Evolution of Production Methods

According to Pliny the Elder12 (see Fig. 4.1) the extraction of oil from the olive fruit was introduced by Aristaios, son of Apollo and the nymph Kyrene. Aristaios was considered also as the inventor of olive press (Pliny the Elder VII, 199). For this reason he was particularly honored in Sicily by the olive producers (Diodorus13, IV, 82).

Olive oil production and trade spanned the centuries since the beginning of the Mediterranean civilizations. In Palestine, olive oil was extracted as early as the Chalcolithic period (after the Neolithic and before the Bronze Age, between about 4500 and 3500 B.C.) and this is attested by the discovery of primitive rock-cut installations. In Crete the finding of oil lamps, which show signs of burning, from the Early Minoan period attest to the knowledge of oil extraction, although proper presses were not used at that time (Hadjisavvas S., 1992).

In antiquity, as today, the production of olive oil involved three essential stages: (i) crushing, (ii) pressing, and (iii) separation of oil from water.

12Pliny the Elder (Gaius Plinius Secundus, A.D. 23-79), Roman naturalist, encyclopedist and writer born in Verona. He served a cavalryman in Germany and from his experiences wrote his first book "On the Use of the Javelin by Cavalry'', the beginning of a literary career of enormous output. His famous Natural History (Historia Naturalis) was published in the year 77 A.D., two years before his death and is the only work of Pliny to survive. The work in 37 volumes is encyclopedic in coverage and includes information on astronomy, chemistry, geography, natural history, agriculture, medicine, astrology, and mineralogy. A popular translation covers five volumes, each of about 500 pages. Over 400 different authors are cited. Pliny was a compiler and the work is a monumental collection of science, technology, and ignorance. Although Pliny appears overly credulous, his encyclopedic coverage is the best known and most widely referred source book of "classical" natural history. Pliny is also a rich source of agriculture and horticulture.

13Diodorus Siculus, late 1st century B.C., Greek historian.


In the most primitive method, the olives are thought to have been placed into a trough and crushed with the use of a large pestle or treaded under the foot. Another simple method of crushing olives in antiquity was by spreading the fruit onto a hard surface and rolling a large cylindrical stone over it. An important change in the production techniques was the invention of the round crushing basin based on rotary motion which enabled the use of animal power. The two classical forms of this equipment, as described by the Roman agricultural writers Cato14 (see Fig. 4.2) and Columella15, were the trapetum and the mola olearia.

14Cato the Elder or Cato the Censor (Marcus Porcius Cato) (234-149 B.C.), Roman statesman and writer. His De Agri Cultura, a treatise on farming, is the oldest surviving prose work in Latin.

15Columella Lucius Junius Moderatus (1st century A.D.), Roman writer on agriculture, born in Gades (now Cadiz), Spain. Of his work there remains the 11-volume entitled De re rustica (On Agriculture), treating general husbandry, the care of domestic animals, and farm management. The 10th book, modeled on Virgil, is in hexameters. A short essay on trees also survives De Arboribus (On Trees). Columella's Latin is facile and elegant, and his information is surprisingly practical and accurate. They are considered to be the most comprehensive and systematic of all Roman agricultural treatises. The works may have been written on request or commission from a certain Publius Sivinus, known only from Columella's references to him. His work is amazingly modern in feeling and devoid of superstition, although the discussion of slaves is disconcerting.

The trapetum (from the Greek word "rgan^xi]&'') was the olive-mill per excellence in his time (Cato, De agri cultura 21-23). The mola olearia comprises roughly the same elements as the trapetum and looks very similar. It is well possible that the mola olearia is a later version of trapetum. Drachmann A.G. (1932) studied in detail the operations of trapetum and mola olearia and gave instructive reconstructions based on Cato's and Columella's accounts, respectively — see Figs 4.3 and 4.4.

The immovable par of a trapetum was made of lava in the shape of a large cup (mortarium) housing a central pillar (miliarium). The miliarium was a few cm higher than the lip of the cup (labrum). On the top of the miliarium there is a square hole, in which an upright iron pin (columella) was fastened by means of lead. The movable part consisted of a wooden beam (cupa), which fitted over the collumela and rested on the miliarium in a horizontal position; on its

two arms were threaded two willstones (orbes), flat on the side towards the miliarium, but convex on the outer side, so that they dipped into the ring-shaped cup. The orbes were kept in their place by a system of washers and wedges. When properly adjusted they would keep a distance of exactly one Roman inch from the miliarium, from the bottom of the hollow and from its outer, curved side. When the trapetum was filled with olives and the cupa, which projected beyond the orbes to form handles, was turned, the orbes would perform a double rotation, going round the miliarium and at the same time turning on their axles. The result was that the olives were crushed, but the olive stones were not, which was indeed the point of the whole arrangement.

Drachmann Ancient Oil Mills

The mola olearia consisted of two cylindrical mill stones rotating on a horizontal axle which was carried by a vertical beam that turned around also, and was placed in the middle of the flat surface on which the grinding took place. The fact that the two mill stones were carried by the short cross piece and did not rest on surface, allowed the mill stones to be adjusted thus preventing the olive stones from being crushed.

Fig. 4.4. The mola olearia.

In early modern Europe, the traditional animal- or water-powered olive-mills used a vertical millstone that turned on a metal pivot around a vertical axle and rolled upon another circular stone (the dormant stone), horizontally placed, crushing the fruit by simple pressure.

In Calabria, olives were crushed in the trappeto. The trappeto — which was different from the Roman olive-mill trapetum — used a vertical millstone approximately 1.1m in diameter and measuring 0.4 m on its edge. The dormant stone was often concave, like a basin, so that the millstone made only partial contact with it. A mule supplied power, while a man fed the olives into the stone with a spade. In Apulia, millstones were bigger (1.5-2.0 m), heavier and rolled on a flat dormant stone. The edge of the millstone was rounded, reducing the contact surface by two-thirds and increasing the force applied at the point of contact. The Apulian olive-mill was carved into the rock, a few meters underground. This type of mill was widespread in southern Apulia because of its relatively inexpensive construction and the insulating properties of stone (warmth being a crucial factor in oil production. By comparison, traditional mills in Provence used smaller millstones and were powered either by a horse (moulin a sang) or by waterwheel (moulin a eau). Mill of the latter type used a horizontal wheel placed under the dormant stone and turning around the same axle as the millstone (Mazzotti M., 2004).


In the early history of olive oil extraction, simple installations consisting of a sloping crushing floor connected to a lower collecting vat were the devices combining the first two stages of olive processing (Frankel 1984, III). The first important technical improvement in oil production was the introduction of the lever and weights press — in the Late Bronze Age in Crete, Cyprus, and Ugarit16 and in the Iron Age in ancient Israel — which became the most popular type in Antiquity. The mode of operation of the lever and the weights press is illustrated is Fig. 4.5. In its basic form, this press consisted of a long wooden lever, one end pinned in a recess in a wall or between two pillars, while the other could be pulled down to exert pressure on whatever was under the lever or beam — in this case, a bag of olive paste. The sacks used with this type of press were made of vegetable fiber to allow the oil to pass through them.

To cope with the increased output, a series of improvements were brought about in the pressing operation. The culmination of these improvements was the employment of the screw (cochlea) in lever press, which became the most popular combination from the time of its introduction up to the middle of the twentieth century — see Fig. 4.6. The introduction of the screw was a major technical improvement in the pressing operation, the second after the lever itself. Its application enabled greater force to be brought in and as a consequence the press bed could be placed anywhere between the anchoring point and the screw. A screw press could easily be operated outdoors as there was no need for a pulley to raise the lever up (Hadjisavvas S., 1992). Although the technical characteristics of the new invention were far more advanced than the lever and weights press, the latter continued to be used up as late as the nineteenth century.

Up to the middle of the eighteenth century, the olive oil extraction was based on the same basic types of machinery used in the antiquity. That is not to say that technology had stagnated. Archaeological and ethnographic research has

16Ugarit (modern site Ras Shamra) was an ancient cosmopolitan port city, sited on the Mediterranean coast of northern Syria.

Gaius Plinius Secundus Natural History

One end of the press beam is anchored either in a wall recess or is attached to a cross piece supported by two wooden uprights. A pile of bags is pressed by the beam and the liquid pours into an open large vessel underneath. Two pierced boulders hang from the free end of the beam to pull it down. A worker adds his weight in this respect (Hadjisavvas S., 1992).

One end of the press beam is anchored either in a wall recess or is attached to a cross piece supported by two wooden uprights. A pile of bags is pressed by the beam and the liquid pours into an open large vessel underneath. Two pierced boulders hang from the free end of the beam to pull it down. A worker adds his weight in this respect (Hadjisavvas S., 1992).

Fig. 4.5. Lever press as depicted on an Attic Skyphos, about 520-510 B.C. (Photograph © Museum of Fine Arts, Boston).

documented the continuously changing forms of oil-production machinery. And always, changes in the socioeconomic setting of the oil-producing regions — such as a shift to large-scale production for export-shaped technological developments. However, the basic process of interconnected social, economic, and technological change is in no way unidirectional (Mazzotti M., 2004). For instance, during the late Roman-early Byzantine period with trade declining on the Mediterranean routes, provinces once renowned for their exports began to rely more on local consumption, and producers in those areas turned from comparatively sophisticated technology back to simpler alternatives. The result was the success and diffusion of a rudimentary new milling-pressing system that involved simply rolling a cylindrical stone over the olives. Oxen were preferred over horses not only because they were stronger, but because of their more regular pace (Mazzotti M., 2004).

The modern golden age of olive oil began around 1750. Increasing consumption of oil for cooking and eating was only one factor accounting for growing demand

and rising prices; industrial uses, which included lighting, lubrication, and the manufacture of soap and wool, also played an important part. As international demand for olive oil steadily grew, the main concern for producers and traders became not the supply but rather the quality of the product. In the middle of the eighteenth century, the centers of production of high-quality oil were Provence (Aix), the Italian Riviera (Genoa), and Tuscany (Lucca). Among the characteristics that distinguished the oils of these regions from those made in the rest of the Mediterranean basin the most important was their low acidity. They were also more transparent, sweeter, and crucially, easier to preserve.

Four basic types of oil presses were in use around 1750, each with endless local variations. Torsion presses were common in Corsica and southern Italy. In this type of press, very ripe olives were put in a large sack made of goat hair, which was then pushed into place in a wooden trough. Two people then twisted the sack using a pair of sticks, forcing oil from the olives, which collected in the trough and drained into a receptacle. Each sack of olives would be pressed in this way several times, with hot water being used at the end to help extract the last remnants of oil from the fruit.

The lever or beam press (presse a arbre) was common in southern France. A more complex variation included the use of a capstan which lifted a counterweight. The lever could also be forced down with the aid of screws. In the first edition of Encyclpopedie, Diderot praised a counterbalanced lever-and-screw press common in Provence and Languetoc, called the pressoir a gran banc or ''Greek press'', and recommended its use in the manufacture of olive oil. Another variation was the pressoir a taissons, in which the screw was fixed to the ground. The other most common type of press, the screw press, worked by means of the direct action of one or two screws. The double screw press, in which a wooden beam is forced downward by two fixed screws, was found all over Italy, along the Adriatic coasts, and on some Greek islands. One problem with this type of machine was that the upper beam and the two lateral pillars broke down rather easily.

During the second half of the eighteenth century, a group of reformer-entrepreneurs in different parts of Mediterranean Europe employed a mix of enlightenment ideas and advanced technology to rationalize and mechanize olive oil production as a way of meeting the increased demand. The reformers sought to build new machines which would not merely produce more oil but high-quality oil. Prices could be increased and new markets created only by changing the nature of the product and widening the range of possible uses. High-quality oil not only lasted longer than common oil, which made it desirable for long-distance trade; it also burned more efficiently in lamps and made a better lubricant for industrial machinery.

According to Mazzotti M. (2004) the modernized methods of making olive oil did not evolve in some sort of natural development but were rather the consequence of the new meaning attached to oil production by reformer-entrepreneurs. In order to produce low-acidity oil, olives must be processed earlier in the season, when they are less ripe. An early ripe meant paying more for labor, as under-ripe olives were harder to pick. Similarly, the practice of leaving olives to ferment after they had been harvested, common all over the Mediterranean had to be abandoned. Traditional mills included large storage facilities — the zimboni in Calabria, the camini in Apulia, the tulhas in Portugal — where the fruits fermented for weeks or even months before being processed. One reason for this practice was that fermented olives were easier to crush and press, a crucial matter in regions lacking waterpower.

Many traditional mills, designed for fully ripe olives, proved unequal to the task of crushing fresh olives. Redesigning the millstones around the need to use fresh olives, however, precipitated other changes to the structure of the mill. Axles and pivots could not bear the weight of the new stones, and therefore had to be reinforced with metal parts and massive masonry. Also, traditional sources of power could no longer drive the stone effectively. Vertical wheels replaced horizontal ones placed under the basin of the mill, preventing water from cooling the basin and, hence increasing the effectiveness of the crushing action.

To facilitate the flow and to avoid it from becoming dense because of cold weather, the mill temperature was kept constantly high, and loads of hot water were poured on the stacked containers. In time, the same procedure was maintained as presses were introduced that were made totally or partially with metal. Meanwhile, the beam press was rapidly abandoned. The longer levers and additional capstans or counterweights did increase the power of beam presses, but in the late eighteenth century this design reached its structural limits. The consequences of a giant lever suddenly freed by the rupture of a capstan or a rope were spectacular and devastating (Mazzotti M., 2004).

The continuous, regular, and synchronized functioning of the new mills required also a new and more intense kind of work. Technological innovation could succeed only where the local workforce could be effectively disciplined to its new role. Disciplining the workforce served other purposes besides maximizing output.

Fig. 4.7. Olive-mill, Nova Reperta (Johannes Stradanus, 1523-1605).

It was also the concrete epitome of a new social order that the bourgeois elite of southern Europe sought to impose upon the rural communities (Mazzotti M., 2004). The traditional design of an olive-mill was a constitutive element of southern European societies — see Fig. 4.7. Modifying it meant modifying traditional landscapes and ways of life as well. Technical innovation succeeded only where the reformers succeeded in reshaping traditional ways of life as well traditional machinery.

At the turn of the twentieth century, hydraulic presses were introduced. The most recent techniques have radically changed the oil extraction concepts and methods. The continuous three-phase centrifugal process was introduced in the 1970s notably to increase processing capacity and extraction yield, and to reduce labor. In the early nineties, the two-phase centrifugal process was introduced, where no process water is used.

Continue reading here: Oil Separation

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