`From Grove to Mill - Olive Oil Times

From Grove to Mill

Feb. 8, 2012

Recent News

The tra­di­tional olive har­vest­ing sys­tem has grad­u­ally evolved since ancient times. Yet, what has not changed is the fact that, unfor­tu­nately, the olive juice also con­tin­ues to grad­u­ally lose qual­ity from the moment it is obtained, dete­ri­o­rat­ing every time it is han­dled. Just for the nos­tal­gic, Andalusia still houses some antique mills that faith­fully demon­strate all the stages the olive fruit is sub­jected to until its trans­for­ma­tion into oil.


The long pil­grim­age by the olive from the moment it is har­vested in the grove to the moment it is trans­formed into olive oil, pro­gresses through var­i­ous phases. Ancient civ­i­liza­tions estab­lished this jour­ney and, in spite of the numer­ous tech­no­log­i­cal advances, the essence of the process is main­tained by the mod­ern mills that obtain extra vir­gins of excep­tional qual­ity.


Go Pro.
The newsletter for olive oil professionals.

Whenever pos­si­ble, the Romans har­vested the olive from the tree itself by either hand-pick­ing them or shak­ing them off the tree. This was, and indeed still is, used for the high­est qual­ity olives or those to be pick­led and con­sumed at the table.

If the har­vest tech­nique used was shak­ing, the olive pick­ers may have used blan­kets or allowed the olive to fall to the ground, con­stantly attempt­ing to avoid dam­age to the fruit, because the qual­ity of the juice depended largely on the integrity of the olive.

It would appear that the large scale har­vests were so bru­tal that some olive pro­duc­ers only pro­duced olives every two years, a cir­cum­stance which may have led to short­ages or scarcity, even in those areas in which the olive groves were abun­dant. Not only the poor soil qual­ity of a large part of the Mediterranean coastal coun­tries con­tributed to this, but also overly aggres­sive prun­ing.

Storage and press­ing

After being picked and when rel­a­tively clean, the olive had to be imme­di­ately trans­ported to the place of press­ing as the qual­ity of the oil is directly pro­por­tion­ate to both the har­vest­ing sys­tem and the time that passes between this and the milling, the stor­age method used and the press­ing sys­tem. It needed to spend as lit­tle time as pos­si­ble piled up in the mill in order to pre­vent dete­ri­o­ra­tion, fer­men­ta­tion and oxi­da­tion, which would sub­se­quently give rise to a very acid oil that eas­ily became ran­cid. The Roman mills were very much aware of this and tended to work, as is cur­rent prac­tice, round the clock, day and night (Pliny, Naturalis Historia XV, 10, 22 and 23). This author rec­om­mended heat­ing the mills by burn­ing the olive stones to fight off the freez­ing win­ter cold which, apart from mak­ing the work more mis­er­able, made it dif­fi­cult to extract the fat. But the rest of the Latin agron­o­mists were against this prac­tice as they believed that smoke, of any ori­gin (even from lamps), could give the oil a bad taste. The solu­tion they pro­posed was to build the mills fac­ing South or to heat them using what we nowa­days call under­floor heat­ing”, that is to say, the hot air com­ing from stoves (prae­fur­nia) located out­side the build­ing, con­ducted under the ground (hypocausta) and through the walls by means of cham­bers (con­cam­er­a­tiones).

The begin­ning of mech­a­nised extrac­tion

Oil extrac­tion using mechanic tech­niques did not begin on a large scale until the Greco-Roman times. Before this, tread­ing, crush­ing or press­ing by large heavy stone rollers was used fol­lowed by wring­ing in fab­rics, fil­ter­ing and sub­se­quently decant­ing the oil obtained, which was gen­er­ally of very high qual­ity.

The areas of the mill

In Andalusia, cra­dle of the for­mer Baetica province, we know of numer­ous mills that faith­fully doc­u­mented the var­i­ous stages of the process. Almost with­out excep­tion, these were asso­ci­ated with the vil­lae, although there are also some urban exam­ples, such as the restored instal­la­tion of Casa 2 de Munigua, Villanueva del Rey y Minas dis­trict, in the midst of the Seville moun­tains.

One of the best pre­served is that exca­vated in the Antequera town of El Gallumbar (Málaga), which groups together all the spaces typ­i­cal of a mill. Here, the press­ing and extrac­tion processes were –and are- essen­tially the same as those used nowa­days:

  • Cella olearia: this held the olive after being har­vested in the grove. This name could also be used to describe the entire instal­la­tion.
  • Tabulatum: an inter­me­di­ate stor­age space from which the olive was directly trans­ported to the presses (Columella, De re rus­tica XII, 52, 3 – 5). The floor was sloped so that the alpechin (amurca) could be eas­ily elim­i­nated.
  • Torcularium: the main press­ing room, occu­pied by a joist or lever press. Nonetheless, the Mill also had a smaller man­ual press known as a trape­tum.
  • Lacus: deposit con­nected to the press into which the oil obtained flowed directly. In this, the olive juice under­went its first decanta­tion process, nec­es­sary to sep­a­rate the oil from the water, among other rea­sons. These deposits could be made of stone, brick, baked clay (like dolia) or lead. Specifically, in El Gallumbar it was made of masonry with a hydraulic coat­ing and had a capac­ity of 2500 litres. Using these sys­tems of pro­gres­sive decanta­tion, the oil (and heav­ier) water impu­ri­ties fell to the bot­tom, in such a way that only the purest and best qual­ity juice was obtained.
  • Labrum: inter­me­di­ate deposit, into which the oil was trans­ferred for a new decanta­tion phase. The one in Antequera could con­tain up to 650 litres.
  • Dolia: large clay jugs in which the oil was pro­vi­sion­ally stored, after being cleaned and puri­fied, until trans­ferred to the amphorae or the skins for trans­porta­tion. Occasionally, it remained in these jugs for fam­ily con­sump­tion, as has con­tin­ued to occur until prac­ti­cally the present day.

The process accord­ing to Columella

We are very famil­iar with all of this process, thanks to the doc­u­ments left by the Latin agron­o­mists. Among them, Lucio Junio Moderato, from Cadiz, who lived in the 1st cen­tury AD, par­tic­u­larly stands out with a descrip­tion that could not be more expres­sive:

As soon as the oils start to change colour and there are already some black olives but the major­ity are still white, it is advis­able to hand­pick them in the good weather and, plac­ing rush mats or reeds under­neath, select and clean them; then, once care­fully cleaned, imme­di­ately take them to the press, place them whole into new bas­kets and beneath the presses, to squeeze them for the min­i­mum time pos­si­ble… In the oil bodega, there should be three rows of churns, one to receive the top class oil, that is, the oil obtained from the first press­ing, the sec­ond for the oil from the sec­ond press­ing, and the third row for the third press­ing; it is very impor­tant not to mix the sec­ond, and even less so the third, press­ing with the first, because the oil from a press sub­jected to less pres­sure tastes far bet­ter” (Columella, De Re Rustica XII, 52, 10).

Olivarama arti­cles also appear in Olivarama mag­a­zine and are not edited by the Olive Oil Times.

Related News

Feedback / Suggestions