CHAPTER ONE

The African locust bean tree, (Parkia biglobosa) is a deciduous perennial dicotyledon tree of the

family Fabaceae, in the genus Parkia. It is commonly called carob because of the a valuable

product called carob derived from it. It is found in a wide variety of environment in West Africa.

It Originates In 5°N and 15°N. The tree grows from sea level up to an altitude of 1350m and

prefer regions where the mean annual temperature range is about 26°C28°C (Sina et al., 2002).

African locust bean tree grows in areas corresponding to a wide range of annual rainfall with a

marked dry season of 57 months. It grows where annual rainfall range is between 2200mm and

4500mm. African locust bean tree can withstand arid zones with less than 400mm rainfall

(Orwa et al., 2009).

The primary product of the African locust bean tree is its sweet pulp and valuable

fermentescible seeds. The African locust bean tree are attractive savanna trees with spreading

crowns and clusters of spherical bright red flowers dangling on it like Christmas decoration on a

Christmas tree The fruit of the African locust bean is a large pod that can grow to be foot long

and wider than the human thumb, it appears in bunches among the spherical bright red

flowers.

The pod is a linear, glabrous and smooth, indehiscent pod that becomes brown at maturity.

Inside the mature pod, seeds are surrounded by a quantitatively important mucilanginous pulp

which is separated from the seeds when they are collected. Almost all parts of the African

locust bean tree is important. The seeds, pods, fruit pulp and leaves are edible and are used as

cooking or drinking ingredients. Some other parts of the tree like the bark is used for nonfood
uses. The wood is used in light construction, poles, mortar, and many kinds of furniture and

untensils. It is valuable firewood and provides pulp to make paper. The bark has traditional uses

in ethnomedicine. A root decoction is reported to treat coccidiosis in poultry. Green pods are

used as fish poison to catch fish in rivers. African locust bean trees are used as ornamental.

They are useful soil improvers and their leaves provide green manure (Sina et al., 2002)

Fig. 1: African locust bean tree(source: en.wikipedia.org)

The African locust bean tree is valued for its fermentescible seeds. The seeds are globoseovoid,

515mm, smooth and glossy back in colour. There are about 28006700 seeds/kg. The seeds are

hardcoated and can remain viable up to 8years (Orwa et al., 2009; NRC, 2006; Sina et al., 2002;

Hopkins, 1983).

The seeds are fermented to prepare a condiment that is called “dawadawa” or “sumbala”.
In Nigeria it is mostly known as “iru”. The condiment is used for sauce and soup seasoning is

one of most important commercial products traded in West Africa. The mealy pulp is

traditionally consumed as fresh food by local African population (Felker., 1981). The seed is

high in protein, fat, and vitamins (Obizoba and Atu, 1993) and it is rich in tannin and mineral

contents (Obizoba and Atu, 1993, Enujiugha and Ayodele-Oni, 2003).

The pods are used for the production of locust bean gum. This gum is used around the world as

a thickening agent and stabiliser in many food products such as mayonnaise and within the

textile industry as a print thickener (Glasson Grain Ltd , 2006).

The fermented bean pulp waste contained protein 11.75 %; ash, 15.86 %; crude fibre, 21.55 %;

starch, 32.14 %; dry matter, 93.5% and moisture, 6.5 % while the unfermented pulp contained

protein 10.13 %; ash content, 14.14%; crude fibre 22.63%; starch, 28.20%; dry matter, 92.5%

and moisture, 7.5%. The unfermented locust pulp waste exhibited a stronger binding effect

than corn starch after 12 weeks storage (Akegbejo-Samsons et al, 2004).

Figure 2: Opened African locust bean pod

Figure 3: African locust bean pod

1.3 Statement of Problem

The production of fermented locust bean from harvested African locust bean pod with basic

utensils is a lucrative income earning activity in the rural areas in Nigeria due to its condiment

benefit. However the traditional method of production is a difficult, tiring, unhygienic, tedious

and time consuming activity. The use of basic equipment and traditional method for the

production of African locust bean leads to low production. Looking at the various processes

involved in the production processes like dehulling and the fermentation of the seeds it is noticed

that the method used is tedious, inefficient, and time consuming. Hence there is a need for the

production of a dehulling machine that will be efficient, hygenic and less tedious than the

traditional dehulling method.

Aim and Objective

Aim:
The aim of this study is to modify and evaluate the hygenic and less tedious African locust bean

dehulling machine.

Objective;

i) To modify and fabricate an efficient and less tedious Africican locust bean dehulling

machine.

ii) To test the African locust bean dehulling machine for its capacity and efficiency.

iii) To evaluate the African locust bean dehulling machine.

Justification

The African locust bean is important for its nutritional value as a source of condiment in

meals. The processing activities involved in the production African locust bean is tedious,

labourintensive, and time consuming. The quality and quantity of the locust bean is also

affected because of the the use of rudimentary equipment for dehulling. Putting the quality of

the locust bean and the human condition into consideration the production of a efficient

locust bean dehulling machine would produce a better dehulled locust bean and it would

reduce drudgery and operation time compared to the traditional method of dehulling.
 CHAPTER 2
The African locust bean (Parkia biglobosa) is a leguminous tree crop of the family Mimosaceae.

It grows in an uncultivated state and is well distributed throughout the tropical regions,

particularly the savannah areas. Some of the known varieties are Parkia bicolor, Parkia

clappertonianna, Parkia fillicoida and Parkia biglobosa with Parkia clappertonianna being one of

the species commonly found in Nigeria and referred to as African locust bean.

The fruit of the locust bean tree is of high economic importance: its edible seed is used as a

food condiment after fermentation; the yellow part of the fruit (pulp) is sweet to taste and is

processed into a valuable carbohydrate food known as sikomu and dodowa among the Yoruba

and Hausa people of Nigeria, respectively. The seeds of the plant are embedded in the pulp and

covered by the pod. The seeds are processed into a food condiment commonly called iru by the

Yorubas and daudawa by the Hausas in Nigeria. Iru is used as a food seasoning and as an

ingredient in preparing household stews.

The pods of Parkia biglobosa and Parkia clappertonianna and other savannah species are

suitable for paper and pulp production when mixed with some imported pines. The fruits are

used in the preparation of protein foods. Locust bean products are a source of income

generation among women and children in the rural areas. (Olaniyan et al)

Description of African Locust Bean

African locust bean is a medium-sized legume tree that reaches 20-30 m high. It has a dense,

widely spreading umbrella-shaped crown and a cylindrical trunk that can reach 130 cm in

diameter, often branching low.

in colour. It exudes an amber gum when cut. The leaves are alternate and bipinnately compound,

30-40 cm long, bearing up to 17 pairs of pinnae. Its beanets are numerous (13-60/pinna),

subopposite, 8-30 mm long x 1.5-10 mm wide, rounded or obtuse at apex, glabrous but slightly

ciliate near apex. The inflorescence is held on a long (10-35 cm) drooping peduncle. It is

biglobose, showy, red in colour, and it looks like an electric bulb. The flowerhead is 4.5-7 cm

long x 3.5-6 cm broad and it has a strong pungent smell.

The many flowers are either bisexual, sterile or nectar-bearing. Bisexual flowers are

pentamerous, 1-1.4 cm long, and corolla lobes are fused at their base. Sterile flowers are shorter

and are borne near the peduncle, in the upper part of the inflorescence, and their nectar is

attractive to bats that pollinate the flowers. The flowers begin to open at dusk, close and wilt at

dawn, lasting only a single night. The fruit is a linear, glabrous and smooth, indehiscent pod that

becomes brown at maturity. It is 12-30 (-35) cm long x 1.5-2.5 cm wide and contains up to

23 seeds embedded in a yellowish mealy pulp. The seeds are globose-ovoid, 5-15 mm, smooth

and glossy dark in colour. There are about 2800-6700 seeds/kg. The seeds are hardcoated and

can remain viable up to 8 years (Orwa et al., 2009; NRC, 2006; Sina et al., 2002; Hopkins, 1983)

Geographical Distribution

African locust bean is native to tropical Africa. It occurs in open savannah woodlands, in bush

fallow and wooded farmland where cultivation is semi-permanent, in areas ranging from tropical

forests with high and well-distributed rainfall, to arid zones (Orwa et al., 2009; Sina et al.,

2002). It was introduced as a food plant into the West Indies and is now naturalized in Haiti. It

has also been introduced into Sao Tomé by the Portuguese (Hopkins, 1983).
African locust bean is found between 5°N and 15°N, from the Atlantic coast in Senegal to

southern Sudan and northern Uganda. It grows from sea level up to an altitude of 1350 m and

prefers regions where mean annual temperature range is about 26-28°C (Sina et al., 2002).

African locust bean grows in areas corresponding to a wide range of annual rainfall with a

marked dry season of 5-7 months.

In Guinea Bissau, Sierra Leone and Guinea, it grows where average annual rainfall range is

between 2200 and 4500 mm. African locust bean can withstand arid zones with less than 400

mm rainfall (Orwa et al., 2009). It is very tolerant of poor soil conditions though it prefers deep

well-drained and fertile soils (FAO, 2017; Sina et al., 2002). It can grow on rocky slopes, stony

ridges or sandstone hills as well as on shallow lateritic soils (Sina et al., 2002). African locust

bean trees are deeply taprooted and have the ability to restrict transpiration, which makes them

able to withstand drought conditions. African locust bean is a fire-resistant heliophyte (FAO,

2017; Orwa et al., 2009; Sina et al., 2002). In West Africa, the fermented seeds of African locust

bean are commercially traded within the region and their use has been described since the 14th

century. In northern Nigeria the annual production of African locust bean seeds is estimated at

200,000 t (Sina et al., 2002). African locust bean is native to Benin, Burkina, Cameroon, Central

African Repu, Chad, Gambia, Ghana, Guinea, Guinea-Bissau, Gulf of Guinea Is., Ivory Coast,

Mali, Niger, Nigeria, Senegal, Sierra Leone, Sudan, Togo.

Geographical distribution of African

locust bean in Africa(source: amoako

2012)
 Overview of African locust beans in Nigeria

 The fruit of the locust bean tree is of high economic importance: its edible seed is

used as a food condiment after fermentation; the yellow part of the fruit (pulp) is

sweet to taste and is processed into a valuable carbohydrate food known as sikomu

and dodowa among the Yoruba and Hausa people of Nigeria, respectively. The seeds

of the plant are embedded in the pulp and covered by the pod. The seeds are

processed into a food condiment commonly called iru by the Yorubas and daudawa

by the Hausas in Nigeria. Iru is used as a food seasoning and as an ingredient in

preparing household stews. The pods of Parkia biglobosa and Parkia clappertonianna

and other savannah species are suitable for paper and pulp production when mixed

with some imported pines. The fruits are used in the preparation of protein foods.

Locust bean products are a source of income generation among women and children

in the rural areas.

Geographical distribution of African locust bean in Nigeria

 The tree are found available throughout the Savannah lands of North-Central-Nigeria covering

Benue, Kaduna, Kwara, Kogi, Nasarawa and Plateau States. It was particularly most common on

farmlands. This finding conforms to the assertion by Dalziel (1963) and Keay (1989), which

reported that the tree extends from Senegal to Sudan and its habitat is in the Savannah land as it
is characteristic of the transition areas from the Sahelian to the Sudananian eco-zones locally on

farmlands.

Economical importance of African Locust bean

Domestic Use

The African locust bean tree is a traditional food plant and has immense economic and social

value to the communities in which it grows. All parts of the tree have one or more uses. The

domestic uses of shea tree and its products include:

● Source of food: African locust bean is a multipurpose tree that is as highly

valued. It’s Fermented seeds (‘soumbala’, ‘dawadawa’, ‘netetu’) serve

primarily as a condiment for seasoning sauces and soups. Roasted seeds are

used as a coffee substitute known as ‘Sudan coffee’ or ‘café nègre’. Ground

seeds are mixed with Moringa oleifera Lam. leaves to prepare a sauce, and are

also used to make doughnuts. The mealy pulp from the fruits is eaten or is

mixed with water to make a sweet and refreshing drink rich in carbohydrates.

The leaves are sometimes eaten as a vegetable, usually after boiling and then

mixed with other foods such as cereal flour (Sina, S. & Traoré, S.A., 2002).

● Treatment of Leather: The bark is rich in tannins and may be used for tanning

hides, but the resulting leather is often of moderate quality especially with

regard to colour, which is often reddish, uneven, and darkens when exposed
 to light. Boiled pods are also used to dye pottery black; the ash is applied as a

mordant (Sina, S. & Traoré, S.A., 2002).

● Ingredient in Traditional medicine: In West Africa the bark, roots, leaves,

flowers, fruits and seeds are commonly used in traditional medicine to treat a

wide diversity of complaints, both internally and externally, sometimes in

combination with other medicinal plants. The bark is most important for

medicinal uses, followed by the leaves. Medicinal applications include the

treatment of parasitic infections, circulatory system disorders, such as arterial

hypertension, and disorders of the respiratory system, digestive system and

skin. In veterinary medicine, a root decoction is used to treat coccidiosis in

poultry (Sina, S. & Traoré, S.A., 2002).

● Agricultural Uses: The fruit pulp is used as an ingredient of feed for pigs and

dogs. The seeds are added to poultry feed after treatment to remove their

antinutritional properties. The leaves are a useful, but not very palatable

fodder. They should be mixed with other feed because the concentrations of

phosphorus, magnesium and sodium are too low. African locust bean has a

reputation for soil improvement; its leaves are applied as green manure. It is

also important in apiculture, being a good source of nectar and suitable for

the placement of hives. It is also used in fishery, the Green pods are crushed
 and added to rivers to kill fish. The nutritional value of the fish is not adversely

affected so long as they are cooked or dried (Sina, S. & Traoré, S.A., 2002).

● Used in construction industry: The wood is suitable for making kitchen

implements, such as mortars, pestles and bowls, and handles of hoes and

hacks, and it is occasionally also used for house building, mainly for indoor

construction. It is also used as firewood, and may be suitable for paper

production. The fibres of pods (husks) and roots are used as sponges, strings of musical

instruments and for the production of small baskets. Burnt pod husks are used

in Senegal as an adulterant of, or additive to, tobacco (adding pungency) (Sina,

S. & Traoré, S.A., 2002).

● Source of income and employment: They are typically gathered by locals and

processed by locals and provide an important source of income and

employment for the people of the west African savannah.

● Other uses: It may serve as a decorative avenue tree. It is also an excellent fuel

wood and can be made into charcoal.

Production process of African locust bean

The traditional method of processing locust beans is usually a reference point from which

mechanical devices are made. Adewumi and Olalusi (1995) reported that the processing of locust

beans is mainly done locally by women in Africa. Processing of locust beans involves shelling of
matured pods, boiling, dehulling, separation of the hull from the beans and fermentation into

various forms of condiments. Women are the key player in locust bean processing. Traditional

Boiling is carried out for cooking the beans with the hull for 8 to 10 h using firewood as fuel

(Oyewole and Odunfa 1990). This initial stage of processing makes the process time consuming

with the seeds usually degraded. Locust bean is dehulled by mashing the boiled seeds with bare

feet near the riverside or using pestle in a mortar (Adewumi and Olalusi 1995). If a mortar is

used some clean sand may be added to ease the removal of the hull. The process of ridding the

edible seeds from the hull in locust bean processing is implied as separation. The separation

process is carried out locally using the principle of buoyancy or by using a screen, most often a

perforated calabash referred to by the Yorubas as ‘Ajere’. The undehulled beans are sorted out

by washing in water. Proximity to water supply is required and for this reason the process is

carried out in a stream. (olaoye, 2010)

Production of Locust Bean Products

The processes involved in the production of Iru condiment which represents one of the major

locust bean products right from the raw substrate are highlighted and as shown in flowchart Fig.

8. Modern processing techniques are required to improve on the traditional methods of

processing and fermentation of the seeds. Appropriate processing conditions need to be

developed to subject the crop to a form that the produce can be stored with a relatively long

storage life. These conditions can also help to eliminate pests and microorganisms that cause

spoilage. The processing stages are identified as primary crop processing and secondary food

processing. It has been observed that each stage needs appropriate machine intervention for

effective product development. The primary crop processing involves drying, decorticating and

depulping of locust bean seeds from the pod. These processes are to enhance the seed quality

conditions and to subject it to a condition that will improve further food processing conditions.

The processes are to condition the seed into an intermediate state that will encourage long

storage life of the finished crop product. The secondary food processing stage is to convert the

seed from the intermediate finished product into the desired cube. This stage requires

fermentation and cubing operations. (olaoye, 2010)

processing are Cabinet Dryer, Decorticating and Depulping Machines. The drying process is to

prepare and subject the moisture content of crop to an optimum value prior decorticating process.

Fig 2.1: Harvested Locust Bean Pod under Fig 2.1 Drying of Locust Bean Pod

storage Condition Prior Decorticating under the Sun Prior Decorticating

Locust Procedure Bean for depulpping at the River

Fig 2.5: A Traditional Tool for Depulpping Fig 2.6: Clean Locust Seeds

Locust Bean Seed

(All pictures gotten from olaoye, 2010)

and separate the seed for further food processing. The decorticated seed must be properly dried

prior storage or it could be used directly through the food processing stage. The required

decorticating machine is to decorticate the locust bean pod through threshing action similar to the

effect created by a tooth peg threshing mechanism. The hydro cyclone developed for the

separation of hulls from the cotyledons of locust bean was designed in accordance with Rietma’s

optimum design for classification. The cyclone has a diameter of 350mm. It has a volumetric

capacity of 0.034m3 and an inlet flow rate and power rating of 0.011m3/s and 0.60kw

respectively. The radical velocity of particles in the cyclone was calculated to be 0.09rad/s.

Separation efficiency of 66%, 37%, 65% and 68% was obtained for common bean, locust bean,

soya bean and cowpea respectively (Adewumi, 1997). Olaoye (2005) reported on a locust bean

depulpping machine. The depulpping machine (Fig. 10) has capacity to depulp the locust bean.

The clean bean can be processed into the desired locust bean product derivatives through

associated food processing procedure. The manually operated concave type locust bean dehuller

has a power rating of 0.16 kW with a capacity of 20 kg/h. It recorded a maximum efficiency of

70.9% at a roller peripheral speed of 300 rpm, concave dehulling length of 240 rpm and concave

clearance of 8 mm. (olaoye, 2010)

Fermentation is a process in which certain bacteria or fungi are allowed to grow in a food to

improve its flavor and / or digestibility. As these microorganisms absorb and process nutrients

and excrete waste products they affect the flavor, nutritional value, texture, and storage life of the

food. The organisms break down proteins, convert starches to simple sugars, and can increase or

make various vitamins and minerals more available. In other words, these organisms are feeding

on and digesting the food. Because the process of breaking foods down into their constituent

parts has already begun, fermented foods can be easier for people to digest than the same food

before fermentation. For example, the seeds of the African locust bean are inedible before

fermentation and processing to make iru, a flavorful condiment. Fermentation lengthens the

storage life of foods because the presence of the fermenting organisms prevents other, spoiling

organisms from becoming established. Often this is because fermentation changes the pH of the

food, for example making it so acidic that only Lactobacilli spp. bacteria will survive.

Fermentation can also reduce or eliminate some anti-nutrients such as phytates and

oligosaccharides. Traditional fermentation processes at the cottage level use simple operations

and equipment. Fermentation may be carried out on a solid substrate or under submerged

conditions. Traditionally, iru is made by boiling the dried locust beans for about 24 hours. With

the addition of ash the seed coats are removed. The seeds are then boiled again for about two

hours. While the seeds are still very hot they are drained, transferred to a basket and covered

with leaves. This helps to retain heat and create a humid atmosphere. The beans are allowed to

ferment or two to three days, after which time the leaves are removed and the seeds are crushed

to a paste. (olaoye, 2010)