Research Explores Olive Oil Co-Extraction with Olive Leaves, Herbs and Spices

A lit­erature review pub­lished in Foods, an aca­d­e­mic jour­nal, has found that olive oil co-extracted with other ​“nat­ural sources of bioac­tive com­pounds” could improve the oil’s health ben­e­fits.

It is well-estab­lished that polyphe­nols and other phe­no­lic com­pounds found in extra vir­gin olive oil are respon­si­ble for the vast major­ity of its health ben­e­fits.

“These prop­er­ties encom­pass antiox­i­dant activ­i­ties, anti-inflam­ma­tory effects, car­dio­vas­cu­lar ben­e­fits, antimi­cro­bial prop­er­ties and can­cer pre­ven­tion, among oth­ers,” Ítala Marx, a researcher at the Instituto Politécnico de Bragança and the University of Porto who authored the review, told Olive Oil Times.

“By increas­ing the nat­ural antiox­i­dant con­tent in oils, their nutri­tional value is enhanced, offer­ing addi­tional health-pro­mot­ing prop­er­ties to con­sumers,” she added.

In the review, Marx inves­ti­gated ways to increase the amount of polyphe­nols in the final prod­uct to improve its healthy qual­i­ties – includ­ing the addi­tion of olive leaves or herbs and spices, such as gar­lic, lemon, hot pep­per, rose­mary, thyme and oregano – to the milling process.

“It is essen­tial to note that the phe­no­lic con­tent and health ben­e­fits of extra vir­gin olive oil can vary depend­ing on fac­tors such as olive vari­ety, har­vest matu­rity and extrac­tion process,” she said.

“These antiox­i­dants act as rad­i­cal scav­engers, neu­tral­iz­ing free rad­i­cals and inhibit­ing the oxi­da­tion process,” Marx added. ​“By increas­ing the nat­ural antiox­i­dant con­tent in oils, their shelf life can be extended, reduc­ing the risk of ran­cid­ity, and main­tain­ing their qual­ity for a longer period.”

According to Marx, inter­est in co-extract­ing olives with other fruits, spices and leaves rich in bioac­tive com­pounds has gained sig­nif­i­cant atten­tion in recent years, with some pro­duc­ers see­ing co-extrac­tion as an oppor­tu­nity for inno­va­tion.

“The co-extrac­tion method, also known as simul­ta­ne­ous extrac­tion, involves the extrac­tion of olive oil together with other nat­ural sources of phe­no­lic com­pounds (in the case of the paper, fresh olive leaves) dur­ing the oil pro­duc­tion process,” she said.

“This method has the poten­tial to enhance the sen­sory and chem­i­cal qual­ity of extra vir­gin olive oil and pro­vide addi­tional ben­e­fits such as improved health-related com­po­si­tion of oils, enhanced antiox­i­dant activ­ity, enhanced sen­sory char­ac­ter­is­tics, and improved nutri­tional pro­file,” Marx added.

While a grow­ing body of research has found that co-extrac­tion with berg­amot, rose­mary, thyme, basil and oregano can increase the oils’ qual­ity and pos­i­tive sen­sory notes, these co-extrac­tions can­not be clas­si­fied as extra vir­gin due to the addi­tion of other ingre­di­ents. Nonetheless, the polyphe­nol counts are quite high.

“[One study] co-extracted olive oils with gar­lic, lemon, oregano, hot pep­per, or rose­mary,” Marx wrote. ​“The results obtained demon­strated that spices or fruits could increase the antiox­i­dant capac­ity of oils while their sen­sory pro­pri­eties are pro­moted.”

In her lit­er­ary review, Marx mainly focused on co-extrac­tion using olive leaves. She pre­vi­ously co-authored research that found how co-extrac­tion with olive leaves in cer­tain con­di­tions can increase olive oil’s polyphe­nol con­tent and sen­sory pro­file.

In the lit­er­ary review, Marx said olive leaves may be most suit­able for co-extrac­tion since they are a nat­ural byprod­uct of olive har­vest­ing and must be dealt with post-har­vest.

Her research found that between 5 and 10 per­cent of the over­all weight of olives trans­formed com­prises olive leaves, which are already present in the olive milling process.

“Olive leaves have been found to exhibit numer­ous bio­log­i­cal activ­i­ties, includ­ing antiox­i­dant, anti­hy­per­ten­sive, car­dio­pro­tec­tive, and anti-inflam­ma­tory effects,” she wrote. ​“Additionally, olive leaves con­tain triter­penoids such as maslinic, urso­lic, and oleano­lic acids, which recent com­pu­ta­tional and in vitro stud­ies have shown to pos­sess anti-SARS-CoV‑2 [Covid-19] prop­er­ties.”

Marx noted that many fac­tors impact the result of olive oil co-extrac­tion with olive leaves, and study results have been incon­sis­tent over the years.

“The cul­ti­var of olives and leaves, the pro­por­tion of leaves added, and the scale of extrac­tion are impor­tant fac­tors that strongly influ­ence the resul­tant qual­ity of oils.” she wrote.

Overall, Marz con­cluded that the devel­op­ment of func­tion­ally enriched olive oil could cre­ate new types of prod­ucts and open new mar­kets to pro­duc­ers. Still, future stud­ies must be done to opti­mize the milling tech­nol­ogy to accom­plish this and fully under­stand the poten­tial health ben­e­fits.

“The results demon­strated that olive oils co-extracted with nat­ural sources of bioac­tive com­pounds could be a promis­ing method to enrich olive oils and pro­mote health ben­e­fits for con­sumers, aim­ing to meet spe­cific needs,” she wrote.

However, Marx added that while this method has remark­able prop­er­ties of increas­ing olive oil’s func­tional capac­ity, pro­duc­ers might encounter some chal­lenges while attempt­ing to carry it out.

“Producers need to address chal­lenges related to extrac­tion con­di­tions, sen­sory char­ac­ter­is­tics, qual­ity con­trol, reg­u­la­tions, and cost con­sid­er­a­tions to effec­tively uti­lize this method and deliver high-qual­ity extra vir­gin olive oils to the mar­ket,” she con­cluded.