Cold Extraction and Malaxation

Three phrases often appear on a label: cold extraction, early harvest, freshness. Behind these words lie specific production choices that agronomic research has studied extensively. Here is what the regulations and studies say, and how we work at Oikos Antalis, on our four estates in Ilia, in the Peloponnese.

Cold extraction or first cold pressing: what the law says

In the European Union, these two terms are governed by Article 10 of Delegated Regulation (EU) 2022/2104 on marketing standards for olive oil. As Olive Oil Times points out, quoting the text, both may only appear on virgin or extra virgin olive oils obtained at a temperature below 27 °C:

"First cold pressing" is reserved for oils from a first mechanical pressing of the olive paste in a traditional hydraulic press system.
"Cold extraction" applies to oils obtained by percolation or centrifugation of the olive paste.

The International Olive Council glossary also uses this 27 °C threshold. In other words, an oil produced in a modern centrifugal mill cannot legally call itself "first cold pressing". That is why we speak of cold extraction. To understand the other terms on a label, see our article Olive oil labels: what the law says.

How a modern mill works

The olives are first crushed. The paste then goes through malaxation, a slow, continuous mixing that helps the fine droplets of oil come together (Tamborrino et al., 2010). Finally it is sent to a decanter, a horizontal centrifuge that separates the liquids from the solids (IOC). In a "three-phase" system, water is added to the paste during centrifugation; in a "two-phase" system, it is not. An Egyptian study comparing the two systems, including on Koroneiki, measured more polyphenols in the oils from the two-phase system, which the authors link to the absence of added water (Effect of extraction systems on quality characteristics of extra virgin olive oil, 2019).

Malaxation: a matter of minutes and degrees

Malaxation is the most delicate stage. Gently warming the paste stimulates enzymatic activity, which affects both yield and quality (Tamborrino et al., 2010). Three types of effect are described:

Phenolic compounds. Lengthening malaxation and raising the temperature reduces secoiridoids and phenolic alcohols, through enzymatic oxidation and the transfer of phenols into the aqueous phase. In the trials by Angerosa et al. (2001), cited by Tamborrino et al., secoiridoids in the Frantoio variety fell from about 179 to 27 ppm between 15 minutes at 25 °C and 90 minutes at 35 °C.
Aromas. The green notes of the oil come from the lipoxygenase pathway, which produces C6 and C5 volatile compounds. Their formation depends on the temperature and duration of malaxation (Morales, Angerosa and Aparicio, Grasas y Aceites, 1999). A high temperature reduces certain C6 esters and can favour compounds associated with the "fusty" defect. This pathway consumes oxygen: in a sealed malaxer, it had disappeared from the headspace after about 20 minutes (Tamborrino et al., 2010).
Yield. Longer malaxation generally improves yield, at the expense of quality. The authors note, for example, that going up to 35 °C adds defects with no gain in yield.

A recent study on Arbequina points the same way: going from 30 to 45 minutes reduced total phenols by about 8 mg/kg, and the best oils were obtained at 20 °C for 30 minutes (Olmo-Cunillera et al., Antioxidants, 2021). A useful nuance: in the same study, oleocanthal on the contrary increased with temperature. Each compound reacts in its own way.

At Oikos Antalis, malaxation lasts 25 minutes. This is a short time compared with the ranges studied, where longer malaxation goes hand in hand with lower phenols. The studies do not, however, test exactly 25 minutes, and the optimum depends on the variety, the temperature and the equipment: we do not claim that there is a universal ideal duration.

Harvesting and extracting on the same day

A picked olive remains a living fruit that begins to deteriorate. A study of 228 batches of olives from seven Italian mills, over three seasons, compared olives processed within 24 hours with those stored for 7 days or more (Rotondi et al., Foods, 2021). With the wait:

free acidity rose from 0.30% to 0.56%;
the peroxide value rose from 6.96 to 9.56 mEq O2/kg;
total phenols fell by about 41%, from 246 to 144 mg/kg;
fruitiness, green notes, bitterness and pungency decreased, while the intensity of defects increased.

The oils remained within the legal limits for the extra virgin category, but the authors conclude that storage time degrades quality, with the clearest losses as soon as 24 hours is exceeded. That is why our olives are milled on the very day they are harvested.

Why harvest early

As it ripens, the olive accumulates oil but loses some of its phenolic compounds. A study by the University of California, Davis followed Koroneiki in the orchard: the oil content of the fruit increased up to a plateau at the end of November, while the phenols in the oil peaked about a month before maximum oil content (Polari, Crawford and Wang, Agronomy, 2021). Harvesting early therefore means accepting a lower yield for an oil richer in phenols.

In Greek Koroneiki, oleuropein in the fruit fell sharply between the earliest and latest stages of ripeness, and antioxidant capacity also decreased (Kafkaletou, Ouzounidou and Tsantili, Agronomy, 2021). In other varieties, phenols, fruitiness, bitterness and pungency decline with ripeness (Gündüz and Bozdoğan Konuşkan, 2022), and harvest date weighs more heavily than variety on bitterness and phenols (Škevin et al.). We harvest our Koroneiki olives by hand in early October. To understand what these molecules bring, read our article on polyphenols.

Key takeaways

"Cold extraction" legally means centrifugation or percolation below 27 °C; "first cold pressing" is reserved for hydraulic presses.
Malaxation strikes a balance between yield and quality: longer and warmer, it tends to reduce phenols and alter aromas.
The time before milling matters: beyond 24 hours, acidity and peroxides rise, while phenols and fruitiness fall.
Early harvesting sacrifices yield in favour of phenols, bitterness and pungency.
Figures matter more than adjectives: our laboratory analyses are published, with 424 mg/kg of polyphenols for Skourochori and 359 mg/kg for Agios Ilias (2026 harvest), and 374 mg/kg for Paliovarvassena (2025 harvest).

FAQ

Is a "cold extraction" oil inferior to a "first cold pressing" oil?

No. Both terms describe a process, not a level of quality. They impose the same 27 °C limit; only the technique differs.

How long does malaxation last at Oikos Antalis?

25 minutes, a short time compared with the studies cited above.

Does an early harvest always produce a more bitter oil?

Studies show that bitterness and pungency generally decrease with ripeness. An early harvest oil is therefore often more intense, but the result also depends on the variety and the year.

Where can I find your oils?

Our four estate cuvées are available in our bottle collection.

Cold extraction, malaxation, harvest: what makes a great olive oil