Olive Oil, Manufacturing Methods

Grinding of Olives to Paste

Stone Olive Mills

• can be adapted to olive and pit size to optimise paste characteristics
• doesn't cut the skin, releasing less chlorophyll so less bitter oil
• formation of larger size drops of oil, minimizing mixing times
• paste isn't heated

• bulky
• stone is difficult to clean
• green olives will prolong grinding time
• costly
• discontinuous process - time consuming
• high labour cost

Hammer Mill

• continuous
• high throughput
• Tolerates debris such as rocks and grit
• know, perfected technology
• extracts more phenols so oil has longer shelf life*

• may form emulsion which impedes oil - water separation
• organoleptic characteristics affected - oil can have bitter, stronger, spicy taste due to more phenols
• wear and tear of metal parts
• oil paste may heat up

Oil Separation

Centrifugal Decanters

• Compact machinery - one decanter can take the place of several presses
• semi continuous and automated
• limited labour

• expensive
• more technical labour required
• may consume hot water
• high energy consumption
• pomace may end up moist
• greater amount of vegetable water to be disposed of
• reduced antioxidants due to added water
• subject to wear from rocks, grit

Sinolea Method

• higher polyphenol content of oil
• low temperature method
• automated
• low labour
• oil/water separation step is not needed
• low energy requirement

• Often must be combined with one of the above methods to maximize oil extraction which requires more space, labour, etc.
• Large surface areas can lead to rapid oxidation