Cassava is one of the most important tropical rootcrops, also known as manioc, sagu, yuca (Spanish),and tapioca.Cassava is the fastest growing crop of the 20th century,yet little has entered world trade.However, export as a dried cattle feed is now increasingto Europe.Cassava is a true cultigen, a crop unknown in the wildstate.
It originated in West and southern Mexico part ofGuatemala and northeastern Brazil.There is evidence that it was grown 5000 years ago inColumbia, 4000 years ago in Peru, and 2000 yearsago in Mexico.It was brought to Africa by the Portuguese and wasencouraged as a famine food and reserve duringlocust attacks.Cassava is the most important root crop of the lowlandtropics.It is the fourth most efficient crop plant:Rice > sugar > maize > cassava.
UsesAn important food and carbohydrate source(65% for human consumption, 20% for animal feed,15% for starch).Eaten raw after peeling.Sliced and dried, stored for several months.Paste (fufu) produced by pounding and cutting upboiled roots.Farinha, grated dried roots (Brazilian sawdust).
Sundried strips ground into flour.Latex and extracted juice may be concentrated byboiling to produce “cassureep”—the ingredient ofWest Indian pepper pot.Meal is fermented in West Africa to form garri.Leaves eaten as potherb.Tuber fermented with Rhizopus or Penicillium toproduce a sweet banana-like product called tepi.Alcohol production: A beer is made from the juice ofbitter cassava.
Starch, produced by grating or grinding washed peeledtubers.Washing out starch with repeated changes of water andthen gently heating washed starch causes it toagglutinate into round pellets called tapioca.The starch is used for food, manufacture of adhesives,cosmetics, sizing textiles, laundering, paper making.Note: it does not contain gluten so does not rise to makeordinary bread but is used for a type of biscuit thatmelts in the mouth.Tapioca is used to make puddings and confectionery:produced from the fine starch which settles whenjuice is squeezed.
Bitter and Sweet: two classes of cassavaThe bitter cassava contains a bitter cyanogenicglycoside (linamarin) that produces a toxic substance(hydrocyanic acid, HCN).HCN is widely distributed throughout tubers and corebut can be destroyed by boiling, roasting, expression,or fermentation.HCN (cyanic acid or prussic acid) is poisonous.The glycoside can be removed (detoxified) by juiceextraction, heating, fermentation, drying, or acombination of these processing treatments.
The cyanogenic glucoside is found in the centralportion and outer layers of the tuber.These bitter types generally have dark leaves and stemsare often reddish.The bitter types are planted for starch production,alcohol, acetone.
Sweet cassava (M. dulcis) contains a low percentage ofthe toxin and is confined to phelloderm (cortex).Probably not a separate species.Leaves and stems are light green.Sweet cassava can be consumed as a starchy vegetablebut is still detoxified.It is interesting to speculate how primitive peoplelearned how to cultivate and detoxify a poisonousplant, probably done to eliminate bitter substances.
Cassava can also be divided into two types:Short season: matures in 6 months and must beharvested 9-11 months.Long season: matures in 1 year and harvestedat 3 to 4 years of age.The long season types tend to be the bitter cassava.
Continent1000tonnes Chief countriesWorld 178,868Africa 95,239 Nigeria (33,854), Congo (15,436),Ghana (8,512)North America 1,068 Haiti (332), Cuba (300), CostaRica (159)South America 32,469 Brazil (24,088), Paraguay(3,854), Colombia (1,982)Asia 49,914 Thailand (18,283), Indonesia(16,158), India (7,000)Oceania 178 Papua New Guinea (120), Fiji(33), Micronesia (12)Cassava: 2001 World Production
MorphologyPlant contains 5 to 10 tuberous roots whichare induced by short photoperiod.Leaves are palmate. Plant is cross pollinated.EcologyA lowland tropical crop which cannot withstand cold orfrost.However it can stand prolonged drought and survivesby shedding leaves.Can be grown on sandy, poor soils.Grows best with 150 inches of rainfall, Yield is sensitiveto drought or standing water.It requires short days to tuberize.
PropagationVegetative propagation by stem cuttings(8 inches long).HarvestPlant is harvested at 10 to 18 months to produce3 to 11 tons roots/acre.Tender leaves are edible and good for livestockfeed.
DiseasesAlthough susceptible to some viruses, generally veryresistant to pests.Some problems with wild pig, rats, hippopotami!YieldAverage world yield is about 4 t/acre (10 t/ha) and goodcommercial yield is 30–50 t/acre but some thinkpotential is 40–90 t/acre.Thus crop has a tremendous future.
Cassava (tapioca)A South American root cropconsumed by about 600 millionpeople in the tropicsFourth largest source of caloriesamong all crops grown in thetropicsCan be grown on poor soil,withstands moderate droughtconditions, and requires little laborinput.The edible root can remain underground up to 3 years providingfood securityVegetatively propagated (stems)
To remove cyanogens cassava may be;fried, dried, soaked, washed, ground,fermented or processed by somecombination of these procedures.
The cassava flour, farofa,was mixed with water toform a batter.This is baked on the griddleto form a large, rathertough, flat bread.Like a pancake, when oneside is roasted, the flatbread is flipped to finishcooking the top side.This flat bread and theroasted farofa form thedietary staple for theseCaribe people.
Although the same griddle is used, here the shredded,dried, and ground cassava is being heated and lightlyroasted to produce a flour, farofa.
CASSAVA BASED INDUSTRIES• Starch and sago production from cassava :an increasingly important agro-industry• Cassava starch : major raw material infood, textile and pharmaceutical industries
Flow Chart for small scale production of cassava starchCassava Fresh roots (1 tonne)Mechanical gratingSievingDryingStarch (180 – 200 kg)Mechanical peeling and peelingSedimentationPeels (20-50 kg)Starch residuePulp waste (600 kg)Waste water (12 – 20 m3)Solid (18 kg)HCN (342 – 570 mg)Water (3-5 m3)Water (3-5 m3)
Waste materials from cassava processing(e.g. starch) are divided into four categories:
Need for cassava residue management• Cassava tubers contain about 20-30% starchwhich is distributed in the sellulose matrix• Tubers also contain cyanoglucosides presentas linamarin and lautostralin• Extraction of starch from cassava consists ofwashing of tubers, mechanical peeling,rasping, grinding, sieving, regrinding, sievingand dewatering
• The recovery of starch from tubers is notcomplete some amount starch, along withfibrous wastes is discharged as residues• The wastewater coming out of the settlingtanks contain unextracted starch, cellulose,carbohydrates, nitrogenous compounds andcyanoglucosidesNeed for cassava residue management
Wastewaters and residues fromcassava processing industries• Waste water : 16-20 m3/tonne of starch/sagoproduced• Peelings : 50-60 kg/tonne of tubers peeled• Solid residues : 55-70 kg/tonne of tubersprocessed
Characteristics of the waste water generated• BOD of effluents : 3400 – 6018 mg/l• COD of the effluents : 3870 – 6670 mg/l• Cyanide concentration : 10 – 66 mg/l• Free sugars : 640 – 2075 mg/l• Total solids : 4000 – 6600 mg/l• Total Nitrogen : 65 – 74 mg/l
Residues management• Citric acid from cassava residues• The low cost residues compared to wheat branmake the process economic• A solid-state fermentation residues usingAspergillus niger• Maximum yield of citric acid recovered whenthe residues were treated with α-amylase andamyloglucosidase prior to fermentation