`Spanish Study Suggests More Effective Way to Transform Cold-Stored Olives - Olive Oil Times
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Spanish Study Suggests More Effective Way to Transform Cold-Stored Olives

By Kenaz Filan
Jun. 2, 2021 06:55 UTC

A recently pub­lished study from researchers in Spain rec­om­mends heat­ing olives dur­ing the wash­ing process to improve yield quan­tity and qual­ity.

Most olive grow­ers keep and ship their fruits in refrig­er­ated stor­age. Refrigeration slows bac­te­r­ial growth and helps stop fer­men­ta­tion.

However, get­ting cold olives to a proper pro­cess­ing tem­per­a­ture can be chal­leng­ing because of the nar­row mar­gin for error.

See Also:What Does Cold Pressed Really Mean?

Olive oil pro­cess­ing starts with milling that grinds the olives into a paste. The paste is then poured into a malaxer, where it is slowly churned or mixed. Malaxing brings oil drops together into larger droplets and helps improve yield.

Warmer paste pro­duces more olive oil dur­ing malax­a­tion. However, this extra heat can lead to a break­down in desir­able polyphe­nols.

The oil can also become oxi­dized, dra­mat­i­cally reduc­ing its shelf life. Under European Union law, no olive oil labeled as ​“extra vir­gin” can be malaxed above 27 ºC.

If the paste is too cold, the oil will suf­fer in terms of both yield and qual­ity. Colder extrac­tions pro­duce fewer phe­nols that give extra vir­gin olive oil its smell, taste and health ben­e­fits.

A 2019 Italian study found that oil from olives malaxed at 20 ºC con­tained 25-per­cent fewer phe­nols than olive oil from olives malaxed at 27 ºC.

Typical approaches to this prob­lem involve warm­ing the olive paste. Ultrasound and microwave heaters and heat exchang­ers are avail­able, but they require large invest­ments in money, instal­la­tion and energy con­sump­tion costs.

Eddy Plasquy and José María García Martos, researchers at the depart­ment of bio­chem­istry and mol­e­c­u­lar biol­ogy of plant prod­ucts at the Spanish Instituto de la Grasa (Fat Institute), decided instead to warm the olives before they were crushed.

Before crush­ing, the olives get washed in indus­trial tubs to remove dirt, chem­i­cals and pes­ti­cides. The water used for wash­ing these olives is typ­i­cally 10 ºC to 12 ºC.

Instead of cold water, Plasquy and Garcia soaked olives in heated indus­trial tubs rang­ing from 25 ºC to 40 ºC.

The paste from crushed cold olives only reached tem­per­a­tures between 12.1 ºC and 17.6 ºC dur­ing malax­a­tion. Paste from olives soaked in hot water for 15 to 45 sec­onds con­sis­tently reached 27 ºC.

Heated water tanks are far cheaper and more energy-effi­cient than the cur­rently avail­able solu­tions. Heating an olive mill’s wash bins is also far sim­pler than shut­ting down a pro­duc­tion line to install new equip­ment.

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