Development of Small Scale Equipment for Depulping Locust ...

International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 06 145

1110306-8484 IJET-IJENS @ December 2011 IJENS I J E N S

Development of Small Scale Equipment for

Depulpping Locust Bean Seeds

J. O. Olaoye

Agricultural and Biosystems Engineering Department

University of Ilorin, P. M. B. 1515, Ilorin, 240003, Nigeria.

[email protected] +2348035812797

Abstract-- This study focused on the development of small scale

equipment for depulpping of locust bean seeds. Processing of

African locust bean seed starts with the pretreatment of the

harvested fruit before the seed can be converted into its

numerous derivatives. Depulpping of locust bean seed is a crucial

pretreatment operation, preceding fermentation of the seed. This

operation is tedious, time consuming and energy sapping for

women and children that are involved in the processing of locust

bean. Small Scale equipment for depulpping of African locust

bean seed was designed, constructed and tested. Techno-

economic status of the women in the rural areas who are directly

involved in the processing of locust bean and its derivatives was

taken into consideration. The depulpping machine comprises of a

vertical cylindrical tank, cylindrical sieve and a vertical rotating

shaft which carries both the paddles and brushes. The vertical

shaft was mounted at the central axis of the depulpping unit. The

machine has a capacity to depulp 10 kg of locust bean seed

during a unit batch operation. Five levels of soaking time

corresponding to five levels of locust bean moisture contents and

five levels of shaft speeds were tested. Test results indicated that

the depulpping efficiency varied between 64 and 98 %. The seed

membrane damage and seed loss were less than 5 and 9.2%

respectively at 45 minutes soaking time and at 350 rpm

depulpping shaft speed. The maximum power requirement was

2.25 kW at a shaft speed of 550 rpm. The operating conditions of

shaft speed at 350 rpm, 45 minutes soaking time indicated higher

depulpping efficiency, lower seed membrane damage and seed

loss during depulpping operation. Result of process performance

showed that the final depulpping process compared favourantly

with that of traditional method.

Index Term-- Depulpping, Locust Bean, Soaking Time,

Fermentation

I. INTRODUCTION

Depulpping of locust bean is an essential and required unit

operation when processing the seeds to its various derivatives

and products. African locust bean (Parkia biglobosa) is very

popular in Africa. The locust bean long pod contains small

beans and sweet edible pulp, the chaff is used as animal feed

and the pulp is a source of chocolate substitute. “Iru” or

dawadawa is a typical example of fermented food obtained

from the small beans. According to UNU [1] Iru is one of the

traditional fermented condiments used to flavor soups and

stews in Nigeria.

The locally woven basket or perforated calabash is used to

depulp locust bean locally. decorticated locust beans are

placed in the basket and submerged in a gentle flowing river,

stream or pond. The mixture of seed and pulp is stirred with

the hands to push out slurry through the pore space while the

basket is vigorously agitated within a fixed location in a

flowing water medium. The pulp is filtered into the water and

the seeds retained inside the basket or calabash. This operation

is labour intensive and time consuming. This operation is

compared to the washing process in scooped melon seeds.

Oloko and Agbetoye [2] found out that the traditional method

of washing melon consumes about 65 % of the total energy

required for the processing of melon seeds. The traditional

method of depulpping locust bean seeds requires large volume

of water. The ease of depulpping operation is a function of

availability of still running stream. The harvesting time and

the processing period correspond to the off season of relative

abundant supply of required water. Therefore, a depulpping

machine that will reduce high dependency on large volume of

water is desirable.

Alonge and Adegbulugbe [3] and Atiku et al. [4] reported that

shaft speed, feed rate, and extraction time affect the

performance of melon extraction and washing machine. They

recommended the average speed of 98 rpm for operating a

manual operated melon washing machine. The feed rate

influences the energy requirement to operate the machine.

Teota and Ramakrishm [5] expressed the significant of the

properties of plant materials and fluid medium in a separation

tank. These properties (apparent density of kernel, seed and

fluid medium of separation) are essential for the design of a

suitable water separation tank either in a batch or continuous

type. Oloko and Agbetoye [2] developed a hand operated

depodding machine. This machine consists of a horizontal

shaft placed inside a cylindrical drum with rotating paddles

arranged at equal intervals and welded at a specific inclination

to a rotating solid shaft which runs through the middle of the

drum. The power required for the washing and separation of

slurry from the seeds was supplied through a shaft which

carries the paddles. Oloko and Agbetoye [2] established that

fermentation period of 10 days made the machine to perform

well at feed rate of 20 kg /hr. Alabi et al. [6], Beaumomt [7]

and Omafuvbe et al. [8] investigated the fermentation of

African locust bean and melon seeds to their respective

condiment iru and ogiri and they reported that the

fermentation process increases the crude protein and the

extract content of the product. The locust bean seed must first

be depulpped before the product can be subjected to

fermentation or further processing conditions.

mailto:[email protected]



Extraction of the mixture of melon seeds and slurry from

melon pod precedes the melon washing operation that

separates the melon seeds from its slurry. In locust bean

depulpping operation, decortications of the locust bean pod

precede depulpping process of locust bean. Locust bean seed

is enclosed within the yellowish pulp. The unique feature of

locust bean explains why a typical melon washing machine

cannot be used to depulp locust bean seeds from the pulp.

This research was set out to establish possible method of

separation of locust bean seed from its pulp and to improve

processing procedure, market value and quality of the derived

products from the locust bean seeds. The overall objective of

the present work is to design, construct and evaluate the

performance of simple and compact equipment for depulpping

of locust bean seeds.

II. MATERIALS AND METHODS

Equipment Description

The depulpping machine consists of a cylindrical head with a

feeding hopper, a cylindrical sieve, a vertical rotating shaft

with paddles and brushes, series of paddles fixed along the

length of the shaft at the two opposite ends, a pair of two

adjoining paddles carries the brush, concave outlet, cover,

handle, sieve control stud, wheels and power transmission

elements. (Figs. 1 and 2).

The cylindrical container holds water for depulpping process.

The container is made from 1.5 mm mild steel sheet. It houses

a vertical rotating shaft. Series of paddles are fixed at the

opposite end and arranged serially along full length of the

rotating shaft. A pair of adjoining paddles is fixed with a

brush. The arrangement of the paddles, brushes on the main

rotating shaft forms the depulpping stirring unit. The

cylindrical container, cylindrical sieve and the depulpping

stirring unit were arranged concentrically. The diameter of the

outer cylinder is 500 mm and 400 mm for the inner cylinder

while each cylinder is 600 mm high. The clearance between

the two cylinders (about 50 mm) was created as a channel

through which the pulp slurry could be discharged out through

the slurry outlet. The depulped seeds are collected inside the

sieve through the clean seed discharge outlet.

Design Assumptions and Considerations

Volumetric Capacity and Cylindrical Tank and Sieve

Arrangement

Volumetric capacity was determined from the dimensional

layout of a cylindrical set up using the struck level method

following the procedure for the determination of bin diameter

in manure spreader. Level full capacity was taken as the struck

level corresponding to the portion included within the

cylinder. The gravimetric capacity was related to the

volumetric capacity of the cylinder by using equation 1 and

the storage capacity of the cylinder was calculated from

equation 2.

Eqn. 1

where,

Gv = Gravimetric Capacity

Vv = Volumetric Capacity

b = Nominal density of the product

The locust bean density is given as 1.18 g / cm3 and if the

depulpping machine is designed to handle 80 kg of locust bean

per unit operation the raw locust bean will occupy 6724.7 cm3.

Eqn. 2



Fig. 1. Front Elevation of a Locust Bean Depulpping Machine Showing the Brush Arrangement

Fig. 2. Plan view of a Locust Bean Depulpping Machine Showing the Concentric Inner Cylinders

Feeding Chute

An Electric Motor as the main

Energy Source

Discharge Sprout

Main Support Frame

Feeding Chute

Brush Arrangement

Depulping Stirring Unit

Top cover of Concentric

Cylinder Assembly

Water Outlet Orifice at

the base of Concentric

Cylindrical Assembly



where,

D = Diameter of the Cylinder (cm 3)

H = Overall Height of the Cylinder

(60 cm)

Lh = Struck Level of Cylinder while

the machine is in operation

= H –

The size of the cylindrical sieve tank determines the capacity

of the depulpping machine. The height of struck level is

related to the overall height of the tank as presented in Eqn. 2.

The difference in height is governed by the nature of fluid

flow (turbulence or laminar) during operation and status of

tank if opened or closed as determined by 0.1% (H) 4 %

(H) (ASAE, [9]; Lingley, [10]). For depulpping operation 2%

(H) was used and D = 60 cm, was chosen for the cylindrical

sieve to accommodate 80 kg of locust bean and required water

to saturation. The dimensions of the cylindrical sieve unit are

60 cm and 40 cm as height and diameter, respectively. The

dimensions of the outer cylindrical container were 60 cm, and

50 cm as height and diameter, respectively.

Sieve Size and Physical Property of the Locust bean Seeds

Sieve holes and clearance between rotating brushes and

cylindrical sieve shell were established in relationship to the

size of the seed. Seed size was determined by measuring the

axial dimension of 100 randomly selected seeds using a venier

caliper reading to 0.05 mm. The number of holes per m2 on

the cylindrical sieve shell was evaluated based on the unit size

of the seed. Experiment had shown that the average values of

the major, intermediate and minor diameters of the seeds are

9.8, 7.9 and 4.6 mm respectively. The result also conformed to

the findings of Ogunjimi et al., [11], Oje [12] and Oni [13].

An approximate hole of 4 mm was drilled with a punch on the

cylindrical sieve shell. This size of the hole woult has no axial

loading and bending moment prevent discharge of depulpped

seed through the slurry outlet and about a hole was drilled per

1 cm2 of the cylindrical sieve size of 7.56 x 10

-1 m

2.

The angle of repose of the undeppulded and clean seeds were

determined following the method described by Oje, [12] for

oil seeds. The average angle of repose at these two conditions

was 30o. The hopper and the seed discharge chute was

constructed at an angle of inclination of 35o to ensure free

flow of the seed during both loading and unloading conditions.

The Depulpping Stirring Unit and rotating Paddles

The depulpping stirring unit was to provide effective means of

removal of locust bean pulp from the seed. This operation is

achieved through combination of cutting, abrasion, and

rubbing actions. The paddle creates the cutting effect on the

pulp by impact and the clearance between the cylindrical sieve

shell and the attached brushes on the paddles creates the

desired abrasion and rubbing actions for the depulpping

operation. (Fig. 2)

The solid rotating shaft has no axial loading and bending

moment and Eqn. 3 was used to calculate the shaft diameter.

The solid shaft is subjected to little or no axial loading and the

maximum bending moment, Mb = 0. The maximum torsional

moment was calculated using standard procedures (Hall et al.,

[14]). Estimate of all the loads on the shaft as shown in Fig. 2

was calculated and Mt = 115502 N/m2.

Eqn. 3

where,

d = Diameter of shaft (mm)

Ss = Allowable stress for shaft (for

mild steel shaft, Ss = 40 N/m2 and

kt = 1.0, (Hall et al., [14]

Kt = Combined shock and fatigue

factor applied to torsional moment

Mt = Maximum torsional moment,

115502 N/m2

T =

From Eqn. 3 the diameter of the shaft was 24.5 mm.

Therefore, a shaft diameter of 30 mm was selected. This was

determined based on the overall length of the shaft and the

maximum height of the cylindrical sieve shell in relation to the

volumetric capacity of the depulpping machine. Three pairs of

depulpping brushes were used. These brushes were attached to

the main shaft through the paddles (Fig. 2). Three adjoining

paddles made of mild steel carry a depulpping brush. The

dimensions of each paddle are 15 mm x 30 mm x 190 mm.

The clearance between the rotating paddles and the cylindrical

sieve shell was set at 12.2 mm. This clearance is sufficient to

create the required surface for effective depulpping action.

Circular holes were created at 1.5 holes per cm2 of the size of

the hole and the adjoining distance between two holes was 4.5

mm. Each hole was created on the cylindrical sieve shell. The

size of the holes and its spatial distribution is crucial in

screening off the seed from been discharged with the pulp

slurry during the depulpping operation.

Belt and Pulley Design

The design and selection of appropriate power requirement for

the rotation of the depulpping stirring unit was selected based

on the speed of the driving motor, speed reduction ratio, centre

to centre distance between the shafts at the condition under

which the depulpping action must take place. An ac motor

with 1410 rev / min (24 rev / s) was used with a pulley

diameter of 50 mm. The depulpping stirring unit of 282 rev /

min (5 rev / s) is desired. A low speed of shaft rotation is

expected during depulpping operation since the stirring unit



must be operated within a fluid medium in an enclosure. The

diameter of a pulley for the driven shaft is calculated using the

equation for the peripheral speed of the belt as shown in Eqn.

4 (Kurmi and Gupta, [15]).

Eqn. 4

where,

d1 = Pulley diameter of the

electric motor (mm)

N1 = Speed of the electric

motor (rpm)

D2 = Pulley diameter of the

stirring unit (mm)

N2 = Speed of rotating the

stirring unit (rpm)

From Eqn. 4 the pulley diameter 250 mm was selected for the

depulpping stirring unit. The length of the belt was determined

by using Eqn. 5. The shaft to shaft centre for both the electric

motor and the stirring unit shaft was chosen to be 42 cm. The

minimum obtainable distance between the radius of the outer

cylindrical container for depulpping process and the distance

of the central axis of the electric motor to its base influenced

the choice of this parameter.

Eqn. 5

Eqn. 6

A flat belt with total length of 134 cm was recommended to

drive the stirring unit.

Fabrication Processes

The construction processes were carried out in the fabrication

workshop, Department and Biosystems Engineering,

University of Ilorin, Ilorin, Nigeria. The basic manufacturing

processes which include cutting, primary shaping and joining

processes were undertaken.

Cylindrical Tanks Arranged Concentrically

The outer cylindrical container and cylindrical sieve were

arranged in a concentric form. The two cylinders were made

from 1.5 mm galvanized mild steel sheet. The outer cylinder

was marked out consisting of 500 mm x 600 mm dimensions

and 400 mm x 600 mm dimensions for the inner cylinder

sieve. A hole of 4 mm was marked per 1 cm2 to cover the

entire cylinder sieve of 7650 cm2. The tow concentric cylinder

tanks were welded to the base plate, 500 mm.

Concentric Cylinder Base Assembly

The base of two cylindrical tanks consists of a metal plate

with two holes 25 mm and 320 mm, diameters. The centre of

each holes are located at 25 mm and 250 mm from one of the

edge of the base plate (Figures 1 and 2). The 25 mm hole

serves as the slurry – draining outlet. Slurry – draining outlet

pipe, 25 mm diameter, 220 mm long and 3 mm thickness was

welded to the 25 mm hole at the base plate. The pipe is made

up of a Galvanized lead pipe. The end of the pipe is fitted with

a cork which serves as an opening for the discharge of locust

bean slurry after the cleaning operation (Fig. 2). A composite

unit of conical and cylindrical components which serve as a

clean seed discharge outlet was welded to the 320 mm hole on

the concentric cylinder assembly base. The composite unit

was made of 3.0 mm galvanized mild steel. The conical

section is welded directly to the base of the cylinder assembly.

The dimensions of the conical section are 1700 mm height,

320 mm and 180 mm as the upper diameters and lower

diameter, respectively. A cylindrical pipe of 180 mm diameter

and 50 cm long was welded to the lower portion of the conical

section. A threaded cap was fitted into the end of the

cylindrical section of the composite unit as shown in Fig. 1.

The cap is only opened at the end of each batch process

operation of the depulpping action for collection of clean

seeds.

Head of the Concentric Cylinder Assembly

The head of the concentric cylindrical assembly consists of a

1580 mm x 30 mm wall and a chute of 500 mm diameter plate

made from 3.5 mm galvanized mild steel. The plate head

holds the inlet and feeding chute in place as shown in Figures

1, 2, and 3. The inlet and feeding chute are made from 1.5 mm

galvanized mild steel and its overall height is 350 mm. The

head is split into two sections and fastened together by bolt

and nut. This creates and access into the interior part of the

concentric cylindrical assembly and the depulpping stirring

unit to ensure ease of maintenance.

Support Components

The support components consist of the main frame, wheel,

electric motor base and the prime mover. The depulpping

machine is held rigidly in position on the main frame

fabricated from 9.8 mm x 9.8 mm angle iron. For the main

frame, ten 1300 mm long and eighteen, 560 mm long 9.8 mm

x 9.8 mm angle iron were cut and welded together to form the

support as shown in Figs. 2 and 4. Four sets of Castor wheel

were connected to the base of the main support as the wheel.

An electric motor, ac (Model VIKING JONCOD, Type YL

90L – 4) was used as the prime mover. The ac motor is

mounted on the electric motor base support and fastened

firmly using four bolts and nuts, M12.



Depulping Stirring Unit

A 30 mm x 1200 mm mild steel shaft was cut and turned on a

lathe machine to serve as the main shaft that carries the

paddles, brushes and pulley (Figs. 1 and 2). The brushes were

arranged along the vertical main stirring shaft. The clearance

between the perforated concentric inner cylinder and the brush

was set to ensure appropriate depulpping action.

Operation of the Depulping Machine

The main function of the depulpping machine is to remove,

clean and set apart the seed of the locust bean fruit from the

yellowish pulp. The machine is to ensure that the thin layer

testa of the seed is retained. The hopper serves as the feeding

point for intake of decorticated locust bean fruit and water.

Depulpping operation takes place using water as a medium of

separation. The depulpping action is activated as soon as the

depulpping stirring unit is set in to rotating motion via an ac

motor. The electric motor drives the depulpping stirring unit

through belt and pulley arrangement.

Vigorous rotation of the depulpping stirring unit induces the

removal, cleaning and detachment of locust bean seed from

the yellowish locust bean pulp. The rigorous rotation of the

stirring unit is reduced as soon as the yellow slurry is formed

inside the depulpping chamber. Clean seeds with enclosed

testa are discharged through the discharged outlet of the

depulpping machine while the pulp slurry is drained out

through the slurry – drain pipe.

Performance Testing

The depulpping machine was assembled after its various

components were fabricated and evaluated for operation

performance and depulpping process performance. The

photograph of the fabricated locust bean depulpping machine

is as shown in Fig. 3.

The depulpping machine was operated at no load at three

different operating speeds of the stirring unit. The shaft is

fitted with five different sizes of pulley diameters 128, 157,

200, 282, and 470 mm to generate five levels of the operating

speed of 550, 450, 350, 250 and 150 rpm respectively. The

electric motor was connected directly to the stirring shaft

through a flat belt. A 1.5 Hp electric motor, ac (Model

VIKING JONCOD, Type YL 90L – 4) was used. This was

undertaken to ascertain the durability of the machine

components. A Geilgy Tachometer was used to determine the

stirring shaft speed. The performance of the machine at no

load was investigated for about an hour for each of the

combination of the operating conditions.

Process performance of the machine was undertaken to test

process performance of depulpping efficiency, percentage

seed loss, recovery efficiency, germination count and seed

with membrane were evaluated. These were investigated

under five operating speeds (550, 450, 350, 250 and 150 rpm)

and five soaking time (15, 30, 45, 60, and 75 min) on the

process performance of the five moisture content of locust

bean seed. The investigation was carried out in a split – split

unit design with operating speed as the main unit, soaking

time as the sub unit factors with three replicates. The process

performance was evaluated on the basis of the following

indices:

Depulpping Efficiency (De),

where,

Mcs = Mass of cleaned (A clean

seed is consider to have more than

¾ of the seed surface exposed and

devoid of locust bean pulp)

Mui = Mass of material collected at

seed outlet of the depulpping

machine discharge outlet

Percentage Seed Loss (Sl),

where,

Mds = Mass of seed damage

Fig. 3. Photographic View of a Locust Bean Depulpping Machine Ready for

Use



Mui = Mass of material collected at seed outlet of the

depulpping machine discharge outlet

Recovery Efficiency (Re),

where,

Mswc = Mass of seed without

membrane

Mui = Mass of material collected at

seed outlet of the depulpping

machine discharge outlet

Membrane Detachment Efficiency (Me), Me = 1 - Re

where,

Re = Recovery Efficiency

Germination Count was undertaken to test the viability of the

depulded locust bean. About fifteen seed samples were

collected and distributed in three seed per petri dish containing

soaked cotton wool in water. The petri dish and its content is

to create appropriate conditions for seed growth and the seed

samples were left for three weeks for observation of the

germinated seed.

III. RESULTS AND DISCUSSION

Data obtained from the tests were also subjected to analysis of

variance (ANOVA) and test of significance using New

Duncan’s Multiple Range Tests. Results of the of the analyses

carried out indicate that there were significance differences in

the magnitudes of depulpping efficiency, recovery efficiency,

and membrane detachment efficiency at all speeds tested

. However, the effects of seed on the percentage

seed loss indicate no significance difference during the

depulpping operation at . The influences of soaking

time indicate significance difference in the magnitude of seed

membrane detachment efficiency and seed loss efficiency

at and show no significance difference at the

magnitude of depulpping efficiency.

Depulpping Efficiency

Depulpping of soaked decorticated locust bean was achieved

at various soaking time when the machine was operated at 5

different operating speeds of the depulpping stirrer. The

soaked locust bean was easily depulpped under the influence

the rotating brushes against the perforated concentric cylinder.

The highest depulpping was observed at depulpping efficiency

of 96 % at soaking time of 45 minutes and depulpping speed

of 350 rpm (Fig. 4). The increase in depulpping efficiency

from speed 150 rpm to 350 rpm clearly indicated that greater

energy impact was induced on the locust bean pulp. Increased

speed beyond 350 rpm reduces the depulpping efficiency this

implied that excessive energy impacted on the pulp causes on

due losses and damage to the bean seed as shown in Fig. 5.

This observation could be responsible for increased

detachment of seed membrane at higher depulpping speed

above 350 rpm. The exerted energy above the depulpping

speed of 350 rpm destroys the membrane and seed testa.

Fig. 4. Depulpping Efficiency against Speed of Depulpping

Percentage Seed Loss, Recovery Efficiency and Membrane

Detachment Efficiency

The trend of the seed loss percentage as shown in Fig. 5

clearly indicated that seed loss increases with the increase in

depulpping speed and increase in soaking time. At higher

soaking time, the presence of the pulp in water increases the

fermentation rate and subsequently subjects the seed to least

depulpping resistance. The highest seed recovery efficiency

was recorded at the soaking time of 45 minutes. The seed

recovery efficiency gradually increases from soaking time of

15 to 45 minutes for all the depulpping speeds investigated. At

soaking time above 45 minutes and between 60 to 75 minutes

of soaking time the seed recovery efficiency reduces (Fig. 6).

The effects of soaking time explain the implication of

moisture content on the deppulping operations. Atiku et al.

[16] investigated the effect of moisture content on the shelling

and winnowing efficiencies of Bambara Nut. Percentage

damage increased to a maximum with decrease in moisture

content and the percentages partially shelled and unshelled

pods increased with increase in moisture content. Jekayinfa

[17] investigated the effect of airflow rate, moisture content

and pressure drop on the airflow resistance of Locust Bean

Seed. This observation confirmed the variation in the recovery

efficiency of the deppulpping seed at machine operating speed

of 350 rpm at all the soaking time investigated.The trends of

variation of the seed detachment efficiency shown in Fig. 7

revealed that increase in soaking time increases the seed

membrane removal. The least seed detachment efficiency was

noticed at soaking time of 45 minutes and at depulpping speed



of 350 rpm. The results indicated that seed recovery efficiency

gradually increases from 150 rpm to maximum value at 350

rpm and beyond this speed the recovery efficiency decreases.

Similarly, the seed membrane detachment decreases from 150

rpm to the least value at 350 rpm and beyond this speed the

detachment efficiency increases for all soaking time

investigated (Figures 6 to 8). The observed characteristics

displayed by the seed recovery efficiency and seed membrane

detachment efficiency between 150 rpm and 350 rpm as

shown in Figures 6 and 7 could be due to the insufficient

energy generated by this low speed for depulpping action.

These speeds may be too low to create required momentum

that would lead to effective separation of the pulp from the

seed without removal of the seed membrane. Whereas at

higher speed between 350 rpm and 550 rpm excessive energy

could be generated to cause total removal of the pulp and

membrane.

Fig. 5. Percentage Seed Loss against Depulpping Speed

Fig. 6. Locust Bean Recovery Efficiency against Depulpping Speed

Fig. 7. Effects of Depulpping Speed on Membrane Detachment Efficiency



Fig. 8. Effects of Soaking Time on Recovery Efficiency

Germination Count

The result of the Germination count test was illustrated with

scatter points and the pattern do not follow any specific curve

variation. The scatter points however indicated that at soaking

time of 45 minutes 4 to 5 seeds germinate. The viability test of

the depulpped locust bean seed also indicated that at

depulpping speed of 350 rpm 4 to 5 seeds tested were found to

be viable at soaking time of 45 and 75 minutes.

Fig. 9. Effects of Deppulpping Speed on Viability of Depulpped Seed

CONCLUSIONS

A machine for depulpping of locust bean has been designed,

fabricated and tested for preliminary performance. The highest

depulpping efficiency of 98% was achieved at depulpping

speed of 350 rpm and at soaking time of 45 minutes. The

highest seed recovery efficiency was recorded at the soaking

time of 45 minutes. All materials used for fabricating the

machine were sourced locally. The machine performed

satisfactorily during the period of operation.

The speeds of the operation of the depulpping machine affect

the magnitude of deppulping efficiency and membrane

detachment efficiency. The effect of the machine speed has no

significant influence on the percentage seed loss. The soaking

time has direct influence on the magnitude of seed membrane

detachment efficiency.

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ACKNOWLEDGEMENT

The Author acknowledges the contribution from Ibitoye, S. A.

and Adedeji, F. A. during the construction and testing

processes

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