⚙️ Olive crushing
Also known as: Olive milling, Olive grinding
Grinding olives with their stones into a paste with millstones or a hammer crusher.
Olive crushing is the first step in making oil: the fruit is ground together with the stones into a thick paste. This breaks the stones, the cell walls and the tiny sacs that hold droplets of oil. The result is a mixture of solid particles of stone, skin and flesh with an emulsion of oil in water.
Crushing is done with traditional stone millstones or with metal crushers: hammer, disc or blade crushers. The flesh is better ground, while the stone has to be broken by impact, and it is the impact that heats the mass strongly. Almost all of the machine's energy turns into heat: the harder the crushing, the warmer the paste. Overheated paste forms an emulsion from which it is harder to separate the oil.
It is during crushing that the flavour of the oil is born. In the broken cells the fruit's own enzymes come to life: some form bitter and pungent phenolic compounds, others form "green" aroma compounds. Oil from metal crushers is usually more bitter and pungent, while oil from millstones is more aromatic and milder. However, millstones work more slowly, and the paste is in contact with the air for longer.
Some machines remove the stones before crushing. Such oil is richer in phenols, because the seed contains a lot of an enzyme that destroys them, but less oil is produced.
How it connects to Olives
⚙️ Olive crushing → kind of → 🏭 Olive harvest and the oil mill → kind of → 🫒 Olives
Links
- Where it happens
- 🏭 Olive oil mill
- Next step
- 🌀 Malaxation
- Part of
- 🏭 Olive harvest and the oil mill
- In other topics
- 🍷 Crushing
Frequently asked questions
Which is better, millstones or a hammer crusher?
Millstones give a more aromatic and milder oil, metal crushers a more bitter and pungent one.
Why does temperature matter during crushing?
Overheated paste forms an emulsion and gives up its oil less easily.
Is it true that a bitter, pungent oil has gone off?
No. Those traits come from the fruit's enzymes working once the cells are broken, and they are stronger in oil that kept more phenols.
What to read next
- 🏭 Olive oil mill — A facility where oil is extracted from olives.
- 🌀 Malaxation — Slow mixing of olive paste before the decanter centrifuge so that tiny oil droplets merge; usually 30–40 minutes at 18–27 °C.
Similar
❄️ Cold pressing · 🧺 Olive harvest · 🔄 Olive oil filtration · 🌀 Malaxation · 🍷 Destemming · 🍷 Sorting table
Sources
- Tamborrino A. et al. Experimental Investigation of a New Modular Crusher Machine Developed for Olive Oil Extraction Plants. Foods 2022, 11, 3035
- Campestre C. et al. The Compounds Responsible for the Sensory Profile in Monovarietal Virgin Olive Oils. Molecules 2017, 22, 1833
- Clodoveo M.L. Industrial Ultrasound Applications in the Extra-Virgin Olive Oil Extraction Process. Foods 2019, 8, 121