Starch can be obtained from cassava, sorghum, maize, sago and
potatoes. But this project focused on the production of starch from
cassava. Starch can be cross-linked a product that will be suitable for
noodle, salad cream custard making. Normally it is easier to make this
product from corn and potatoe starch, but cassava which is readily
available and cheap can be employed to meet the demand of the people.
Other synthetic starch produced from cassava includes; carboxymethyl
starch (which is produced when one of the hydrogen atom of the starch is
replaced by carboxymethyl groups, starch acetate, starch xanthate and
hydroxyl alkyl starch. These are used as thickening agents, sterbilizer
and emulsifier in products. Cassava starch when treated with phosphate
are used in frozen products when they are defrosted to prevent them from
dripping. This study investigated the production of starch from cassava
and preparation of cross-link derivatives.
1.1 MEANING AND COMPOSITION OF STARCH
Starch is one of the most abundant substances in nature, a renewable
and almost unlimited resource with a chemical formula (C6H10O5)n. It is a
polysaccharide, a chain of many glucose molecules. It is the most
carbohydrate stored in roots and seeds of plants. There are two types
of glucose chain in starch which are the amylose and amyloeptin.
1.2.1 COMPLEX BRANCH CHAIN (AMILOPECTIN)
Amylopectins are made up of several million glucose units. It forms
branched structures with about 30 glucose units in a chain between
branches. This makes the molecule somewhat stripped in appearance with
the knotted branch point in all rows and smooth chain separating them.
These molecules are so large that this stripped appearance show up under
a light microscope forming what appears to be ‘growth rings’ in the
1.1.2 AMYLOSE CHAIN
Amylose chain tend to curl up into tielice (spirals) with the
hydrophobic part inside. This allows them to trap oil and fat inside the
helix as well as aroma molecules.
1.1.3 STARCH GELATINIZATION
WHAT IS GELATINIZATION?
This is a colloidal structure that is, it has interparticle bonds
(usually hydrogen bonds) or lower potential energy than starch in true
Starch gelatinization is a process that breaks down the
intermolecular bonds of starch molecules in the presence of water and
heat, allowing the hydrogen bonding and oxygen sites (the hydroxyl) to
engage more water. This irreversibly dissolves in starch granules.
Penetration of water increases randomness in the general granule
structure and decreases the number and size of crystalline regions .
Hence crystalline region do not allow water entry. Heat causes such
region to be diffused so that the chain begin to separate into an
amorphous form. This process is used in cooking to make roux sauce,
pastery custard or popcorn.
1.1.4 GELATINIZATION PROCESS
Gelatinization is also known as the thickening of a liquid, the
starch or flour granules absorb the liquid. When heated, the
grains/granules swell and burst releasing the starch into liquid
1.1.5 STARCH RETRO GRADATION
This is a reaction that takes place in gelatinized starch when the
amylose and amylopectin chain realign themselves causing the liquid to
When native starch is heated and dissolves in water, the crystalline
structure of amylose and amylopectic molecules are lost and they hydrate
to form a viscous solution. If the viscous solution is cooled at lower
temperature for long enough period, the linear molecule amylose and the
lower part of amylopectin molecule retrograde and rearrange themselves
again to a more crystalline structure. Hence, retrogradation can expel
water from the polymer network. This is a process known as SYNERESIS. A
small amount of water can be seen on top of the gel. Retrogradation is
directly related to stalling or aging of bread 
1.2.0 SOURCES OF STARCH
1.2.1 CASSAVA STARCH (Manihot esculanta)
Cassava starch has many remarkable characteristics including high
paste viscosity, high paste clarity and high freeze-thaw stability which
are advantageous to many industries.
Several workers have reported the production of starch and its cross
linked derivation . This report described the principle of using
cassava starch to produce some vital products because cassava are
readily available and cheap. Hence, they are available at low cost .
Over the years, the ability to produce some synthetic starch from
cassava has been reported in literature and this includes crosslinked
starch, carboxyl methyl starch, starch acetate, starch xanthate etc.
1.2.2 ORIGIN, TYPES AND COMPOSITION OF CASSAVA STARCH
Cassava is a staple crop that is particularly important in South
America, America and African countries. It is a perennial shrub that
grows to approximately 2 meters tall and has the ability to grow on a
marginal land in low-nutrient soil where other crops do not grow well.
It is also fairly drought tolerant. It is grown for its enlarged starch
rich tuberous roots.
Although cassava is a staple crop, it is poisonous in its raw state
as the plant contains cyanogenic glucoside. These glucosides are
converted to HCN by enzymes called Linamarase which is present in
cassava and acts on the glucosides when the plant cell are ruptured
during the consumption stage.
The amount of cyanide contained in cassava depends on the variety and stage of the cassava. There are two types of cassava .
Bitter cassava (Manihot utilissiana)
Sweet Cassava (Manihot patinate)
The bitter cassava has a higher level of cyanide than the sweet
cassava. The poison tends to be more concentrated in the skin of the
root and can be readily removed during processing resulting in a safe
and versatile product.
1.2.3 ADVANTAGES OF CASSAVA STARCH
- High level of purity
- Excellent thickening characteristics
- A neutral taste
- Desirble textural characteristics
- A relatively cheap source of raw material containing a high
concentration of starch that can equal or surpass the properties offered
by other starches.
Appropriate composition of the cassava tube 
TABLE 1.0 APPROXIMATE COMPOSITION OF THE CASSAVA TUBER
20 – 30%
2 – 3%
95 – 80%
1 – 1.5%
Nigeria is the world’s largest producer of cassava (F.A.O of the
United Nations). However based on the statistics from F.A.O of the
United Nation, Thiland is the largest exporting country of dried cassava
with total of 77% of world export in 2005.
Fig 2.0 TABLE
TONNES OF CASSAVA GROWN
1.3.0 TYPES OF STARCH
1.3.1 DEFINITION AND REASONS FOR STARCH MODIFICATION
This native starch that has been changed in its physical and chemical
properties. This can be used for other industrial application through
series of techniques, chemical, physical and enzymatic modification.
Modification may involve altering the form of granules or changing
the shape and amylopectin molecules. It is carried out on the native
starch to confer it with properties needed for specific uses. Which are;
- To modify looking characteristics (gelatinization).
- To reduce reterogradation.
- To reduce paste’s tendency to gelatinize.