Level 1 2 - MALAWI OIL SEED CROPS EXTENSION ...os.aiccafrica.org/media/extracting and refining...

Extracting and Refining Oil - Level 1&2

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ISBN 978-99960-977-9-9

Extracting and Refining Oil

Level 1 Level 1 Level 1 Level 1 Level 1 & 2 2 2 2 2

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Table of contents

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Chapter 1: Extracting Crude Oil from pulse 1

Introduction 1

Identifying the types of pulses 1

Identifying equipment and machinery for Oil extraction 2

Oil extraction by pressing 8

Roasting pulses 8

Types of roasting 9

Importance of roasting 9

Milling the pulses 9

Pressing Pulses 10

Storing Oils 13

Chapter 2: Extracting Crude Oil from oil seeds 14

Identify oil seeds 14

Description of some of the common members of

the oil seed group 14

Identify tools and machines 17

Clean the oil seeds 17

Activity 1 Pressing the pulses 20

Activity 2 Pressing oil seeds 21

Activity 3 Label the parts of the UNATA Press 22

Self-Assessment 23

Further Reading 23

Chapter 3: Refining Oil 24

Introduction 24

Identifying crude Oil 24

Identifying equipment and machinery 25

Objectives of refining 27

Manual method 29

Traditional Methods 30

Packaging 30

Labelling 31

Activity Refining Groundnut oil 32

Self Assessment 33

Further Reading 33


Acknowledgement

The Ministry of Labour, Youth and Manpower Development, is so grateful

to UNESCO for the financial and technical support in development of

these books. Appreciation is also extended to Korean Research Institute

for Vocational Education and Training (KRIVET), and Technical and Vo-

cational Education and Training (TEVET) Authority for facilitation of the

development of the curriculum.

The following are also recognized for their special roles in different

capacities in the development of the material;

• Malawi Bureau of Standards, Natural Resources College,

• Magomero Training College,

• Ministry of Agriculture, Irrigation and Water Development,

• Export Trading Group (ETG),

• Transglobe Produce Export Limited,

• DAPP Mikolongwe Vocational Training Centre,

and all those who took part in the labour market assessment, develop-

ment of the curriculum, validating, and development of this booklets.

The Ministry also recognized the role played by journalists from different

media houses in editing the booklet and LYPH Outlet for the designing of

the material.

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Preface

Malawi though being agro-based economy, has failed to maximise

benefits from the agricultural trade because it has been taking raw

produce to both domestic and international markets which is subject

to declining terms of trade. The current Government agenda of

transforming Malawi from predominantly importing to export led growth

therefore needs a catalyst of skills development to enable the

achievement of the goal. Skills have a fundamental place in turning

the vision to reality and knowledge to products.

This booklet is therefore part of the first curriculum that has been

developed to achieve the stated national agenda as enshrined in the

Malawi Growth and Development Strategy. The processing of the agro-

raw materials has the potential of contributing to the much desired

economic growth through creation of jobs and employment,

development of products, and increasing of income at large. The

ultimate goal in all this will be the attainment of poverty reduction.

Ministry of Labour, Youth and Manpower Development with support

from UNESCO has developed this booklet on Extracting and Refining

Oil Level 1 & 2 that aims at empowering both young and old, males

and females in agro-processing skills which are applicable to the nation.

The Government therefore is greatly indebted to UNESCO for the great

technical and financial support through the Better Education for Africa's

Rise Project in coming up with these booklets. It is the Ministry's belief

that the trainers and trainees will use the booklet to their best in

transferring and acquiring knowledge respectively.

Godfrey B.C. Kafere, PhD

ACTING SECRETARY FOR LABOUR, YOUTH

AND MANPOWER DEVELOPMENT

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Introduction

Most agricultural products must be processed before they can be used.

Processing transforms raw agricultural commodities into a high value

product. For example, groundnuts, soya beans, cotton; sunflower can

be processed into oil. The by-product produced from the processing of

oil from sunflower is seed cake which can be used as an animal feed.

On completion of this module, the learner should be able to extract crude

oil from pulses and oil seeds in the agro food processing industry and be

able to refine the processed oil. During oil extraction process the operator

should be conscious on quality, hygiene, safety and accuracy.

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Introduction

Pulse is a type of leguminous crop that is harvested solely for the dryseed. Dried beans, lentils and peas are the most commonly known andconsumed types of pulses. Pulses do not include crops which areharvested green (e.g. green peas, green beans) these are classified asvegetable crops. The following are the examples of pulses that can beused for oil extraction; black gram, green gram, pigeon peas.

On completion of this learning outcome, the learner must have thefollowing competencies:1. Identify types of pulses2. Identify equipment and machinery for oil extraction3. Oil extraction by pressing4. Roast pulses5. Mill the pulses

6. Press the pulses

Identifying the types of pulses

Pulses among others include: all varieties of dried beans, kidney beans,

lima beans, butter beans, broad beans, ground beans, chick peas,

cowpeas, black-eyed peas, pigeon peas and lentils. The Figure below

shows some of the pulses:

Types of the pulses

Extracting Crude Oil from pulse

Chapter 1

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Identifying equipment and machinery for

Oil extraction

Extraction involves the separation of the raw materials into oil, oil residues,

and cake. There are three types of extracting machines which include

extruder, expeller and oil extractor. These extract oil through crushing,

pressing and solvent extraction respectively.

Oil extrudersThere are two types of extruders namely single and dual or duplex extruder.

Below are the examples of extruder machines as shown in the figure below

This equipment consists of gearboxes offered by P.G.Drive. The following

are the features of single screw extruder; improved power efficiency due

to helical tooth gearing and reduced power tariff & operational cost

that directly add to the profit for any business, it has inbuilt thrust HSG for

better reliability, durability & space saving, and it has profile ground gears

meeting international ‘din quality standard’ to ensure low noise

performance.

Single screw extruder

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The Table below defines technical details for single screw

extruder.

Technical Details Spectrum

Input Power (Pn) 2 to 250 kW

Ratio (iN) 5 to 18

Output Torque (T2) 346 to 25000 Nm

Screw Diameter (D) 20 to 200 mm

Dual or Duplex oil extruder

Side view of dual oil extruder

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A dual extruder combines a first pass with low pressure and second pass

at high pressure level. In this case the cake which is produced from the

first conveyor is fed automatically to the second conveyor, which then

leads to the middle section where the heating is being done at high

temperature and oil is produced.

Oil expeller/PressOil expellers can be categorized into two; manual and mechanical.

Manual expellers are those which depend on human effort to press the

oil out of oil seeds. Among these are Ram Press and UNATA Press specifically

for groundnuts. These are cheaper. However, they have low efficiencies

in production. On average their extraction levels are 90 percent.

Manual Oil expeller

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The mechanical oil expellers are those which are motorized or have

hydraulic systems which enable and ease oil expelling. These have higher

level pressing power and are of high oil extraction efficiency which on

average 99 percent. However the mechanical oil expellers are of higher

cost than the manual press. Below are the pictures of the two.

Ram Press and Hydraulic Press

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The mechanical oil expellers are also of different types with the common

being single oil expellers and dual expellers. In single screw oil expelling

the drive can be operated by either an electric motor or diesel engine.

Single screw oil expellerSingle screw oil expellers have one screw shaft that moves the pressing

dishes towards a pressing direction for extraction of oil. This expels oil in a

single oil pass. The figure below depicts a screw expeller which is capable

of producing the oil in a single pass.

Single screw oil expeller

Dual ExpellerIn the same respect as single screw expeller, there is also a dual oil expeller

which combines a first pass at low pressure and second pass at high

pressure. In this case, the cake which is produced from the first pass is

fed automatically to the second stage. In principle duplex expeller

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Dual expeller

Oil ExtractorOil extractors are machines that remove oil from the seeds with by-

products like cakes. These machines mill and heat the seed to produce

oil. The figure below depicts a picture of an oil extractor.

An oil extractor

employs screw conveyor of varying pitch and differently shaped barrel

areas. This arrangement increases the pressure as the material is forced

through the barrel.

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Oil extraction by pressing

Operations and capacities vary from machine to machine. However,

the general extraction mechanism is that the scorched seed is fed through

the intake at lower pressure, the seed goes through a moving roller and

driven towards a compressed point. In the process of moving higher

temperature is generated, which facilitate the burning and change of

enzymatic conditions of the seed. This combined with pressing, oil comes

out into filtration chamber separating the oil from residues. Most of the

oil is extracted in the middle section whereby the temperature is above

100°C. However, significant additional amount of oil is yielded by second

pass. From this process, two products come out, oil and the cake as a

by-product. It is worth noting afore that this is process oil which is not

refined and edible.

Roasting pulses

Roasting , as shown in the figure below, is a cooking method that uses

dry heat where hot air envelops or covers the food. The importance of

roasting prior to oil extraction comes from the fact that oil is solid at

room temperature. By roasting rises the temperature of the food product

so that fat transforms into oil in the oil seed cells.

Mini Roasting Machines

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Types of roasting

There are various methods of roasting. Some of them are broiling, grilling,

deep –frying and baking. Roasting can be done either manually

(traditionally) or mechanically. Manual roasting is applied to light weight

operations such as flying of groundnuts for home consumption as opposed

to mechanical roasting which calls for higher capacities such as roasting

of soybean in the process of oil extraction.

Importance of roasting

• It helps in taking out detrimental enzymes and anti-growth

factors that are hazardous to health.

• It softens the final product

• It improves digestibility and flavor of final product

• It reduces the cooking time

Milling the pulses

Milling is grinding or crushing of pulses into smaller particles. Other

methods of oil extraction require size reduction by milling the pulses prior

to oil extraction. The figure below shows side view of mill and oil extractor

Mill and Oil extractor

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Pressing Pulses

Oil extraction is the process of removing oil from seed/nut/plant such as

algae . There are three main ways to extract oil such as cold oil pressing,

expelling, and solvent extraction. The cold oil pressing and expelling

involve the use of machines while solvent extraction involves the use of

chemicals. Pressing pulses is done by a machine shown below, whereby

the extraction of edible oils from pulses and oil seeds is done by using a

press.

Oil Pressing Machine

At household level oil pressing is done using a simple machine which canbe locally made. This machine is made from a car jack, either hydraulicor screwed, which pushes a shaft within a chamber towards a pointwhere the pulse is compressed and allows oil to be released from thecells. Figures below shows Hydraulic, UNATA, and Ram press includingtheir cross section (isometric view for hydraulic). It is worth noting thatsome of these can be manufactured locally even for home use. However,efficiency and optimization levels are lower.

Hydraulic Press

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1000 mm

800 mm

spindle

nut in bronze

10 mm

pressplate

270 mm

iron

wood

70mm

bolts

330mm

holesperforated

cage

container

UNATA Press

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Handle

Tie arms

HopperPiston pin

Piston CageCompression

cylinder

Adjustable

restriction

cone

Pivot pins

Feed

FeedGear box

Feed

screw

Pressing

screw

Perforated

cylinder

Cone

Adjustable nut

with spring

Ram Press

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Storing Oils

Storing crude oil is of critical importance even though it is one of the final

stages in the extraction. However, storage of the product has critical

importance in the whole production. Among the conditions that must

be taken into consideration when storing oil are temperature, light, and

humidity. Temperatures affect the chemical composition of oil. Oil is fat

at room temperature, the heating when extracting enables the change

of fat to oil for ease extraction from the cells. When the temperatures are

below room temperature then it returns to fat and can't be used in that

form. It is however worth noting that fat storage helps increase shelf life

and enables easy transportation. The disadvantage however is that it

requires maintenance of the temperatures. This therefore needs high

technology like air conditioned facilities.

Oil contains nutrients which react with the ambient light. The reaction

will result in changes of the extracted oil. Oil is carbohydrate, therefore

the light will either hydrolyse or oxidize resulting in dis-colour of the oil,

rancidity, and loss of flavour. In this reaction, light act as a catalysis of

the ambient air and the oil.

Humidity has close to similar effect on oil as is the light. Humidity increased

the catalytic conditions of oxygen which increases the oxidation process.

It also increases the water content in the ambient air, therefore

decreasing the quality of oil.

Considering the effects of the environment in which crude oil is stored,

facilities and equipment for storing oil has to be selected carefully. Mostly

oil is stored in drums (barrels), tanks, and containers which are either

made of metal or plastic. The storage in these facilities or equipment

depends on the state and temperature of the oil. Liquid oil is easily stored

in drums with tight closures than fats. The storage therefore should consider

the transitions of oil which largely depends on temperature. Furthermore,

hot oil cannot be stored in plastic containers because it will rapture the

container resulting to loss of oil. It has to be noted that boiling point of

oil is higher than most substances including plastic, as such hot oil can

be a source for rapturing.

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Extracting Crude Oil from seeds

Chapter 2

a. Cotton Seedsb. Ground nuts

ü Chalimbanaü CG 7ü Malimbaü Manipintaü RG1ü Mawanga

ü Fitalac. Sunflowerd. Soya

ü Makwachaü Nansoko

e. Pigeon Peasü MwaiWathuAlimi (White)ü 1512 (white)

On completion of this learning outcome, the learner must have thefollowing competencies:1. Identify oil seeds2. Identify tools and machinery3. Clean oil seeds4. Crush oil seeds5. Press oil seeds6. Filter oil product

Identify Oil seeds

Oilseeds are staple foods for millions of poor people in developingcountries, and are these days developing an even more important roleas cash crops. The most important crops in these categories are oilpalm,beans (soybean, cowpeas, broad beans, red beans) and groundnuts.Further can be mentioned cashew, sheanut, sesame, sunflower, coconutand olives. Oilseeds add nutritional value to the diet by high qualityprotein and/or vegetable oil, together with oil soluble vitamins likevitamin A.

Description of some of the common members of the Oil seed group

Crops belonging to the oil seed group are divided into two subgroups:Major and minor. Among the major oil producing crops are; oil palm,coconut palm, groundnut and sheanut. Among the minor are sesame,melon, cotton, castor, sun flower, cocoa bean, kapok and locust beans.As far as Malawi is concerned, soya, groundnut and sunflower areconsidered as the most important group.

The oil content varies in different species. Most contain 1% fat contentbut groundnuts and soya beans have a very high fat content, about 30%for soya beans and 49% in groundnuts. In Malawi several oil producingvarieties exist. These are;

Cotton seedCotton seed is obtained from the cotton bowl. The seeds are obtained

after the fibres have been removed. When obtained from gin, cotton

seed includes remnants of unginned lint and the fuzz. It yields an average

16 percent crude oil, 45.5 percent cake or meal, 25.5 percent hull and

less than 1 percent linters. There is principal Chapter 1

poisonous pigment in the seed known as gossypol which interferes with

protein digestion when consumed. Chickens and pigs are sensitive to

the feed from cotton because of that

SunflowerThere are various varieties of sunflower: giant, semi dwarf and dwarf types.

The seeds are contained in pocket like cells called achenes.

The giant types are about 190-450cm tall with large heads, about 30 to

Sunflower

45 com in diameter. They

are white or grey with black

stripes and have rather

lower oil content. The semi

dwarf types are about 135-

190cm tall and their heads

are about 20-25cm in

diameter. The seeds are

smaller, black, grey or

stripped and are higher in

oil content than the giant

types. The dwarf types are

rather small but contain the

highest amount of oil. The

seeds can be eaten raw,

roasted or salted. They are

also used as livestock feed,

and for poultry and cage

birds. The seeds contain

semi drying oil (20-35

percent of the seeds) which

is pale yellow and of high

quality.

GroundnutsAs a food crop groundnut

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10 percent. These constituents make groundnut one of the mostconcentrated food crops, high in energy. Groundnut protein is highlydigestible and has many uses both for human and animal consumption.It is an excellent source of the B vitamins and high in Vitamin E.

is one of the mostimportant sources ofedible oil and is mainlygrown for this product.It contains 47-50% oil inshelled nut. Somevarieties contain lessoil content about 38-47percent. It is rich inprotein, containingabout 30 percent, andit also contains somecarbohydrate, about

Soya beansThe nutritional content of soy depends on variety. Black seeded types are

one of the richest in protein but low in oil. The yellow seeded one is high

in oil but low in protein. The mature bean contains higher percentage of

protein than any other beans except winged bean.

The seed contains semi drying oil. The proportion depends (14-24 percent)

depends on variety.

Oil produced from soya is very useful in the manufacture of margarine

and shortening, and is exclusively in the manufacture of paints, limonium,

oil cloth, printing ink, soap, insecticides, disinfectants, detergents and

also in pharmaceutical preparations.

Groundnuts

Soya beans

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The residue after the extraction of oil is very rich in protein. This is used in

various food preparations. It is used in artificial adhesives, textile sizing

material, water proofing material and firefighting foam.

As a feed, soy bean cake is a good source of protein for cattle and

poultry and the beans and haulm are good folder and as fertilizer. The

seed are also used as green vegetables.

Identify tools and machines

There are different kinds of tools and equipment, and machinery used in

extracting oils from oil seeds. Before oil extraction, the following tools

and equipment are used for preparing the seed for oil extraction and

maintenance of quality;

• Decorticators: These they help in removing the seed cort. Though

sometimes these are also used in extracting oil.

• Dehullers: These machines help in removing the hard seed cort.

• Delinters: These remove lint from seeds.

• Copra cutters: This cuts the copra as means of size reduction.

• Seeds Cleaners: For maintenance of quality, the equipment helps

in cleaning the seeds.

• Destoners: This helps in removing stones from the seed.

Below are machinery used in oil extraction. These are the same as in

extracting oil from pulses.

• Ram press

• UNATA press

• Hydraulic press.

Clean the oil seedsThis involves the removal of all foreign materials other than the oil seeds.

It starts with sieving, sorting, grading and ends with polishing.

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Crush Oil seedsThis refers to the breaking down of oil seeds into smaller particles in

readiness for pressing. Usually machines are used to break down the oil

seeds. This increases the surface area for heat penetration and absorption

in readiness for pressing.

Press oil seedsThe extraction of oil from oil seeds using a press involves forcing the oil

out of the plant cell at high extraction pressure. This can be achieved by

employing compression, or vacuum extraction.

Filter OilThe need for filtering oil is aimed at separating the oil from residues

contained in the crude oil. During this process, biological membrane or

heating is employed. For biological membrane filtration, the plant

particles absorb or collect undesirable compounds from crude oil in the

process of filtration. Membrane oil-filtration employs use of the following

machines:

• plate and frame type

• chamber press

• vertical leaf tank or pressure filter

• centrifugal self-cleaning

• Local vertical filtration

Furthermore, filtering by heat involves adding 1litre of crude oil to 10

parts of water and boil until all the water is evaporated. However, this

method is energy intensive.

It should be mentioned that there are two methods of refining edible oils

namely Alkali refining (Classic chemical refining) and Physical refining.

a) Alkali refining process can treat almost any kind of edible oils and fats

but involves the production of soap stocks and has a refined oil yield

lower than the one physically obtainable even if of more stable quality in

the time. Below are the standard steps in the commercial refining process:

• Neutralization,

• Combined neutralization and Dewaxing,

• Bleaching

• Deodorizing

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Table 2: Factors for consideration in oil refining systems

Refining Method Chemical Method Physical Methods

Applicability Almost no limit Not recommended for some

oils and fats

Final quality and

storability Good to excellent limited storability

Oil yield Standard Higher

Bleaching agent

requirements Standard Higher

Degumming

requirements - Very critical

By products Diluted soap stocks Fatty acids and deodorizing

distillates

Effluents waters

(Quantity/quality) Higher quantity/ Lower quantity/

heavy pollution minor pollution

b) Physical refining basically consists of removing fatty acids by steam

distillation under vacuum, which has the following advantages:

• Higher yield of refined product

• No soap stocks formation

• Lower quantity of polluted effluents

• Lower refining costs

In comparison to the two refining systems the following facts in Table

below should be considered.

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ACTIVITY 1

Pressing the pulses

Task description

After treating the pulses, you are requested to identify type of pulses,

equipment and machinery, roast, mill, press and store oils. Time

allocated for this activity is 4 hrs.

Tools and materials required for the exercise.

Extruder, expeller, hammer mill

Trainer’s Instructions

· Ensure trainees are given appropriate tools and materials

· Demonstrate how to extract oil

Trainee’s Instructions

· Select tools and materials for extracting oil

· Put on appropriate protective gear

· Identify type of pulses

· Identify equipment

· Roasting pulses

· Milling pulses

· Pressing pulses

· Storing oils

· Follow the procedures for extracting oil step by step

Procedure for extracting oil

· Identify type of pulses

· Identify equipment and machinery

· Roast pulses

· Mill pulses

· Press pulses

· Store oils

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ACTIVITY 2

Pressing oil seeds

Task description

After treating the oil seeds, you are requested to identify type of oil

seeds, equipment and machinery, roast, mill, press and store oils.

Time allocated for this activity is 4 hrs.

Tools and materials required for the exercise.

Extruder, expeller, hammer mill


· Ensure trainees put on appropriate PPE

· Ensure trainees are given appropriate tools and equipment

· Demonstrate how to extract oil

Trainee’s Instructions

· Select tools and equipment for extracting oil

· Put on appropriate protective gear

· Identify type of oil seeds

· Identify equipment

· Roasting oil seeds

· Milling oil seeds

· Pressing oil seeds

· Storing oils

· Follow the procedure for extracting oil step by step

Procedure for extracting oil

· Identify type of oil seeds

· Identify equipment and machinery

· Roast oil seeds

· Mill oil seeds

· Store oils

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ACTIVITY 3

Label the parts of the UNATA Press here below

1

2

3 4

5

6

7

8

9

10

11

12

13

14

15

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Self-Assessment

a) What is the difference between pulses and oil seeds?

b) Mention two methods of extracting edible oil

c) Differentiate the products of crushing and pressing?

d) Give three types of crude oil storage facilities?

e) Compare and contrast roasting and baking?

Further reading

Muhammad S. and Mark A.U., (2012) Dry beans and pulses: Production,

Processing and Nutrition.

Chavan and Pawar, (2012). Postharvest Management and Processing

Technology: cereals,

pulses, oilseeds, fruits and vegetables. Daya Publications, New Delhi.

Pall W. (1998). Small-Scale Manufacture Of Compound Animal Feed,

Natural Resources Institute. UK.

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Introduction

Crude oils as received from the extraction plant which contains several

non-triglyceride components which must be removed. Refining processes

comprises several processes that accomplish this aim of removing

impurities through use of machines, modern technologies and traditional

methods.

In refining, physical and chemical processes are combined to remove

undesirable natural as well as environmental related components from

the crude oil. These components comprise of for example phosphatides,

free fatty acids, pigments such as (chlorophyll), odours, flavours (including

aliphatic aldehyde and ketone), waxes, as well as heavy metals pesticides.

Learners are advised that while learning they should make an effort to

improve their safety, time, cost and environmental consciousness.

Learning Outcome

On completion of this learning outcome, the learner must have the

following competencies;

• Identify crude oil

• Identify tools and equipment

• Select method of oil refining

• Package refined oil

• Label refined oil

Identifying crude Oil

Crude oil can be obtained after extraction from various sources such as

leguminous crops (groundnut, soya, sesame and oil seeds (baobab and

sunflower).

Refining Oil

Chapter 3

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Crude oil

Identifying equipment and machinery

Edible oils obtained from coconut, corn, cottonseed, olive, palm, peanut,

soybean and sunflower etc. contain gums and other impurities which

are removed by degumming, neutralizing and bleaching processes with

the use of oil refining machines of various capacity

Crude oil has a deep dark colour or extreme right as shown in the fugure

below.

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Figure below shows an example of a complete edible oil refinery of 5-

ton capacity

1&2-Neutraliser;3-Bleacher;4-Deodoriser;5-Cooler;6-Thermic Fluid

boiler;7&8-Filter Press;9-Raw oil tank;10-Bleach oil tank;11&12-Soap pan.

The edible oil refinery can refine almost all types of oils. The refined oil

quality depends on the type of crude oil and its chemical structure. Some

refineries can have a higher capacity of up to 1000 litres or more depending

on the design, requirements and specification.

Factors affecting selection of machine for oil refining include capacity of

the refinery and the nature of crude oil. For example on capacity, a refinery

of capacity ranging from 1- 5 tonnes can be used to refine palm oil, palm

kernel oil, peanut oil, rapeseed oil, cottonseed oil, sunflower oil, corn

germ oil, animal oil among others. Nature of crude oil involves viscosity

which is determined by the source of crude oil. The viscosity affects choice

of sieves to be used when crude oil is being refined.

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Objectives of refining

Most crude oils contain impurities that must be removed before further

processing can take place. These impurities can include;• Solid particles (such as dirt), gums, free fatty acids, pigments and

substances that affect smell and taste.

• Removal of undesirable products from crude oils is crucial in ensuringthe desired product quality, and the way it is done must complywith required standards.

• Preservation of valuable vitamins such as vitamin E ortocopherol-natural anti-oxidants

• Minimising oil losses

• Minimising oil losses

• Protection of the oil against degradation

. Select Method of Oil Refining

Methods of refining crude oil to include; mechanical, manual andtraditional Mechanised method use oil refineries which are done asfollows: degumming, neutralizing, bleaching, and deodorizing.

Step 1 - Degumming

This is the first stage in the refining process. It is used to separate thegums, phospholipids, proteins and impurities that are insoluble in oil whenhydrated.

Importance of degumming is because it removes the emulsification ofphospholipids which increases oil losses during alkali refining and maylead to brown discolourisation of oil after heating during deodorization

There are two main types of gums that need to be removed such ashydratable phosphatides (NHP) that are easy to remove and Non-hydratable phosphates(NHP) which are hard to remove from oil such thatthey require the use of acid to convert to hydratable for completeremoval.

Degumming technique comprise of the following processes:

• Water degumming: treatment of crude oil with hot water to remove

hydratable phospholids. Water degumming is commonly used with

palm and coconut oils and is not associated with significant oil

loss, saponification or environmental pollution.

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• Dry acid degumming: treatment of crude oil with phosphoric acid,

citric acid, oxalic acid or maleic anhydride. In this treatment, the

acid is dispersed in oil followed by raising the pH with a base and

some trapped triglycerides.

• Wet acid degumming uses very small amount of water to increase

degree of hydration.

• Enzymatic degumming is modification of phospholipids with

enzymes to obtain the water soluble compounds.

Step 2 - Neutralizing

The purpose of neutralization is to remove free fatty acids (FFA) that are

responsible for the oil acidity. There are two different processes in this

operation, the Alkali Neutralization and the Distillative Neutralisation.

The usual method of alkali neutralization is treatment with weak lye. The

method comprises the conversion of FFA in soaps and dilution of the

resulting soaps in water phase. These soaps are removed by separators.

In the separation stage other undesirable substances such as gums,

oxidized component, metal ions, pigments and insoluble impurities are

also removed.

In distillative neutralization (physical refining) the free fatty acids are

continuously removed from the crude oil with water vapor normally after

degumming.

Step 3 - Bleaching

The major purpose of bleaching is the removal of undesired colour

materials in the oil. Heated oil (~85OC) may be treated with various

bleaching agents such as fuller’s earth, activated carbon, or activated

clays. Many impurities, including chlorophyll and carotenoid pigments,

are adsorbed onto such agents and removed by filtration. However,

bleaching also promotes lipid oxidation since some natural antioxidants

are removed together with the impurities. Bleaching is done with acid-

activated clay minerals to absorb colouring components and to

decompose hydro peroxides.

Step 4 - Deodorising

This is usually the last stage of the refining process of edible oils. Deodorizing

is done to remove volatile components, mainly aldehydes and ketones,

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with low threshold values for detection by taste or smell. Deodorization

is essentially a steam distillation process carried out at low pressures (2-6

mbar) and elevated temperatures (180-220°C).

For some oils, such as sunflower oil or rice bran oil, a clear table product

is obtained by a dew axing step or crystallization of the wax esters at low

temperature, followed by filtration or centrifugation.

Two main refining routes are alkaline refining and physical refining (steam

stripping, distillative neutralization) which are used for removing the free

fatty acids.

Figure 3 below is a flow diagram of the major processes in the refining

process according to method.

The classical alkaline refining method usually comprises the following

steps;

Manual method

• Manual method involves the removal of fatty acids by a steam

distillation (stripping) process similar to deodorization. The low

volatility of fatty acids (depending upon chain length) requires

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higher temperatures in physical refining than those required for

only deodorization.

• In practice, a maximum temperature of 240-250°C is sufficient to

reduce the free fatty acid content to levels of about 0.05-0.1

percent. A prerequisite for physical refining is that phosphatides

be removed to a level below 5 mg phosphorus/kg oil. In the

classic refining process, this level is easily achieved during the

neutralization stage, but special degumming processes may be

required for physical refining of high-phosphatide seed oils.

• These procedures rely on improved hydration of phospholipids by

intimate contact of the oil with an aqueous solution of citric

acid, phosphoric acid andlor sodium hydroxide, followed by

bleaching (Segers and van de Sande, 1988).

Traditional Methods

Traditional methods include roasting, crushing to break cells in order to

release the fatty acids, squeezing and sieving.

Some of the traditional methods are as follows; Clean, dry and roast the

raw materials, cooling, crushing in mortar or grinding in mills of the seeds,

squeezing the rushed material in a manual oil press till oil starts dripping

from it and collecting the oil. At this stage the oil can be further filtered

or it is collected in withholding tanks where is it left for a number of days

through a process of sedimentation.

The sediments remain in the tank bottom and the refined oil form a clear

top layer. It is then checked and packed in bottles and containers for

safety.

Packaging

Various packaging materials are used for refined oil to ensure that the oilquality is maintained and protected from damage and spoilage.

Plastic containers are a relatively new means of edible oil packagingdue to their comparatively low price and low weight. The polymers mostfrequently used are PET, HDPE, and PVC. Although they do not provideas long a shelf life as metal containers, they are economical comparedto tinplate and therefore suitable for use where a very long shelf life is notrequired.

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Metal containers for vegetable oils are manufactured using tinplate or

aluminium and in two different ways such as bottom and top closed at

the metal fabrication plant with an orifice on the top for subsequent

sealing and capping or bottom seamed onto the body blank and the

top closed only after filling and bottling.

Figure below shows the plastic, metallic (aluminium) containers for

packaging oil.

Aluminium is also employed as a packaging material for edible oils as it

is light and very resistant to corrosion.

Glass containers are widely used for bottling olive oils and virgin olive oils

in particular. This is due not only to marketing requirements but also

because glass containers prevent the permeation molecules into the

bottle, slowing down the autoxidation rate.

Labelling

Labelling is required by law and must appear on food products includingrefined oil. It helps to provide information such as manufactured date,ingredients, best before, storage, usage general information about theproduct. Further information can be added to labels such as the amountsof polyunsaturated, monounsaturated, starch, cholesterol, vitamins orminerals.

Figure below shows oil in packages of 1-5 litres.

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ACTIVITY

Refining Groundnut Oil

Task descriptionAfter obtaining the groundnuts crude oil, you will be required to putcrude oil into a machine, filter crude oil, refine, package and labelfor storage. Time allocated for this activity is 2 weeks. Below is a listof tools and equipment for this exercise.

Tools and materials required for the exercise.Holding tank, drums, bottles, labeling material, boxes, filteringmachine, expeller, oil press


• Ensure trainees put on appropriate PPE

• Ensure trainees are given appropriate tools and materials

• Demonstrate how to carry out each activity.Trainee’s Instructions

• Select tools and materials for handling raw materials

• Put on appropriate protective gear

• Prepare storage facility


• Identify tools and equipment

• Select method of oil refining

• Package

• Label

• Follow the procedures for refining oil step by step

Procedure for refining oil


• Place in oil refinery

• Check after refining

• Pack in containers and bottles

• Label containers

• Store refined oil

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Self Assessmenta) Identify agro sources of crude edible oil?

b) Mention three types of refining methods

c) Classify packaging materials for refined oil?

d) What are the factors to consider when labelling

products?

e) How can you maintain quality of refined oil?

f) What is the most important information required when

labelling?

Further Reading

Dunford N.T and Durnford H.B (2004) Nutritionally enhanced Edible Oil

Processing

FAO Publication (2010) Fats and Oils in Human Nutrition

Wilson et al (2013) Edible Oils Processing. John wiley and Sons Inc.

Woffham, et al. (2013) Edible Oils Processing. John wile and Sons.Inc

Segers,J.C. and R.K.K.M.(1988) Proceedings of the world conference on

edible fats and oils.

Muhammad Siddiq and Mark A.Uebersax (2012) Dry beans and pulses:

Production, processing and nutrition

Oi Mig Lai et al (2012) Palm Oil Production and Processing Characterisation

and uses.AOCS Press.

0

Chavan U and Pawar, V. (2012). Postharvest Management and Processing

Technology: cereals, pulses, oilseeds, fruits and vegetables. Daya

Publications, New Delhi.

George A, (2010) Principles of Crop Production, Theory, Techniques and

Technology. Eastern Economy Edition

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Level 1 2 - MALAWI OIL SEED CROPS EXTENSION ...os.aiccafrica.org/media/extracting and refining...

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