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7 Olive Oil David Firestone United States Food and Drug Administration Washington, DC 1. INTRODUCTION AND HISTORY Olive oil, an important component in the diet of Mediterranean people, is obtained by mechanical extraction from the fruit of the Olea europaea L. tree, which belongs to the Olive family, comprises some 400 species, and thrives in temperate and tropical climates (1). Of the 35 species in the genus Olea, mainly of African, Indian, and Australian origin, O. europaea is the only Mediterranean species. Although its origin is not known, one theory is that it originated in ancient Iran and Turkestan, spreading westward to Anatolia, Syria, and Israel along commercial and migratory routes (2). Olives appeared in Israel about 45,000 years ago (1). Charred pieces of olive wood have been found in excavations at Lower Boker-Har Hanegev in layers dating to 42,980 B.C. Both charred wood and carbonized stones have been found in many archeological sites in Israel dating from 8000 B.C. onward, and indirect evidence suggests the use of wild olives (O. oleaster) by humans as early as the seventh millennium B.C. (3). It is not known whether the carbonized stones and charred wood obtained from Chalcolithic (fourth millennium B.C.) and Early Bronze Age (2900–2700 B.C.) sites represented cultivated or wild olives. Olive farming and an olive oil industry appear to have been well established throughout the region bordering the Mediterranean from Palestine and Syria to Greece in the middle and late Bronze Age (4). Olive farming in Palestine and Syria Bailey’s Industrial Oil and Fat Products, Sixth Edition, Six Volume Set. Edited by Fereidoon Shahidi. Copyright # 2005 John Wiley & Sons, Inc. 303
Transcript
Page 1: 14 olive oil

7Olive Oil

David Firestone

United States Food and Drug Administration

Washington, DC

1. INTRODUCTION AND HISTORY

Olive oil, an important component in the diet of Mediterranean people, is obtained

by mechanical extraction from the fruit of the Olea europaea L. tree, which belongs

to the Olive family, comprises some 400 species, and thrives in temperate and

tropical climates (1). Of the 35 species in the genus Olea, mainly of African, Indian,

and Australian origin, O. europaea is the only Mediterranean species. Although its

origin is not known, one theory is that it originated in ancient Iran and Turkestan,

spreading westward to Anatolia, Syria, and Israel along commercial and migratory

routes (2).

Olives appeared in Israel about 45,000 years ago (1). Charred pieces of olive

wood have been found in excavations at Lower Boker-Har Hanegev in layers dating

to 42,980 B.C. Both charred wood and carbonized stones have been found in many

archeological sites in Israel dating from 8000 B.C. onward, and indirect evidence

suggests the use of wild olives (O. oleaster) by humans as early as the seventh

millennium B.C. (3). It is not known whether the carbonized stones and charred

wood obtained from Chalcolithic (fourth millennium B.C.) and Early Bronze Age

(2900–2700 B.C.) sites represented cultivated or wild olives.

Olive farming and an olive oil industry appear to have been well established

throughout the region bordering the Mediterranean from Palestine and Syria to

Greece in the middle and late Bronze Age (4). Olive farming in Palestine and Syria

Bailey’s Industrial Oil and Fat Products, Sixth Edition, Six Volume Set.Edited by Fereidoon Shahidi. Copyright # 2005 John Wiley & Sons, Inc.

303

Page 2: 14 olive oil

increased dramatically at the turn of the first millennium B.C. (2). An olive oil indus-

try became well established in Palestine, and the export of olive oil from Palestine

to Egypt is documented in Old Kingdom Egypt. Olive cultivation provided materi-

als useful as a lamp fuel, lubricants, and body ointments; the fruit was easily cured

by salting, and the wood was used for carpentry and fuel. Later, the olive fruit

became a source of edible oil.

The manufacturer of olive oil became a mass production industry during the

Israelite period when processing methods improved (3). In Judea, oil presses gen-

erally consisted of large stone beds with a collecting vat in the center of the pressing

surface. A beam, which acted as a lever and was weighted down by several stones,

was used for pressing. The end of the beam was anchored to a wall behind the press

(niche wall) with a special niche stone. Olives were crushed in a rectangular basin

by a roller, which an operator set into forward and backward motion by means of an

attached shaft.

A typical Iron Age industrial site is that of the seventh century B.C. biblical town

of Timnah (Tel Batach), which was a center of olive oil production along with other

towns in the Tel Aviv area (5). The oil presses of the town were constructed simi-

larly to those of other Iron Age sites in the area. Each press consisted of a crushing

basin with two pressing vats on either side. Olives were crushed in the basin with

stone rollers, each of which had wooden handles fitted into sunken depressions at

the sides. The crushing basin was a shallow trough made of one large chalk stone.

Each pressing vat contained a large stone with a flat top and an inner hollowed

space for collecting the oil. Because there was no means of draining the oil from

the vet, pottery jugs were used to withdraw the oil. Baskets with crushed olives

were pressed by wooden beams anchored at one end to niches in the wall; the other

end of each beam was pressed down with three heavy stone weights (Figure 1).

Olive growing reached Cyprus and the Aegean area around the sixteenth century

B.C. As Renfrew (6) pointed out, the olive was one of three important constituents,

along with the vine and domesticated wheat, that contributed to the emergence of

civilization in the Aegean region. Oil production and trade played important roles in

the Minoan–Mycenaen economy of Crete and main-land Greece in the second mil-

lennium B.C. (7). Olive oil was used in the manufacture of scented perfumes and

unguents in the palace industries of Crete and Mycenae. Wild rather than cultivated

olives were apparently preferred for Aegean perfume and unguents because of the

low fat content of the wild olive.

Initially, olives were harvested by beating the trees with flails (6). After harvest-

ing, the olives were drenched in hot water and pressed to extract the oil. The oil was

separated from the water in a vat from which the water was drawn off, and then

stored in jars similar to those used to hold wine. Oil was used locally for lighting,

hygienic purposes (to clean the body), and as food, especially for cooking.

Mycenaen documents suggest that scented olive oil was used for religious purposes

and as a body ointment for the rich (8).

The earliest evidence of olive oil extraction in Cyprus dates to about 1300 B.C.

(9). (Wild olives grew on the island at least as early as 4000 B.C.) An olive press

(probably a lever and weight press) found at a Maroni excavation site consisted

304 OLIVE OIL

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Figure 1. Oil press at Tel Batach (biblical Timnah), 7 km west of Beth-Shemesh, Israel.

Isometric plan and sections (5). [Reprinted with kind permission of the editors of Olive oil in

Antiquity (5).]

INTRODUCTION AND HISTORY 305

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of a large rectangular trough (pressing bed) set on a mudbrick platform and sloping

downward. The trough is a flat stone with channels cut to meet at a small projection,

permitting the liquid to pour off into a jar standing on the floor below the press.

Other presses of the late Roman period found on the island were of the lever and

screw type in which the horizontal beam is immobile while the screw presses

down on the pressing bed. The screw was already used for pressing in Italy in

the first century B.C., initially as a lever and screw press and then in a direct frame

press (10).

Olive orchards continued to be extensively cultivated in Palestine throughout the

Byzantine and Arab periods (11). The chain of mountains from the upper Galilee to

Hebron were covered with olive trees. Olive oil was used regularly for food and

cooking as well as for lighting and manufacture of soap by boiling the oil with

ashes. During the early period under the Umayyides (661–750 A.D.) and Abbasides

(750–1258 A.D.), oil surpluses were exported from Palestine by land to neighboring

countries. With revival of maritime commerce under the Fatimids (909–1171 A.D.),

oil was transported to Egypt and other countries by boat.

Phoenician settlements in the Mediterranean basin introduced olive farming into

Sicily, Sardinia, southern France, and Spain (2). The Greeks later spread farming

independently of the Phoenicians, reintroducing the olive into Sicily. The Romans

spread olive farming throughout their territories and used the olive tree in their land

reclamation projects, particularly in North Africa where they instituted olive farm-

ing and other projects to reclaim desert areas. Although of variable quality, olive oil

was a staple food and an important industrial product in Roman times.

Olive growing continued to prosper in the Mediterranean region until the fifth

century A.D., when the Roman Empire was invaded from the north and maritime

routes were closed (2). Olive farming was later revived with commercial develop-

ment of Venice and other maritime republics during the Renaissance. In 1709, olive

growing entered a new modern age when all of Europe was hit with a deep cold

spell and new orchards were planted to replace those destroyed by the cold weather.

As modern farming techniques evolved, large-scale state enterprises were begun

and olive farming reached a peak in the first half of the nineteenth century.

2. STATISTICS AND DEFINITIONS

Currently, more than 95% of the world’s olive trees grow in the Mediterranean

Basin. About 81% of total olive production comes from the European Community

(EC) (Spain, Italy, Greece, Portugal, and France), with the Near East contributing,

ca 7% and North Africa supplying about 11%. The remaining 1% is of American

origin, chiefly from Argentina, Mexico, Peru, and the United States (Table 1). Olive

oil consumption is growing in the developed countries that produce little or no olive

oil (Table 2).

The fruit of the olive tree is an egg-shaped drupe, consisting of a pericarp and an

endocarp. The pericarp includes an epicarp (skin) of variable thickness according to

the variety, and a mesocarp (pulp) surrounding the endocarp (woody pit) in which

306 OLIVE OIL

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the seed is enclosed. The yield per hectare is about 2.45 tons. Oil yield per 100 kg

of fruit is 19.6 kg (based on yields in Italy during the past 10 years).

In addition to oil, the pulp and epicarp contain a variety of natural components

soluble in the oil. As will be seen later, the oil is obtained from the olive by a

variety of techniques, always physical, leaving a residue (pomace) that contains

up to 8% oil, which is then extracted by solvent (usually hexane) and named

pomace oil.

Because of the behavior of the solvent, solvent-extracted oil contains more

minor components at higher levels than those found in physically extracted oil.

This provides the basis for designating pomace oil as a commercial product distinct

from virgin oil (obtained only by mechanical means) or refined (lower grade) virgin

oil mixed with virgin oil (olive oil, Riviera type).

The following internationally recognized definitions of oils derived from olives

and available on the market were promulgated by the International Olive Oil

Council (IOOC) (12):

1. Olive oil is that oil produced by extraction of the fruit of the olive tree (Olea

Europaea Sativa Hoffman et Link) to the exclusion of oils obtained using

solvents or reesterification processes and of any mixture with oils of other

TABLE 1. World Production of Olive Oil (Thousand Metric Tons).a

2002/03 2003/04

Country 1997/98 1998/99 1999/00 2000/01 2001/02 (prov.) (est.)

Algeria 15.0 54.5 33.5 26.5 25.5 16.5 40.0

Argentina 8.0 6.5 11.0 4.0 10.0 11.0 22.0

Cyprus 1.5 2.5 3.5 5.5 6.5 7.0 7.0

EC 2,116.5 1,707.0 1,878.5 1,940.5 2,463.5 1,942.5 2,307.0

Croatia 5.0 9.0 5.5 5.0 7.0 3.0

Israel 3.0 4.5 2.5 7.0 3.5 9.0 2.5

Jordan 14.0 21.5 6.5 27.0 14.0 28.0 11.5

Lebanon 3.5 7.0 5.0 6.0 5.0 6.0 4.0

Morocco 70.0 65.0 40.0 35.0 60.0 45.0 80.0

Palestine 9.0 5.5 2.0 20.0 18.0 21.5 5.0

Syria 70.0 115.0 81.0 165.0 92.0 165.0 110.0

Tunisia 93.0 215.0 210.0 130.0 35.0 70.0 180.0

Turkey 40.0 170.0 70.0 175.0 65.0 160.0 60.0

Australia 0.5 0.5 1.0 1.0 2.0 3.0

Egypt 1.0 0.5 2.5 0.5 1.5 5.0 2.0

USA 1.0 1.0 1.0 0.5 0.5 1.0 1.0

Iran 3.0 2.5 2.5 3.0 2.5 1.5 4.0

Libya 6.0 8.0 7.0 4.0 7.0 6.5 6.5

Mexico 2.0 2.5 1.0 1.5 2.0 2.5 2.5

Yugoslavia 0.5 1.0 1.0 0.5 0.5 0.5 0.5

Serbia and

Montenegro 8.5 7.5 6.5 7.5 7.5 7.5 7.5

World Total 2,465.5 2,402.5 2,374.5 2,565.5 2,825.5 2,515.0 2,859.0

a Source: International Olive Oil Council (IOOC).

STATISTICS AND DEFINITIONS 307

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kinds. In no case shall the designation ‘‘olive oil’’ be used to refer to olive–

pomace oils.

A. Virgin olive oil is the oil obtained from the fruit of the olive tree solely

by mechanical or other physical means under conditions, particularly

thermal conditions, that do not lead to alterations in the oil, and which

has not undergone any treatment other than washing, decantation,

centrifugation, and filtration.

TABLE 2. Olive Oil Consumption (Thousand Metric Tons).a

2002/03 2003/04

Country 1997/98 1998/99 1999/00 2000/01 2001/02 (prov.) (est.)

Algeria 31.5 44.0 42.0 26.0 25.0 16.0 39.0

Argentina 8.0 8.0 7.0 6.0 5.5 5.5 6.0

Cyprus 2.0 2.5 4.0 5.0 5.5 6.0 6.0

EC 1,705.5 1,709.0 1,728.0 1,835.0 1,894.0 1,904.5 1,932.0

Croatia 4.0 8.5 6.5 5.0 6.0 3.0

Israel 6.5 9.5 12.5 13.5 14.5 14.5 13.5

Jordan 19.0 19.0 9.0 17.0 20.0 25.0 15.5

Lebanon 8.0 9.0 8.0 8.0 7.0 7.0 7.0

Morocco 55.0 55.0 55.0 45.0 60.0 55.0 70.0

Palestine 5.5 4.0 4.0 8.0 10.0 12.0 12.0

Syria 95.0 88.0 90.0 110.0 86.0 100.5 115.0

Tunisia 52.0 49.0 60.0 58.0 28.0 30.0 60.0

Turkey 85.5 85.0 60.0 72.5 55.0 55.0 40.0

2,073.5 2,086.0 2,088.0 2,210.5 2,215.5 2,237.0 2,319.0

Australia 17.5 24.0 25.5 31.0 27.5 31.0 31.0

Brazil 29.0 23.5 25.0 25.0 22.5 20.0 21.0

Chile

Egypt 1.0 1.0 1.5 1.0 1.5 3.5 2.5

USA 142.5 151.0 169.5 194.5 188.5 190.0 195.0

Iran 4.0 2.5 2.5 3.0 2.0 2.0 3.5

Libya 7.0 16.0 11.0 7.0 8.0 8.5 8.5

Mexico 4.5 5.0 5.0 6.5 8.0 10.0 10.0

Yugoslavia/Serbia and

Montenegro 0.5 1.0 1.0 0.5 0.5 0.5 0.5

Other producing

countries 13.5 12.5 13.0 13.0 14.0 14.5 14.5

219.5 236.5 254.0 281.5 272.5 280.0 286.5

Saudi Arabia 5.0 5.5 4.5 4.0 5.0 7.0 7.5

Canada 17.5 18.5 23.0 24.5 24.0 24.0 24.5

Japan 34.0 28.5 27.0 30.0 31.5 32.5 33.0

USSR/Russia 1.5 2.0 3.0 4.0 4.0 6.0 7.0

Switzerland 5.5 6.0 8.0 8.0 9.0 10.0 10.0

Taiwan 4.5 7.0 6.0 8.0 6.5 5.5 6.0

Other nonproducing

countries 20.5 23.0 29.0 20.0 38.0 38.5 38.5

88.5 90.5 100.5 98.5 118.0 123.5 126.5

Total World 2,381.5 2,413.0 2,442.5 2,590.5 2,606.0 2,640.5 2,732.0

a Source International Olive Oil Council (IOOC).

308 OLIVE OIL

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Virgin olive oil fit for consumption as is (and can be designated as

‘‘natural’’) includes:

a. Extra virgin olive oil: virgin olive oil that has an organoleptic

rating of 6.5 or more as determined by the IOOC method (13) and

a free acidity, expressed as oleic acid, of not more than 1 g per

100 g.

b. Fine virgin olive oil: virgin olive oil that has an organoleptic

rating of 5.5 or more and a free acidity, expressed as oleic acid, of

not more than 1.5 g per 100 g.

c. Semifine virgin olive oil (or ordinary virgin olive oil): virgin olive

oil that has an organoleptic rating of 3.5 or more and a free

acidity, expressed as oleic acid, of not more than 3.3 g per 100 g.

(This class of olive oil is normally traded in bulk for blending

purposes.)

B. Virgin olive oil not fit for human consumption, also designated as

lampante virgin olive oil: virgin olive oil that has an organoleptic rating

of less than 3.5 and/or a free acidity, expressed as oleic acid, of more

than 3.3 g per 100 g. This class of olive oil is used to produce refined

olive oil or is intended for technical (nonfood purposes).

C. Refined olive oil: olive oil obtained from virgin olive oils by refining

methods that do not lead to alterations in the original triglyceride

structure.

D. Olive oil: the oil consisting of a blend of refined olive oil and virgin

olive oil in various proportions.

2. Olive–pomace oil: the oil obtained by solvent extraction of olive–pomace and

not including any oil obtained by a reesterification procedure or any mixture

with other kinds of oils. (The various categories of olive–pomace oil are

described below.)

A. Crude olive–pomace oil: olive–pomace oil intended for refining to

produce a product (as B, below) suitable for human consumption, or

intended for technical purposes.

B. Refined olive–pomace oil: the oil obtained from crude olive–pomace

oil by refining methods that do not lead to alterations in the original

triglyceride structure.

C. Olive–pomace oil: a blend of refined olive–pomace oil and virgin olive

oil (any A, B, or C). In no case may this be called ‘‘olive oil.’’

Because the yearly production of olive oil is variable, low-production years can fol-

low years of high production. Therefore, it is customary to record average values

(Table 1).

STATISTICS AND DEFINITIONS 309

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3. EXTRACTION TECHNOLOGY

Ripe olives contain a variety of components, including water, oil, sugars, proteins,

organic acids, and cellulose. Olive cultivars with medium-size fruits generally pro-

vide the best oil yields. The pulp-to-kernel ratio of olives for oil production ranges

from 4:1 to 8:1.

The epicarp contains a number of components of relatively high polarity that are

not removed by mechanical extraction and remain in the pomace. Removal of these

components along with the oil by solvent extraction of the pomace accounts for

the higher unsaponifiable content of olive–pomace oil.

Most of the oil (96–98%) is in the pulp along with most of the water ‘‘vegetation

water’’ (VW), which accounts for 40–60% of the weight of the fruit.

The woody pit inside the mesocarp holds a seed whose oil is more unsaturted

than the mesocarp (pulp) oil because of a higher content of linoleic acid. The ratio

of fruit oil to seed oil is 50:1.

The approximate chemical composition of olive fruit is as follows: water 52.4%;

oil 19.6%; proteins 1.6%; sugars 19.1%; cellulose 6.8%; and ash 1.5%. Oil yield

and quality depend on the cultivar of olive tree, ratio of the various anatomical

parts, and levels of minor components as well as growing conditions and health

of the trees. Soil moisture is very important during fruit development.

Harvesting of fruit for oil production begins in the middle of autumn and lasts

until the end of February. In some regions, it begins earlier, and in other locales, it

lasts until March. Accordingly, differences in oil quality and composition can be

expected along with variations caused by climatic and soil conditions. Variations

in quality are chiefly related to the levels of minor components and flavor com-

pounds, acidity, and the presence of mono- and diglycerides (14–16).

Analytical and organoleptic data show that oil content is lower at the

beginning than at the end of the harvesting period, but it is of higher quality

(15). Harvesting technology is very important for production of high-quality

oil. Olives should be collected as soon as they reach optimal maturity; however,

it is difficult to have mechanical collection devices available where and when

needed. In addition, because of the conformation of the tree branches, strong adher-

ence of the fruit to the tree, and limited accessibility, most olives are picked by

hand.

Another harvesting procedure is to wait until the olives drop naturally and then

collect the fruit with a system of nets. When the ripening period is delayed, both

this procedure and handpicking are used. Although attempts have been made in the

past to use chemicals to influence dropping time, chemicals are seldom used.

Mechanical devices must be used with caution so that neither the tree nor the

branches are damaged. When mechanical devices are used, the olives are caught

in nets to avoid contact with the ground and damage to the fruit.

Under optimum conditions, the olives are transferred from the nets to cages

(usually plastic), forming layers not higher than 30 cm each, and the olives are

sent promptly to the extraction plant. In most regions of Italy and Greece, cages

are stored no more than 3 to 5 days before extraction. This procedure ensures

310 OLIVE OIL

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high-quality oil if climatic conditions were good, the trees received proper care, and

the fruit was not damaged by pests.

If proper precautions are not taken and the olives are collected in large

batches and held in piles several meters high, the fruit may be damaged. The

enzymes released will cause hydrolytic and oxidative transformations resulting in

off-flavors that affect the quality of the oil. Even with low acidity, such oils will

have an unpleasant taste not acceptable for virgin oil and will have to be refined.

Because of the difference in price between virgin and refined oils, economic losses

to the farmer can be high.

Three systems are used for mechanical extraction of oil from the olive fruit:

pressure processing (Figure 2); centrifugation (Figure 3); and adhesion filtering

(Figure 4) (17). Pressing is the oldest and most often used method for olive oil

extraction. High-speed rotating machines are used for centrifugation extraction.

With adhesion filtration, a series of steel plates or blades are dipped into olive paste;

when withdrawn, the oil drips off the blades.

Several processing steps are required before extraction. The fruit must first be

cleaned to eliminate branches and leaves and any extraneous materials that might

damage plant equipment. The fruit is then washed to remove dirt and agricultural

contaminants, and finally crushed and milled to a coarse paste (Figure 5). During

the last step, enzymatic action breaks up the bitter components and reduces the level

of peppery constituents while increasing the amount of minor polar components

Figure 2. Pressure extraction of oil. 1, movement of the rack; 2, movement of the oil; A, mobile

head; B, fixed head.

EXTRACTION TECHNOLOGY 311

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and tocopherols in the oil. If enzymatic action is prolonged, the minor polar com-

ponents break down into water-soluble compounds that are removed from the oil,

causing the loss of much of the antioxidant strength of the oil. Milling releases the

oil from the oil-bearing cells and helps smaller droplets of oil to merge into larger

drops, thus preparing the fruit for the following extraction step. A solid residue and

vegetation water are produced during extraction in addition to oil (Figure 6). The

vegetation water must be purified before discharge into a municipal sewer. Waste

water has been used to grow yeast, to produce butanol using microorganisms, to

isolate anthocyanin compounds for use in the food industry, and to produce steam.

Figure 3. Centrifuge for oil extraction from olive–pomace.

Figure 4. Diagram of adhesion extraction of oil.

312 OLIVE OIL

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Figure 5. Flow diagram of steps to prepare olives for extraction of oil.

Figure 6. Flow diagram of olive oil extraction and processing to yield olive oil products and

byproducts.

EXTRACTION TECHNOLOGY 313

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Efforts are being made to reduce waste water by recycling in the milling process

and to decrease its environmental pollution by treatment with biological or physical

processes prior to its discharge (22). A number of alternative technologies are avail-

able for waste water purification (18–21); however, they are costly and difficult to

apply.

If suitable for consumption, the oil is centrifuged after extraction to eliminate

solid impurities and residual water. If the free fatty acid content is too high or orga-

noleptic properties are unsatisfactory, the oil is refined.

At the solvent extraction plant, the cake (pomace) containing up to 8% residual

oil is dried in a rotary kiln before proceeding to the solvent extraction unit, usually a

semicontinuous system (Figure 7). The extracted pomace oil is always refined.

Spent cake is used as fuel or is separated into two fractions, the pulp (including

skin) and the pit. In addition to use as fuel, the pit is occasionally used to produce

fiberboard (23).

4. REFINING OF OLIVE OILS

Olive oil refining is carried out in either of two ways: by alkali refining, generally

used for animal and vegetable oils and fats; or by physical refining, a technology

not usually used for seed oils. Flow diagrams of the two procedures are shown in

Figures 8 and 9.

Figure 7. Flow diagram of solvent extraction of pomace.

314 OLIVE OIL

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Figure 8. Flow diagram of alkali refining.

Figure 9. Flow diagram of physical refining.

REFINING OF OLIVE OILS 315

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In the first procedure, the oil is treated with dilute acid to precipitate the gums

(phosphatides and proteinaceous material), which are separated by settling or

centrifugation. Phosphoric acid and citric acid are the two most common degum-

ming agents. After degumming, the oil is neutralized (alkali refined) either in a

batched or continuous system. Batch neutralization is currently preferred because

centrifuging of only the settled soap fraction lowers the neutralization coefficient

values, thereby shortening the washing time of the oil. The separated soap solution

is acidified with sulfuric acid to recover the free fatty acids (containing 30–40%

triglycerides) for industrial applications.

The alkali-refined oil is then bleached under vacuum with mixtures of various

adsorbents (bleaching earth or clay and sometimes small amounts of activated

carbon) and filtered by any of a number of available filter presses occasionally

equipped with a solvent system for recovering oil entrained in the bleaching

earth.

The bleached oil is deodorized in a semicontinuous or continuous deodorizer

operating at a vacuum of less than 2 mm Hg. The final step involves mixing refined

oil with virgin oil to improve the organoleptic and keeping properties of the oil. A

good olive oil will contain at least 20% virgin oil, but the product must, of course,

meet consumer preference, which sometimes requires a very light flavor and

taste.

With physical refining, the oil is first degummed and bleached and then fed to a

continuous distillation (deodorization) unit, which removes the free fatty acids (92–

95%) and volatiles. The refined oil is blended as above. Frequently, distillation is

stopped before removal of all of the free fatty acids, and the oil is alkali refined to

remove the remainder of the free fatty acids. This procedure has the advantage of

eliminating oxidation byproducts and pro-oxidant metals, thus improving product

stability.

5. REFINING OF POMACE OIL

The technologies adopted for refining pomace oil are based primarily on physical

refining because the acidity of pomace oils is about 10% (expressed as oleic acid).

Because degumming of pomace oil requires more drastic conditions than those for

pulp oil, larger amounts of acidulant are used (phosphoric acid is preferred), and

occasionally, the precipitate (gum) that entrains a high proportion of oil is centri-

fuged to recover the oil. Larger amounts of bleaching earths are required to remove

the intense green color of the oil. Additional processing of the bleached oil usually

follows the same procedures described for physical refining of olive oil, including

incomplete distillation (deodorization) followed by alkali refining of the partially

deodorized oil.

Dewaxing (winterization) of pomace oil is mandatory because of its high content

of waxes (olive oil may also be winterized, especially if it is used to produce

margarine or mayonnaise). Higher melting point triglycerides are also removed.

Winterization can be carried out after bleaching or following partial deodorization

316 OLIVE OIL

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and alkali neutralization (alkali refining). If alkali neutralization is performed at a

low temperature, winterization can be carried out simultaneously. A continuous

apparatus is generally used for winterization (Figure 9) coupled with continuous

filtering units. The winterization oil is then blended with virgin oil to restore the

oil’s antioxidant properties.

6. OLIVE OIL COMPONENTS

Glycerides account for at least 97% of a virgin oil if the acidity is disregarded. The

free fatty acid content is used to distinguish the various classes of virgin oil, from

extra virgin to lampant. It must be emphasized that virgin olive oil is a natural

product and therefore subject to variations in composition, both qualitative and

quantitative. The origin, cultivar, extraction technology, state of ripening of the

fruit, climatic conditions, and rainfall all influence biosynthesis within the fruit

and, therefore, the composition and quality of the oil. The fatty acid composition

of olive oil is shown in Table 3, which lists typical compositions of European,

Turkish, and African (Tunisian) oil as well as IOOC limits (12). Differences in

composition are due chiefly to linoleic, linolenic, and palmitic acid content. Olive

oils from Argentina resemble those from Tunisia. The triglyceride composition of

European, Turkish, and Tunisian olive oils is shown in Table 4 (main glycerides

are shown). Fatty acid distribution in the triglycerides follows the 1,3-random,

2-random rule (24–26).

Several classes of minor components are present in virgin olive oil. The struc-

ture, concentration, and number of these substances are characteristic of virgin oils.

Some are minor glyceridic components (MGCs); others fall into other categories as

listed below.

TABLE 3. Fatty Acid Composition of Olive Oil (%).

Acid CANa European Turkish Tunisianb Limits (12)

Palmitic 16 : 0 8.4 12.1 15.3 7.5–20.0

Palmitoleic 16 : 1 0.7 0.7 1.6 0.3–3.5

Heptadecanoic 17 : 0 0.1 0.2 0.1 0.0–0.3

Heptadecenoic 17 : 1 0.1 0.2 0.1 0.0–0.3

Stearic 18 : 0 2.5 3.1 2.1 0.5–5.0

Oleic 18 : 1 78.0 71.3 62.5 55.0–83.0

Linoleic 18 : 2 8.3 10.6 16.5 3.5–21.0

Linolenic 18 : 3 0.8 0.7 0.8 0.3–0.9

Arachidic 20 : 0 0.5 0.4 0.5 0.2–0.6

Eicosenoic 20 : 1 0.3 0.3 0.3 0.1–0.4

Behenic 22 : 0 0.1 0.2 0.1 0.0–0.2

Lignoceric 24 : 0 0.2 0.2 0.1 0.0–0.2

aCAN ¼ Carbon atom number.bTypical values for Tunisian olive oil analyzed during 1994.

OLIVE OIL COMPONENTS 317

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Hydrocarbons

Tocopherols

Linear short chain alcohols and their esters

Linear long chain alcohols and their esters

Sterols and their esters

a-Methyl sterols

Monohydroxytriterpenes

Dihydroxytriterpenes

Triterpenic acids

Phytol

Geranylgeraniol

Phenols and related compounds

Flavor components

Methyl and ethyl esters

Other components

6.1. Minor Glyceridic Components

Monoglycerides (MGs) and diglycerides (DGs) in the olive fruit are caused by

enzymatic hydrolysis of the triglycerides and incomplete triglyceride biosynthesis

(16). In general, DGs are more abundant than MGs. Determination of DG concen-

tration is useful for evaluating oil freshness and time of fruit harvesting because the

DG level is strongly related to climatic influences. DG concentration can even be

used to determine the source of an oil, even a refined oil, because the DG content of

edible virgin olive oils differs from that of high acidity oils or solvent-extracted oils.

Phospholipids are essentially absent from olive oil.

TABLE 4. Main Triglycerides of Olive Oil (%).

ECNa Triglycerideb European Turkish Tunisianc

42 LLL, TLOd, TLPd 0.5 0.8 1.6

44 LLOd 2.4 3.2 10.6

TOOd, LLP 2.6 2.9 1.7

46 LOOd 13.3 13.8 16.0

LOPd, PLP 8.0 9.7 16.2

48 OOO 39.9 34.0 23.2

POO 26.0 24.4 22.0

POP — — 5.1

50 SOO 5.1 5.1 4.3

SOP 1.0 1.4 1.2

52 OSS, PSS 0.8 — 0.5

aECN ¼ equivalent carbon number.bL ¼C18 : 2; T ¼ 18 : 3; O ¼ C18 : 1; P ¼ C16 : 0; S ¼ C18 : 0.cTypical values for Tunisian olive oil analyzed in 1994.dMixture of isomers.

318 OLIVE OIL

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6.2. Nonglyceridic Minor Components

Hydrocarbons. Both even- and odd-chain n-paraffins, including branched-chain

(iso and anteiso) compounds, which are minor components of the hydrocarbon

fraction, are present in virgin olive oil. The polyunsaturated triterpenic hydrocarbon

squalene, and biochemical precursor of sterols, is the main component of the hydro

carbon fraction. The squalene content of olive oil ranges from 150 to 700 mg per

100 g (27–30). b-Carotene is also present in olive oil as are aromatic hydrocarbons,

including benzenoid, napthalenic, and more complex aromatic hydrocarbons

(30–37).

Linear Short Chain Alcohols and Their Esters. Methanol and ethanol esters of

the fatty acids present in olive and in the same proportions as in the olive are

present among the volatile compounds in virgin olive oil (31–37).

Straight Long Chain Alcohols. Linear long-chain alcohols with carbon numbers

between C22 and C32 are present in olive oil both free and esterified (waxes). The

components are abundant in the epicarp of the fruit and concentrate in solvent

extracted oil. Phytol, probably derived from biodegradation of chlorophyll, is

also present along with geranyl (38).

Cyclic Monohydroxy Compounds. Triterpenic tetra- and pentacyclic mono-

hydroxy compounds are characteristic of olive oils (34–49). The following com-

pounds have been shown to be present, accompanied by small amounts of

lanosterol and obtusifoliol:

Tetracyclic: cycloartenol

24-methylene cycloartanol

Pentacyclic: a-amyrin

b-amyrin

Methylsterols (4-desmethyl triterpenes) and sterols (4,4-di-desmethyl triterpenes)

present in olive oils are derived from the tetracyclic alcohols. The following methyl

sterols (4a-methyl-7-cholesten-3b-ol compounds) are present: 24-methylene,

24-methyl-, 24-ethylidene, and 24-ethyl.

The main sterols of olive oil are (40, 43, 45–66) campesterol, stigmasterol,

clerosterol, b-sitosterol, sitostanol, and d-5-avenasterol.

These are accompanied by small amounts of cholesterol (max. 0.5%), brassica-

sterol (max. 0.1%), 24-methylenecholesterol (max. 0.5%), campestanol (max.

0.5%), d-5,24,-stigmastadienol (max. 1%), d-7-stigmastenol (max. 0.5%), and

d-7-avenasterol (max. 1.1%).

Analysis of the sterol fraction isolated from the unsaponifiable fraction is very

important, as will be seen later, for determining the authenticity of the oil. The

triterpenes and sterols are present both as free alcohols and as fatty acid esters

(46, 47).

Cyclic Dihydroxy Compounds. Pentacyclic triterpenes in olive oil include

3b,17b-dihydroxy-12-oleanene (erythrodiol) and its parent compound uvaol,

obtained largely from the epicarp and therefore characteristic of solvent extracted

oils (42, 65).

OLIVE OIL COMPONENTS 319

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Triterpenic Acids. The following pentacyclic mono- and dihydroxy triterpenic

acids are present in virgin olive oil (35, 43, 44): 3b-hydroxy-17-carboxy-d-12-olea-

nene (oleanolic acid); 3b,2a-dihydroxy-17-carboxy-d-12-oleanene (maslinic acid);

3b-hydroxy-17-carboxy-d-12-ursene (ursolic acid); 2a,3b-dihydroxy-17-carboxy-

d-12-ursene (2a-hydroxyursolic acid); and deoxyursolic acid (structure not fully

elucidated).

Chlorophylls. Both chlorophyll a and chlorophyll b are present in olives and are

partially extracted into the oils.

Flavor Components. Olive oil volatiles contain at least 100 compounds (33–37)

in several categories: hydrocarbons (5 compounds), aliphatic alcohols (13 com-

pounds), terpenic alcohols (4 compounds), aldehydes (27 compounds), ketones

(8 compounds), ethers (2 compounds), furans (3 compounds), thiophenes (6 com-

pounds), and esters (29 compounds).

6.3. Minor Polar Components

The olive mesocarp contains a number of phenolic and polyphenolic compounds

and their esters, small amounts of which are present in olive oil (35, 43, 44). These

include monohydroxy- and dihydroxy-phenylethanol, including tyrosol and other

phenols and a series of carboxy–phenols, including caffeic, o-coumaric, p-coumaric,

cinnamic, ferulic, gallic, p-hydroxybenzoic, protocatechuic, sinapic, syringic,

and vanillic acids. Benzoic and cinnamic acids are produced by hydrolysis of

flavonoids. The hydroxyphenyl–ethanols arise from hydrolysis of oleoeuropein.

Their esters are responsible for the bitterness and pepperlike sensation occasionally

dominant in the taste of olive oils.

Olive oil contains a-tocopherol in the range of 12–190 mg/kg. According to one

report (43), olive oil tocopherols were found to consist of 88.5% a-tocopherol,

9.9% b- þ g-tocopherol, and 1.6% d-tocopherol. Tocopherol content can be used

to detect adulteration of olive oil with seed oils.

7. ANALYSIS OF OLIVE OILS

Olive oil is initially examined to determine purity, then to place it in the proper

category, and finally to establish its quality.

7.1. Determination of Purity

Sterol Composition. Sterol analysis involves preparation of the unsaponifiable frac-

tion, fractionation by thin-layer chromatography (TLC), and gas chromatographic

analysis of the TMS derivatives (66). The following limits apply to all types of olive

oil (12):

320 OLIVE OIL

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Total Sterol Content. The gas liquid chromatographic method for sterol determi-

nation using an internal standard (cholestanol) is used to calculate the absolute

(total) sterol content of an oil (68, 69). Gravimetric, enzymatic, colorimetric, and

liquid chromatographic methods have also been reported (69). Limits (mg/100 g)

are as follows (12): virgin olive oil, refined olive oil, and olive oil (mixture of

refined and virgin) >100; crude olive–pomace oil >250; and refined olive–pomace

oil, olive oil and olive–pomace oil (mixture) >180.

Fatty Acid Composition. Olive oil triglycerides are converted into methyl esters,

and the methyl esters are analyzed by gas–liquid chromatography (GLC) (70, 71).

The limits of genuine olive oil are as follows (% m/m) (12):

Saturated Fatty Acids in Position 2 of the Triglycerides. Hydrolysis with pan-

creatic lipase is followed by thin-layer chromatographic isolation of the monogly-

ceride fraction, which is converted to methyl esters. The methyl esters are analyzed

Sterol Sterol Fraction (%)

Cholesterol Max. 0.5

Brassicasterol Max. 0.1

Campesterol Max. 4.0

Stigmasterol Less than 4.0

d-7-Stigmastenol Max. 0.5

The sum of the following sterols must be more than 93.0% of

the sterol function:

b-Sitosterol

d-5-Avenasterol

d-5,23-Stigmastadienol

Clerosterol

Sitostanol

d-5,24-Stigmastadienol

Acid CANa Minimum Maximum

Myristic 14:0 — 0.05

Palmitic 16:0 7.50 20.00

Palmitoleic 16:1 0.30 3.50

Heptadecanoic 17:0 — 0.30

Heptadecenoic 17:1 — 0.30

Stearic 18:0 0.50 5.00

Oleic 18:1 55.00 83.00

Linoleic 18:2 3.50 21.00

Linolenic 18:3 — 0.90

Arachidic 20:0 — 0.60

Eicosenoic 20:1 — 0.40

Behenic 22:0 — 0.20

Lignoceric 24:0 — 0.20

aCAN ¼ carbon atom number.

ANALYSIS OF OLIVE OILS 321

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by GLC (72, 73). Maximum acceptable level is the sum of palmitic and stearic acid

(% m/m) (12):

Virgin olive oil �1.5

Refined olive oil �1.8

Olive oil (mixture of refined and virgin) �1.8

Crude olive–pomace oil �2.2

Refined olive–pomace oil �2.2

Absolute Difference Between Found and Theoretical Equivalent Carbon Number

(ECN) 42 (Trilinolein) Values. The triglyceride composition of the oil is deter-

mined by high-performance liquid chromatography (HPLC) (74). (A chromatogram

of an olive oil sample (ECN 42, 0.8%) is shown in Figure 10.) The theoretical tri-

glyceride composition is calculated with a Lotus 123 program provided by the

IOOC. The maximum difference of theoretical ECN 42 vs. ECN 42 found is calcu-

lated. (ECN ¼ CN-2n, where CN is the carbon number and n is the number of dou-

ble bonds.) The maximum difference between the real and theoretical ECN content

Figure 10. HPLC chromatogram of olive oil triglycerides. Column: LC-18, 200 � 4:6 mm i.d.;

mobile phase : acetone : acetonitrile (60 : 40, v/v); flow rate : 0.75 mL/min; refractive index

detector; oven and detector temperature : 40�C. IUPAC Method 2.324 (72) with injection of 10-mL

test sample diluted 1 : 20 with acetone. ECN 42, 0.8% of total glycerides.

322 OLIVE OIL

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of olive oils and olive–pomace oils should be 0.3 and 0.5, respectively. This proce-

dure avoids errors because of miscalculation of trilinolein alone (75).

Trans-Fatty Acid Content. Trans-fatty acids arise during refining of vegetable

oils as well as during hydrogenation, or from attempts to eliminate the sterol frac-

tion of seed oils with a fatty acid composition similar to that of olive oil. Methyl

esters are analyzed by capillary column GLC (76, 77). The following limits

(% m/m) are mandatory (12):

7.2. Differentiation Between Olive Oil and Olive–Pomace Oil

Wax Content. Olive oil fatty acid esters of straight chain alcohols (wax esters pre-

sent in solvent extracted olive–pomace oil are isolated by column chromatography

on silica gel (LC) and quantitated by GLC to determine if olive–pomace oil is

present in olive oil (78). LC separation of the wax esters can be replaced with

HPLC to automate the separation step and improve reliability and repeatability

(79). Limits for content of C40 þ C42 þ C44 þ C46 wax esters (mg/kg) are as

follows (12):

Virgin olive oil �250

Lampant olive oil �350

Refined olive oil �350

Olive oil (mixture of refined and virgin) �350

Dihydroxyterpene Alcohol Content. Olive–pomace oil contains relatively high

levels of erythrodiol, uvaol, and wax esters. Erythrodiol and uvaol (total diol) con-

tent is determined by the same procedure as that used for sterol analysis (80, 81).

Limits for total diol content (as % of total sterols) are as follows:

Virgin olive oil �4.5

Lampant olive oil �4.5

Refined olive oil �4.5

Olive oil (mixture of refined and virgin) �4.5

18:1 18:2 trans þOil trans 18:3 trans

Virgin olive oil <0.03 <0.03

Lampant olive oil �0.10 �0.10

Refined olive oil �0.20 �0.30

Olive oil (mixture of refined and virgin) �0.20 �0.30

Crude olive–pomace oil �0.20 �0.10

Refined olive–pomace oil �0.40 �0.35

Olive–pomace oil and olive oil mixture �0.40 �0.35

ANALYSIS OF OLIVE OILS 323

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7.3. Differentiation Between Virgin and Refined Olive Oil and Detectionof Refined Olive Oil and Seed Oils in Virgin Olive Oil

Concentration of Stigmasta-3,5-Diene. When olive oil and seed oils are refined,

stigmasta-3,5-diene is produced by dehydration of b-sitosterol, the parent

sterol (82). Refined olive oils contain significant amounts of stigmasta-3,5-diene

(3– 100 mg/kg) not present in any significant amount in virgin olive oils. Refined

seed oils also contain significant amounts of steroidal hydrocarbons, including

campesta-3,5-diene and stigmasta-3,5,22-triene in addition to stigmasta-3,

5-diene. The relative amounts of these steroidal hydrocarbons can be used to

detect refined seed oils or seed oils desterolized for the purpose of adulterating

olive oil. Isolation of the hydrocarbon fraction from the unsaponifiables by col-

umn chromatography on silica gel followed by GLC is used to determine the con-

centration of stigmasta-3,5-diene and accompanying hydrocarbons (83, 84). A

chromatogram of the hydrocarbon fraction from an olive oil is shown in Figure 11.

Figure 11. Capillary GLC of the hydrocarbon fraction of olive oil (blend of refined and virgin olive

oil). Column: DB-5, 25 m � 0 :25 mm i.d., 0.2-mm film thickness; split ratio; 1 : 15; temperature

program: 235�C, 6 min; 20�C/min; 285�C final temperature; injector: 300�C; detector; 320�C,

1, cholesta-3,5-diene (internal standard); 2, stigmasta-3,5-diene.

324 OLIVE OIL

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A chromatogram of the hydrocarbon fraction from an olive oil admixed with des-

terolized, refined seed oil is shown in Figure 12. Ratios of stigmasta-3,5-diene to

campesta-3,5-diene (R1) and stigmasta-3,5-diene to stigmasta-3,5,22-triene (R2)

are determined when the level of stigmasta-3,5-diene exceeds 4 ppm (12).

However, a July 1994 IOOC report (84) noted that the R1 and R2 values of many

Italian and Greek olive oils were considerably lower than those proposed by the

IOOC (12) and that the composition of steroidal hydrocarbons should be identical

to that of the sterols from which they are derived when the R1 and R2 ratios are

used to identify extraneous oils in refined olive oil.

UV Absorption at 268 nm. K (1%, 1 cm) and related value, d-K, are useful

for readily classifying olive oil quality according to the following values

(12, 85):

Both K and d-K are altered when oxidation products are present. In this case, the oil

is dissolved in hexane and passed through an alumina column before measurement

of K and d-K.

Oil K 270 nm d-K a

Extra virgin olive oil �0.25 �0.01

Virgin olive oil (fine) �0.25 �0.01

Virgin olive oil (semifine) �0.30 �0.01

Lampant olive oil No limits No limits

Refined olive oil �1.10 �0.16

Olive oil �0.90 �0.15

Crude olive–pomace oil No limits No limits

Refined olive–pomace oil �2.00 �0.20

Pomace and olive oil mixture �1.70 �0.18

ad-K ¼ K268 � ð½K 262 þ K274=2Þ.

Oil Stigmasta-3,5-diene (ppm) R1a R2b;c

Virgin olive oil �0.1 — —

Lampant olive oil �0.5 — —

Refined olive oil �50.0 �15 �15

Olive oil �50.0 �15 �15

Crude olive–pomace oil �0.5 �15 �15

Refined olive–pomace oil �120.0 �15 �15

Pomace and olive oil mixture �120.0 �15 �15

aR1 ¼ ratio of stigmasta-3,5-diene to campesta-3,5-diene.bR2 ¼ ratio of stigmasta-3,5-diene to campesta-3,5,22-triene.cProvisional limits.

ANALYSIS OF OLIVE OILS 325

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7.4. Quality Parameters

Organoleptic Characteristics. Organoleptic properties of virgin oil can be deter-

mined by a ‘‘panel test’’ (13, 86), which gives results that are often controversial.

Organoleptic testing is currently undergoing revision. Currently the IOOC is pre-

paring a draft method for the organoleptic assessment of virgin olive oil using a

designation of origin (DO) code. It is intended for use by DO authorities to ensure

that the oil meets requirements (87). The panel test method is based on examination

of virgin oil by a panel of 8 to 12 trained personnel who grade various character-

istics and defects that are then converted into a number score. The following scores

apply to various grades of virgin olive oil:

Extra virgin olive oil >6.5

Fine virgin olive oil >5.5

Semifine virgin olive oil >3.5

Lampant virgin olive oil <3.5

Figure 12. Capillary GLC of the hydrocarbon fraction of olive oil admixed with a desterolized

seed oil (GLC column and operating conditions as described for Figure 11). 1, Cholesta-3,

5-diene (internal standard); 2, campesta-3,5-diene; 3, stigmasta-3,5,22-triene; 4, stigmasta-3,

5-diene.

326 OLIVE OIL

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Free Fatty Acid Content. Free fatty acid content (expressed as % oleic acid) (88)

is used to define the various grades of virgin olive oil (12):

Extra virgin olive oil <1.0

Fine virgin olive oil <1.5

Semifine virgin olive oil <3.3

Lampant virgin olive oil >3.3

Refined olive oil and mixtures have the following limits (12):

Refined olive oil �0.3

Olive oil �1.5

Refined olive–pomace oil �0.3

Olive–pomace and olive oil �1.5

Olive oil and mixtures of olive–pomace and olive oil have higher free fatty acid

contents because they are generally mixed with virgin olive oils of high acidity.

Peroxide Value (PV). PV (expressed in meq per kg oil) (89) allowed for various

grades of olive oil is as follows (12):

Extra virgin, fine, and semifine virgin olive oil �20

Refined olive oil �10

Olive oil �15

Refined olive–pomace oil �10

Pomace oil and olive oil mixture �15

Virgin olive oil contains components that interfere with conventional PV determi-

nation. Even freshly expressed olive oil has PV values of about 10, and under

certain climatic conditions (dry weather), the PV value can be higher than 10.

Tocopherol Content. Tocopherols can be determined by colorimetry or GLC

(90), or by HPLC (91, 92). Added tocopherols are not permitted in virgin olive

oils and crude olive–pomace oils (12). Added a-tocopherol is allowed in refined

olive oil, olive oil, refined olive–pomace oil, and olive–pomace oil to restore natural

tocopherol lost during refining with a maximum level of 200 mg/kg of total a-toco-

pherol in the final product (12).

Impurities. Water content (93) of virgin olive oil should not exceed 0.2% (m/m);

for refined oil and mixtures (olive oil, olive–pomace and olive oil), the maximum

value is 0.1%; for lampant olive oil, 0.3%; for crude olive–pomace oil, 1.5% (12).

Allowable hydrocarbon (hexane, petroleum ether) residues (94) are as follows

(% m/m):

Extra virgin, fine, and semifine virgin olive oil �0.10

Refined olive oil, olive oil �0.05

Refined olive–pomace oil, olive–pomace and olive oil �0.05

ANALYSIS OF OLIVE OILS 327

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The occurrence of mg/kg to mg/kg amounts of tetrachloroethylene in some olive

oils (95) led to an EEC regulation limiting the tetrachloroethylene content of olive

oil and products containing olive oil to not more than 0.1 mg/kg, as determined by a

head space/electron capture GLC method (96).

Maximum allowable contents of iron and copper (97) are 3 ppm and 0.1 ppm,

respectively.

Smoke point (98) is a function of acidity level in the oil. The smoke point for

olive oil generally ranges from 150�C to 163�C.

7.5. Combined Gas Chromatography–Mass Spectrometry (GC/MS)

GC/MS is a powerful tool for identification and confirmation of the various com-

ponents of olive oil. With GC/MS in the selective ion mode, unresolved GC peaks

can be identified and accurately quantitated. For example, an apparent b-sitosterol

peak in the sterol fraction was resolved into clerosterol (m/z 218) and �-5-avenas-

terol (m/z 314), and both sterols measured regardless of inadequate GC resolution.

Italian and Spanish olive oil from the 1991–1992 crop year contained a very high

level of 9,19-cyclolanosterol (>400 mg/kg), which was not found with the standard

method for sterol analysis. Two isomers of this sterol were identified by GC/MS of

the unsaponifiable fraction, and their levels were found to be inversely proportional

to the levels of b-sitosterol in the oils. GC/MS of the unsaponifiable fraction with

high-resolution GC capillary columns provides a relatively rapid means of checking

product purity and the identity of individual components. Thus, triterpene diols

were identifiable at m/z 203, a-tocopherol at m/z 165, squalene at m/z 69, choles-

terol at m/z 386, and brassicasterol, characteristic of canola oil and other Brassica

oils, at m/z 398.

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