Abstract--- The need for alternative safe means and sources of

food and nutrition has been the major preoccupation of the

development and scientific communities. Purpose of the study is to

design a wild fruit pulp processing machine to harness Baobab and

Parinari Curatellifolia fruit contents for the benefit of the local

populace, the goal being to enhance food security and income

generation through fruit pulp products and new tastes. The operating

principle is to convey the fruits by auger screw against a stationary

sieve, due to frictional and shear forces the fruit pulp will be

separated from the seed (peeling principle). The results of the project

will be based on the prototype output and efficiency of the concept.

Keywords—Baobab, fruit pulp, Parinari Curatellifolia, auger

screw

I. INTRODUCTION

HE design project is a hybrid machine that uses peeling

principles to mechanically separate fruit pulp through

shear by pressing the fruit against a sieve. The project is aimed

at utilizing the available indigenous wild fruit through the

extraction of the much needed vitamins and nutrients with the

goal of enhancing food security (eradicating hunger),

nutrition, new tastes and income generation.

II. BACKGROUND OF THE PROBLEM

The world today faces urgent food and nutritional crisis, in

1996 FAO [1] estimates reported that as many as 840 million

people face chronic or perpetual hunger, however in 2009 the

number exceeded 1 billion [2], which implies that one-sixth of

the world’s population is facing acute hunger. A major

preoccupation of the development and scientific communities

since 1935 (first account of hunger and malnutrition in the

world) has been how to resolve the conflict between

increasing demand for food and the degradation of the

environment due to climate changes. Zimbabwe for instance is

facing severe and widespread food shortages, the ZimVAC

report identified approximately 6 percent of the rural

population (560 000 people) will be in need of food assistance

at the height of lean season between January and March 2015

[3].

Dickson T Manditsera, Harare Institute of Technology, Zimbabwe, Email

id: manditserad@gmail.com

Thus the need for alternative sources of food and nutrition

has resulted in the production of food supplements used to

correct nutritional deficiencies or maintain an adequate intake

of certain nutrients [4]. However in some cases excessive

intake may be harmful and have adverse effects such as liver

damages and other diseases. So the need for a 100% safe

alternative source to compliment agriculture is still a problem

which can be solved by providing organic natural sources of

nutrients and vitamins from wild fruits which is an excellent

and rich source.

III. PROBLEM STATEMENT

The deficiency of vital micronutrients and vitamins in the

dietary system are a form of hidden hunger. In many countries

health problems related to dietary inadequacy are an ever

increasing threat, in fact malnutrition and foodborne diseases

(Ebola) are becoming a double burden [5]. Therefore the

extraction of wild fruit pulp and value addition fruits will help

alleviate poverty.

Purpose of this study is to design and manufacture a pulp

processing machine for Chrysobalanaceae (Parinari

Curatellifolia) and Adanasonia Digitata (Baobab fruits)

IV. LITERATURE

The objective of the project is to design a means to harness

macronutrients and vitamins from wild fruits, however due to

vastness of the resource the project limits its focus on small

scale extraction of pulp from Baobab and Parinari

Curatellifolia fruits. Nutritional analysis to assess the potential

of these wild fruits has proven that they are rich in

macronutrients and vitamins that help solve the great central

issues of the world economic, health and environmental

development. The focus was on the fruit’s relevance to the

three biggest needs for human survival and social security

which are Nutrition, Food Security and Income Generation.

Although pertinent wild fruit nutritive information is often

poorly available, it can be concluded that all African fruits are

useful sources of nutrients particularly Vitamin C. They offer

substantial levels of calcium, phosphorus, potassium and iron.

For instance Baobab fruit contains six times as much Vitamin

C as oranges, twice calcium as milk and packed with B

Vitamins [7] while Parinari contains proteins, fats, Vitamin C,

calcium, magnesium, zinc and iron [6].

The words “Food Security” imply the concept of access to

sufficient safe food at all the time. The fruits’ most vital use is

to provide food security to those who cannot buy their way out

of hunger and overall to the world in times of hunger and bad

harvest. For this purpose the pulp can be beaten into pancakes,

Wild Fruit Pulping Machine

Manditsera Dickson

T

International Conference on Mechanical and Industrial Engineering (ICMIE'15) July 14-15, 2015 Harare (Zimbabwe)

11

which when dried can be stacked and stored for months and

even years.

For purposes of relieving local poverty (income

generation) in most rural and urban areas, wild fruits are

powerful tools. The food and beverage industry searches

constantly for new flavors, so wild fruits offer an

advantageous opportunity and good market share earner.

Possibly there is no long term answer more basic or more

beneficial of merger local empowerment than this ancient food

source.

Fig. 1 Baobab fruit

Fig. 2 Parinari Curatellifolia

Existing machines

All the existing machines principles for fruits with or

without seeds is based on crushing, however the project is to

bring a new dimension to the industry by concentrating on

smart means of separating the pulp from the seed. By the

adaptation of conveying screw, the pulping will be done due to

the friction and shearing effect between the screw and a

stationary sieve.

a. Manual type

These are slow means of extracting pulp by human

interaction with the machine. These range from small kitchen

utilities for making pulp for example tomatoes, fruit juices

from fruits etc. to small scale productions such as coffee

production. The variations are the means of human effort

application and output required by end user, mostly

considering the fruit types.

b. Electrical Pulping Machines

These are much faster than manual machines and are

powered by means of an electric motor. The type ranges from

crushing machines to pulp extractors varying due to the means

and the idea of operation.

c. Baobab Fruit pulp processor

The design of a baobab fruit pulp machine is different from

other machines because of the fruit structure and components,

which is not juicy but powdery. Apart from mechanisms that

where latterly designed the rural means of extracting the pulp

is still practiced nowadays in most area.

i. Traditional Baobab Pulp processing

This is a method practiced for many years and in some parts

of Zimbabwe is still existing, the use of continuous repeated

pounding of the seed and pulp then separated by a food sieve.

However despite the method yielding results there is risk of

contamination of the pulp due to handling and also the process

is very slow.

ii. Electric power Baobab pulp Machine

The design emphasize on simplicity, productivity and ease

to use. Conveniently the energy of the machine is provided by

a pedal or an engine, connected to the tubes inner shafts that

separate the pulp from its seed and fiber. The combination

consist of a tube and mesh wire, the tube is hooked up to the

motor causing it to rotate with milled grooves grinding against

a stationary mesh grinding baobab fruit into pulp.

Project material requirements

For the machine pulping components material with high

corrosive, oxidation and ordinary rusting is required therefore

stainless family is more advantageous for the machine internal

components (screw, sieve and the covers),while the frame

requires a material that is easy to weld and less costly.

The design project (machine) estimate cost price in the

market is to be $600 from bill of material and costing, which

is an affordable price to locals and small food processor in

Zimbabwe.

V. METHODOLOGY

In order to achieve the objective of the project, the

methodology was based on the project development life cycle

concept, utilizing three major steps planning, implementation

and testing. Planning stage was centrally rooted on data

collection, which was collected in two forms primary data

(experiments) and secondary (investigations).

VI. EXPERIMENTS

The experiments were done in real life setting rather than

laboratory (Field experiment method).

International Conference on Mechanical and Industrial Engineering (ICMIE'15) July 14-15, 2015 Harare (Zimbabwe)

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Experiment 1: Determination of the relative of easy pulp

removing (Parinari Curatellifolia)

Objectives: To determine the principle to pulping Parinari

Curatellifolia and also determine the best preservation method

for easy pulping.

Apparatus: Grater (6mm and 4mm), Slicer/Peeler (5mm),

Perforated bowl holes screen (9mm)Stop watch ,Vernier

caliper

Fruit Conservation and treatment: Unripe fruits collected

where stored for maturity which took about 10 days from the

day collected to mature and to ripen. For experiment purpose

the fruits where stored using different methods both collected

ripe and unripe. Thus some were refrigerated, some stored

under room temperature and the rest were buried underground.

Thus all ripe and unripe were treated separate in storage to

observe the differences in the pulp behavior due to storage

method. This is done because the fruit is seasonal and it will

be subjected to storage before pulping and also to review the

easy state to preserve the fruit for easy pulping.

Tests: The experiment was to determine the changes of the

fruit pulp and skin in accordance with method of preservation

and time from collection. The tests were done under time, with

different tools (Grater (6mm and 4mm), Slicer/Peeler (5mm),

Perforated bowl holes screen (9mm)), under approximately the

same variables (temperature, force) and the time was recorded.

Three individuals for each test where timed. Using the same

tool to remove the pulp, also the behavior of the skin and pulp

structure was observed and noted. For each tool the two tests

were done, for each collection criteria used.

Conclusion: Basing on the experiment results and

observations it can be noted that the capacity of any pulping

machine for Parinari Curatellifolia is dependent on the

preservation method and size of mesh wire holes used, thus

the relative ease of pulping in all cases depended on the peeled

area on the fruit (capacity). The pulping force was determined

through shear.

Experiment 2: determine best pulping techniques for

Baobab

Objectives: To determine how best to separate Baobab Fruit

pulp from the seed.

Apparatus: Sieve, Pounding equipment, Scale, Tap

measure, Vernier Calipers

Procedure and Methods: Also the experiment was done in

real world setting. The experiments were considered on two

traditional methods of pulping Baobab used by locals, which

water and physical means of removing the pulp. However the

water was screened out as it reduces the pulp’s shelf live and

destruction of other nutrients. Thus the experiment was done

using physical methods.

Tests: Two tests were done, using the pounding method and

using a food sieve to separate the pulp from the seed. Time

taken by the individuals was recorded, three tests for each

method. Pounding method is where the fruit pulp is removed

by continuous beating, using traditional means (duri and

mutswi) while the sieve method the fruit will be rubbed

against a food sieve mesh wire continuously until the seeds

were left without pulp. The fruit sizes were not distinct so the

quantity measure was used for the tests (20g, 50g and 70g).

Results: The pulp removed depends on the method and

individual’s ability and expertise in using the tool. However

the pounding technique is bit slower and tedious than the

sieving method. Also from results and observations the pulp

from pounding is not completely removed from the seed

implying the crushing principle is tricky in pulping Baobab.

VII. PROJECT DESIGN CONSIDERATIONS

The machine feed mechanism consists of a feeding chute

that regulates the amount of material input to the pulping

system. Due to the machine inclination (10º) the material does

not require external energy but will flow due to gravitational

acceleration. Also at the heart of the process there is an auger

screw which consists of several blades of helix shape welded

to the rigid shaft which is rotated in a fixed sieve to feed and

convey the fruit through the pulping process. The screw

creates a translational movement so that fruits are pulped due

to collision and frictional resistance. The sieve was designed

to offer shearing perforated holes to help separate the pulp

from the conveyed fruits, the hole size were determined from

fruit peel resistance tests. The sieve is treated as a thin walled

cylinder which is subject to internal pressure from the pulping

effect.

However the machine efficiency is highly dependent on the

screw-sieve gap, machine’s speed and fruits’ (Parinari

Curatellifolia) ripeness state. The gap was designed based on

the Baobab fruit, and also Baobab requires higher speed to

increase collision and inertia (increase shear force).

Screw and sieve due to stresses involved are made from

stainless steel, type 304 because of its excellent forming and

welding characteristics, thus it is readily roll formed into a

variety of parts. The covers are made from type 430 because

corrosion resistance is not so demanding while the frame is of

mild steel.

Design Calculations

Screw pitch: The pitch ranges between 0.5 and 1 times

diameter and bigger for light material. From the data the

largest fruit measured is 35mm.

……………………(1)

Screw diameter (D): Screw diameter is taken to be 4-12 times

bigger than the diameter of the material particles being

transported (homogeneous material) and 2- 4 times bigger

than the bigger diameter of the material particles being

transported (heterogeneous material)

……………………(1)

A smaller clearance is needed to prevent the jamming of the

fruit material being sheared. Therefore the clearance will be

taken as the diameter of the smallest fruit seed which is the

baobab seed of 6mm.

Sieve filled area (S):

…………...(2)

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Screw capacity (Q): The capacity of a screw depends on the

screw diameter, screw pitch, speed of the screw and the

loading efficiency of the cross sectional area of the screw. The

capacity of a screw conveyor with a continuous screw:

…………………………...(4)

=21.38kg/hr

Sieve: Sieve was treated as a thin walled cylinder which is

subject to internal pressure to internal pressure form the

pulping effect. The stress in the sieve include

Circumferential stress: The sieve is fixed on both end and the

pressure on end plates were assumed negligible

p internal pressure, - circumferential stress, d sieve internal

diameter , t sieve thickness

F- is the rotational inertia force of each fruit against the

sieve given by the formula

Where r = 42mm

m- mass of the fruit

F = 17.64 N

Is the area where were the fruits exerts the force, assuming a

square area concentrated by one Parinari fruit, given that the

largest fruit size is 35mm therefore

A= =

Thus the internal pressure is 0.0144 ⁄

= ⁄

The sieve was also tested for thickness in finite analysis.

Frame: Frame design parameters were obtained from finite

element analysis, the consideration being to come up with the

best stress bearing section. However considerations of the

members were treated as struts and subjected to a vertical

pressure.

By Euler formula

- is the Euler buckling load, E- modulus of elasticity, I-

Section moment of area

For the test in finite element analysis the struts where

assumed one end fixed and the other end pinned.

=

-is the length of the strut.

VIII. FIGURERS

IX. CONCLUSION

The project aims to bring a new dimension to the industry

by concentrating on the smart means of separating the pulp

from the seed, saving energy and providing an alternative

source of food supplements and taste. Also the machine cost

is relatively cheap to produce and maintain. By the adoption of

the expelling and screw conveying concepts the pulping will

be done due to the friction and shearing effect between the

screw and the sieve (peeling principle)

International Conference on Mechanical and Industrial Engineering (ICMIE'15) July 14-15, 2015 Harare (Zimbabwe)

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APPENDIX

Parinari Curatellifolia experiment results

Baobab experiment results

λ Value (handbook)

Type of load Λ

heavy and abrasive 0.125

heavy and little abrasive 0.25

light and little abrasive 0.32

light not abrasive 0.4

1. Ψ Value data sheet

Type of material Ψ

Abrasive material 0.12 - 0.15

Mildly abrasive material 0.25 - 0.5

Abrasive free flow 0.4 - 0.45

ACKNOWLEDGMENTS

The following individuals provided the much needed

support, in every aspect of the project and their assistance in

gratefully acknowledged, Eng. R Masike, Eng. L Masiyazi,

Eng. M Dzanya and Mr Topotsa.

REFERENCES

[1] Shah. M, Strong .M, (1999) Food in the 21st Century: From Science to

Sustainable Agriculture. Washington DC, CGIAR System Review

Secretariat, World Bank.

[2] World Summit on Food Security, Declaration Of The World Summit On

Food Security, pg 1, note 2,Rome 16-18 Nov 2009 Retrieved from

http://www.fao.org/fileadmin/templates/wsfs/Summit/Docs/Final_Decla

ration/WSFS09_Declaration.pdf

[3] World food programme: Zimbabwe , Retrieved from

https://www.wfp.org/countries/Zimbabwe/Overview

[4] European Food Safety Authority: Food Supplement. Last updated: 2

October 2013 ,Retrieved from

http://www.efsa.europa.eu/en/topics/supplements.htm

[5] World Health Organization: Food Security.

http://www.who.int/trade/glossary/story028/en/

[6] Benhura .M.A.N, Muchuweti.M, Gombiro.P.E, Benhura. C (September

2013) Properties of Fruits (Parinari Curatellifolia/Hacha/Chakata)

from different parts of Harare, Zimbabwe, Vol 13, Issue 4, pg. 8004.

African Journal of Food, Agriculture, Nutrition & Development.

[7] Dr. Wilkinson, Dr. Matt.H. Baobab: The Baobab Fruit Pulp Powder

Benefits, retrieved from http://www.baobab.com/category/english-

language/baobab-health-benefits/

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