The Plant, Production, Olives and Olive Oil and Their ... · 1.1 The Plant, Production, Olives and...

1.1

The Plant, Production, Olives and Olive Oil and Their Detailed Characterization

The Plant and Production

Olives and Olive Oil

The Detailed Characterization of Olives and Olive Products

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5Olives and Olive Oil in Health and Disease Prevention.ISBN: 978-0-12-374420-3

Copyright © 2010 Elsevier Inc. All rights of reproduction in any form reserved.

2010

Table Olives: Varieties and Variations

Luis Rejano , Alfredo Monta ñ o , Francisco Javier Casado , Antonio Higinio S á nchez and Antonio de Castro Food Biotechnology Department, Instituto de la Grasa CSIC, Seville, Spain

Chapter 1

1.1 INTRODUCTION

Table olives are the products prepared from sound fruits of the cultivated olive tree ( Olea europaea L.). Consumption of table olives dates back to antiquity, with Columela, in the year 42 CE , being the first author to describe several methods to prepare edible olives according to their variety and degree of ripeness. Table olive production was initially restricted to the producing regions, mainly around the Mediterranean Sea. Today, however, olive preparation has extended to both North and South America, and even Australia.

The world production of table olives is around 1.7 – 1.8 million tonnes. The main producers are the European Union, Turkey, Egypt, Syria, and Morocco. The United States of America and Argentina are also important. Inside the European Union, Spain is the main producer, followed by Greece and Italy. Table 1.1 presents detailed data on production, export and import, and consumption for the main countries involved in the table olive trade ( IOOC, 2007 ). The first group of coun-tries is that with the highest production and exportation (75% world total). The second group is formed by countries with 25% of production and exportation, but 40% consumption (always referred to world total), which means that this group of countries imports 80% of the total importations.

Each olive-growing country has its own typical olive varieties. Of all the olive varieties that exist, only those hav-ing suitable characteristics ( Table 1.2 ) are used for table olive processing, and even fewer varieties are used for industrial preparation and international trade. The suitabil-ity of olives for table consumption depends on size, shape, flesh-to-stone ratio, flesh finesse, taste, firmness, and ease of stone detachment. Olives weighing between 3 and 5 grams are considered to be medium-sized; over 5 grams they are large. Olives that are more or less spherical in shape facili-tate processing operations and have a better market, although some elongated fruits also find favor. The stone should sepa-rate easily from the flesh; the higher the flesh-to-stone ratio, the better the commercial value of the olives – a ratio of 5:1 is acceptable. The skin of the fruit should be fine, yet elastic

and resistant to blows and to the action of alkalis and brine. At the international trade level, the most important table olive varieties are Manzanilla, Gordal Sevillana, Hojiblanca, Kalamata and Conservolea, and to a lesser extent Bella de Cerignola, Ascolana Tenera, and Picholine.

A characteristic common to almost all olive varieties is their extreme bitterness when tasted fresh. The glucoside oleuropein is responsible for this, and the different process-ing methods are aimed at removing this compound in order to obtain fruits with more-palatable attributes. It could be said that there are as many processing methods as places where olives are consumed. In an attempt to normalize the different products, the International Olive Council has a Trade Standard Applying to Table Olives ( IOOC, 2004a ), in which the types, trade preparations, quality factors, and other properties are described.

The objective of this chapter is to describe in detail the different kinds or classifications applicable to table olives, explaining the distinctive traits for each case.

1.2 TYPES OF OLIVE ACCORDING TO RIPENESS

Table olives are classified as one of the following types, depending on the degree of ripeness of the fresh fruits:

(a) Green olives: Fruits harvested during the ripening period, prior to coloring and when they have reached normal size. Once processed, green olive color may vary from green to straw-yellow.

(b) Turning-color olives: Fruits harvested before the stage of complete ripeness is attained, at color change. After processing, this type of olive may vary from pink to ros é wine or brown.

(c) Black olives: Fruits harvested when fully ripe, or slightly before full ripeness is reached. Once processed, black olives may range from reddish black to violet-black, deep violet, greenish black, or deep chestnut.


SECTION | I The Plant and Production6

TABLE 1.1 World table olive production, exportation, importation, and consumption along the last six seasons ( IOOC, 2007 ).

This table shows data on production, export and import, and consumption for the main countries involved in the table olive trade. Countries are grouped into two groups (A and B). The group A is that with the highest production and exportation (75% world total), whereas the group B is formed by countries with 25% of production and exportation.

Country

Production Average ( %)

Exports Average ( %)

Imports Average ( %)

Consumption Average ( %)

Algeria 67.6 (3.9) 0.2 (0.0) 0.2 (0.0) 68.4 (4.0)

European Union 706.3 (41.2) 233.4 (49.2) b 75.7 (16.4) b 561.6 (32.5)

Cyprus 9.8 (0.6) 0.3 (0.1)

Croatia 0.9 (0.1) 0.1 0.1 (0.0) 0.9 (0.1)

Egypt 195.8 (11.4) 30.2 (6.4) 0.4 (0.1) 160.5 (9.3)

Iran 23.8 (1.8) 1.0 (0.2) 24.8 (1.4)

Israel 16.1 (0.9) 0.9 (0.2) 6.3 (1.4) 21.8 (1.3)

Jordan 23.9 (1.4) 4.6 (1.0) 2.8 (0.6) 22.1 (1.3)

Lebanon 6.1 (4) 0.8 (0.2) 1.6 (0.3) 6.8 (0.4)

Libya 3.3 (0.2) 0.1 (0.0) 3.8 (0.8) 7.0 (0.4)

Morocco 93.3 (5.4) 61.6 (13.0) 0.0 (0.0) 31.8 (1.8)

Serbia-Montenegro 0.5 (0.0) 0.2 (0.0) 0.7 (0.0)

Syria 148.3 (8.7) 21.1 (4.4) 0.0 (0.0) 129.1 (7.5)

Tunisia 15.6 (0.9) 0.5 (0.1) 0.0 (0.0) 14.9 (0.9)

Total A 1294.9 (75.5) 353.3 (74.5) 91.8 (19.9) 1043.7 (60.4)

Saudi Arabia 19.7 (4.3) 19.7 (1.1)

Argentina 63.0 (3.7) 47.7 (10.1) 0.0 (0.0) 15.3 (0.9)

Australia 3.4 (0.2) 0.3 (0.0) 14.3 (3.1) 17.4 (1.0)

Brazil 0.5 (0.0) 52.5 (11.4) 52.9 (3.1)

Bulgaria 8.2 (1.8) 8.2 (0.5)

Canada 23.8 (5.1) 23.8 (1.4)

Chile 9.1 (0.5) 0.8 (0.2) 1.5 (0.3) 9.8 (0.6)

USA 87.0 (5.1) 4.5 (0.9) 122.5 (26.5) 210.8 (12.2)

Japan 2.3 (0.1) 2.3 (0.1)

Mexico 11.2 (0.7) 5.0 (1.1) 4.6 (1.0) 10.9 (0.6)

Palestine 6.9 (0.4) 0.6 (0.1) 7.8 (0.5)

Peru 29.8 (1.7) 9.9 (2.1) 0.1 (0.0) 19.7 (1.1)

Romania 17.7 (3.8) 17.7 (1.0)

Russia 28.8 (7.7) 45.0 (2.6)

Switzerland 20.8 (4.5) 4.5 (0.3)

Turkey 192.5 (11.2) 52.7 (11.1) 0.0 (0.0) 147.7 (8.6)

Venezuela 2.7 (0.6) 2.7 (0.2)

Other prod. count. 16.2 (0.9) 12.8 (3.5) 29.0 (1.7)

Other non-prod. 42.0 (9.1) 42.0 (2.4)

Total B 419.5 (24.5) 120.8 (25.5) 370.3 (80.1) 682.8 (39.6)

Total world 1714.4 (100) 474.1 (100) 462.2 (100) 1726.5 (100)

a Average data (1000 tonnes) corresponding to harvest seasons 2001/2 to 2006/7, this last season’s data are provisional. b Without intra-Community trade.


CHAPTER | 1 Table Olives: Varieties and Variations 7

TABLE 1.2 World olive varieties suitable for table olive or both table olive and oil extraction ( IOOC, 2000 ).

This table shows the major olive varieties grown worldwide suitable for table olive processing as well as those suitable for both table olive and oil extraction. The most important table olive varieties are Manzanilla, Gordal Sevillana, Hojiblanca, Kalamata and Conservolea, and to a lesser extent Bella de Cerignola, Ascolana Tenera, and Picholine.

Country Table Table and oil

Albania Kalinjot

Algeria Azeradj, Blanquette de Guelma, Sigoise

Argentina Arauco Chile Azapa Cyprus Ladoelia

Croatia Oblica

Egypt Aggezi Shami, Hamed, Toffahi France Lucques Aglandau, Grossane, Picholine Languedoc,

Salonenque, Tanche

Greece Chalkidiki Amigdalolia, Kalam ó n, Konservolia, Mastoidis, Megaritiki

Israel Kadesh, Merhavia Barnea

Italy Ascolana Tenera, Giarraffa, Nocellara del Belice, Oliva di Cerignola, SantÁgostino, Santa Caterina

Carolea, Cassanese, Cellina di Nard ò , Cucco, Itrana, Majatica di Ferrandina, Nocellara Etnea, Pizzé Carroga

Jordan Rasií

Lebanon Soury

Morocco Meslala Haouzia, Menara, Picholine Marocaine

Palestine Nabali Baladi

Portugal Carrasquenha, Cordovil de Castelo Branco, Cordovil de Serpa, Galega Vulgar, Ma ç anilha Algarvia, Redondal

Spain Alore ñ a, Gordal de Granada y Sevillana, Loaime, Manzanilla de Sevilla, Mollar de Cieza, Morona

Hojiblanca, Manzanilla Cacere ñ a, Manzanilla Prieta, Morisca, Rapasayo, Villalonga

Syria Abou-Satl, Kaissy Doebli, Sorani

Tunisia Meski Ch é toui, Gerboui, Oueslati

Turkey Domat, Izmir Sofralik, Uslu Ç ekiste, Ç elebi, Erkence, Gemlik Memecik, Memeli

USA Mission

Yugoslavia F.R. Zutica



1.3 TABLE OLIVES ACCORDING TO TRADE PREPARATIONS

For thousands of years, olives have been an important foodstuff, possibly essential, for inhabitants living around the Mediterranean basin and in the Middle East. Methods of processing are diverse, and include not only traditional, but also those derived from them and improved by new technologies. The bitterness of olives may be removed by alkaline treatment, by immersion in a liquid to dilute the bitter compound oleuropein, or by biological proc-esses. The product so obtained may be preserved in brine (depending on its specific characteristics), in dry salt, in a modified atmosphere, by heat treatment, by preservatives, or by acidifying agents. Generally, the complete name includes information on the type of raw material, the pro-cedure used for eliminating the bitterness, and the method of preserving the product.

Olives may be subjected to the following trade prepara-tions ( IOOC, 2004a ):

(a) Treated olives: Green olives, turning-color olives, or black olives that have undergone alkaline treatment, then been packed in brine in which they undergo com-plete or partial fermentation, and preserved or not by the addition of acidifying agents:

(a-1) Treated green olives in brine. Examples are Spanish-style green olives, Picholine style, and Castelvetrano style;

(a-2) Treated olives turning color in brine; (a-3) Treated black olives. Bitterness of treated olives is removed by alkaline

treatment. (b) Natural olives: Green olives, turning-color olives, or

black olives placed directly in brine in which they undergo complete or partial fermentation, preserved or not by the addition of acidifying agents:

(b-1) Natural green olives; (b-2) Natural olives turning color; (b-3) Natural black olives. Bitterness of natural olives is mainly removed by

dilution. (c) Dehydrated and/or shrivelled olives: Green olives,

turning-color olives, or black olives that have under-gone or not mild alkaline treatment, preserved in brine or partially dehydrated in dry salt and/or by heating or by any other technological process:

(c-1) Dehydrated and/or shrivelled green olives; (c-2) Dehydrated and/or shrivelled turning color

olives; (c-3) Dehydrated and/or shrivelled black olives. Black

olives in dry salt are a principal example of this preparation.

(d) Olives darkened by oxidation: Green olives or turning-color olives preserved in brine, fermented or not,

darkened by oxidation in an alkaline medium, and pre-served in hermetically sealed containers subjected to heat sterilization; these should be of a uniform black color.

(d-1) Black olives. Other denominations for these olives are canned ripe olives, or Californian-style olives.

(e) Specialities: Olives may be prepared by means distinct from, or additional to, those set forth above. Such spe-cialities retain the name ‘ olive ’ as long as the fruit used complies with the general definitions laid down above.

1.4 MAJOR PROCESSING METHODS

Although numerous processing methods are used around the world, only some of them are economically important from a global standpoint. At the same time, some local methods are highly valued. The most important of them are explained below.

1.4.1 Treated Green Olives

Green olives are olives harvested during the ripening cycle when they have reached normal size, but prior to color change. Manual picking is still mainly used for table olive fruit harvesting, in spite of the high cost of this method ( Figure 1.1 ). Table olives are machine-harvested in some cases, but – owing to the large proportion of bruised fruit – the catching frames ( Figure 1.2 ) have to be handled with care, and the fruit may even have to be immersed in a dilute alkaline solution while still in the orchard ( Vega et al., 2005 ). Freshly harvested, the olives are taken to the processing plant, if possible on the same day. There are two main ways of processing treated green olives: one with fer-mentation (Spanish-style) and the other without fermenta-tion (Picholine and Castelvetrano styles).

1.4.1.1 Spanish-style Green Olives

Also known as Sevillian-style green olives, this is one of the three main table olive products in the world. A flowchart with the steps of the process is presented in Figure 1.3 . The olives, once carefully harvested and transported to the fac-tory, are treated in a dilute lye solution (sodium hydrox-ide) with concentrations ranging from 2.0% to 3.5% (w/v, NaOH in water), depending on the variety and ripeness of the olives, the temperature, and the water quality. This alkaline treatment has several effects, such as the hydroly-sis or elimination of the oleuropein, an increase of the fruit permeability, and other changes which aid subsequent fer-mentation ( Rodr í guez de la Borbolla, 1981 ; Brenes and de Castro, 1998 ). Treatment takes place in varying sizes of container, usually 10 tonnes capacity ( Figure 1.4 ), in which the solution completely covers the fruits. The olives remain in this solution until the lye has penetrated two-thirds of the



way through the flesh. The lye is then replaced by water, removing part of the NaOH. Lengthy or numerous washing steps adequately eliminate alkali, but also drag over soluble sugars needed for fermentation ( Rodr í guez de la Borbolla and Rejano, 1978 ). After washing, the olives are covered with brine and put into suitable containers. Nowadays, sim-ilarly to lye treatment, fermentation is carried out in large containers ( Figure 1.5 ) with an inert inner covering ( Rejano et al., 1977 ; Rodr í guez de la Borbolla and Rejano, 1979, 1981 ). The brine triggers the release of the fruit cell juices, forming a culture medium suitable for fermentation. Brine concentrations are 9 – 10% NaCl to begin with, but rapidly drop to 5% owing to the high content of interchangeable

water in the olives. In this broth culture, a complex and variable microbiota grows. The origin of this microbiota is diverse: fruits, water, brine, pipes, containers, equipment in general, and atmosphere each play a role. Raw material control, cleaning and disinfection, and hygienic practices are the recommended methods to reduce contamination that can spoil the product. Initially, only alkali-tolerant organ-isms (Enterobacteriaceae and other Gram-negative bacte-ria, and Enterococci) multiply actively, but these disappear when the brine pH drops as a consequence of their own metabolism ( de Castro et al., 2002 ). In fact, acid produc-tion by these early microorganisms encourages the growth of lactobacilli, the indispensable bacteria in all normal

FIGURE 1.1 Manual harvesting. (Illustration courtesy of Dr. Rejano.) This figure shows the traditional procedure of picking olives. It involves hand-picking the fruit and letting it fall into baskets which workers have hanging from their necks and suspended in front of them at waist level.

FIGURE 1.2 Mechanical harvesting. (Illustration courtesy of Dr. Rejano.) In the mechanical harvester shown, the picking up of the olives occurs through a mechanic method with the use of an umbrella-shaker directly from the tree without falling on the ground.



Spanish-style green olive brines. Lactobacilli are hardly present in brines during the first days – they grow exponen-tially only when pH values are around 7.0 ( S á nchez et al., 2001 ). Lactobacillus plantarum has always been consid-ered the species mainly responsible for the fermentative process. However, taking into account the current status of

the genera, Lactobacillus pentosus should be considered equally or even more important. As a consequence of the homolactic fermentation by this species, lactic acid con-centration increases, causing the pH to fall below 4.5. Actually, a pH below 4.0 is preferable, and can be attained when the fermentation proceeds properly. This is essential, as Enterobacteriaceae, spoiling Clostridia, and other prob-lematic organisms are killed or fail to grow at these low pH values. Acid formation ceases when all the fermentable car-bohydrates are consumed. Yeasts appear together with the lactobacilli. Fermentative yeasts do not cause deterioration, but oxidative yeasts forming films on the brine surface con-sume lactic acid and raise the pH, and may compromise the fermented product.

Normal fermentation processes can be altered by the presence of undesirable microorganisms that can transmit poor sensorial properties to the olives, or impair their keep-ing properties. Gas pocket formation is usually caused by Enterobacteriaceae during the first stage of fermentation. Clostridia may cause butyric or putrid spoilage during the first days as well. In all cases, fermentation is controlled by ensuring the right pH and salt level. Obviously, it is also crucial to maintain good hygiene with containers and the rest of the equipment, and to use good-quality water. When properly fermented, olives can be kept for a long time. However, the spoilage known as zapateria may arise during preservation of the fermented product. Zapateria produces an unpleasant taste and odor, often coinciding with rising temperatures in the spring or early summer. Cyclohexanecarboxylic acid, in combination with other volatile acids, seems to be responsible for the unpleasant odor ( Monta ñ o et al., 1992, 1996 ). The bacteria responsible belong to the genera Clostridium and Propionibacterium ( Kawatomari and Vaughn, 1956 ; Plastourgos and Vaughn, 1957 ). Again, the right combination of brine concentration (which must be increased before summer to more than 8%)

SPANISH-STYLE GREEN OLIVES

Harvesting

Transport

Grading (optional)

Lye (NaOH) treatment

Washing

Brining

Fermentation

Preservation

Sorting

Grading

Whole Pitting

Stuffing (optional)

Packing

FIGURE 1.3 Process steps for Spanish-style green olive production. This figure shows the main steps of Spanish-style green olive processing. It includes an alkaline treatment, a washing step to remove the excess alkali, a stage in brine, where the fruits undergo a spontaneous fermentation, carried out mainly by lactic acid bacteria.

FIGURE 1.4 Alkaline treatment area in an olive processing plant. (Illustration courtesy of Dr. Rejano.) Alkaline treatment of olives in the Spanish-style processing usually takes place in large containers (10 tonnes capacity) made of fiber-glass.



and pH (values below 4.2) helps to guarantee the correct keeping conditions.

When olives are going to be marketed, the fruits are sorted and graded for the first or second time ( Figure 1.3 ). The original brine is replaced by a new one, and the olives are packed in barrels, cans, or glass jars. Sometimes they are stoned (pitted), sliced, or stuffed with diverse stuffing materials. The levels of acidity and salt determine the prod-uct stability. Traditionally, this has been obtained by setting high values of free acidity and salt (0.5 – 0.7% and 5 – 7%, respectively) and low pH ( � 3.5). However, the progres-sive preference of consumers for milder conditions (low salt and acid percentages) has modified such conditions. In these cases the stability of the product is guaranteed by pasteurization ( Gonz á lez-Pelliss ó et al., 1982 ; Gonz á lez-Pelliss ó and Rejano, 1984 ; S á nchez et al., 1991 ).

1.4.1.2 Picholine-style Green Olives

Figure 1.6A shows the process diagram for this product, an example of NaOH-treated, but not fermented, fruits. Olives belonging to the Picholine Languedoc and Lucques varieties are prepared in this manner in the south of France, as are other varieties in Morocco (Picholine Marocaine) and Algeria.

The bitterness of the olives is removed by treating them in lye (2.0 – 2.5% NaOH) in which they are left for 8 – 12 hours until the lye has penetrated three-quarters of the way through the flesh. They are rinsed several times over one or two days and then placed in 5 – 6% brine for two days. A second brine is used at 7%, and the acidity is corrected by adding citric acid (pH 4.5). After 8 – 10 days, the olives retain their bright green color, and are ready to be eaten. In the case of delayed shipment, it is necessary to store the olives.

This is straightforward as long as the temperature does not rise. The olives can be left in 8% brine until the spring, but then the concentration has to be raised to 10%. In large-scale facilities, they are kept in 3% brine in cold store, with the temperature maintained between 5 ° C and 7 ° C. Before ship-ping, the olives are washed repeatedly, and packed in suit-able containers in brine at 5 – 6% ( IOOC, 2004b ).

1.4.1.3 Castelvetrano-style Green Olives

A flowchart for this product is presented in Figure 1.6B . As with Picholine-style, these are olives where fermentation

FIGURE 1.5 Fermentation area in an olive processing plant. (Illustration courtesy of Dr. Rejano.) This figure shows a fermentation yard in an olive processing plant with underground 10-tonnes capacity fermenters.

CASTELVETRANO

Harvesting

Transport

Grading


Salt addition

Fresh conservation

Washing

Packing

PICHOLINE

Harvesting

Transport


Washes (3 in 1 day)

Washes (2 in 1 day)

Brining (2 or 3)

Cold storage (5-7°C)

Packing

(A) (B)

FIGURE 1.6 Process steps for Picholine- (A), and Castelvetrano-style (B) green olive production. In this figure, the main steps of the Picholine-style processing are shown in comparison with those of Castelvetrano-style processing. In both cases, fermentation does not constitute a key step.



does not constitute a key step. This is a production method used in Italy, almost exclusively in the Castelvetrano region and with the variety Nocellara del Belice, and the product is mainly consumed in central and southern Italy. Once the olives arrive at the processing plant, they are graded, since only fruits of more than 19 mm in diameter are used. The selected olives are put into plastic vessels and covered with 1.8 – 2.5% NaOH solution, depending on the fruit ripeness and size. These vessels have 220 L total capacity, and are filled with around 140 kg of fruits. One hour after the lye treatment begins, 5 – 8 kg salt are added to each container, and the olives are kept in this alkaline brine for 10 – 15 days. A mild washing step, carried out before marketing, does not totally eliminate the soda, whose taste is appreciated by the consumers of these olives ( Salvo et al., 1995 ).

1.4.2 Natural Olives

The designation ‘ natural olives ’ is applied to those fruits placed directly in brine, without any lye treatment to remove their bitterness. Although natural olives can be pre-pared from green, turning-color, or black fruits, the latter are more common. In fact, natural black olives in brine, Spanish-style green olives, and olives darkened by oxida-tion are the three main preparations globally ( Garrido et al., 1995 ). A flow diagram for this method of olive processing is outlined in Figure 1.7 . Natural black olives in brine are typical of the eastern Mediterranean and northern African countries. In Greece they are made with the Conservolea variety, which grades at around 200 fruits per kilogram, and in Turkey they are made with the Gemlik variety ( IOOC, 2004b ). To prepare natural black olives, the fruit is picked by hand when black ripe, but before the olives over-ripen or are shrivelled by frost. They have to be trans-ported as quickly as possible to the processing plant, where they are washed, and immersed in 8 – 10% NaCl brine.

Large-scale plants use big (10 – 20 ton) tanks, while small-scale processors continue to use wooden vats. At the start of fermentation, the tanks are tightly sealed because the olives must not be exposed to air. The brine stimulates the microbial activity for fermentation and reduces the bitter-ness of the oleuropein. Fermentation of these olives takes a long time because diffusion of soluble components through the epidermis, in fruits not treated with alkali, is slow. A diverse microbiota grows in these brines, although yeasts are the microorganisms always present throughout the process. Enterobacteriaceae can be found during the first 7 – 15 days, but they disappear as the brine characteristics do not support their growth. The presence of lactic acid bac-teria depends on the salt concentration and the polyphenol content of the variety used. The traditional brining is car-ried out under anaerobic conditions. However, an aerobic method can be applied, using a central column in the fer-menter through which air is bubbled. This system changes the ratio between fermentative and oxidative yeasts, and a final product with better quality is attained ( Garc í a et al., 1985 ; Garrido et al., 1995 ).

When the bitterness has been sufficiently weakened, the fruit can be marketed. The color fades during the process, but is corrected by aerating the olives for two or three days; sometimes they are treated with 0.1% ferrous gluconate or lactate to make them a deeper black. Lastly, the olives are selected and packed in barrels or internally varnished cans, which are filled with 8% fresh brine. They are popu-lar with consumers because of their slightly bitter taste and aroma. Natural black olives can also be packed in vinegar (25% of brine volume) and may even be heat-processed; a few grams of oil are then added to each can to form a surface layer. The Kalamata variety is prepared in this way ( Fern á ndez-D í ez et al., 1985 ).

1.4.3 Black Olives in Dry Salt

Also of Greek origin, dehydrated black olives are encoun-tering a great consumer acceptance in many producing areas. They are prepared using overripe olives. They are vigorously washed and placed in baskets with alternating layers of dry salt equivalent to 15% of the weight of the olives. The final product is not bitter, but salty, and looks like a raisin; it is for local consumption. The flowchart for these olives is outlined in Figure 1.8 .

1.4.4 Olives Darkened by Oxidation

These olives are also known as Californian-style black olives, ripe or semi-ripe olives, or simply black olives ( USDA, 1983 ; IOOC, 2004b ). The production flowchart for these olives is outlined in Figure 1.9 . Fruits are harvested when their color is starting to change, before full maturity. Once in the production plant, olives are selected and may

NATURAL BLACK OLIVES

Harvesting

Transport

Brining

(Aerating)

(Ferrous gluconate/lactate)

Packing (vinegar-kalamata)

FIGURE 1.7 Process steps for natural black olive production. Operations in brackets are optional. This figure shows the main steps of natural black olive processing. The traditional method of fermentation is carried out in anaerobic conditions. A diverse microbiota grows in brine, although yeasts are the microorganisms always present throughout the process.



be directly processed or – more commonly – preserved before oxidation. Preservation is usually in brine, and a fermentative process comparable to that of natural black olives takes place. Nevertheless, this preservation can also be done in acidified water ( de Castro et al., 2007 ). With this method, the discharge of sodium chloride into waste-water streams is reduced strikingly. From a microbiologi-cal point of view, the addition of acetic acid results in a pH incompatible with Enterobacteriaceae growth, might favor lactic acid bacteria in some instances, and – in any case – yeasts continue being the most important microorganisms

in these solutions. As this preservation step is not neces-sary, a complete fermentation is not required. The essential operation is the oxidation.

In general, fruits are treated successively with sodium hydroxide solutions for varying periods of time to achieve a progressive penetration of the lye into the flesh. After each alkaline treatment, the olives are put into water and oxidized by injecting air under pressure into the water. This oxidation of the phenolic compounds permits a complete blackening of the fruit skin and a uniform coloration of the flesh. The promoters of the polymerization involved have been identified as hydroxytyrosol (3,4-dihydroxyphenyl acetic acid) and caffeic acid, the decrease of which in the flesh is strongly correlated with fruit darkening ( Brenes-Balbuena et al., 1992 ). Olives are darker and oxidation rates higher with higher pH values ( Garc í a et al., 1992 ; Garrido et al., 1995 ). The number of lye treatments is gen-erally between 3 and 5, although some processors apply two or even only one. Penetration into the fruit is controlled so that the sodium hydroxide of the first treatment passes merely through the skin. Subsequent treatments are cho-sen so that they penetrate increasingly deeper into the pulp. The final lye treatment must reach the pit. The concentra-tion of sodium hydroxide in the lye solution depends on the ripeness of the fruit, its variety, the environmental tempera-ture, and the desired penetration speed. It varies between 1% and 2% NaOH (w/v). The highest concentration is usually used for the first treatment. The blackened olives are washed several times with water to remove most of the sodium hydroxide and lower the pH in the flesh to around 8.0 units. Generally, 0.1% (w/v) of ferrous gluconate or lactate is added to the last wash to stabilize the color. The final canned product has sensorial properties very different from those of fermented fruits obtained by other processes. The pH values are between 5.8 and 7.9, and the NaCl con-tent is between 1% and 3%. Due to these chemical charac-teristics, which do not guarantee safety, olives darkened by oxidation have to be sterilized to prevent any possibility of foodborne pathogen growth.

1.5 CHARACTERISTICS OF FINAL PRODUCTS

The numerous procedures to prepare table olives imply a broad range of characteristics in the different final prod-ucts. However, to be marketed they have to comply with the limits displayed in Table 1.3 ( IOOC, 2004a ). The limits vary depending on both the preparation system and the way preservation is guaranteed. Sodium chloride concentration, pH, and titratable acidity (as lactic acid) are the parameters to monitor. They can be analyzed in the brine or from the fruit juice, but always once the osmotic balance between olives and packing brine has been attained. Olives dark-ened by oxidation have no requirement regarding the cited

BLACK OLIVES IN DRY SALT

Harvesting

Transport

Washing

Dry salt layers

Local consumption

FIGURE 1.8 Process steps for black olives in dry salt production. These olives are obtained from fruit harvested when fully ripe. Olives are vigor-ously washed and placed in baskets with alternating layers of dry salt.

OLIVES DARKENED BY OXIDATION

Harvesting

Transport

Previous handlings

Washing

(Preservation in brine, fermentation)

Lye treatment and air oxidation

Washing (alkali neutralization)

Brining (pasteurization)

Sorting and grading

(Pitting, slicing, etc.)

Packing

Sterilization

FIGURE 1.9 Process steps for olives darkened by oxidation. Operations in brackets are optional. These olives are obtained from fruit which, when not fully ripe, has been darkened by oxidation and whose bitterness has been removed by lye treatment. They are packed in brine and preserved by heat sterilization.



TABLE 1.3 Physicochemical characteristics of the packing brine or of the juice after osmotic balance ( IOOC, 2004a ).

This table shows the limits for the physicochemical parameters established in the ‘ Trade Standard Applying to Table Olives ’ of the International Olive Council according to processing type and preservation method.

Processing Minimum sodium chloride content (%)

Maximum pH limit Minimum lactic acidity (% lactic acid)

SCC, MAT PR, R P, S SCC, MAT PR, R P, S SCC, MAT PR, R P, S

Treated olives 5 4 GMP 4.0 4.0 4.3 0.5 0.4 GMP

Natural olives 6 6 GMP 4.3 4.3 4.3 0.3 0.3 GMP

Dehydrated and/or shrivelled olives

10 10 GMP GMP GMP GMP GMP GMP GMP

Olives darkened by oxidation

GMP GMP GMP GMP GMP GMP GMP GMP GMP

SCC: Specific chemical characteristics; MAT: Modified atmosphere; PR: Addition of preservatives; R: Refrigeration; P: Pasteurization; S: Sterilization; GMP: Good manufacturing practice.

parameters, since they have to be sterilized to guarantee safety. Dehydrated olives must contain a minimum of 10% NaCl unless they are thermally treated. Natural or NaOH-treated olives vary in their requirements, according to the preservation method.

Apart from brine (water and food-grade salt) and olives, other possible ingredients are vinegar, olive oil, sugars, spices or aromatic herbs or natural extracts, and author-ized additives. Furthermore, any single or combination of edible material used as an accompaniment or stuffing is also allowed. Typical examples (among many others) are pimiento, capers, and onions.

SUMMARY POINTS

● Fruits from olive trees may be prepared following many different methods, usually related to the various pro-ducing areas.

● The different methods may, or may not, include a fer-mentation stage, and most of them are aimed at elimi-nating the natural bitterness of the fresh fruit.

● Spanish-style green olives are the only ones that include fermentation by lactic acid bacteria as a neces-sary step.

● Olives not treated with alkali usually support a fermen-tation by yeasts while maintained in brine.

● Keeping quality may be guaranteed by physicochemical characteristics or thermal treatment.

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