Olive-oil production
Olives in various stages of ripening
01. Scheduled and meticulous harvest
The production of high-quality olive oil starts from the first step. During the final stage of fruit ripening, significant changes occur in the parameters that affect the quantity and quality of the oil. These should be carefully monitored, as they help determine the optimal harvest time. The following factors should be taken into account when determining the quantity/quality of olive oil: 1. Increase in fruit weight. 2. Changes in oil content. 3. Number of olives on the tree and natural fruit fall. Other characteristics of the fruit that are subject to fluctuations are color change, fruit firmness and moisture content.
The color change varies from variety to variety. Some varieties may change from green to violet early in the season, while others remain mostly green even until advanced ripeness. The color change is influenced by crop load and irrigation. The color of the fruit affects the color of the oil because some of the chlorophyll remains in the oil. In contrast, yellow and orange pigments predominate in oils obtained from olives that have changed color.
Harvesting generally begins in late October to early November and the production process is completed in January at the latest. Various types of vibrators are used for olives harvesting (compressed air beaters with a single or double pulsating comb at the tip that does not injure the tree; arm or trunk vibrators). Almost immediately, or as soon as possible, after harvesting, the olive fruits are transported to the oil mill for the next stage of olive oil production. Until the oil is pressed, the olive fruits should not be exposed to weather/environmental conditions such as sun heat and rain.
[INTERNATIONAL OLIVE COUNCIL, Production techniques in olive growing, https://www.internationaloliveoil.org/wp-content/uploads/2019/12/Olivicultura_eng.pdf, pp. 1-348, ISBN: 978-84-931663-6-6]
[Olive-tree cultivation, MINISTRY OF AGRICULTURE, RURAL DEVELOPMENT AND ENVIRONMENT DEPARTMENT OF AGRICULTURE – Edition 2022, Nicosia – Cyprus https://www.moi.gov.cy/moa/da/da.nsf/All/]
Fresh olive oil as it results after olive processing
02. Olive-fruits management in the olive mill
In the production of extra virgin olive oil, the time between olive harvest and milling is a critical period that must be carefully controlled to maintain the quality of the oil. In particular, various detrimental phenomena can occur during storage. Therefore, a key issue for producers is to optimize the conditions to maintain the quality of the fruit before milling. Many studies show that storage temperatures between 5 and 10°C are optimal for delaying fruit deterioration. On the other hand, current findings suggest that there are no clear advantages due to the use of a controlled atmosphere (i.e., reducing the O2 percentage and/or increasing CO2).
The olive fruit is transported in suitable plastic containers so that it is not compressed by the weight. It is transported and thrown into the receiving hopper, while it is then led by a conveyor belt to the defoliator. The separation of the olive fruit from the leaves and other carried materials is carried out by a stream of air, in conditions that do not injure the fruit. Then, the olives are cleaned with water of appropriate quality and are mechanically transferred to the oil extraction stage.
[Guerrini, Lorenzo & Corti, Ferdinando & Cecchi, Lorenzo & Mulinacci, Nadia & Calamai, Luca & Masella, Piernicola & Angeloni, Giulia & Spadi, Agnese & Parenti, Alessandro. (2021). Use of refrigerated cells for olive cooling and short-term storage: Qualitative effects on extra virgin olive oil. International Journal of Refrigeration. 127. 10.1016/j.ijrefrig.2021.03.002]
[Uceda, Marino & Beltrán, Gabriel & Jiménez Marquez, Antonio. (2006). Olive oil extraction and quality. Grasas y Aceites. 57. 10.3989/gya.2006.v57.i1.19]
Olive oil centrifuge machine (two-phase, in the Meramvello area)
03. Extraction, storage and standardization of olive oil
The olives are crushed in crushers and become a paste and then kneaded. The kneading temperature has a great influence on the efficiency of the process, as the oil droplets are grouped due to a decrease in the viscosity of the oil. However, with excessive heating, undesirable effects can be observed: loss of aromatic compounds responsible for the taste and aroma of the oil, and acceleration of its oxidative process. The kneading is done at approximately 27 οC and the olive-paste mass is transferred for centrifugation. There, the olive pomace is separated from the olive oil. The olive oil passes through two separators and is isolated from unnecessary liquids and other foreign materials. All types of centrifugal separators have the potential to give good yields of oil, if the olive paste is sufficiently mixed and for this reason the kneading process is very important for the quality of the oil.
Olive oil is stored in metal (stainless) storage tanks, with minimal contact with oxygen. The olive oil is now ready to be bottled, after being analyzed per batch. Packaging can directly affect the quality of olive oil, by protecting it from both, oxygen and light. The shelf life of oils exposed to intense artificial light and diffused daylight is shorter than that of oils kept in the dark. In addition, storage temperature, the use of a nitrogen atmosphere and the reduction of oxygen in the overhead volume of the bottle, can significantly control quality changes during storage time.
[Uceda, Marino & Beltrán, Gabriel & Jiménez Marquez, Antonio. (2006). Olive oil extraction and quality. Grasas y Aceites. 57. 10.3989/gya.2006.v57.i1.19]
[Giovacchino, L. & Costantini, N. & Ferrante, M. & Serraiocco, Arnaldo. (2002). Influence of malaxation time of oil extraction yields and chemical and organoleptic characteristics of virgin olive oil obtained by a centrifugal decanter at water saving. Grasas y Aceites. 53. 10.3989/gya.2002.v53.i2.302]
[Piscopo, Amalia & Poiana, Marco. (2012). Packaging and Storage of Olive Oil. Olive germplasm-the olive cultivation. 201-222. 10.5772/51827]
Modern Olive-Oil Extraction Unit in Meramvello