New Process Increases Sustainability, Phenolic Profile of Olive Leaf Extracts

Researchers at the University of Barcelona have dis­cov­ered a new envi­ron­men­tally friendly method for extract­ing polyphe­nols from olive leaves.

In a study recently pub­lished in Food Chemistry, the sci­en­tists detailed a novel extrac­tion method using Natural Deep Eutectic Solvents (NaDES).

The extrac­tion method is cru­cial because it influ­ences the costs and fea­si­bil­ity of pro­cess­ing olive leaves on a large scale out­side the lab­o­ra­tory.

Additionally, it affects the com­po­si­tion of the extracted sub­stances and their poten­tial appli­ca­tions.

The researchers cre­ated the NaDES from nat­ural com­po­nents, com­bin­ing a glyc­erol-like liq­uid sub­stance with choline chlo­ride, a solid salt used in ani­mal feed.

“When you com­bine these two sub­stances, a new sol­vent is formed,” said Sónia Sentellas, a researcher in the university’s depart­ment of chem­i­cal engi­neer­ing and ana­lyt­i­cal chem­istry and co-author of the study.

“It is a nat­ural sub­stance that does not have toxic impacts on human health,” she told Olive Oil Times.

The first step in pro­duc­ing the extract is to crush the leaves into a fine pow­der.

“Next, we mix a spe­cific pro­por­tion of this pow­der with the sol­vent at 80 ºC for two hours and wait for the extract to be pro­duced,” Sentellas said.

“The entire process is sim­i­lar to mak­ing tea,” she added. ​“The tea leaves are steeped in hot water, which acts as a sol­vent. After a while, you get col­ored water with some tea com­po­nents, and then you sep­a­rate the leaves from the liq­uid.”

The researchers found that using NaDES improved extrac­tion effi­ciency while adher­ing to envi­ron­men­tally friendly prac­tices.

The study iden­ti­fied sev­eral polyphe­nols in the olive leaf extracts, includ­ing hydrox­y­ty­rosol, lute­olin and oleu­ropein.

These com­pounds, also found in extra vir­gin olive oil, are known for their antiox­i­dant prop­er­ties and abil­ity to pro­tect car­dio­vas­cu­lar and brain health.

While researchers are still explor­ing poten­tial appli­ca­tions, this extrac­tion process could ben­e­fit olive oil pro­duc­tion, food pack­ag­ing and cos­met­ics.

Additionally, large-scale pro­duc­tion of olive leaf extracts could sig­nif­i­cantly impact the dis­posal of olive leaves.

Using nat­ural, envi­ron­men­tally friendly, non-toxic sol­vents broad­ens the appli­ca­tion pro­file of the obtained sub­stances.

“Some research is directed into under­stand­ing how such extracts could be added to olive oil to enhance its healthy pro­file and taste,” Sentellas said.

Away from olive oil, the researchers are inves­ti­gat­ing how the extracts might be used in other appli­ca­tions, includ­ing extend­ing the shelf life of pack­aged food prod­ucts and as an antimi­cro­bial agent.

“Within our research team in Barcelona, we are also work­ing on devel­op­ing films,” Sentellas said. ​“Those are based on biodegrad­able mate­ri­als and enriched with the polyphe­nol extract, which opens the oppor­tu­nity of using these films to extend the shelf life of food and pre­vent bac­te­r­ial growth.”

The research team focused on meth­ods to max­i­mize extract purifi­ca­tion to broaden the scope of extract appli­ca­tions. Additionally, they are work­ing on recy­cling the sol­vent used in the extrac­tion process.

“Recycling the sol­vent is not only cost-effec­tive and envi­ron­men­tally friendly, but it also makes the entire process more appeal­ing to the indus­try,” Sentellas said.

Spain is the world’s largest olive oil pro­ducer. Significant bio­mass, includ­ing olive leaves, is cre­ated dur­ing the olive har­vest and sub­se­quent prun­ing. According to some esti­mates, high-den­sity and super-high-den­sity farms yield 30 tons of olive tree prun­ing bio­mass per hectare each year in Spain.

“The goal of our research team is to pro­mote sus­tain­abil­ity within the olive oil indus­try by inte­grat­ing olive waste into the cir­cu­lar econ­omy,” Sentellas said. ​“In this research, we aim to recover com­pounds to cre­ate a rich extract with health ben­e­fits, adding value to this residue.”

“This aligns with the prin­ci­ples of the cir­cu­lar econ­omy, where waste is min­i­mized and resources are effi­ciently reused,” she added. ​“Scaling up the extrac­tion process to an indus­trial level could trans­form how the olive oil indus­try han­dles its waste.”

The process is cur­rently being tested in a lab­o­ra­tory set­ting. ​“The next step is to pre­pare a pilot plant to see how our lab work can be scaled up to an indus­trial level,” Sentellas con­cluded.