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CHAPTER ONE

1.0 INTRODUCTION

Production and consumption of fruit juice is increasing year by year in Ghana (FAO,

2001). In view of this, exportation and importation rates in Ghana are changing every

year to suit consumption rates. Powdered orange concentrate which will be produced

according to food quality standards in the fixed plant, will contribute to conscious food

consumption by correct marketing techniques. Fruit juice, fruit nectar, fruit drinks,

powdered fruit concentrate and concentrated fruit juice are most preferred products

which are produced in fruit process plants. Orange is very rich in minerals and vitamins.

It is also healthy when is consumed in orange juice prepared from a powdered

concentrate. Orange juice can be consumed with all meals. Especially consuming the

orange juice in the mornings is helpful to diet as an anti-oxidant. Orange juice industry

has continued to develop. But insufficient marketing techniques and unconscious food

consumption are preventing the development to speed up in Ghana.

This project is focusing mainly on the powdered concentrate form, particularly because;

i. It has a relatively longer shelf-life.

ii. It is consumer-convenient

iii. It is relatively easy to transport in bulk.

The reasons mentioned above are the main factors for the establishment of this plant.

However, it should be noted that the proposed plant is to be sited close to source of raw

material.

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1.1 OBJECTIVES

1.1.1 Main Objective

To design a plant for the production of powdered citrus concentrate from orange fruit

1.1.2 Specific Objectives

The precise objectives in this project are:

a) To draw a process flow diagram for the production of powdered orange

concentrate

b) To carry out a material and energy balance of plant and individual units therein

c) To determine raw material properties to be used in business, the factory's social,

economic, industrial and legal status

d) To specify the environmental issues to be mitigated against in operating the

plant

e) To design the majority of the various units within the plant and

f) To evaluate the economic viability of the designed plant.

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CHAPTER TWO

2.0LITERATURE REVIEW

Citrus species are small to medium-size shrubs or trees that are cultivated throughout

the tropics and subtropics (Hepfer, 2010). They are native to parts of India, China,

Northern Australia, New Caledonia and North and South of Africa and partly West

Africa. Attesting to how citrus has been embraced by native cultures, most species

have been given names in many native languages. Citrus is primarily valued for the

fruit, which is either eaten alone (e.g. sweet orange, tangerine, grapefruit, etc.) as fresh

fruit, processed into juice, or added to dishes and beverages (lemon, lime, etc.). All

species have their respective traditional medicinal values (Kimball, 1999). Citrus has

many other uses including animal fodder, craft and fuel wood. Although commercial

production for export markets has not been significant in Ghana, there is potential for

farmers to supply local markets with fresh fruit and unique varieties. Orange is the

most common of citrus fruits. The other types of citrus are lemon, tangerine, lime,

kumquat, pummelo and grapefruit, just to mention a few. Citrus are grown between 36

degrees north and south parallel, middle and North America, Mediterranean countries in

the northern hemisphere, South Africa in the southern hemisphere and West African

countries.

2.1 BOTANICAL DESCRIPTION OF CITRUS

Citrus is a common term and genus (Citrus) of flowering plants in the rue family,

Rutaceae, originating in tropical and subtropical southeast regions of the world. The

most well known examples are the oranges, lemons, grapefruit and limes.

The generic name originated in Latin, where it specifically referred to the plant now

known as Citron (C. medica). It was derived from the ancient Greek word for cedar,

k (kedros). Some believe this was because Hellenistic Jews used the fruits of C.

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medicaduring Sukkot (Feast of the Tabernacles) in place of a cedar cone (Kimball,

1999), while others state it was due to similarities in the smell of citrus leaves and fruit

with that of cedar (Pinchas and Goldschmidt, 1996). Collectively, Citrus fruits and

plants are also known by the Romance loanword agrumes (literally "sour fruits").

The taxonomy and systematics of the genus are complex and the precise number of

natural species is unclear, as many of the named species are clonally propagated

hybrids, and there is genetic evidence that even some wild, true-breeding species are of

hybrid origin (Nicolosiet al., 2000). Cultivated Citrus may be derived from as few as

four ancestral species. Natural and cultivated origin hybrids include commercially

important fruit such as the oranges, grapefruit, lemons, some limes, and some

tangerines.

Research suggests that the closely related genus Fortunella (kumquats), and perhaps

also Poncirus and the Australian Microcitrus and Eremocitrus, should be included in

Citrus; most botanists now classify Microcitrus and Eremocitrus as part of the genus

Citrus (Nicolosiet al., 2000).

2.2 TYPES OF CITRUS FRUITS

Citrus fruit is a hesperidium, fleshy, indehiscent berry that ranges widely in size,

colour, shape and juice quality. Citrus fruit range in size from 4 cm for lime to

over 25 cm in diameter for Pummelo. Fruits are globose to oval in shape. The

fleshy endocarp is divided into 1014 sections containing the stalked pulp and

separated by thin septa. Each section contains pulp (juice vesicles) that contains a

sour or sweetish watery juice. A whitish rag or mesocarp (also known as the

albedo) covers the endocarp. In turn, the thin outer section of the leathery peels

(exocarp) containing many oil glands are known as the favedo (Purseglove, 1974).

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According to Purseglove (1974), there are innumerable types of citrus fruits ranging

from small to large ones. It is not possible to list all of them, but the most common ones

are listed below based on their colour, shape, size, mineral content and modes of

consumption.

1. Lemon (Citrus limon): It is one of the most common citrus fruits, which is oval or

round in shape, yellow or green in colour depending on fruit maturity and having a juicy

acidic flesh. Lemons are very much rich in vitamins and are used in making many soft

drinks like genuine lemonade.

2. Orange (Citrus sinensis): It is round in shape, reddish-yellow in colour with a thick

skin when ripe but green at initial fruiting stage. It is high in citric acid and vitamins.

Oranges can be consumed fresh or in soft drinks.

3. Lime (Citrus aurantifolia): It is an oval-shaped, small bright green fruit rich in acid

and vitamins. It is also used in many drinks.

4. Leech Lime: It is an oval-shaped, yellow or green coloured depending on fruit

maturity. Generally, the fruit is slightly bigger than lime. Leech lime juice can be drunk

by mixing it with water and sugar.

5. Grapefruit (Citrus paradisi): It is a round-shaped, large yellow citrus fruit with acid

juicy pulp. It can be eaten raw or used in preparing genuine marmalades.

6. Citron (Citrus medica): It is a yellowish-green coloured, large lemon-like fruit with a

thick peel. The preserved and candied citron peel is used in fruitcakes, cookery and

confectionery.

7. Kumquat (Citrus japonica): It is a small, oval-shaped, orange-yellow fruit with thin

sweet edible peel and acidic flesh. It can be eaten fresh or even with the edible peel.

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8. Mandarin Orange (Citrus reticulate): It is a small, reddish-orange coloured, loose-

skinned citrus fruit. It can be eaten fresh or used as a sweetener in grapefruit juices.

9. Pummelo (Citrus maxima): It is large, pear-shaped, yellow coloured fruit with coarse

dry pulp. It is similar to grapefruit and is called the father of grapefruits due to its large

size.

10. Tangerine (Citrus tangerine): It is a type of mandarin orange having an orange-red

colour and citrus taste.

2.3 PHYSICAL PROPERTIES OF CITRUS TREE

2.3.1 Size

Citrus trees sizes range from 6 m to 12 m in height, although some species can

reach as high as 15 m. Rootstocks can greatly affect the height of grafted trees.

These trees have thin, smooth and grey-brown to greenish barks. Most species are

single-trunked with very hard wood. Canopy widths range from slender to broad,

depending on species. Many cultivated species are pruned so that the canopy is as wide

as the height of the tree (Hepfer, 2010).

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Table 2.1 Table showing Species, common name, size and spines of citrus

SPECIES COMMON NAME SIZE AND SPINES

C. aurantifolia Lime Shrub or small trees grow to

about 4m and are spiny.

C. aurantium Sour orange Trees grow to about 10 m,

with short spines

C.grandis Pummelo Trees grow to about 12 m, and

are spiny

C. hystrixKafr Lime Trees grow to about 5m with

short spines

C. limon Lemon Trees grow to about 6 m with

stout spines.

C. macroptera Wild orange Trees grow to about 5m,

usually spiny.

C. medica Citron Shrub trees grow to about 3

m.

C. mitis Calamondin Trees grow to about 12 m,

usually spiny.

C. paradise Grapefruit Trees grow to about 15 m.

C. reticulate Mandarin Trees grow to 9 m, usually

spiny.

C. sinensis Sweet orange Trees grow to 12 m, often

spiny stems

Source : (Manner et al., 2006)

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2.3.2 Flowering

Flowers are 2 to 4 cm in diameter, auxiliary, fragrant, single and often perfect

(having both functional stamens and pistils) or staminate. The carlyx is 45 lobed

and are usually five petals with oil glands. Stamens number between 20 and 40.

Petal colours range from white to pinkish in Kafr lime, pink to purplish in citron

and reddish in lemon varieties. The subglobose ovary is superior, with 818 locules

(cavities), with 48 ovules per locule in two rows.

2.3.3 Leaves and branches

Leaves are entire, 4 to 8 cm in length, unifoliate, fairly thick, with winged

petioles. Leaves are ovate, oval or elliptical, with acute to obtuse tips containing

oils in glands, which are released when crushed. Young twigs are angled in cross-

section, green and axillary single-spined, while older twigs and branches are circular in

cross-section and spineless.

2.3.4 Seeds

Seeds are pale white to greenish, fattened and angular. The seeds are usually

polyembryonic, meaning they have multiple embryos that can germinate. The embryos

are either zygotic or nucellar. The zygotic embryos are derived from pollination of

the ovary, and therefore are not always similar in horticultural qualities to the parent

tree. The nucellar embryos are derived wholly from the mother plant and display very

similar characteristics to the parent plant.

2.3.5 Rooting habit

Over 70% of citrus tree roots are in the top meter (1.0 m) of soil. Citrus trees produce a

taproot that can extend 2 m below the surface. Fibrous roots commonly extend well

beyond the canopy.

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2.4 ENVIRONMENTAL PREFERENCES AND TOLERANCES

2.4.1 Climate

Suitable climates for citrus are the tropical and subtropical humid regions of the world.

The fruit is said to achieve its highest flesh quality in subtropical humid climates or the

drier regions with irrigation (Rieger, 2002). Limes seem to be the citrus best adapted to

all environments (Taman and Whistler, 1996).

2.4.2 Elevation

In the subtropics, citrus grows between sea level and 750 m above sea level. In the

tropics, citrus does well below 1600 m.

2.4.3 Mean annual rainfall

Citrus trees require between 900 and 3000 mm per annum rainfall for maximum fruit

yielding. Without irrigation, 900 mm per annum is typically needed for any significant

fruit production.

2.4.4 Temperature

Mean maximum temperature of the hottest month is between 31 and 32 C but

temperatures can reach 43 C especially in Ghana and other citrus-growing regions.

Mean minimum temperature of the coldest month is between 8 and 14 C. Low

temperatures typically limit the range in which citrus can be grown. Citrus

becomes quiescent at temperatures below 13C. Theoretically, the fruits can be killed

by 30 minutes of temperatures from -3 to -2 C. Stems and leaves can be killed by a few

minutes at -7 to -3 C (Rieger, 2002). This is dependent on previous climatic conditions

and age of fruit, leaves and branches.

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2.4.5 Soils

Citrus tolerates a wide range of soils from almost pure sands, organic mucks to

heavy clay soils (Rieger, 2002). The trees do not stand waterlogged soils but grow well

in freely draining soils. They are sensitive to excessive boron, sodium carbonate and

sodium chloride (Purseglove, 1968).

2.4.5.1 Soil texture

Citrus grows in a wide range of light, medium and heavy soils (sands, loams, clay

loams, and sandy clays). Citrus can however tolerate soils that are too dry to be

productive for other crops (soybean, cotton, wheat, sugarcane, etc.).

2.4.5.2 Soil drainage

Citrus performs better on freely draining soils compared with poorly drained soils,

and does not tolerate water logging.

2.4.5.3 Soil acidity

Citrus grows in acid to neutral soils with pH between 5 and 8; however, their

growth is greatest at pH 67. Trees on swingle root-stock will grow in pH range 5 to 7.5

and do not perform well on soils with high pH as a result of high calcium content.

2.4.6 Drought

Citrus growth in subtropical climates where the rainfall averages less than 250 mm/yr or

less is only possible with irrigation. Citrus can generally tolerate 3 to 4 months of

minimal rainfall. Drought tolerance depends on temperatures, soils, wind and the

desired level of fruit production. In Ghana, citrus productivity is low during drought and

therefore requires irrigation during the hot months to sustain intense fruit production.

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2.4.7 Shading

Citrus can tolerate minimal shading. Shading or low light levels will affect the fruit

bearing of citrus trees (Jifon and Syvertsen, 2002). Grapefruit is more susceptible to

shading than oranges. Fruit productivity may be reduced by up to 50 % by shading for

more than 6 months.

2.4.8 Fire

Trees can handle minimal amounts of smoke and heat from fires. Fires that raise the

internal tree temperatures above 54C will damage the trees.

2.4.9 Frost

The species do not tolerate frost well. Previous environmental conditions dictate the

trees level of cold tolerance. When trees experience consistently cooler temperatures

with little rainfall before a freeze, they can demonstrate greater tolerance of the

subfreezing conditions than trees that have been actively growing.

In Ghana and other subtropical climates where citrus is grown commercially, smudge

pots are used to maintain air circulation during frost at the nursing stage. When

available, micro-sprinkler irrigation is the preferred method of cold protection.

Irrigation water is applied prior to the arrival of freezing temperatures to warm the soil

and then again during the freezing events to provide heat to the trees that is released

during the formation of ice crystals.

2.4.10 Water logging

Citrus does not tolerate water logging. When temperatures are over 24C, fibrous root

death from lack oxygen (anoxia) can begin within 7 and 14 days. As citrus roots die,

trees develop water stress symptoms such as leaf wildering, yellowing and dropping.

How quickly water stress develops depends on water movement, soil pH and the

amount of hydrogen sulphide present in hot weather will speed up the development of

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visible symptoms. Moving water delays the development of anoxic symptoms, so it is

important to start drainage operations as soon as possible. If drainage reduces water

levels from 10 to 15 cm per day, root loss can be avoided. Hydrogen sulphide (H2S)

minerals produced by anaerobic bacteria have an odour of rotten eggs (in acid soils but

not in all cases), which is an indication that fibrous roots are dying. This process can be

slower at higher soil pH.

2.4.11Salt

Salinity does not favour effective citrus growth well. For this reason, most citrus

grows poorly in coastal and at all environments. High levels of salt in water will

increase the osmotic pressure and reduce the ease of water uptake by trees

(Boman and Stover, 2002).

Citrus species are differentially sensitive to salt depending on type of salt (Mass, 1992).

2.4.12Wind

Citrus trees are susceptible to leaf, branch and fruit damage in strong winds.

2.5 THE CITRUS FRUIT CHOSEN FOR THIS PROJECT: ORANGE

2.5.1 Description

The orange tree, reaching 7.5 m to 15 m, has a rounded crown of slender branches,

twigs which are twisted and angled when young and may bear slender, semi-flexible,

blunt spines in the leaf axils. There may be faint or conspicuous wings on the petioles of

the aromatic, evergreen, alternate, elliptic to ovate, sometimes faintly toothed "leaves"

technically solitary leaflets of compound leaves. These are between 6.5 and 15 cm long

and 2.5 to 9.5 cm wide. Borne singly or in clusters of 2 to 6, the sweetly fragrant white

flowers, about 5 cm wide, have a saucer-shaped, 5-pointed calyx and 5 oblong, white

petals, and 20 to 25 stamens with conspicuous yellow anthers. The fruit is globose,

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subglobose, oblate or somewhat oval, 6.5-9.5 cm wide. Dotted with minute glands

containing an essential oil, the outer rind (epicarp) is orange or yellow when ripe; the

inner rind (mesocarp) is white, spongy and non-aromatic. The pulp (endocarp), yellow,

orange or more or less red, consists of tightly packed membranous juice sacs enclosed

in 10 to 14 wedge-shaped compartments which are readily separated as individual

segments. In each segment there may be 2 to 4 irregular seeds, white externally and

internally, though some types of oranges are seedless. The sweet orange differs

physically from the sour orange in having a solid centre.

2.5.2 Reasons for Choosing Orange over other Citrus Fruits

1. They thrive very well in the subtropics like Ghana and most neighbouring countries.

2. They last longer than many other citrus fruits when they are stored.

3. They are easy to transport because each orange comes in its own tough skin which

acts as a container.

4. They can be piled into heaps or carried in bags, lunchboxes and shipping containers

without being easily damaged.

5. They are a commonly available source of vitamin C.

2.6 VARIETIES OF ORANGES

2.6.1 Persian (sweet) orange

The Persian orange, grown widely in southern Europe after its introduction to Italy in

the 11th century, was bitter. Sweet oranges brought to Europe in the 15th century from

India by Portuguese traders, quickly displaced the bitter and are now the most common

variety of orange cultivated. The sweet orange will grow to different sizes and colors

according to local conditions, most commonly with ten carpels, or segments, inside.

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2.6.2 Navel orange

A single mutation in 1820 in an orchard of sweet oranges planted at a monastery in

Brazil yielded the navel orange, also known as the Washington, Riverside, or Bahia

navel. The mutation causes navel oranges to develop a second orange at the base of the

original fruit, opposite the stem. The second orange develops as a conjoined twin in a

set of smaller segments embedded within the peel of the larger orange. From the

outside, it looks similar to the human navel. Because the mutation left the fruit seedless

and sterile, the only means available to cultivate more of this new variety is to graft

cuttings onto other varieties of citrus tree. The fruit eventually gained worldwide

popularity due to migration of people.

2.6.3 Dream Navel

Dream Navel is known for its easy peeling and separation; but it is also a sweet, juicy,

less acidic orange than most other navels it is a round shape, with nine to twelve

segments and is often seedless. The Dream is small to medium-sized with a pale orange

rind, light orange pulp and a pleasant ripe-mango aroma. The Dream Navel, a name

patented in 1944, was discovered in Orlando, Florida.

2.6.4 Valencia orange

The Valencia or Murcia orange is one of the sweet oranges used for juice extraction. It

is a late-season fruit and therefore a popular variety when the navel oranges are out of

season. Primarily grown for processing and juice production, valencia oranges have

seeds, varying in number from zero to six per fruit. However, its excellent taste and

internal colour make it desirable for the fresh markets, too. The fruit has an average

diameter of 2.7 to 3 inches (70 to 76 mm). After bloom, it usually carries two crops on

the tree, the old and the new. The commercial harvest season starts from March to June.

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2.6.5 Blood orange

The blood orange has streaks of red in the fruit and the juice is often a dark burgundy

colour. The trees are mostly found in northern and West Africa. The fruit has found a

niche as an interesting ingredient variation on traditional Seville marmalade, with its

striking red streaks and distinct flavour. The scarlet navel is a variety with the same

dual-fruit mutation as the navel orange.

2.6.6 Cara cara

Cara cara is also known as the Red Navel and is likely the product of a Washington and

the Brazilian Bahai navel union. The fruit and juice are a dark red color and extremely

sweet with a low acid content. It originated at the Hacienda de Cara Cara in Valencia,

Venezuela. It is a medium-sized round fruit with 10 to 12 segments and few, if any,

seeds. The yellowish orange rind and rich red pulp make it quite distinguishable and its

appeal increases because of its cherry-flavoured overtones.

2.6.7 Hamlin

Hamlin is a medium small globular, bright orange which has thin rind, fleshy pulp;

making it one of the most productive oranges for processing. It has a sweet flavour

lacking in acid and usually with few seeds. When matured, it is harvested between

October and January. Hamlin originated as a chance seedling in a grove near Glenwood,

Florida, owned by A. G. Hamlin, and has become the most widely grown orange variety

in Florida.

2.6.8 Jaffa

Jaffa and another fruit of the genus Joppa are seedlings from the Israel Beledi tree,

which also produced the Shamouti. The Jaffa was first introduced to Europe, America

and Southern Africa in the 1880s as a potentially cold-tolerant, high quality, midseason

species and soon became popular for its flavour enjoyed as juice or in cooking. The fruit

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is oblique-shaped, with a slightly rough, light orange rind. The flesh is a pale orange,

with only ten segments and a few seeds.

2.6.9 Moro

Moro is a "blood" orange, so named for its dark burgundy color of its rind. Originally

from Sicily, it is common throughout Europe and quite versatile fresh or cooked. This

medium-sized fruit has a relatively long harvest, lasting from December through to

April. The orange has 10-12 segments and is almost seedless. The flavour is unequaled,

ranging from sweet to tart with berrylike overtones. The Moro is now known as the

"connoisseur's citrus".

2.6.10 Moro Tarocco

Moro Tarocco is Italy's finest orange variety and among the best of the Mediterranean

fruit, having the perfect balance between sweetness and acidity. The ovoid shape

resembles that of the tangelo or Minneola. It is a medium-sized seedless fruit with a

rich, juicy, raspberry flavour, which is excellent for juicing or cooking. The original

mutation occurred in the 17th century in Sicily, creating the striking caramel-toned

endocarp. This color is the result of the pigment called anthocarpium, not usually found

in citrus, but is common in other red fruits and flowers.

2.7 GROWTH AND DEVELOPMENT OF SWEET ORANGE

During the first year after planting, tree growth is usually minimal. Providing the

adequate moisture and nutrients, trees greatly increase in height and diameter

between the second and fourth year after planting. For grafted trees, during the first

3 to 4 years after planting, the tree undergoes primarily vegetative growth, but fruit

may occasionally be produced. Vegetative growth flushes occur during the rainy

seasons.

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Quiescence in citrus normally occurs during the rainy season, when lower

temperatures are experienced.Vegetative growth and the annual increase in tree

height and diameter slow down once fruits bearing begins. The desired tree size is

typically achieved between ten and fourteen years after planting. Fruiting typically

declines from its peak after 2025 years, but trees are known to survive and bear

fruit for 250 years (Hume, 1938).

2.7.1 Growth rate

Growth rates are highly variable based on climate, cultural practices, tree spacing, scion,

and rootstock (Wheaton et al., 1999). Younger trees (approximately 510 years old)

tend to have greater growth rates in relation to beginning tree size. In Ghana, trees grew

10 cm/yr in height between 3 and 6 years. Comparatively, trees between 6 and 12 years

grew at a rate of 30 cm/yr in height. Trunk cross-sectional areas can increase from 5 to

33 cm2 each year.

2.7.2 Flowering

Flowering can occur within the second year after planting, but regular flowering occurs

4 years after planting. Seasonal flowering occurs after the rainy season when trees have

experienced a period of quiescence. Over 300 hours of temperature below 20C

followed by warm temperatures will induce flowering.

Multiple blooms each year can be experienced on trees growing in tropical conditions.

Only a small percentage of flowers produce fruits; large numbers of flowers drop after

opening and large numbers of fruits drop between 10 to 12 weeks after pollination.

Fruits take between 7 to 14 months to mature (Purseglove, 1974).

2.7.3 Reaction to competition

Sweet orange trees have demonstrated resiliency to competition from some annual

broad leaf weeds. In the first year after planting the tree, trunk and canopy growth

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of citrus trees were affected by Spanish needle (Bidensbipinnata). The canopy is

more affected by competition than the trunk growth (Buker, 2005). The greatest

reported impact by weeds on citrus yields was from a perennial grass; Bermuda grass

(cynodondactylon) reduced yields 50% after season-long competition (Jordan, 1981).

2.8 COMPOSITION OF ORANGE

Table 2.2 Composition of the edible portion of orange

Component Amount (g)

Carbohydrates (g/l) 67-122

Niacin (g/kg ) 7000-3000

Thiamine (g/kg ) 300-600

Water ( % ) 82.7-89.3

Protein (g/l) 8-11

Acidity of titration (g/l) 12.1-15.9

Ascorbic acid (mg/l) 50-152

Potassium (mg/l) 1900-3700

Calcium (mg/kg) 120-200

Phosphorus(mg/kg) 180-230

Magnesium (mg/kg) 70-140

Beta carotene (g/kg ) 4500-35000

(Source: TSE 34, 2007)

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Table 2.3 Composition of sweet orange (~100 g)

Component Amount (g)

Water 86.6

Protein 0.7-1.3

Oil 0.1-0.3

Fiber 0.5

Ash 0.5-0.7

Calcium 0.04-0.043

Phosphorus 0.017-0.022

Iron 0.0002-0.0008

Carotene 200 IU (vitamin A)

Thiamine 0.00010

Riboflavin 0.00004

(Source: TSE 34, 2007)

Table 2.2 and Table 2.3 show a combination of orange in the edible portion. Orange

fruit nutritional value as determined by the TSE.

2.9 PROPAGATION

Sweet orange can be propagated by many methods including seeds, cuttings, air-

layering, grafting by many methods and tissue culture. Although some cultivars can be

reproduced by seed, this method is considered inferior. Varieties that are reproduced by

seed require more time to produce fruit, are more susceptible to diseases, are more

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difficult to keep true to type and tend to produce more thorns than grafted varieties.

Their fruit is also harder to pick as a result of the upright and thorny growth. In

commercial practice, the orange is commonly propagated by grafting an individual bud

of a selected variety onto a rootstock seedling.

2.9.1 Vegetative propagation known as T-budding

Budding uses a bud cut from the parent tree (scion) that is grafted onto a

seedling rootstock. Once the bud is in place, the foliage of the rootstock above it

is cut of or tied down to force the bud growth. There are however, several

horticultural advantages to budding. A major advantage is the known success in

reproducing the characteristics of the parent tree (Williamson and Jackson, 1994).

Producing trees through budding allows the selection of rootstocks that can

impart disease tolerance and allow production in soils not suited for the scion.

2.9.2 Propagation area

Survival of budded plants is greater in protected environments. Shade houses or

green houses with adequate water are sometimes used.

2.9.3 Early growth

Buds that are successfully growing will be green and have callus forming around

the edges from 14 to 21 days after cutting. Wraps can be removed at this time.

2.10 PESTS AND PATHOGENS

Citrus is affected by numerous species of insects, mites and disease pathogens that

infest the leaves, flowers, bark, fruit and branches of citrus. Insects and mites

2.10.1 Mites

Several species of mites are pests of citrus, most notably the citrus rust mite

Phyllocoptrutaoleivora, which causes minimal damage to foliage but extensive damage

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to fruit. They move from the leaves to the young fruit when it sets andextract the cell

contents from the skin. The damage is generally minor in regard to production but

causes a russetting of the fruit, making it unmarketable. Other mite pests are the citrus

bud mite, Eriophyessheldoni, the red spider mite, Panonychuscitri, and the broad mite,

Polyphagotarsonemuslatus.

2.10.2 Scales, mealybugs, and whitefies

These groups of related insects are very common and they feed on the foliage,

fruit, and roots of citrus. Generally, they pierce plant cells with their needle-like

mouthparts and suck out the liquid; many then secrete honeydew. Ants, such as the

longlegged ant, Anoplolepis longipes, feed on the honeydew and protect the pest

insects from predators.

2.10.3 Aphids, psyllids, and sharpshooters

This group of insects cause similar damage to that caused by the group above but

is notable due to their ability to transmit diseases agents such as viruses and

bacteria. They usually feed on new leaves and stems and can cause significant

damage; however, the diseases vectored are usually more serious than the feeding

damage.

2.10.4 Fruit flies

The Oriental fruit fly, Bactroceradorsalis and the Mediterranean fruit fly,

Ceratitiscapitata, are the main fruit fly pests of citrus. The major problem they pose is

that they deposit their eggs in the fruit as soon as there is any colour break and the

larvae burrow into the fruit and feed. This makes the fruit unpalatable as well as having

the potential to introduce these pests, which cause serious damage to numerous

agricultural products, into new areas.

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2.11 DISEASES AND DISORDERS

Physiological disorders (not caused by pathogens) are listed below.

2.11.1 Fruit splitting

This disorder is common on fruits with thin peels such as navel oranges (Washington

navels are particularly prone to this) and tangerines. Although its specific cause is

unknown, no pathogen has been associated with it, and it is likely due in part to uneven

growth caused by weather or by erratic irrigation and fertilization. Addition of

potassium fertilizer (foliar spray) will reduce splitting in some years (Tucker et al.

1994).

2.11.2 Root rot

There are many possible cause of root rot, one common cause is watering too

frequently. Root rot can be a direct result of the lack of oxygen in the

root zone due to over-irrigation or an indirect result when over irrigation

predisposes the roots to infection by a root rotting pathogen.

2.11.3 Nutrient deficiencies

Nutrient deficiencies can be caused by leaching due to excessive irrigation or rain

by naturally low soil nutrient levels, by soil nutrient imbalances, improper pH or

insufficient or incorrect fertilizer application. Nitrogen, zinc, magnesium and iron

deficiencies are common and correctable.

2.11.4 Root rot and Phytophthora gummosis

There are many pathogenic species of the Phytophthora fungus causing root rots

that prevent the citrus plant from taking up sufficient water and nutrients. The

leaves will turn yellow, wilt, and may drop; the tree slowly declines and often

will die. Gummosis, which is another disease caused by Phytophthora spp., affects

the base of the trunk and lower limbs from which a clear gum is secreted. The

23

bark dries upward, hardens and cracks; the lesions spread and often girdle the branch

or trunk. Most scion wood is very susceptible to this disease; be sure the graft union is

well above the soil level at planting.

2.11.5 Melanose

Melanose is widespread but is a problem only when inoculum levels are high

and there is extended rainfall during early fruit development. The symptoms begin

as small, brown, sunken spots, which become raised as they develop, on the leaves

and fruit. On the fruit the spots may combine and expand to become relatively large

diseased areas, depending on the stage of fruit development when they are

infected.

2.11.6 Greasy spot

Greasy spot, a common disease in hot, humid areas, is caused by the fungus

Mycosphaerellacitri. It produces brown to black lesions on the undersides of leaves,

which appear as grease-soaked spots, and very small lesions on the skin of the fruit. If

severe, the disease causes defoliation leading to a signifcant reduction in yield.

2.11.7 Scab

Citrus scab, caused by Elsinoefawcetti, is the most widespread of three scab diseases.

Infection causes a small bulge on one side of the leaf and a corresponding depression on

the other side. Raised, brown pustules form on the fruit rind, becoming corky as they

develop. The symptoms resemble scaring from wind; scab and wind scar may occur

together where a leaf is in contact with the fruit.

2.11.8 Black spot

Black spot infects leaves and fruit but is only a problem as a disease of the fruit. Leaves

infected by Guignardia citricarpa may develop small necrotic spots with a gray center

but most often do not show symptoms. On fruit, the black spots may take various forms,

24

making the disease difficult to identify. The spots make the fruit unmarketable as fresh

fruit but they can be used for processing. When the infection is severe, fruit may drop

prematurely.

2.11.9 Greening

Greening, one of the most devastating citrus diseases, is caused by a bacterium

that grows in the bark, leaves, and veins of infected trees. It had previously been

thought to be caused by a virus, but the pathogen has now been identified as

Liberobacter species. The affected fruit do not colour properly or remain green,

consequently the name, greening. Other names for the disease, yellow dragon and

yellow shoot, may be more descriptive, because newly infected trees produce shoots

that are yellow. Leaf symptoms on chronically infected trees infected trees may

resemble nutrient deficiencies. Trees will die back and decline severely.

2.11.10 Tristeza

Tristeza virus is one of the most serious pathogens of citrus and is widespread

throughout citrus-growing areas. Symptoms are highly variable among citrus

species and cultivars and are affected by the strain of the virus and the environmental

conditions. Stunting, stem pitting, vein clearing, leaf cupping, yellowing and reduced

fruit size are common symptoms. Vein clearing (disappearance of green colour in or

along the leaf veins, visible when the leaf is held up to light) and stem pitting (small

holes in the stem underneath the bark) can often be used to diagnose this

disease. Tristeza is often severe; resulting in significantly reduced yields and often

tree death.

25

2.12 PROCESS DESCRIPTION FOR PRODUCTION OF POWDERED

ORANGE CONCENTRATE

Upon maturity the ripped fruit are harvested for the production of the powdered

concentrate to begin. The following processes as presented in the order below converts

the harvested orange fruit to the powdered concentrate product.

2.12.1 Transportation and Unloading

Oranges maturity is related to several factors, including colour, sugar content, acidity,

and juice content. Packing oranges for transport should be gentle and sanitary. The

harvested fruit is handpicked into harvesting sacks that are manually dumped into bins

in the grove. These bins are lifted by small trucks and taken to the edge of the grove

where they are dumped into a semi-trailer. Each semi-trailer can haul about 22 MT of

fruit to the processing plant that can be many kilometres away.

2.12.1.1 Transportation

Temperature management is critical during long distance transport, so loads must be

stacked to enable proper air circulation to carry away heat from the produce itself as

well as incoming heat from the atmosphere and off the road. Transport vehicles should

be well insulated to maintain cool environments for pre-cooled commodities and well

ventilated to allow air movement through the produce. During transport, produce must

be stacked in ways that minimize damage, then be braced and secured. An open air

vehicle can be loaded in such a way that air can pass through the load, and provide some

cooling of the produce as the vehicle moves. Travelling during the night and early

morning can reduce the heat load on a vehicle that is transporting produce.

Transportation can be done by

open vehicles,

refrigerated trailers

26

2.12.1.1.1 Open Vehicles

Bulk loads of produce should be carefully loaded so as not to cause mechanical damage.

Vehicles can be padded or lined with a thick layer of straw. Woven mats or sacks can be

used in the beds of small vehicles. Other loads should not be placed on top of the bulk

commodity. Cooling open loads is desirable whenever possible. A truck ventilating

device can be constructed for an un-refrigerated open vehicle by covering the load

loosely with canvas and fashioning a wind catcher from sheet metal. The scoop should

be mounted at the front of the bed and should reach somewhat higher than the height of

the cab. High transportation speeds and/or long distance transport run the risk of causing

excess drying of the crop.

2.12.1.1.2 Refrigerated Trailers

For optimum transport temperature management, refrigerated trailers need insulation, a

high capacity refrigeration unit and fan, and an air delivery duct. The condition of the

inside of a refrigerated trailer affects its ability to maintain desired temperatures during

transport. Handlers should therefore inspect the trailer before loading.

2.12.1.2 Unloading

A loading dock can ease the work associated with handling horticultural produce at

destination. Containers can be transferred more rapidly and with less bending and

lifting. For large trucks, a loading dock 117 to 122 cm high (46 to 48 inches) functions

well, while for small trucks or pickups a height of 66 to 81 cm (26 to 32 inches) is

recommended.

2.12.1.2.1 Unloading via Pulley

A simple device for easing the work of unloading transport vehicles can be constructed

using a two pulleys and a strong rope. One pulley can be mounted inside the truck at the

front of the bed, the second outside on a portable post or on a stationary object like the

27

side of a building. Containers can be hung directly by their handles or placed into a

sling.

2.12.1.2.2 Unloading Staircase

Also a simple set of stairs can be constructed to ease the work of loading and unloading

produce. The steps can be made of wood or steel matting and steel bars can be used for

supports. Using a ramp is a simple and safe method for unloading produce. The ramp

should be wide enough to prevent accidents and strong enough to carry the full weight

of the handler and the package being carried. Providing hand-trucks or small carts can

also ease the work associated with unloading.

2.12.1.2.3 Unloading via Dry or Water Flume System

The harvested oranges may also be unloaded by trucks into storage either via a dry or

water-flume systems. The dry system includes aerated silos with sloping planes on

which the product is placed in layers to protect integrity of orange. The water system

involves large concrete tanks at ground level; the product is discharged directly into

these tanks and moved by means of water circulation which conveys the product to a

special elevator.

Any time produce is dumped from one container into another, care should be taken to

reduce mechanical damage to the commodity. When dumping produce from field bins

or from transport vehicles into the packinghouse, dry or wet dumping can be practiced.

When using dry dumping practices, the field container should be emptied slowly and

gently onto a tilted ramp with padded edges.

Wet dumping is sometimes used to reduce mechanical damage, either by dumping into

water rather than onto a dry ramp, or by immersion and floatation. If the specific density

of the produce, such as orange is lower than that of water the produce will float

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2.12.2 Storage

Under normal weather conditions, fruit store better on the tree than in cold storage. Cold

storage should not be attempted if the fruit storage potential has been expended by

prolonged tree storage. Once harvested, fruit quality will not improve. Before placing

into storage, fruit should be pre-cooled to slow respiration and treated with an approved

fungicide to reduce decay. Oranges can be stored for up to 12 weeks under optimum

storage conditions. Ultimate storage-life depends on cultivar, maturity, pre-harvest

conditions, and postharvest handling. Oranges begin to freeze in storage at about -1 C

(Whiteman, 1957). During storage, fruit should be inspected often for signs of decay or

disorders. Such problems will advance rapidly once the fruit are removed from cold

storage.

Only fruit which have not been damaged in harvest are used for storage, although it is

difficult to harvest fruit without some minor damage. Sometimes a chemical treatment

is applied to the fruit before storage, to reduce the incidence of postharvest diseases.

Commercial growers and handlers can store orange for three to eight weeks when

refrigerated at 3oC to 9oC, depending on the initial condition of the fruit. Optimum

humidity for storage of oranges is 90 to 95%.

Plastic crates or boxes are used for storing fruit. Sweet oranges such as Valencia or

Liucheng should be stored with three or four layers per box. Too many layers in one

box may cause bruising of the fruit. Boxes should be stacked inside the storage room in

a way that maintains good ventilation. For the first few weeks of storage, ventilation

windows should be left open. Throughout the storage period, the windows should be left

open at night or in cold weather, in order to cool the fruit. When temperatures are high

in the day time, the ventilation windows should be closed. Sunlight should not be able

to penetrate inside the storage room. Storage rooms should be constructed in places

29

where cold air can flow into the room at night. The storage room should have a high

roof, to allow better circulation of cold air at night. Ventilation windows should be

small but there should be a large number of them, to allow better air circulation. It is

recommended that some ventilation pipes should be buried under ground, to bring in

cool air through the floor of the room. The roof and walls should have good heat

insulation, to keep temperatures as cool as possible. The storage room should be insect-

proof and rat-proof. A good storage room is the key for extending the shelf life while

maintaining fruit quality. The room should be kept clean, and all rotting fruits should be

removed. Before storage, the room should be sanitized by washing the walls and floor

with 5%formalin.

Another way of storing fruit is to leave them on the tree. In California, Valencia oranges

can be left on the tree for five months, from May to October. In Taiwan, this has been

tried for the very similar Liucheng orange. However, the harvest can only be delayed for

one month and then the fruit drop to the ground.

Since most processors cannot use the whole harvest they receive as they receive it, some

fruit is stored, short term, as they come in, not refrigerated. The harvested fruits can also

be stored in storage bins, made of wood and metal prior to further processing. These

bins is designed with baffles in zigzag arrangement to minimize impact as fruit

descends through to the base of the bin avoiding bruising of bottom fruits

Unwholesome fruits are removed during unloading before the oranges are conveyed to

storage bins. From the storage bins the fruits is rolled out into conveyor belts and

transported to the main extraction line via a bucket elevator and on to a surge bin. This

surge bin would serve as a buffer to control and maintain an adequate fruit flow for the

extraction line.

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2.12.3 Sorting

Following harvesting, the preparation of fruits for processing involves reducing and/or

eliminating external contamination by visual inspection and sorting of the incoming

fruits (colour, size, maturity).Direct hand contact is a common practice during

inspection and sorting. During the sorting process, the washed fruits are inspected as a

check for quality assurance. In view of this immature, fragmented, corrupt and rotten

fruits are sorted and picked out of the lot before they are transferred to the main

extraction line.

Post harvest sorting and grading of fruits is a difficult and labour intensive component

of the commercial fresh fruit market. Although mechanical equipments are available to

perform operations like sorting and grading of fruits, manual effort is still indispensable.

Typically people are positioned along the packing lines, sorting by visual inspection as

the fruit passes on a conveyor belt and mechanical sorting is limited to size sorting.

Manual sorting is costly and unreliable since human judgment in identifying the

multiple varying parameters is inconsistent, subjective and slow. For tomato, apple,

pear, peach, persimmon, orange, plum and so on orbicular fruits classification is by

weight.

2.12.3.1 Automatic Fruit Sorting and Grading Machine

Automatic fruit grading and sorting has not been implemented widely for all types of

fruits. In the present scenario manual sorting is more popular but slow in process and

grading is done by visual inspection that could be error prone. Grading is done on the

basis of various criteria like weight, shape, colour, size. In this kind of machine these

factors are taken care by image processing and weight measurement through load cell.

In this type the sorting and grading is done principally by photographing the entire

surface of the fruit and subsequently by processing the image. The main advantages of

31

this type of machine is its ability to facilitate automatic grading and sorting of apple in a

non destructive method. The whole machine is cheap compared to other existing

machines where robotic arms are used. It also increases sorting and grading of fruits as

it can process large volume in short time.

2.12.3.2 Citrus Fruits Sorting Machine

This machine is applicable to sorting of citrus fruits with a maximum production output

(orange) of 35 t/h. The general configuration of the machine is three levels and four

grades. The level interval of every level can be adjusted and the interval is gradually

bigger from the material inlet end. The fruit will move forwards under the driving of the

moving belt and the rotary rolling rail will also drive the rotation. The interval of every

level is different. Passing the level is defined as grade 1, and not passing the last level is

defined as the maximum grade. Every level is provided with a separate collecting

hopper, so as to achieve the purpose of sorting fruit.

2.12.3.3 Stainless Steel Rolling Rail Type Fruit Sorting Machine

The materials of rolling rail can be 304 stainless steel tube and PVC. The stainless steel

chain drives the rolling rail to make revolution and the rolling rail on the working

surface will abrade at the rubber track to make rotation, so as to drive the fruit and

vegetable to rotate freely. It can coordinate with manual sorting to sort out the

unqualified fruit and vegetable, which will be transferred by the waste material

conveyor allocated upwards or downwards.

2.12.4 Washing

Washing is an essential part of good hygiene and health. A high pressure washing

system may be used to remove scale insects and debris. This technology allows more

fruit to meet quality standards and quarantine requirements as insect bodies and other

heavy film deposits from mould growth are removed. It also improves fruit appearance

32

and facilitates identification and removal of unsound fruit at the grading stage. At this

point unwholesome fruit and other fruit that do not meet external quality standards are

removed.

Washing oranges in a sink filled with water is not recommended since the standing

water can spread contamination from one orange to another. The use of soap or

detergent is also not recommended or approved for washing oranges because the fruits

can absorb some detergent residue. Therefore the oranges is pulled from the surge bin

into a brush washer, washed, sanitized and graded again before juice extraction takes

place.

Steel drums can also be used to make a simple washing stand. The drums are cut in half,

fitted with drain holes, and all the metal edges are covered with split rubber or plastic

hose. The drums are then set into a sloped wooden table. The table top is constructed

from wooden slats and is used as a drying rack before packing. Because steel drums are

often used to store petroleum and chemical products, they should be thoroughly cleaned

before being used as a washing stand. This tank for washing produce is made from

galvanized sheet metal. A baffle made of perforated sheet metal is positioned near the

drain pipe and helps to circulate water through the produce. Fresh water is added under

pressure through a perforated pipe, which helps move floating produce toward the drain

end of the tank for removal after cleaning.

Chlorination of wash water is very important. Chlorine can reduce the spread of

contamination form one item to another during the washing stage. The pH of the wash

water should be maintained at 6.5 to 7.5 for best results. Typically 1 to 2 ml of chlorine

bleach per litre of clean water will provide 100 to 150 ppm total Cl. More chlorine will

be required if temperatures are high or if there is a lot of organic matter in the wash

water.

33

2.12.5 Extraction

Extraction of juice would be carried out by means of an extractor on a large scale. Thus

the mode of extraction would depend on the type of extractor. Nevertheless, the

extraction process would ensure the separation of fruit juice from seeds and peels.

2.12.5.1 Types of Extractors

There are almost endless lists of juice extractors to choose from. This can make the

process overwhelming, but the reality is that all these juice extractors fit neatly into just

three basic kinds

centrifugal juice extractors,

masticating juice extractors and

triturating juice extractors

2.12.5.1.1 Centrifugal Juice Extractors

Centrifugal juice extractors are the most popular of juicer machines because they are,

generally speaking, the cheapest. These juicers are easy to spot because of their

upright appearance. Their feed chute is a vertical tube through which fruits and

vegetables are dropped down so that they come in contact with the centrifugal style

blade below. The blade spins at very high a speed that rapidly chops down fruits in

small pieces that are then thrown outwards from the blade by centrifugal force against a

mesh filter that surrounds the blade. The force then pushes juice out of the small pieces

of fruits and vegetables.

The main advantages of centrifugal juice extractors are that they make juice very

quickly, they are relatively inexpensive, the feed chutes are usually large and can

34

accommodate large pieces of fruits and vegetables which cuts down preparation time,

and they are usually easy to clean up.

On the negative side, the heat generated by the high-speed operation does kill some

nutrients (but just some, they still deliver a nutritious drink) and they extract less juice

from fruits than the other extractors.

2.12.5.1.2 Masticating Juice Extractors

Masticating juice extractors are generally more expensive. They also tend to be longer

and less high because the feed chute is usually horizontal. Masticating juice extractors

dont use a blade to chop up fruits but instead chews the juice out of them. Its mode

of operation gives it the name masticating juice extractors which comes from the word

masticate which means chew. So, to chew the fruits a masticating juice extractor uses

a gear system. The gear looks something like a screw, long and ribbed and fits tightly

inside a tube. Small pieces of fruits are then passed down the tube and come into contact

with the gear. The gear rotates very slowly and squeezes a very high juice yield out of

the fruits as they pass by it. So that is the basic mechanism of a masticating juice

extractor.

The advantages of masticating juice extractors are higher juice yield and less nutrient

loss because they generate very little heat.

On the negative side they take longer to make a fresh juice, fruits need to be chopped

into smaller pieces to fit in the feed tube increasing preparation time and they cost more.

2.12.5.1.3 Triturating Juice Extractors

Triturating juice extractors take the single gear mechanism of the masticating juice

extractor and take the process one step further by adding another gear. For this reason,

35

triturating juice extractors are also commonly known as twin gear juicers. These twin

gears actually sit side by side with their ribbed edges sitting extremely close together.

This helps to extract a slightly higher juice yield and even less heat than masticating

juice extractors. A few more nutrients are saved using this mechanism.

The advantages of a triturating juice extractor are basically the same as a masticating

juice extractor only a little better more juice yield and higher nutrient preservation.

On the negative side triturating juice extractors are the most expensive machines and are

very slow at making juice.

2.12.6 Separation of Pulp from citrus

During extraction, juice-laden tissue burst up to release juice from the fruits. The juice

flows from the extractor outlet with the drained soft tissue mass pulp dispersed within it.

This introduces the need for separation of the pulp material from the juice product.

2.12.6.1 Types of Separation

The separation process can be accomplished via several means as discussed below;

2.12.6.1.1Centrifugation or Cyclonic Separation

Centrifugation is a process that involves the use of the centrifugal force for the

separation of mixtures (fruit juice), used in the citrus industry and in laboratory settings.

More-dense components of the mixture migrate away from the axis of the centrifuge,

while less-dense components of the mixture migrate towards the axis. Chemists and

biologists may increase the effective gravitational force on a test tube so as to more

rapidly and completely cause the precipitate (pulp) to gather on the bottom of the tube.

The remaining solution which is the juice also called the "supernatant liquid". The juice

is then either quickly decanted from the tube without disturbing the pulp, or withdrawn

36

with a Pasteur pipette. The rate of centrifugation is specified by the acceleration applied

to the sample, typically measured in revolutions per minute (RPM) or g. The pulp's

settling velocity in centrifugation is a function of their size and shape, centrifugal

acceleration, the volume fraction of pulp present, the density difference between the

pulp and the juice, and the viscosity. In the chemical and food industries, special

centrifuges can process a continuous stream of particle-laden liquid (juice).

2.12.6.1.2 Decantation

Decantation is a process for the separation of mixtures. This process is generally used to

separate a liquid (fruit juice) from an insoluble solid (pulp). This is achieved by

carefully pouring the extracted fruit juice from a container in order to leave the pulp in

the bottom of the original container. Usually a small amount of the fruit juice must be

left in the container, and care must be taken to prevent a small amount of pulp from

flowing with the juice out of the container. Another practical application of decantation

in the process industry is in red wine, where the wine is decanted from the potassium

bitartrate crystals.

2.12.6.1.3 Filtration

Filtration is a mechanical or physical operation which is used for the separation of solids

(pulp) from liquid (juice) by interposing a medium through which only the fluid can

pass. In this case however, oversize pulp in the fluid are retained, but the separation is

not complete; pulp will be contaminated with some fluid and filtrate (juice) will contain

fine particles depending on the pore size and filter thickness.

2.12.6.2 Equipment for Separation of Pulp from Fruit

A centrifuge may be useful in successfully decanting a solution. The centrifuge causes

the pulp to be forced to the bottom of the container; if the force is high enough, the pulp

may form a compact solid. Then the juice can be more easily poured away, as the pulp

37

will likely remain in its compressed form. A filter centrifuge and a hydrocyclone are the

types of centrifuges that can be used. Filtering centrifuges are able to apply up to over

3,000 G-forces on the liquid/solids mixtures, which separates the heavier solids from the

lighter solids. Additionally, high G-forces separate fine solids from liquid which implies

that the higher the G-forces applied, the higher the efficiency.

2.12.6.3 Theory and Design of Decanter Centrifuge

Decanter centrifuge design consists of a solid container, called a bowl, which rotates at

high speed. Inside the bowl tube, a screen conveyor rotates in the same direction, but at

a slightly different speed. A differential gear is typically used to adjust speed.

1. The decanter centrifuge slurry is fed through a stationary pipe, which is inside a

hollow shaft connected to a screw conveyor or scroll.

2. The slurry enters a feed compartment located inside of the conveyor and is forced

through discharge nozzles to the bowl section.

3. Once inside the bowl, centrifugal force causes the material to separate.

4. The screw conveyor moves the solids to the tapered end where they are discharged.

5. Clear fluid flows out the other end.

2.12.6.4 Decanter Centrifuge Application

Decanter centrifuges are used to extract solid materials (pulp) from liquids (juice) when

they are mixed together in slurry. Decanter centrifuges are used in many industrial

applications such as:

1. Oil /solids separation (oil well drilling, refining, de-watering)

2. Industrial and biological wastewater treatment

3. Food processing (olive oil, wine, fruit juice)

4. Fish processing (fish meal, fish oil)

5. Chemical slurry

38

The main drive motor supplies power to turn the centrifuge. AC drives are commonly

used to power the main drive motor. There are several different types of decanter

centrifuges, such as: Vertical, horizontal, or scroll (conveyor).

2.12.7 Preservation Methods

The presence of micro-organisms in the powdered concentrate may reduce product

shelf-life to a considerable extent, the least; three to four weeks. The term shelf-life

refers to the time that a food takes to decline to an unacceptable level. In extreme cases

of microbial activity, it may lead to the deterioration of product even before hitting the

market. Food deterioration is however not limited to the presence of micro-organisms

alone; reactions of certain food enzymes may as well cause the same fate. To curb this;

the processing would be done so as to eliminate micro-organisms or any such enzyme or

reduce them to the barest minimum possible. The processing technique chosen would be

based on the final properties such as flavour and taste. In view of this the following

preservative methods in food processing were examined for scrutiny before selection.

2.12.7.1 De-Aeration

The term de-aeration refers to the removal of oxygen from the juice product. In juice

processing operations the fruit and juice are subjected to considerable aeration. The

inclusion of oxygen can promote enzymatic browning, destroy nutrients, modify flavour

and otherwise damage quality. Therefore, the de-aeration stage in the processing would

mainly seek to reduce levels of dissolved oxygen in addition to the following;

Reduces flavour deterioration

Prevents degradation of ascorbic acid as well as

Reduction of frothing

39

De-aeration can be carried out by means of a de-aerator. The de-aerator works in a

process that expels oxygen from the juice by reducing pressure, hence solubility of the

gas (Henrys Law). De-aerators fall under two main types namely;

The tray type and

The spray type

2.12.7.1.1 Tray-type De-aerator

The typical horizontal tray-type de-aerator has a vertical domed de-aeration section

mounted above a horizontal feed storage vessel. The feed enters the vertical de-aeration

section above the perforated trays and flows downward through the perforations. Low-

pressure de-aeration steam enters below the perforated trays and flows upward through

the perforations. Some designs use various types of packing material, rather than

perforated trays, to provide good contact and mixing between the steam and feed.

The steam strips the dissolved gas from the feed and exits via a vent at the top of the

domed section. Some designs may include a vent condenser to trap and recover any

water entrained in the vented gas. The vent line usually includes a valve and just enough

steam is allowed to escape with the vented gases to provide a small and visible telltale

plume of steam.

2.12.7.1.2 Spray-type De-aerator

The typical spray-type de-aerator is a horizontal vessel which has a preheating section

and a de-aeration section. The two sections are separated by a baffle. Low-pressure

steam enters the vessel through a sparger in the bottom of the vessel.

The feed is sprayed into preheating section where it is preheated by the rising steam

from the sparger. The purpose of the feed spray nozzle and the preheating section is to

40

heat the feed to its saturation temperature to facilitate stripping out the dissolved gases

in the following de-aeration section.

The preheated feed then flows into the de-aeration section, where it is de-aerated by the

steam rising from the sparger system. The gases stripped out of the water exit via the

vent at the top of the vessel. Again, some designs may include a vent condenser to trap

and recover any water entrained in the vented gas. Also again, the vent line usually

includes a valve and just enough steam is allowed to escape with the vented gases to

provide a small and visible telltale plume of steam

2.12.7.2 Pasteurization

The pasteurization stage during the juice processing involves heating the juice to a

given temperature for a length of time that will destroy all organisms and natural

enzymes that can develop to cause deterioration of the product (Bates, Crandall and

Morris, 2001). At sufficiently high temperatures in the range of 80- 95oC, most micro-

organisms( E. coli and Salmonella) and natural enzymes( pectolytic enzymes) that cause

deterioration in food become inactive; the residence time for pasteurization would

depend on the process temperature the residence time increases with decreasing

temperature. Pasteurization is grouped under six different types based on the process

technique. These are listed below;

1. Batch holder process

2. Continuous Holding process

3. In bottle process

4. Flash process

5. High temperature, short time

6. Ultra-high temperature

41

2.12.7.2.1 In-bottle Process

The juice feed is heated in a large jacketed container by steam or hot water circulating

an interspace. The temperature to which the juice is raised and held varies (in different

countries depending on the margin of safety to allow) from not less than 60oC to as

much as 65.5oC, for at least thirty minutes. The juice is then cooled, still in the container

to 10oC or less. The batch holder vessel has to be emptied, and there is a break in the

operation for at least one hour before the next batch is ready for filling.

2.12.7.2.2 Continuous Holding Process

This is an extension of the batch system, by which juice is heated and subsequently

cooled by a plate heat exchanger outside the actual holding vessel of which there may

be four or more and each of which may have a capacity of up to five hundred litres. The

heated juice, at say 65oC is run into the first holding vessel, where its temperature is

maintained by a hot-water jacket or other means. When the first holder is full, which

takes perhaps 10-15 minutes, the filling of the second holder begins automatically and

so on. By the time the first holder has been held for 30 minutes, the last is just being

filled. A virtually continuous flow of pasteurized juice can be obtained. Large volumes

can be treated in few hours.

2.12.7.2.3 In-Bottle Process

This involves the heating of juice to relatively colder pasteurization temperature and

filled into special bottles which are then hermetically sealed. The filled bottles are

maintained at those temperatures for about thirty minutes.

2.12.7.2.4 Flash Process

This is the process by which juice is heated as rapidly as possible to75oC or 80

o C, or

even above, and then cooled rapidly.

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2.12.7.2.5 High Temperature, Short Time

This is a continuous process by which juice is rapidly brought to a temperature of 71-

72o

C, and held at that temperature for not less than 15 seconds, and is then rapidly

cooled to 10 or below. These temperature and time give a good margin of safety.

Heating is usually by hot water, and the rapid heat exchange is effected through

stainless steel plates, or in one type f machine, by passing the juice through the annular

space between concentric water-heated tubes.

2.12.7.2.6 Ultra-high Temperature

This is another continuous process by which juice is heated rapidly usually in two stages

(the second stage being under pressure), to between 135oC and 150

oC for times of the

order of a few seconds only, and is cooled rapidly.

2.12.8 Homogenisation

The pasteurized juice product would be mixed or agitated for homogeneity to ensure

even distribution of colour, aroma and taste flavours. The word, homogenize means

causing two or more phases, such as a fluid and a powdered solid, or two or fluids, and

causing them to be randomly distributed through one another. Homogenizing effects can

also significantly reduce the amount of additives required. This step is essential in

keeping all products at the same level of component dosage.

2.12.8.1 Types of Homogenisers

Generally, liquids are agitated in a cylindrical vessel which can be opened or closed to

the air. An impeller is mounted on a shaft and is driven by an electric motor that powers

the blades to move in a circular motion causing even distribution of the contents of the

tank. There are different types of homogenizers or agitators used in the process

industries, which includes;

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2.12.8.1.1 Three-Blade Propeller Agitator

There are several types of agitators commonly used. A common type is the three-blade

marine-type propeller similar to the propeller blade used in driving boats. The propeller

can be a side-entering type in a tank or be clamped on the side of an open vessel in an

off-center position. These propellers turn at high speeds and are used for liquids of low

viscosity.

2.12.8.1.2 Paddle Agitator

Various types of paddle agitators are often used at low speeds between about 20 and

200rpm. Two-bladed and four-bladed are often used. At low speeds, mild agitation is

obtained in an unbaffled vessel. At higher speeds baffles are used, since without baffles,

the liquid is simply swirled around with little actual mixing. The paddle agitator is

ineffective for suspending solids since good radial flow is present but little vertical or

axial flow. An anchor or gate paddle is often used. It sweeps or scrapes the tank walls

and sometimes the tank bottom. It is used with viscous liquids where deposits on walls

occur and to improve heat transfer to the walls. However, it is a poor mixer. These are

often used to process starch pastes, paints, adhesives and cosmetics.

2.12.8.1.3 Turbine Agitators

Turbine turbines that resemble multi-bladed paddle with shorter blades are used at high

speeds for liquids with a very wide range of viscosities. The diameter of a turbine is

normally between 30 and 50 % of the tank diameter. Normally, the turbines have four or

six blades. The turbines with flat blades give radial flow. They are also useful for good

gas dispersion where the gas is introduced just below the impeller at its axis and is

drawn up to the blades and chopped into fine bubbles. In the pitched-blade turbine with

the blades at 45o, some axial flow is imparted so that a combination of axial and radial

44

flow is resent. This type is useful in suspending solids since the currents flow downward

and then sweep up the solids.

2.12.8.1.4 Helical-ribbon Agitators

This type of agitator is used in highly viscous solutions and operates at a low RPM in

the laminar region. The ribbon is formed in a helical path and is attached to a central

shaft. The liquid move in a tortuous flow path down the center and up along the side in

a twisting motion. Similar types are the double helical ribbon and the helical ribbon

with a screw.

2.12.9 Food concentration

After the juice has been extracted and pasteurized, the next chemical process is to

produce a concentrate and powder from the orange juice. All this is done with the idea

to meet customers expectations of appealing and appetizing product; colouring is a

prerequisite to compensate process-related losses to improve overall appearance

(Newsome, 1986).

Juice concentrates and fruit powders are produced by evaporation, drying and

crystallisation. The water part of the juice can be removed by evaporation under vacuum

and heat to remove most of the water before it is frozen and crystallised. As pressure is

reduced in a vacuum, the boiling point for the water in the juice will be reduced, thus

requiring lower temperatures to evaporate the mixture. This process however cannot be

used to reduce all the moisture to the point that it turns powder. This is because

exposure to heat may damage the sugars in the concentrate and may also affect visual

appearance of the product. Orange juice is famous for the high content of vitamin C and

provides a number of health benefits. However, vitamin C is water soluble and that it is

easily destroyed by cooking and freezing. Hence this process would require the removal

45

of essences and oils separately during the evaporation and added back after obtaining

the concentrated juice.

Evaporation can be defined as the process where liquid water is transformed into a

gaseous state. Evaporation can only occur when water is available. It also requires that

the humidity of the atmosphere be less than the evaporating surface (at 100% relative

humidity there is no more evaporation). The evaporation process requires large amounts

of energy. For example, the evaporation of one gram of water requires 600 calories of

heat energy. Evaporation plants are used as a thermal separation technology, for the

concentration or separation of liquid solutions, suspensions and emulsions. A liquid

concentrate that can still be pumped is generally the desired final product. Evaporation

may however also aim at separating the volatile constituents, or distillate, as would be

the case in a solvent separation system. During these processes, it is usual that product

qualities are maintained and preserved. These, together with many other requirements

result in a wide variety of evaporator types, operating modes and arrangements. The

types of evaporators include:

2.12.9.1 Falling Film Evaporators

This type of evaporator is generally made of long tubes which are surrounded by steam

jackets. The uniform distribution of the juice into this equipment is important when

using this type of evaporator. This evaporator is usually applied to high viscous

solutions so it is frequently used in the chemical, food and fermentation industry.

2.12.9.2 Plate Evaporators

This type of evaporator has a relatively large surface area. The plates are usually

corrugated and are supported by frame. During evaporation, steam flows through the

channels formed by the free spaces between the plates. The steam alternately climbs and

46

falls parallel to the concentrated liquid. The concentrate and the vapour are both fed into

the separation stage, where the vapour is sent to a condenser. Plate evaporators are

frequently applied in the dairy and fermentation industries since they have spatial

flexibility. A negative point of this evaporator is that, it is limited in its ability to treat

viscous or solid-containing products.

2.12.9.3 Forced Circulation Evaporators

Natural circulation evaporators are based on the natural circulation of the product

caused by the density differences that arise from heating. In an evaporator using tubing,

after the water begins to boil, bubbles will rise and cause circulation, facilitating the

separation of the liquid and the vapour at the top of the heating tubes. The amount of

evaporation that takes place depends on the temperature difference between the steam

and the solution.

2.12.9.4 Multiple-stage Evaporators

These evaporators can be made of up to seven evaporator stages or effects. Putting

together several evaporators saves heat and thus requires less energy and adding another

evaporator to the original decreases the energy consumption to 50% of the original

amount and so on.

2.12.9.5 Rising Film Evaporators

In this type of evaporator, boiling takes place inside the tubes, due to heating made by

the steam outside the tubes. This equipment is quite efficient, the advantage being prone

to quick scaling of the internal surface of the tubes. This design is usually applied to

clear, non-salting solutions.

47

On a large scale, concentration can be carried out using a multiple-stage column

evaporator under a vacuum. The obtained semi-concentrates and the final concentrates

are rapidly cooled to 0oC and then frozen at a low temperature (about -26

oC) prior to

drying. Yield at each stage can be calculated as:

Apparent yield, % = ..(1)

Where;

Mjc = mass prior to concentration

Mconc = mass after concentration.

2.12.10 Drying

After obtaining the concentrate, it is then dried. Drying is a method of food preservation

that works by removing water from the food which prevents the growth of

microorganisms and decay. Drying can be done with drying agents to minimize the

stickiness of the powder. Natural hygroscopic and thermoplastic property of fruit juice

is the basic problem in transport and handling of fruit juice powder (chegini, ghobadian,

2007).

Forms of drying include freeze-drying, spray drying, pulse combustion drying and

tunnel drying. Among these, spray dying may be more economical. Spray drying has

become the most important technique for dehydrating fluid foods such as milk, coffee

and egg powders, and is used extensively in the pharmaceutical and chemical industries.

This is the preferred method of drying of many thermally-sensitive materials such as

foods and pharmaceuticals. Fruit juice powder obtained by spray drying favors the yield

of high sugar content solids, most of them present in amorphous state.

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There are many different types and variation of dryers, and selecting the proper dryer is

crucial to achieving the desired results.

Different types of Dryers are required depending on factors such as:

Capacity

Product quality

Product size

Product consistency

Hours of operation

Amount of water to be evaporated

Acidity of the product

Operational environment

2.12.10.1 Flash Dryers

A Flash Dryer uses ductwork, which acts as a container for the uniform transfer of

thermal energy from a hot gas stream to a moisture laden product, for the purpose of

moisture reduction in the product. For proper drying the particle size must be uniform

and relatively small. Wet product is introduced in the gas stream where the moisture is

flashed off, and then the dried product is removed from the gas stream.

2.12.10.2 Fluid Bed Dryer

A Fluid Bed Dryer uses a container equipped with vertical jets of hot gases, which acts

as a container for the uniform transfer of thermal energy from a hot gas stream to a

moisture laden product, for the purpose of moisture reduction in the product. For proper

drying the particle must have near spherical shape as well as uniform small size and

moisture content. The wet product must be uniformly introduced into the drying gas

49

stream where the moisture is flashed off. The dried product is removed from the exiting

gas stream.

2.12.10.3 Rotary Dryers

A rotary dryer uses a rotating cylindrical drum, which acts as a container for the

uniform transfer of thermal energy from a hot gas stream to a moisture laden product,

for the purpose of moisture reduction in the product. Wet product is introduced into the

inlet of the drum where it is dried as it is conveyed to the drums outlet. The drum is

equipped with flighting to disperse the product into the drying gas stream as the drum

rotates. The product can either be conveyed pneumatically or it can be conveyed by

gravity if the drum is on a slope. There are several different types of rotary dryers and

they can be used in many different applications. The two common types of rotary drying

systems are single and triple pass; however, there are several other types and hybrids of

these designs.

2.12.10.4 Steam Tube Dryer

A steam tube dryer is a constant temperature drying process. The drying process always

takes place at the steams saturation temperature for the steams pressure. Product can

be conveyed with gravity, screw flighting, or pneumatics..

2.12.10.5 Spray Dryer

A spray dryer is a device used in spray drying. It takes a liquid stream and separates the

solute or suspension as a solid and the solvent into a vapor. The solid is usually

collected in a drum or cyclone. The liquid input stream is sprayed through a nozzle into

a hot vapor stream and vaporized. Solids form as moisture quickly leaves the droplets.

A nozzle is usually used to make the droplets as small as possible, maximizing heat

50

transfer and the rate of water vaporization. Droplet sizes can range from 20 to 180 m

depending on the nozzle.

Spray dryers can dry a product very quickly compared to other methods of drying. They

also turn a solution or slurry into a dried powder in a single step, which can be

advantageous for profit maximization and process simplification.

2.12.10.6 Freeze-dryers

Freeze dryers are devices used in Freeze-drying. Freeze drying is a dehydration process

typically used to preserve a perishable material or make the material more convenient

for transport. Freeze-drying works by freezing the material and then reducing the

surrounding pressure and adding enough heat to allow the frozen water in the material

to sublime directly from the solid phase to the gas phase.

2.12.10.7 Sun Drying

Sun drying is the old-fashioned way to dry food because it uses the heat from the sun

and the natural movement of the air. This process is slow and requires a good deal of

care. The food must be protected from insects and covered at night. Sun drying is not as

sanitary as other methods of drying. In sun drying the use of a natural-draft dryer is

required. The advantage of this kind of dryer is that it hastens drying by trapping heat

from the sun. Natural heat is slower and less dependable than controlled drying in an

oven or food dryer. If you are thinking about buying a juice extractor then you will

notice that there are almost endless lists of juice extractors to choose from. This can

make the process overwhelming, but the reality is that all these juice extractors fit neatly

into just three basic kinds centrifugal juice extractors, masticating juice extractors and

triturating juice extractors.

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CHAPTER THREE

3.0 PROCESS DESCRIPTION AND SELECTION

3.1 Unloading via Dry System

The harvested oranges may also be unloaded by trucks into storage via a dry system.

The dry system includes aerated silos with sloping planes on which the product is

placed in layers to protect integrity of orange. Any time produce is dumped from one

container into another, care should be taken to reduce mechanical damage to the

commodity. When using dry dumping practices, the field container should be emptied

slowly and gently onto a tilted ramp with padded edges.

3.2 Storage

Since most processors cannot use the whole harvest they receive as they receive it, some

fruit is stored, short term, as they come in, not refrigerated. The harvested fruits can also

be stored in storage bins, made of wood and metal prior to further processing. These

bins is designed with baffles in zigzag arrangement to minimize impact as fruit

descends through to the base of the bin avoiding bruising of bottom fruits

Unwholesome fruits are removed during unloading before the oranges are conveyed to