Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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See also: Antioxidants: Natural Antioxidants; Ascorbic

Acid: Properties and Determination; Physiology; Chilled

Storage: Principles; Dietary Fiber: Properties and

Sources; Enzymes: Functions and Characteristics; Folic

Acid: Properties and Determination; Physiology;

Potassium: Physiology; Spoilage: Chemical and

Enzymatic Spoilage; Bacterial Spoilage; Yeasts in

Spoilage; Storage Stability: Mechanisms of Degradation;

Parameters Affecting Storage Stability; Parameters

Affecting Storage Stability

Further Reading

Fellers PJ (1985) Citrus: sensory quality as related to root-

stock, cultivar, maturity and season. In: Pattee H (ed.)

Evaluation of Quality of Fruits and Vegetables, pp.

83–128.Westport, Connecticut: AVI Publishing.

Fellers PJ (1993) Citrus fruits: oranges. In: Macrae R,

Robinson RK and Sadler MJ (eds) Encyclopaedia of

Food Science, Food Technology and Nutrition, vol. 2.

London: Academic Press.

Food and Agriculture Organization of the United Nations

(2000) Citrus Fruit: Fresh and Processed. Annual

Statistics.

Food and Drug Administration (2001) 21 CFR Part 120:

Hazard analysis and critical control point (HACCP);

procedures for the safe and sanitary processing and

importing of juice; final rule. Federal Register 66:

6138–6202.

Kefford JF and Chandler BV (1970) The Chemical Con-

stituents of Citrus Fruits. New York: Academic Press.

Nagy S (1980) Vitamin C contents of citrus fruit and their

products: a review. Journal of Agriculture and Food

Chemistry 28: 8–18.

Nagy S and Attaway JA (eds) (1980) Citrus Nutrition and

Quality. Washington, DC: American Chemical Society.

Nagy S, Shaw PE and Veldhuis MK (eds) (1977) Citrus

Science and Technology, vols I and II. Westport, Con-

necticut: AVI Publishing.

Pao S, Petracek PD and Ismail MA (1997) Advances in

preparing peeled fresh-cut citrus. Food Technology

International 39–42.

Pao S, Davis CL and Parish ME (2001) Microscopic

observation and processing validation of fruit sanitizing

treatments for the enhanced microbiological safety of

fresh orange juice. Journal of Food Protection 64: 310–

314.

Peeples WW, Albrigo LG, Pao S and Petracek PD (1999)

Effects of coatings on quality of Florida Valencia oranges

stored for summer sale. Proceedings of the Florida State

Horticultural Society 112: 126–130.

Redd JB, Shaw PE, Hendrix CM Jr and Hendrix DL (eds)

Quality Control Manual for Citrus Processing Plants,

vol III. Auburndale, Florida: Agscience.

Tetra Pak Processing Systems AB (1998) The Orange Book.

Lund, Sweden: Tetra Pak.

Wardowski WF, Nagy S and Grierson W (eds) (1986) Fresh

Citrus Fruits. Westport, Connecticut: AVI Publishing.

Processed and Derived

Products of Oranges

C M Lanza, University of Catania, Catania, Italy

0001It seems that the sky had scattered gold dust and the

earth had moulded this into shining spheres. (Abu

l-Hasan Ahmad – Arabian poet in Sicily)

Background

0002Wine and the olive in the west, and the mango and

litchi in the east, have played a determining role in the

culture in which they have flourished, whereas citrus

fruits, with their high quality and high content of

vitamin C, have become well established across all

continents, societies, and cultures, from man’s first

interests in agriculture through to the most sophisti-

cated technology to date. At the beginning of the last

century, countries dedicated to citrus fruit cultivation

processed one or two products per species, discarding

the rest (for example, lemon growing in Sicily was

mainly used for essential oil and citric acid produc-

tion). Today, such countries must concentrate their

efforts on an industrial system providing the best

utilization of the fruit to minimize costs and to offer

a wide range of products on the basis of the con-

sumer’s economic status. High-value products are

aimed at wealthy markets, whereas a large propor-

tion of the less expensive byproducts can be added to

the diets of consumers in economically weak coun-

tries. This new perspective is not really a techno-

logical problem, because equipment for the citrus

industry is being continually developed. Rather, the

problem concerns the political decisions to organize

the citrus agricultural sector for production for indus-

trial utilization. This is, perhaps, more difficult for

those countries that have a citrus fruit-growing

history. Traditionally, there has often been a lack of

flexibility and holistic management in dealing with

production problems.

0003Sweet orange constitutes by far the most important

class of commercial citrus fruits grown in tropical and

subtropical regions around the world. Approximately

55 million tonnes of orange are produced per year

worldwide. About 40% of the total tonnage is pro-

cessed, the rest being consumed as fresh fruit. Their

quality, and the quality of the extracted juice, is

greatly influenced by grove practices and pedocli-

matic conditions (Table 1).

0004As a whole fruit, the orange is widely recognized

for its nutritional (Figure 1) and sensorial characteris-

1346 CITRUS FRUITS/Processed and Derived Products of Oranges

tics of freshness, juiciness, crispness and sugar/acid

content.

0005 To extend the availability of orange fruit during the

year and utilize better processing equipment, varieties

with different ripening periods are grown. Together,

Brazil and the USA grow 50% of the world’s oranges

and produce around 90% of the world’s orange juice.

Some Mediterranean regions, such as Italy, are

oriented to the fresh fruit market, because of more

profit. Italian orange production, concentrated

primarily in the south of Italy, comprises 70% of

pigmented orange (‘Tarocco,’‘Sanguinello,’ and

‘Moro’), and the remainder blonde (‘Navel’ and

‘Valencia late’).

0006Blonde oranges contain relatively large amounts of

a mixture of carotenoids, whereas the red color of

blood oranges is due to (besides carotenoids) antho-

cyanins, water-soluble pigments such as cyanidin-

3-glucoside and delphinidin-3-glucoside in Moro

oranges. Many of the biological properties of these

compounds have been correlated with their ability

to scavenge oxygen-generated free radicals and to

tbl0001 Table 1 Quality parameters of orange juices



Brix Min 10.0 Potassium 1300–2500 mg l

1

Density Min 1.040 Magnesium 70–160 mg l

1

L-Ascorbic acid Min 200 mg l

1

Titratable acid 90–240 meq

Volatile acids Max 0.4 g l

1

Citric acid 6.3–17.0 g l

1

Volatile oils Max 0.3 mg l

1

L-malic acid 0.8–3.0 g l

1

Ethanol Max 0.3 g l

1

Calcium 60–150 mg l

1

Lactic acid Max 0.5 g l

1

Phosphorus 115–210 mg l

1

D-Malic acid Absent Nitrates Max 10 mg l

1

Sulfurous acid Absent Sulfates Max 150 mg l

1

Hydroxy methyl furfurol Max 20 mg l

1

Formol index 15–26

Arsenic Max 0.1 mg l

1

Esperidin Max 1000 mg l

1

Lead Max 0.2 mg l

1

Total pectin Max 700 mg l

1

Copper 5.0 mg l

1

Soluble pectin Max 500 mg l

1

Zinc 5.0 mg l

1

Carotenoids Max 15 mg l

1

Iron 5.0 mg l

1

Glucose 20–50 g l

1

Tin 1.0 mg l

1

Fructose 20–50 g l

1

Mercury 0.01 mg l

1

Saccharose 10–50 g l

1

Cadmium 0.02 mg l

1

Ethanolamine Max 36.6 mg l

1

Sodium Max 30 mg l

1

Ammonium Max 25.5 mg l

1

Source: Association of the Industry of Juices and Nectars from Fruits and Vegetables of the EEC (24/1/1996).

Flavedo

essential oil, carotenoids a/o anthocyanins

Albedo

flavonoids, cellulose,

pectins, amino acids

Seed

lipids, proteins,

mineral salts

Pulp

vitamins, amino acids, oxiacids,

carotenoids a/o anthocyanins

sugars

Membrane

flavonoids, pectins, sugars,

cellulose

Oil gland

Juice sacs

fig0001 Figure 1 Transverse section of orange fruit with constituents and enlarged views of juice sacs and oil gland.

CITRUS FRUITS/Processed and Derived Products of Oranges 1347

inhibit lipid peroxidation. With regard to therapeutic

properties, anthocyanins are largely used in the

pharmaceutical industry because of their ability

to prevent capillary fragility. The most important

objective at the moment in Italy is the qualitative

improvement of pigmented oranges and their juice,

which has created a niche market for export in North-

ern Europe (Denmark, Germany, Holland, Sweden,

Switzerland) (Figure 2).

Juice

0007 Orange juice, the predominant product of the citrus

industry, has the sensory and nutritional properties

of the fresh fruit (Table 2), but, being a complex

beverage sensitive to treatments, it is very difficult to

preserve the same level of quality of orange juice

squeezed directly from fresh oranges. The maximum

juice yield from an orange is 40–60% by weight,

depending on the fruit variety and local climate.

0008 Even if orange fruit is not climacteric, its quality

begins to deteriorate after picking, and so it must be

processed into juice and other products as quickly as

possible to insure that the microbiological, nutritional

and sensorial qualities are maintained (Figure 3).

0009 Oranges unloaded by hydraulic lifts from storage

silos on the waiting conveyors undergo a first wash-

ing to remove dirt, leaves, and stems, and then, in the

first grading process, damaged or substandard fruit is

removed. The oranges are then conveyed to the final

washing and grading area, where they are inspected

and automatically sorted by size for entry to the

extractor.

0010 Two extraction systems are used: (1) squeezing and

(2) reaming, either whole or halved, under mechan-

ical pressure. In the first system as shown in Figure 4

the fruit are often lined up (up to 15 per line). The

cups (upper and lower) are brought together as the

corresponding cutters cut two holes in the fruit (Step

1). As the cups continue to come together, the peel

is separated from the fruit, which is forced into the

prefinisher tube (Step 2). The peeled fruit moves into

the orifice tube through the holes of the prefinisher

tube, forcing the juice to flow into the manifold (Step

3). The juice is instantaneously separated from the

seeds, and the rest of the fruit, including the oil emul-

sion, is sent to the centrifugal processing part.

0011In the reamer type of extractor, the fruit is cut in

half, and the halves are penetrated and rotated by a

series of nylon reamers mounted on a rotating turn-

table. The juice, pulp, rag, and seeds are separated

from the peel by a strainer, and the juice and pulp are

separated from the rag and seeds and passed to the

Frozen

Defrosted

DefrostedReconstituted

Chilled −20 ⬚C

Freshly squeezed

Heated 70 ⬚C

8 days

2 days 30 days60 days

Juice extracted

fig0002 Figure 2 Orange juices in the European market. Shelf-lives

shown (in days) are applicable to a storage temperature of 4



Source: Maccarone E, Campisi S, Cataldi Lupo MC, Fallico B and

Nicolosi Asmundo C (1996) Effetti dei trattamenti tecnologici sui

costituenti del succo di arancia rossa di Sicilia. Industrie delle

Bevande XXV: 335–341.

tbl0002Table 2 Chemical composition and energy of orange fruit and

orange juice

Orange fruit Orange juice

Edible part (%) 80 100

Water (g) 87.2 89.3

Protein (g) 0.7 0.5

Lipid (g) 0.2 0

Carbohydrate 7.8 8.2

Fiber (g) 1.6

kcal 34 33

kJ 142 138

Sodium (mg) 3 3

Potassium (mg) 200 200

Iron (mg) 0.2 0.2

Calcium (mg) 49 15

Phosphorus 22 17

Thiamin (mg) 0.06 0.05

Riboflavin (mg) 0.05 0.03

Niacin (mg) 0.2 0.4

Vitamin A retinol equivalents (mg) 71 38

Vitamin C (mg) 50 44

Source: National Institute of Nutrition, Rome.

Fruit

Extraction

Pulpy juice

Clarification Pulp Pulp wash

EssenceConcentrate

DistributionPackaging

Not from concentrate

Peel oil

Feed millPeel, rag, seed

fig0003Figure 3 Flow chart of orange processing.

1348 CITRUS FRUITS/Processed and Derived Products of Oranges

finishers. In this system, peel oil can be recovered in a

separate step by puncturing the oil sacs of the flavedo

and washing the oil out.

0012 Another extraction system is the rotary press,

popular in the Mediterranean area since the turn of

the twentieth century. This machine consists of a

combination of two units arranged in a cascade, one

to extract essential oil by rasping the outer surface of

the whole fruits and the other to extract juice. Fruits

introduced into the machine are pushed forward by

paddles along couples of rotating rasping cylinders.

The essential oil is then gathered by sprays of water,

the mixture flows into a finisher to eliminate any solid

particles, and essential oil is recovered by centrifugal

separators. After oil extraction, the fruits are cut into

two halves and squeezed against a stainless steel

screen, and then seeds, pulp, and peels are removed

from the juice. Juice obtained by the different ex-

traction processes has a high content of pulp derived

from juice vesicles and membrane material. These

represent the principal part of the segments, which,

during processing, are destroyed by enzymes and

microorganisms in the peel. Lactobacillus and Leu-

conostoc are the most common genera of lactic acid

bacteria that cause spoilage of orange juice, pro-

ducing diacetyl and, consequently, off-flavors. The

yeasts Saccharomyces cerevisiae, Rhodotorula, and

Zygosaccharomyces can impart a fermented taste,

transforming the delicate aroma of orange juice into

an unpleasant smell. Only rarely are molds respon-

sible for juice spoilage, because, even if they grow in

juice, they are generally sensitive to heat treatment.

(See Yeasts.)

0013The pulpy juice therefore must be finished and

clarified by centrifugation to remove the oil, if neces-

sary, before undergoing further treatments. A recent

improvement of clarification has been introduced,

using ultrafiltration to separate the serum from the

pulp. The latter is then subjected to thermal treatment

before being remixed with the serum to obtain a

product with a better flavor and nutritional value.

After this step, the juice takes different paths, leading

to different products:

0014Freshly squeezed juice: This has a shelf-life of 5–6-

day and is a product that is not thermally pro-

cessed, thus satisfying increasing demands for

natural products. The raw materials are selected

with great care, and washed, squeezed, aseptically

packaged, and distributed for retail.

0015Not-from-concentrate juice: Minimal thermal

treatment is used for this juice. It is processed and

stored frozen, or quickly pasteurized and stored

in aseptic form. Most of these juices also consist

of a blend, differing in quality in terms of color,

sugar content, etc., being extracted throughout

the picking season and/or in different producing

countries.

0016Frozen concentrate orange juice: This form is very

advantageous for storage and freight, requiring

less than five to six times volume than fresh juice.

It provides a year-round supply to consumers

and consists of a concentrate of a blend of specified

quality from different orange varieties. Analytical

control of blends uses the following characteristics:



Brix, per cent acid, Brix/acid ratio, per cent oil, per

Upper cutter

Upper cup

Lower cup

Lower cutter

Prefinisher

tube

Juice

manifold

Orifice tube

Step 1 Step 2 Step 3

fig0004 Figure 4 (see color plate 29) FMC juice extractor principle. Courtesy of FMC Food Tech Citrus System, Catania (Sicily) Italy.

CITRUS FRUITS/Processed and Derived Products of Oranges 1349

cent pulp and color. Today, a ‘thermally accelerated

short-time evaporator’ is often used (Figure 5),

which yields a concentration of up to 65/75



Brix

in a very short time, thus insuring a high product

quality. (See Heat Treatment: Chemical and Micro-

biological Changes.)

During a preheating cycle, juice is pasteurized to

deactive pectinase enzymes (which cause cloudiness)

and prevent spoilage, thus prolonging the shelf-life. It

then undergoes a variable number of stages under

vacuum until the required concentration is obtained.

The disadvantage is that the heat treatment reduces

the oxidative balance and removes some of the flavor

components. Particularly in blood-orange juice, a

considerable change in color is ascribed to the deg-

radation of anthocyanins and the different distribu-

tion of carotenoids between the serum and pulp

structure in juices reconstituted from concentrate.

There is also a remarkable loss of aroma components

and generation of off-flavors such as p-vinylguaiacol,

p-vinylphenol, and decarboxylation products of

hydroxycinnamic acids in red juices processed and

stored for up to 4 months.

Byproducts

0017The use of whole fruit in citrus processing is necessary

to reduce costs and justify new investments in equip-

ment, providing a correct solution for the pollution

problem connected with the process. Any improve-

ment in the recovery process would be of great inter-

est, especially if this were obtained using technologies

respectful of product quality such as the use of

enzymes, peeling of the fruit, reduction of bitterness

juices, reduction in the viscosity of pulp wash, and

hydrolysis of peel solids to produce fermentable

sugars.

Comminuted juice

0018Originally developed in the UK, this byproduct is

made by milling the whole fresh fruit or by mixing

juice concentrate with milled peel. The comminuted

citrus base has a stronger flavor and provides more

cloud than pure orange juice, thus imparting a good

orange flavor in fruit drinks of low fruit content.

Peel Oil

0019Valuable oil recovered (about 0.3% of the fruit

intake) from peel is used to produce various flavor

compounds in the beverage, chemical and cosmetic

industries. ‘Cold-pressed peel oil’ is obtained by

mechanical pressure of oil glands (using different

methods), whereas a less valuable oil can be re-

covered by distillation of waste peel residue. Among

the numerous compounds, the major component is

d-limonene, which is also used in the electronics

industry and in the manufacture of synthetic resins

and adhesives. Other hydrocarbons produced include

myrcene, a-pinene, sabinene, and valencene. Import-

ant aromatic compounds include aldehydes, esters,

alcohols, ketones, and phenols, and the nonvolatile

residues include waxes, coumarins, flavonoids, fatty

acids, and sterols. To avoid the problem of dissolved

wax from peel, the oil is stored at 1



C (winterization)

to allow successive sedimentation of wax.

0020Colored essential oils rich in carotenoids can be

obtained from orange peels, for use as colorants in

the drink industry. The increased use of citrus essen-

tial oil to aromatize baking products promotes the

technology of encapsulation by drying spray obtaining

powders capable of maintaining the aroma intensity

during cooking. Another interesting technology is the

extraction of essential oil using supercritical fluid,

fig0005 Figure 5 (see color plate 31) Model thermally accelerated

short-time evaporator. Courtesy of FMC Food Tech Citrus

System, Catania (Sicily) Italy.

1350 CITRUS FRUITS/Processed and Derived Products of Oranges

especially CO

. Among the citrus peels, the most

important essential oil is extracted from bergamot

(C. bergamia, Risso) hybrid, a close relative of the

sour orange cultivated only in the narrow strip of land

of Southern Italy (Calabria). It is indispensable to the

international perfume industry and is also used in the

pharmaceutical industry as an antiseptic and as an

aroma for liqueurs, tea, sweets, and candied fruits.

Essence

0021 The recovery of volatile components (essence) from

the evaporation process constitutes an interesting use

of this component. Two phases are separated: the first

containing the water-soluble compounds (essence

aroma) and the second (essence oil), containing fruit

flavor. The latter is more desirable than peel deriva-

tives in the manufacture of flavor mixtures for the

beverage and other food industries.

Hesperidin

0022 In sweet orange, the predominant flavonoid is the

tasteless and odorless hesperidin, located in the mem-

brane and peel, which is not soluble in neutral solu-

tions but slightly soluble in acidic solution as citrus

juice. After extraction of the juice, the hesperidin

forms crystals that appear as white flakes; these are

more evident during evaporation and concentration

of juice. The recovery of this product is a profitable

investment for its therapeutic properties in the treat-

ment of capillary fragility. The traditional extraction

method, with a very low recovery, treats triturated

peel with alkaline compounds to dissolve the flavo-

noids, which, after separation of solid residue, are

precipitated by acidification. An innovative method

to recover hesperidin from orange peel and waste

water utilizes (at a pH of around 7) styrene-divinyl-

benzene as the absorbing phase and removing the

flavonoid with alcoholic NaOH. The results may be

a useful starting point for industrial applications.

Pectin

0023 Pectin is a product found mainly in the albedo and

juice sac, and has a high molecular weight (100 000–

200 000 Da). Very important for the stability of juice

cloud, pectin consists of long chains of polygalacturo-

nic acid units linked together by a (1–4) glycosidic

bonds with side chains of rhamnose, arabinans, galac-

tans, and xylose. Many of the carboxyl groups are

esterified with methanol to form methoxy groups;

these determine the gelling ability of the pectin used

in jam, marmalade, jelly, and preserve production.

Lemon peel is the most common source for extraction

of commercial pectin. After oil extraction, the peel is

shredded and washed with water to remove sugars

and other soluble material. The peel is heated to

deactivate the pectinase enzymes and then treated

with hot mineral acid to extract pectin. To the con-

centrated solution (containing a low content of

pectin) alcohol is then added to 50–70% by weight,

resulting in a precipitate of pectin in a gelatinous

mass, which can be washed and dried as a powder.

(See Pectin: Food Use.)

Peel in Brine and Candies

0024The peel in this case must be processed by a soft

system, as ‘sfumatura,’ or peeling to extract the oil.

First, the peel is hardened using lime, dried, and

dipped for 24 h in tanks containing 3% sodium chlor-

ide. Then, the peel is dripped, stored in containers,

and transferred to candy factories. Immersion in hot

water for a few minutes softens the peel. The peel is

cut by machine to undergo a cold or warm liquid

sweetening process, depending on the technology

chosen. The former process requires more time, be-

cause the diffusion of sugar into peel is slow, but the

sensory characteristics of these candies are more valu-

able than those obtained by the latter process.

Fruit Sections

0025Very popular in the USA and Israel, fruit sections have

good nutritional characteristics and a long shelf-life.

Prior to processing, orange should be held in storage

bins to allow the fruit to soften. Hot-water treatment

at 100



C for a few minutes facilitates peeling by hand

or machine. The fruit is then subjected to a hot caustic

spray (about 2.0% NaOH) for a few seconds and

water sprays to remove the basic solutions. The peeled

fruit is then chilled in water to facilitate sectioning of

the fruit. A sweetener solution containing water, juice,

and sugar is finally added to the fruit sections.

Pulp

0026Pulp recovered after the extraction process usually

can be added back to juice and juice drinks to im-

prove the mouth feel and give a natural appearance

to the product. After the different components are

separated by an in-line extractor, it is possible to

recover whole juice sacs (premium pulp) by the pre-

mium pulp recovery system (Figure 6) (FMC Food

Tech Citrus System).

0027Specially designed extractor components separate

the juice, pulp, core, and seeds into a single stream.

The core material is gently separated from the seeds,

juice, and pulp and sent to the core wash system or

CITRUS FRUITS/Processed and Derived Products of Oranges 1351

waste. The core stream is finished to separate and

recover any remaining juice. The remaining juice,

seeds, and pulp are sent to a classifying finisher,

which separates the seeds from the pulpy juice stream.

Minor impurities are then removed, and the premium

pulp, finally separated from the juice, is ready for

pasteurization and packaging.

Pulp Wash

0028 Product referred to as ‘water-extracted soluble

orange solids’ is reclaimed from the pulp stream and

is often used in fruit drinks as a source of sugars. It is

also added, where the law permits, as a clouding

agent to provide body and mouth feel because of its

pectin content. The diffusion techniques currently in

use for the preparation of pulp wash are optimized

using a citrus finisher (Figure 7).

0029 The unfinished juice feeds into the finishing cavity,

a space created by a spiral with specially designed

flights inside 360



cylindrical screens, resulting in a

finishing action. Once inside the finisher cavity, the

product is immediately carried outward on to

the screw’s helical spirals, thus making full use of

the entire screen area, which results in high-capacity

finishing. As the screw rotates, air restriction at the

discharge end places pressure on the product causing

the liquid to move toward the lower-pressure area

outside the screen. Once through the screens, the

liquid flows into a fully enclosed pan and discharges.

The pulp discharges through the plug valve assembly.

Animal Feed

0030Unprocessed citrus peel, rag, pulp, and seed consti-

tute waste products, but they can provide substantial

profits if they are processed as feed. As the product is

susceptible to spoilage (owing to its 78–90% mois-

ture content), it must be consumed quickly and pre-

sents expensive transportation costs. The principal

qualitative parameters are the amounts of protein,

crude fiber, fat, ash, and nitrogen-free extract, pri-

marily carbohydrates, which varies somewhat. The

total quality of the feed is generally estimated from

the total digestible nutrients: nitrogen-free extract,

protein, crude fiber, and fat. The type of animal, effect

of these products on food, economics involved, and

storage capabilities must all be considered before

using these waste products.

0031The high acidity of orange peel requires blending

with lemon peel, usually by ensilage with straw and/

or other material. Research carried out in 1960

showed, in mixtures of orange pulp and straw (10%)

ensiled for 2 months, good fermentation and digest-

ibility characteristics without any effluent being

released.

Pressed Peel

0032To reduce transportation costs, the peel is limed, shred-

ded, and pressed to improve the texture and compos-

ition. The reaction between lime and peel removes (by

pressing) about 10% of the peel moisture. After this

Juice, pulp

and defects

Defects

removal

systeml

Juice

Pasteurizer Chiller

Juice and pulp

Pulp and juice

Pump

Defects

Classifier

finisher

Packaging

finisher

Extractor

Juice recovery Juice

Primary

finisher

Pulp to packaging

Pulp and defects to

'pulpwash' or wastet

Pump

Concentrator

FMC

fig0006 Figure 6 (see color plate 30) Premium pulp recovery process. Courtesy of FMC Food Tech Citrus System, Catania (Sicily) Italy.

1352 CITRUS FRUITS/Processed and Derived Products of Oranges

treatment, the peel is shredded and then conveyed to

the peel press. Warm molasses is added to the peel

(1:3), along with some press liquor, and the slurry is

pumped to the feed mill (‘pumped peel’). Using a

supercharger and a sealed screw air pockets are re-

moved, thus allowing the peel to feed into the press

under pressure and to leave the press at a moisture

content as low as 60%.

Dried Peel and Pulp

0033 Dried citrus peel is one of the most common feeds. It

is manufactured by pressing peel through a rotary

dryer and adding citrus molasses to help the drying

process and help prevent the peel from burning. The

moisture content of dried peel must be below 10%.

Many experiments published in the 1970s have

shown that dried orange pulp, partially or completely

replacing cereals in concentrate mixtures, are particu-

larly useful in reducing feeding costs in dairy cows,

have no influence on production, and have a good

palatability. Dried pulp has also been used in swine,

which have been shown to utilize it at a ratio of up to

20–25%. Besides its use as a substitute for maize, up

to 20% in diet has no influence on the growth and

production of laying hens. The dried pulp can be

pelletized and is consumed more easily by ruminants

with advantages of storage, shipping, and microbial

spoilage. Pellets made from dried pulp have different

dimensions, and several factors affect their character-

istics, such as the energy used in pelletizing and the

proportions of citrus molasses (about 5–15% of the

total weight gives excellent results) used as binding

agents.

Citric Molasses

0034The solution obtained from shredded and limed peel

(press liquor) containing 10% sugar is principally

concentrated to citric molasses. It is used as an addi-

tive to animal feed and for the production of citrus

alcohol by fermentation, and also can be mixed with

Finished juice

Product discharge

Pulp discharge

Unfinished juice Pulp

fig0007 Figure 7 Citrus finisher. Courtesy of FMC Food Tech Citrus System, Catania (Sicily) Italy.

CITRUS FRUITS/Processed and Derived Products of Oranges 1353

pressed peel to facilitate drying. In the manufacture of

citric molasses, antifoaming agents are used, or the

suspended solids are removed by centrifugation, to

prevent foaming from microbial spoilage and alkaline

processing. The advantages of citric molasses in terms

of press liquor are a reduction in cost during storage

and a better microbial protection owing to the sugar

content.

Alcohol Production

0035 Citrus press liquor and citric molasses can be used as a

feedstock for commercial alcoholic fermentations

carried out by yeasts in continuous fermentators. The

presence of peel oil, which is toxic to most microorgan-

isms, must be at levels of no more than 0.08%. Press

liquor contains at least 0.2% oil (based on 11.8



Brix),

whereas citric molasses usually contain much less oil

stripped out during evaporation. Liquor is removed

from the citrus press before fermentation, often using

direct steam injection. Also, the oil removed in this

way (steam-distilled oil) can be sold as a fuel, herbi-

cide, or feedstock in chemical manufacture.

Final Consideration

0036 In industrialized countries, the citrus industry cannot

be static, but must apply scientific and technological

know-how to increase the value added to the market

prices of products. It is necessary to develop new mild

technology to limit the damage during processing,

to re-evaluate minor products, and to obtain a new

ingredient better suited to consumer requirements:

fresher products that retain their nutritional charac-

teristics, especially the active components (vitamins,

antioxidants, fermentation agents), have a longer

shelf-life, and are more convenient for ecologically

compatible cultivation and animal rearing systems.

See also: Citrus Fruits: Types on the Market; Composition

and Characterization; Oranges