may be supplemented from other sources, particularly legumes; for example,
fortification of cassava flour or gari with protein-rich soyflour can be
achieved. Such fortified products will be nutritionally advantageous, and thus
economical and acceptable to consumers.
Although cassava is regarded as subsistence crop of low-income
families or as a "famine-reserve crop", about 60 percent of the
cassava output of households in the Oyo area of Nigeria is sold for processing
(mostly into gari) while the remaining 40 percent is consumed at home (Ikpi et
al. 1986). A high proportion (50 percent) of cassava was also sold to food
processors in the western region of Cameroon (Okezie et al. 1988), suggesting a
changing status for cassava.
Cassava contains the cyanogenic glucosides, linamarin and
lotaustralin which are hydrolyzed after tissue damage, by the endogenous
enzyme, linamarase to the corresponding cyanohydrins and further to hydrogen
cyanide [HCN](Conn 1969). The hydrogen cyanide is responsible for chronic
toxicity when inadequately processed cassava products are consumed by humans
and animals for prolonged periods. Therefore, traditional processing procedures
must aim at reducing cyanide and improving storability, convenience and
palatability.
Cassava processing procedures vary, depending on products,
from simple processing (peel, boil and eat) to complicated procedures for
processing into gari, for example, which involve many more steps, namely
peeling, grating, pressing, fermenting, sifting, and roasting. Some of these
steps reduce cyanide more effectively than others. Processing techniques and
procedures differ with countries and localities within a country according to
food cultures, environmental factors such as availability of water and
fuelwood, the cassava varieties used, and the types of processing equipment and
technologies available. The most important traditional culinary preparations of
cassava in Africa are "boiled or roasted roots", "fufu"
(cassava flour stirred with boiled water over a low-heat fire to give a stiff
dough), "eba" (gari soaked in hot water to produce a thick paste) and
"chickwangue" (steamed fermented pulp wrapped in leaves).
Fermentation
Fermentation consists of two distinct methods: aerobic and
anaerobic fermentation. For aerobic fermentation, the peeled and sliced cassava
roots are first surface-dried for 1-2 hours and then heaped together, covered
with straw or leaves and left to ferment in air for 3-4 days until the pieces
become moldy. The fermented moldy pieces are sun-dried after the mold has been
scraped off. The processed and dried pieces (called "Mokopa" in
Uganda) are then milled into flour, which is prepared into a "fufu"
called "kowan" in Uganda. The growth of mold on the root pieces,
increases the protein content of the final products three to eight times (Amey
1987, Sauti et al. 1987). This fermentation method is also very popular in
other parts of East Africa such as Tanzania, Rwanda, and Zaire.
In anaerobic fermentation, grated cassava for processing
into "gari" is placed in sacks and pressed with stones or a jack
between wooden platforms. Whole roots or pieces of peeled roots for processing
into "fufu" are placed in water for 3-5 days. During the first stage
of gari production, the bacterium Corynebacteria manihot attacks the
starch of the roots, leading to the production of various organic acids (such
as lactic and formic acids) and the lowering of substrate pH. In the second
stage, the acidic condition stimulates the growth of a mold, Geotrichum
candida, which proliferates rapidly, causing further acidification and
production of a series of aldehydes and esters that are responsible for the
taste and aroma of gari (Odunfa 1985). The optimum temperature for the
fermentation for gari processing is 35°C, increasing up to 45°C.
For "lafun" production in Nigeria, peeled or
unpeeled cassava tubers are immersed in a stream, in stationary water (near a
stream) or in an earthenware vessel, and fermented until the roots become soft.
The peel and central fibres of the fermented roots are manually removed and the
recovered pulp is hand mashed or pounded. The microorganisms involved in
"lafun" production include four yeasts: Pichia onychis, Candida
tropicalis, Geotrichum candida, and Rhodotorula sp.; two molds: Aspergillus
niger and Penicillium sp.; and two bacteria: Leuconostoc sp.
and Corynebacterium sp. (Nwachukwu and Edwards 1987). Moisture, pH and
temperature conditions are critical for the growth of these microorganisms in
roots and thus for fermentation.
Dewatering the fermented cassava
During or after fermentation of roots for gari production,
the grated pulp is put in sacks (jute or polypropylene) on which stones are
placed or jacked-wood platforms are set to drain or press off the excess liquid
from the pulp. In Zaire, the cassava pulp is taken out and heaped up on the
racks in the sun for further fermentation and draining of the excess moisture.
In this way, much of the cyanide is effectively lost with the liquid.
Tissue disintegration
Tissue disintegration in the presence of excess moisture
during grating or fermenting in water permits the rapid hydrolysis of
glucosides, effectively reducing both free and residual cyanide in the
products. Fermentation in water appears a more efficient method for reducing
the cyanide of roots. For example, this process reduced cyanide by 70-95
percent of the original level after the roots were soaked in water for 3 days
(Hahn et al. 1987). Gari obtained through the processing procedures involving
grating and/or fermentation showed 80-90 percent reduction in total cyanide
content relative to freshly peeled roots (Mahungu et al. 1987). Oke (1968)
reported HCN content of 1.9 mg/100g
Drying
Drying is the simplest method of processing cassava. Drying
reduces moisture, volume and cyanide content of roots, thereby prolonging
product shelf life. This processing is practiced primarily in areas with less
water supply.
Total cyanide content of cassava chips could be decreased by
only 10-30 percent through fast air drying. Slow sun-drying, however, produces
greater loss of cyanide. Sun-dying the peeled cut pieces of roots gave a HCN
concentration lower than 10 mg/100g and loss was more effective than oven
drying (Mahungu et al. 1987). Drying may be in the sun or over a fire. The
former is more common because it is simple and does not require fuelwood.
Boiling
Boiling the peeled roots did not effectively remove HCN.
Pounding the boiled roots into "pounded fufu" decreased the HCN
concentration by only 10 percent. Therefore, only cultivars containing low
cyanide are recommended for this method of preparation (Mahungu et al. 1987).
Processed leaves
Cyanide in pounded cassava leaves ("pondu" or
"sakasaka") remained high at 8.6 mg/100g although 95.8 percent of
total cyanide in leaves was removed through further processing into soup
(Mahungu et se. 1987).
Milling
The dried root pieces and fermented/dried pulp are milled
into flour by pounding in mortar or using hammer mills. Milling with hammer
mills, done at village level, may also reduce cyanide. The dried cassava roots
(both fermented and unfermented) are often mixed in a ratio of 2-3 parts
cassava with one part of sorghum, millet and/or maize and milled into a
composite flour. Mixing cassava with cereals increases food protein, and
enhances palatability by improving consistency.
Gari
Fresh roots are peeled and grated. The grated pulp is put in
sacks (Jute or polypropylene) and the sacks are placed under heavy stones or
pressed with a hydraulic lack between wooden platforms for 3-4 days to express
excess liquid from the pulp while it is fermenting. Fermentation imparts an
acidic taste to the final product. The dewatered and fermented lumps of pulp
are crumbled by hand and most of the fibrous matter is removed. The remaining
mass is sieved with traditional sieves (made of woven splinters of cane) or
iron or polyethylene mesh. After being sieved, the fine pulp is then roasted in
an iron pan or earthen pot over a fire. If the sieved pulp is too wet, it takes
longer to roast resulting in a finished lumpy product with dull colour. Palm
oil may be added to prevent the pulp from burning during roasting and to give a
light yellow colour to the gari. When palm oil is not added, a white gari is
produced. Palm oil contains substantial quantities of vitamin A, therefore,
yellow gari is 10-30 percent more nutritious and expensive than white gari. The
garification or conversion rate of fresh roots into gari is 15-20 %. This value
varies with cassava varieties, time of harvesting, age of plant and other
environmental factors. Gari is very popular in Nigeria and less so in Cameroon,
Benin, Togo, Ghana, Liberia, and Sierra Leone. In Brazil, this method is used
for the production of "farinha de madioca".
Peeling is done mainly by women and children. The peeled
roots are grated by women, using a simple traditional grater, but it is done by
men if a power driven grater is used. Pressing is done by women in the
traditional way but done by men when a hydraulic presser is used. The sieved
fermented pulp is roasted almost exclusively by women in a pan or pot on the
fire with fuelwood as the energy source.
Fermented and dried cassava pulp
"Lafun" in Nigeria, "cossettes" in Zaire
and Rwanda, "kanyanga. and "mapanga. in Malawi, and
"makopa" in Tanzania are various names for fermented and dried
cassava products. The processing method to ferment and dry cassava pulp is very
simple and does not require much labor. It is thus widely used for processing
high cyanide cassava varieties in many parts of Africa where water for soaking
is available. Whole or peeled roots are immersed in water for 3-4 days for
fermentation and softening the tissues. The fermenting roots are then removed
and broken into small crumbs, sun-dried on mats, racks, fiat rocks, cement
floors or roofs of houses. Drying the fermented roots takes 1-3 days, depending
on the prevailing weather. The dried crumbs are then milled into flour.
Wet pulp
The processing procedures for "wet pulp" and of
fermented and dried pulp production are similar except for the drying. The wet
pulp may be molded into balls, 3-5 cm diameter, put in boiling water and
stirred thoroughly to obtain a stiff Wet pulp of about 0.5-1.0 kg is packed in
a plastic or polypropylene bag and marketed in cities in Nigeria, Ghana and
Cameroon. Urban dwellers therefore do not need to buy fresh roots for processing
into wet pulp to prepare wet fufu.
Smoked cassava balls ("kumkum")
Cassava is processed into smoked cassava balls in the same
way as fermented and dried pulp is produced except that the fermented wet pulp
is pounded and molded into round balls of about 4-7 cm diameter. These balls
are then smoked and dried on a platform above the fire place in a special
structure hung above the hearth. The dark coating caused by smoke is cleaned
off and the cleaned balls are milled into flour before reconstitution into fufu
(Numfor end Ay 1987).
Chickwangue
"Chickwangue" is the most popular processed food
from cassava in Zaire. "Myondo" and "Bobolo" in Cameroon
belong to this "Chickwangue" group. Similar products are produced in
Congo, Central African Republic, Sudan, Gabon, and Angola.
Cassava roots are peeled, steeped in water for 3-5 days to
ferment and become soft. The fermented pulp is taken out and the flares are
removed from it. The pulp is then heaped on racks for further fermentation or
the heap is covered with leaves and pressed with heavy objects to drain off
excess liquid. The pulp is then ground on a stone or pounded in a mortar to
obtain a finer pulp. The fine pulp is wrapped in leaves of plantain or any
plant of the Zingiberaceae family and tied firmly with fibres from banana.
These are steamed in pots. Chickwangue is about 10 cm wide and 20 cm long.
Myondo has a diameter of 1.5-2.0 cm and a length of 15 cm to 20 cm. Bobolo has
a diameter of 2-4 cm and a length of 30-40 cm. The Gabon "Chickwangue"
is smaller in size than that of Zaire.
Starch
Cassava roots are peeled, washed and grated. The grated pulp
is steeped for 2-3 days in a large quantity of water, stirred and filtered
through a piece of cloth. The filtrate stands overnight and the supernatant is
then decanted. The starch sediments are air-dried under shade.
Dried cassava
The roots are peeled, sliced into small pieces and sun-dried
on racks or roofs for 4-5 days or sometimes up to 3 weeks, depending on the
weather and the size of pieces. Later, sun-dried pieces are milled into flour.
This processing system is very simple but the processed products contain
considerable amounts of cyanide. This method is widely used in many areas in
Africa, particularly where water supply for fermentation is seriously limited.
Traditional cassava processing does not require
sophisticated equipment. Processing cassava into gari requires equipment such
as grater, presser and fryer. The traditional cassava grater is made of a
flattened kerosine tin or iron sheet perforated with nails and fastened onto a
wooden board with handles. Grating is done by rubbing the peeled roots against
the rough perforated surface of the iron sheet which tears off the peeled
cassava root flesh into mash. In recent years, various attempts have been made
to improve graters. Graters which are belt-driven from a static 5 HP Lister
type engine have been developed and are being extensively used in Nigeria. Its
capacity to grate cassava is about one ton of fresh peeled roots per hour.
For draining excess liquid from the grated pulp the sacks
containing the grated pulpy mass are slowly pressed down using a 30-ton
hydraulic jack press with wooden platforms, before sieving and roasting into
gari. Stones are used in traditional processing to press out the excess
moisture from the grated pulp. Tied wooden frames are used for this purpose in
places where stones are not available. Pans made from iron or earthen pots are
used for roasting the fermented pulp. Fuelwood is the mad or source of energy
for boiling, roasting, steaming and frying. Fuelwood may not be easily and
cheaply obtained in the future because of rapid deforestation.
Slight changes in the equipment used in processing can help
to save fuel and lessen the discomfort, health hazard, and drudgery for the
operating women. The economic success of any future commercial development of
cassava processing would depend upon the adaptability of each processing stage
to mechanization. However, the first step to take for improvement of cassava
technologies should be to improve or modify the simple processing equipment or
systems presently used, rather than to change entirely to new, sophisticated,
and expensive equipment.
Processing, particularly drying and roasting, increases
shelf life of cassava products. Good storage depends on the moisture content of
the products and temperature and relative humidity of the storage environment.
The moisture content of gari for safe storage is belong 12.7%. When temperature
and relative humidity are above 27°C and 70% respectively, gari goes bad
(Igbeka 1987). The type of bag used for packing also affects shelf life
depending on the ability of the material to maintain safe product moisture
levels.
Jute and hessian bags are recommended in dry cool
environments because they allow good ventilation (Igbeka 1987). When gari,
dried pulp and flour are well dried and properly packed, they can be stored
without loss of quality for over one year. Dried cassava balls ("kumkum")
can be stored for up to 2 years (Numfor end Ay 1987). "Chickwangue",
"Myondo" and "Bobolo" can be preserved for up to 1 week but
they can be kept for several more days when recooked.
Cassava shoots of 30 cm length (measured from the apex) are
harvested from the plants. The hard petioles are removed and the blades and
young petioles are pounded with a pestle in a mortar. A variation of this
process involves blanching the leaves before pounding. The resulting pulp is
then boded for about 30-60 minutes. In some countries, the first boiled water
is decanted and replaced. Pepper, palm-oil and other aromatic ingredients are
added. The mixture is then boiled for 30 minutes (Numfor and Ay 1987). Unlike
the roots that are essentially carbohydrate, cassava leaves are a good source
of protein and vitamins which can provide a valuable supplement to
predominantly starchy diets. Cassava leaves are rich in protein, calcium, iron
and vitamins, comparing favorably with other green vegetables generally
regarded as good protein sources. The amino acid composition of cassava leaves
shows that, except for methionine, the essential amino acid values in cassava
exceed those of the FAO reference protein (Lancaster and Brooks 1983).
The total essential amino acid content for cassava leaf
protein is similar to that found in hen's egg and is greater than that in oat
and rice grain, soybean seed, and spinach leaf (Yeoh and Chew 1976). While the
vitamin content of the leaves is high, the processing techniques for preparing
the leaves for consumption can lead to huge losses. For example, the prolonged
boiling involved in making African soups or stews, results in considerable loss
of vitamin C.
Cassava leaves form a significant part of the diets in many
countries in Africa. They are used as one of the preferred vegetables in most
cassava growing countries, particularly in Zaire, Congo, Gabon, Central African
Republic, Angola, Sierra Leone, and Liberia. The cassava leaves prepared as
vegetable are called "sakasaka" or "pondu" in Zaire, Congo,
Central African Republic and Sudan, "Kizaka" in Angola,
"Mathapa" in Mozambique, "Chigwada" in Malawi,
"Chombo" or "Ngwada" in Zambia, "Gweri" in Cameroon,
"Kisanby" in Tanzania, "Cassada leaves" in Sierra Leone,
"Banankou boulou nan" in Mali, "Mafe haako bantare" in
Guinea, and "Isombe" in Rwanda. They are mostly served as a sauce
which is eaten with chickwangue, fufu, and boiled cassava.
Utilization in this paper includes cooking or preparation,
and consumption. Cooking cassava consists of boiling, steaming, roasting and
pounding. The peeled fresh cassava roots are eaten raw or eaten boiled and
roasted. The fresh roots are boiled and pounded to obtain "pounded
fufu". This is most popular in Ghana, and to some extent, in Nigeria and
Cameroon. The processed cassava, either in the form of flour, wet pulp or gari
is cooked and eaten in three main food forms: "fufu", "eba"
and "chickwangue". The "fufu" group includes
"amala" in Nigeria, "fufu" in Zaire, Congo, Cameroon and
Gabon, "ugali" and "kowon" in Uganda and Tanzania,
"nchima" in Mozambique, "nsima" in Malawi,
"ubugali" in Rwanda, and "funge" in Angola.
Gari can be eaten dry or it may be soaked in cold water to
which sugar is added. "Eba" is a very popular food in Nigeria and is
gaining popularity in Cameroon, Benin, Ghana, Liberia and Sierra Leone because
of its fast and easy reconstitution into a convenient food.
"Chickwangue" is a very stiff paste or porridge
and is much stiffer than "fufu" and "eba". The size, shape
and texture of the "chickwangue" food group vary among countries.
"Myondo" and "bobolo" in Cameroon are essentially the same
as "chickwangue" in preparation although shapes and sizes are
different. "Chickwangue" and its analogues are produced from more
hygienic procedures and contain less cyanide but they require much more labor
for processing and preparation.
People in Zaire call maniac "all sufficient"
because "we get bread from the root and meat from the leaves".
Cassava root based foods are all consumed with soups or
stews. The soup is essential in the food system in Africa without which most
foods cannot be eaten. Soup made of cassava leaves is often eaten with cassava
root based foods. Therefore, the cassava root based foods which are essentially
carbohydrate are supplemented for protein when consumed with protein rich soups
or stews.
The major future market for increased cassava production is
as livestock feed. Cassava has long been recognized by researchers in Africa as
an appropriate animal feed and it has been used as an important and cheap feed
in many European countries. Both roots and leaves are usable as food to
livestock. Cassava is one of the most drought tolerant crops and can be
successfully grown on marginal soils, giving reasonable yields where many other
crops cannot do well. It is estimated that approximately 4 million tonnes of
cassava peeling-useful as livestock feed-are annually produced as a by-product
in Nigeria alone during processing of cassava roots. Therefore, cassava offers
tremendous potentials as a cheap source of food energy for animals, provided it
is well balanced with other nutrients. There is a great deal of current
interest in supplementing feeding of animals with cassava in Africa.
The future of cassava depends very much upon development of
improved processing technologies and of improved products that can meet the
changing needs of urban people, and, on its suitability for alternative uses
such as animal feeds. Also important is the overall ratings of different
products to meet the expectations of producers, transporters and consumers
(table 1). Whereas the future is bright, more quantitative information on postharvest
aspects of cassava culture in tropical Africa will help scientists orient their
efforts to satisfy the many needs of both rural and urban dwellers.
Table 1: Subjective ratings of traditionally processed
Cassava products In Africa based on selected features
Feature (parameter)
|
Boiled cassava
|
Fufu
|
Gari
|
Chickwangue
|
||
fermented
|
unfermented
|
|||||
Shelf life
|
1
|
5
|
5
|
4
|
3
|
|
Transportability
|
1
|
5
|
5
|
5
|
4
|
|
HCN content
|
2
|
5
|
3
|
4
|
5
|
|
Ease of:
|
||||||
Processing
|
5
|
5
|
5
|
2
|
1
|
|
Preparation
|
4
|
4
|
4
|
5
|
2
|
|
Utilization
|
4
|
4
|
4
|
5
|
5
|
|
Processing hygiene 5
|
1
|
3
|
5
|
5
|
||
Total (ratings)
|
22
|
29
|
29
|
30
|
25
|
|
Note:
Subjective ratings for desirability based on scale 1-5, 1 = lowest and 5 =
highest.
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