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Source: FAOSTATS, Statistical database, Food and Agriculture Organization of the United Nations, 1998, http: ! ! apps.fao.org.

Source: FAOSTATS, Statistical database, Food and Agriculture Organization of the United Nations, 1998, http: ! ! apps.fao.org.

sidered a drought-resistant species because it thrives in areas where water stress is frequent, such as Mediterranean climates. It has been postulated that the minimum water requirement for olive is 2,000 m3/ha per year, mainly during flowering and fruit setting in late spring and again in the summer as the fruit increases in size (2). Olive trees will grow on poor soils and rocky hillsides, but deep soils produce the best-quality fruit. They tolerate saline or alkaline soils and those with a high lime content. Their root system is relatively shallow and will not tolerate waterlogged soils.

The first reference to the existence of the olive tree is found in the Old Testament Book of Genesis, where the flight of the dove with an olive branch announces the end of the Flood. The origin of the cultivation of the olive tree is known through legends and tradition. It can be situated within a wide strip of land in the Mediterranean area (3) and adjacent zones comprising Asia Minor and parts of India, Africa, and Europe. However, the botanical ancestor of the olive tree is not precisely known (4). The two possible candidates are the oleaster Olea sylvestris and O. chrisol-phylla, both of which might have had a common ancestor that covered most of the Sahara desert before the last glaciation. There also different hypotheses regarding the spread of its cultivation in the Mediterranean basin. This might have involved originally the Phoenicians and later the Greeks and the Romans. At the end of the Roman Empire, the olive trees were cultivated throughout the Arab and Roman worlds (5).

During the fifteenth and sixteenth centuries, colonizers and Spanish Franciscan monks extended the planting of the olive tree to various parts of the New World, finally reaching California during the eighteenth century. In the same manner, Italian and Spanish emigrants and missionaries spread the olive tree to Australia, South Africa, and Japan, completing its extension in both hemispheres. It is now distributed approximately between lat. 25 and 45° N and 15 and 35° S.

The Fruit

Composition and Changes during Growth and Maturation.

The fruit of the olive tree is an edible, fleshy drupe, more or less oblong according to the variety, of a green color that changes to purple or black when mature and reaches a weight range of 1.5 to 12 g. The length of the fruit is generally between 2 and 3 cm and its transverse diameter between 1 and 2 cm. The specific weight is close to unity. The percentage of flesh, intensely bitter mainly when still green, varies between 70 and 90% of the fruit. The pit or stone represents 10 to 30% of the fruit, according to the variety, extent of growth, and maturity. The seed it contains accounts for less than 10% of the weight of the stone.

All the physical characteristics mentioned herein as well as the chemical composition of the edible flesh depend on several factors, among which the predominant are variety and degree of growth and ripeness when the fruits are harvested (6,7). Table 4 gives an overview of the composition of the fruit.

The main quantitative constituents of the flesh are water and oil, which show an inverse relationship for the same degree of maturity. The moderate degree of saturation of their fatty acids, and specifically, the high content of oleic acid, contributes to the fact that olive oil and table olives are considered high in biological and nutritive value. Water represents the main constituent of the olive fruit, accounting for up to 70% of its weight. Water serves as a

Table 4. Composition of the Fruit of the Olive Tree and of the Fresh Pulp

Weight %

Fruit

Epicarp

Pericarp Pulp 70-90 Mesocarp

Stone 9-27

Endocarp

Seed 1-3

Pulp

Moisture 50-75

Lipids (oil) 6-30

Reducing sugars, soluble 2-6

Nonreducing sugars, soluble 0.1-0.3

Fiber 1-4

Organic acids and their salts 0.5-1

Phenolic compounds 1-3

Pectic substances 0.3-0.6

Other components 3-7

solvent for water-soluble substances, including organic acids, tannins, and oleuropein.

Oil is dispersed within the fruit cells in droplets that vary from 40 to 60 //m in diameter. The amount of oil increases through autumn and winter, reaching its maximum between late November and January when the fruit displays a reddish-bluish color, an indicator that it has reached the optimum-maturity stage. The oil content is lower in colder climates.

Soluble reducing and nonreducing sugars are the most important compounds for the fermentation and preservation stages of the process involved in the preparation of table olives. Glucose as a major component, followed by fructose and to a minor extent by sucrose, have been quantified; small amounts of xylose and rhamnose are also present, as well as mannitol (in the range of 0.5-1%), which is a poliol also important as fermentative matter. The evolution of all these components during the growth and maturation of the fruits has been studied for different varieties by gas-liquid chromatography (8).

Fiber is the fundamental support for the structure of the fruits. Its major components for fresh green fruits, in order of decreasing percentage, are cellulose, lignine, and hemicelluloses, with cellulose accounting for more than 50%, depending on the variety. However, when the degree of maturity advances, enzymatic degradation may produce changes in the relationship of the components. Thus, for Hojiblanca variety at different stages of ripeness, cellulose percentage goes from 40 to 45% down to 23%; lignine remains almost steady, between 33 and 38%; and hemicelluloses goes from 22 to 23% up to 41% when fruits are completely ripe (9).

Hemicellulose isolated from fruits of the Gordal and Manzanilla varieties have been studied (10,11). Cellulo-lytic enzymes were detected in the flesh of the Hojiblanca variety (12). These enzymes partially hydrolyze the cellulose fraction of the fiber to glucose and contribute to the softening of the fruits. Different factors influencing their action, such as incubation time, presence of sodium chloride, temperature, storage time, and degree of maturity when fruits are harvested, have been studied (13,14). Characterization and partial purification of the enzymatic complex cellulases and their inhibitors have been carried out (15,16).

Protein content is relatively low, between 1 and 3%, and remains almost constant during growth and ripening of the fruits. Hydrolysis shows that all essential amino acids are present (17). Ash percentage varies from 0.6 to 1, and the ash includes, in order of decreasing importance, K, Ca, P, Na, Mg, S, and, to a lesser extent, Fe, Zn, Cu, and Mn. The importance of the presence of organic acids and their salts in the juice of the fruits must be emphasized because of their buffering action during the fermentation stage. They range between 0.5 and 1%, based on the weight of the flesh.

Phenolic compounds, ranging from 1 to 3%, are responsible for color changes; pectic substances (0.3-0.6%) and pectic enzymes are related to texture (18); oleuropein, the most abundant phenolic glycoside found in olives (up to 2% in immature olives), is responsible for the bitterness of the fruit. It diffuses into the aqueous phase during the processing of the olive fruit and is hydrolyzed by alkaline so-

lutions. Finally, certain vitamins, such as carotene, thiamine, and riboflavin, complete the known picture of the composition of the fresh fruit (19,20).

The chlorophyll and carotenoid presence in fruits of Ho-jiblanca and Manzanilla olive varieties have been studied (20,21). The qualitative composition is the same for both and does not change with maturation time. However, during the growth and development of the fruit, a gradual, homogeneous decrease is observed in the individual concentration of both chlorophylls and carotenoids (22). Hoji-blanca variety always shows a greater amount of pigments than does Manzanilla.

As a general rule, water content decreases. Conversely, oil percentage, weight, and volume of the fruits, and flesh-to-pit ratio increase during growth and maturation. Soluble reducing and nonreducing sugars also decrease in a continuous manner. On the contrary, protein, ash, and total fiber remain almost stable, although qualitative changes may be produced in the total fiber.

Main Varieties The chemical composition and physical properties of the fruit that are closely related to variety and harvesting time are decisive factors in the quality of the final product. Varieties of olive trees in different countries may be either autochthonous or imported. Autochthonous varieties, because of their nature, and imported varieties, because of changes in climate, soil, and methods of cultivation, may yields products with diverse characteristics (23-27). Olive tree varieties are not well known in many cases, so national or local names rather than botanical classification are used to identify them.

Among available varieties, it is necessary to select the most suitable for the specific use (olive oil vs. table olives), the type of processing, and a definite style. For that selection, different factors must be carefully analyzed: (1) geographical situation of planting age and distribution on the soil; (2) agricultural characteristics, such as productivity of the trees, ripening cycle, and pest resistance; (3) type of culture (irrigated or nonirrigated system); (4) pruning methods; and (5) harvesting procedure (manual or mechanical). All these variables have an important influence on composition and hence on parameters to be considered in further processing.

Physical properties of fruits also have a relevant importance at the time a certain variety is selected for a definite type of processing. Among them, the most important are size, shape, flesh-to-pit ratio, ease of pitting, color, and texture.

Varieties used for oil production have a ratio of flesh to pit ranging from 4:1 to 8:1 and a ripe fruit that contains 15 to 40% of oil, whereas table oil varieties have a ratio of 7:1 to 10:1 and a lower upper range of oil content.

Spanish Varieties Among the 22 dominant Spanish varieties (Seed and Plant Genetic Resources Service B AGPS. Olive Germplasm: Cultivars and World-Wide Collections. Food and Agriculture Organization of the United Nations), the major cultivars used for oil production include Picual, Hojiblanca, and Lechin de Sevilla, whereas those for processing table olives are the Gordal (or Sevillana), Manzanilla, Morona, and Cacereña.

Picual. Picual has the widest spread of any single cultivar in Spain and is well suited to oil production. It is the main tree for the Jaen area (Andalucía), the largest olive-growing region in the world. It grows well in hilly to mountainous areas and is able to withstand cold winters. The fruit is elongated and nearly symmetrical, with a slight bend at the apex. At green maturation it has a somewhat dark shade. Blackening starts from the apex, and the ripe fruit is uniformly dark black. Fruit size varies from 3 to 5g according to yield and growing conditions. The mesocarp is light colored, smooth, and relatively firm. The oil content is medium-high, 21 to 25%, on a fresh-weight basis. The flesh-to-pit ratio oscillates between 3.8 and 5.9:1.

Hojiblanca (O. europaea arolensis). Hojiblanca ripens later than Gordal and Manzanilla and has a higher oil content, between 23 and 29%. It is the second most common Spanish variety with regard to market volume, being the most appreciated for processing either as natural black olives in brine or as pickled black olives in brine, although it is also used as pickled green olives in brine. The shape of the fruits is regular, the pit is straight and the olives vary greatly in size, from 230 to 700 fruits/kg. Smaller-size grades are used for oil extraction. The flesh-to-pit ratio oscillates between 4.9 and 6.6:1.

Lechin. Lechin has its origin between Cordoba and Seville and is cultivated in the area of Seville and Granada. The fruit is ellipsoidal and slightly bulged on the back. The size ranges from 3.58 to 3.80 g, with an oil content between 23.5 and 26.8%. The flesh-to-pit ratio ranges between 4.0 and 6.1:1.

Cordal or Sevillana (O. europaea Regalis Clemente). Gordal or Sevillana is a big, ellipsoid hearth-shaped fruit, with an average size of 100 to 120 fruits/kg and a relationship of flesh to pit of 7.5:1. The form is ellipsoidal with an incision in the area of the peduncle that gives it a shape resembling a heart. It has a fine epicarp, a mesocarp with good texture, and a right and regular endocarp. The color is deep green that changes to purple-black when the fruit is fully mature. Oil content is low, generally below 10%, and the sugar content is around 4 to 6%. Early ripeness is characteristic.

Manzanilla (O. europaea pomiformis). Different sub-varieties, depending on the region, are known by different local names, including Fina, Serrana, and Carrasqueña. The fruits are the most appreciated variety in the international market, mainly because of their prominent organoleptic properties. It is the most important variety in Spain and together with Gordal and Morona is almost exclusively destined for the preparation of Spanish-style pickled green olives in brine. Average size is 200 to 280 fruits /kg; the flesh-to-pit ratio is 6:1. Manzanillas are apple-shaped, with fine skin and flesh with an excellent texture. The color is light green with mottled white spots, the fruit turns black-violet when fully mature. The pit is right and presents a very smooth surface. This variety reaches ripeness later than Gordal and shows a higher oil content, sometimes up to 15% by weight of the fruit, and a lower sugar content.

Morona. The Morona variety is very close to Manzanilla, it is perhaps the same variety. Its production is re-lativey small and is located around Moron de la Frontera (Sevilla province).

Cacerena. Although quite close to Manzanilla, Cacerena generally presents a lower average size and rougher texture. It is most suitable for processing pickled black olives in brine.

Greek Varieties. The major cultivars used for oil production include Koroneiki, Megaritiki, and Tsounati. Those for processing table olives include Conservolea, Ka-lamata, and Halkidiki.

Megaritiki (O. europaea argentata). Variety with fruits of small size (2-5 g) with a curved, cylinder-conic shape. About half of the production is dedicated to oil and half to dry salt black olives.

Conservolea (O. europaea media rotunda). Conservolea is the most important Greek variety, representing 80 to 85% of olive production in the country. Fruits, varying in shape between round and oval, show certain characteristics similar to those of Manzanilla and Hojiblanca, although closer to the latter. Average size is 180 to 200 fruits/ kg; flesh-to-pit ratio is around 8:1. The flesh is fine and the texture consistent. Oil content varies from 22 to 25%.

Halkidiki. Some authors consider the not-well-defined Halkidiki variety a subvariety of Conservolea. However, its shape is more elongated, its pit is slightly curved, and the flesh does not present as good a texture as does Conservolea. Average size is 120 to 140 fruits/kg, and flesh-to-pit ratio is 10:1. Used mainly for pickled green olives in brine, it is the second-most-produced Greek variety on the market. The oil content ranges from 19 to 20%.

Kalamata (O. europaea ceraticarpa). This excellent variety, of limited culture, is third in production in Greece. Fruits are cylindric-conic shaped and curved, showing a prominent tip at the end. Average size is 180 to 360 fruits/ kg; the flesh-to-pit ratio is analogous to that of Conservolea (8:1). It reaches a nice natural black color on late ripeness, and the oil content is high (25.5%). It is used mainly for special styles of natural black olives in brine.

Italian Varieties. Italy is the second-largest producer of olive oil, with cultivars such as Leccino and Frantoio, but lags behind in table olive varieties.

NoceUara di Belice. Considered the prime Italian table olive. The fruit is medium size, round or oval, and similar to Manzanilla or Conservolea. Flesh-to-pit ratio is 6.5:1 to 8:1.

Ascolana Tenera. This is the most common variety in Italy and is also cultivated in Argentina, California, Israel, and Mexico. The average size is 115 fruits/kg, with an ellipsoidal, slightly asymmetric shape. For the production of Spanish-style olives, the fruit is harvested when the skin color is yellowish green. The flesh is soft and the skin has little resistance to alkaline treatment (soaking the olives in a strong alkaline solution for several days). Oil content varies from 17 to 18%.

Cucco. A resistant variety exclusive to Italy. The fruit maintains the green color for a longer time than other varieties and changes to a violet black when it reaches full maturation. Oil content is about 17%.

Sant' Agostino. The fruits are clustered in groups of two or three with an oblong ellipsoidal form. The average size is 135 fruits/kg with an oil content of 14 to 15%.

Santa Caterina. Variety from central Italy with an average size of 120 fruits/kg with an asymmetric ellipsoidal shape. The oil content is about 17%.

Bella di Spagna or Cerignola. Variety from central Italy with fruit of large size (110 fruits/kg). The shape is oblong ellipsoidal and the mature color is black with white spots.

Moroccan Varieties. The main cultivated variety for pickling in Morocco is denominated Picholine. It comes from Argelia, although its origin is probably French. Average size is around 280 fruits/kg. It is oval shaped, with an elongated, slightly curved pit. The flesh-to-pit ratio is around 5.1:1. It is a resistant variety, well adapted to different kinds of soil. The flesh is flavorful.

Argentinian Varieties. Argentina prepares and exports mainly the Arauco variety, also called Criolla, of Spanish origin. This olive has flesh-to-pit ratio of 7:1 and high oil content (22-24%); the fruits are elongated with a tip at the end. Pits are slightly curved. It is used mainly as pickled green olives in brine.

Turkish Varieties. The most appreciated Turkish varieties are Domat, for pickled green olives in brine, and Gem-lik, for natural black olives in brine or in dry salt. Domat averages 180 to 190 fruits/kg; Gemlik 270 to 280 fruits/kg. Oil content is high for both, oscillating between 22 and 24%.

Californian Varieties. The United States is the main importer of olives, but it also produces a significant amount of table olives (see Table 3): 82,000 tons in 1988-1989 and 86,500 tons in 1991-1992. Five varieties are cultivated in California: Manzanilla, Mission, and Gordal or Sevillana, of Spanish origin; Ascolana from Italy; and Barouni, from Tunisia, the last being the least important in production. The Mission variety is the oldest in California. The oil content is about 22%; average size, 240 to 260 units/kg; and the ratio of flesh to pit is 6.5:1 for processed fruits. This is a very tasty variety that shows a nice black color when ripes.

Ascolana variety averages 110 to 120 fruits/kg, with a flesh-to-pit ratio of 8.2:1. Oil yield is not very high (19%), and the flesh is very delicate. It may be used as pickled green or black olives in brine.

French Varieties. France is the smallest European producer, with nearly 40,000 ha planted with olive trees. French production during 1993-1994 was 2 million t of olive oil.

Table olives and olive oil from France are products of high quality. Olive growing represents an important economic and social factor in the Mediterranean region. The major varieties used in France for olive oil are Aglandau, Bouteillan, Dcayet roux, Cayon, Salonenque, Brun, and Ri-bier. For table olives the varieties most commonly used are Belgentieroise, Picholine, and Lucque.

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