Slovenian Cooperative Focuses on Phenol Levels

The sea­son in the Mediterranean will be remem­bered for the early start of the 2024 olive har­vest.

In the south of Italy, mills have been work­ing since September 1^st and in Andalusia, Spain, the har­vest of Gordal table olive vari­ety is already under­way.

Meanwhile, the first new oil is already flow­ing in Slovenia, the small European coun­try sand­wiched between Italy and Croatia on the north­east­ern coast of the Adriatic Sea.

“Last year, we har­vested on September 14^th, and this year, we moved the date three weeks ear­lier,” said Danijel Stojković Kukulin, an olive farmer and bio­chemist.

“We were inter­ested in what kind of oil would be pro­duced from the olives har­vested and processed in August, what its char­ac­ter­is­tics would be and ulti­mately what the yield would be,” he added.

Stojković is a mem­ber of Terra Centuria, a coop­er­a­tive of young olive grow­ers. Many of them focus on organic cul­ti­va­tion and early har­vests.

Stojković’s first extra vir­gin olive oil of the year, made from the Istarska bjel­ica vari­ety on August 23^rd in the cooperative’s mill, pleas­antly sur­prised every­one. Along with other vital com­po­nents, the first analy­sis showed more than 1,500 mil­ligrams of polyphe­nols per liter.

“This is a con­cen­trate of the olive fruit itself,” Stojković said. ​“In addi­tion to many polyphe­nols, the oil is intensely green in color, has a lot of chloro­phyll and is extremely spicy.”

Stojković became a pro­fes­sional olive grower about ten years ago when he inher­ited a grove with about 50 trees from his grand­fa­ther Oreste in Čežarji, near Koper, the largest city in coastal Slovenia.

He later planted 300 Istarska bjel­ica, Grigan, Coratina, Leccino and Storta olive trees on a neigh­bor­ing hill, which he plans to cul­ti­vate organ­i­cally. Stojković also plans to add 150 trees of Greek vari­eties.

After receiv­ing a bachelor’s degree in bio­chem­istry, Stojković earned a doc­tor­ate in mol­e­c­u­lar genet­ics and biotech­nol­ogy.

He has tried new things in olive farm­ing and milling, from organic farm­ing tech­niques and cul­ti­va­tion of lesser-known olive vari­eties to inno­v­a­tive tech­no­log­i­cal approaches in the mill, which give greater added value to the oil.

Stojković is espe­cially inter­ested in polyphe­nols, first learn­ing that green olives con­tain the high­est con­cen­tra­tion of polyphe­nols by read­ing about the grow­ing skills of the ancient Romans and Greeks. In ancient Rome, they knew five basic cat­e­gories.

“The most expen­sive, often cel­e­brated as the oil of the gods, was pro­duced from per­fectly green olives, har­vested usu­ally from the end of August to the end of September,” Stojković said. ​“They called that oil: Oleum aes­tivum (sum­mer oil), Oleum acer­bum, Oleum omphacium or Oleum ex albis ulivis. This oil was mostly used for med­ical and cos­metic pur­poses.”

Modern sci­en­tific meth­ods have since con­firmed what the Romans described, iden­ti­fy­ing oleo­can­thal, oleu­ropein, olea­cein, hydrox­y­ty­rosol, tyrosol and other bioac­tive com­pounds that give extra vir­gin olive oil unique fla­vors and enhanced health ben­e­fits.

Extra vir­gin olive oil’s polyphe­nols have been asso­ci­ated with pre­vent­ing and mit­i­gat­ing some of the most com­mon chronic dis­eases, includ­ing car­dio­vas­cu­lar dis­ease, can­cer, demen­tia and dia­betes.

The Terra Centuria coop­er­a­tive has been study­ing and exper­i­ment­ing with dif­fer­ent har­vest­ing, milling, and stor­age meth­ods for sev­eral years. ​“The goal is for our oil to reach more than 5,000 mil­ligrams of polyphe­nols per liter,” Stojković said.

He explained that this year, among other things, they kept the olives in a cold cham­ber dur­ing the har­vest and used dry ice dur­ing milling.

“Decreasing the tem­per­a­ture, espe­cially in aro­matic vari­eties, greatly increases the cre­ation of fresh and pleas­ant aro­mas while at the same time reduc­ing the extrac­tion of polyphe­nols,” Stojković said. “ It is impor­tant where we reduce the tem­per­a­ture, but we are still work­ing to deter­mine by how much and for how long.”

In the final stage, every detail in the oil mill affects the amount and com­po­si­tion of polyphe­nols in olive oil. Even a small blade speed or mix­ing time change can sig­nif­i­cantly change the oil’s prop­er­ties.

“This year, we also con­firmed the hypoth­e­sis that tech­nol­ogy in the oil mill can influ­ence the com­po­si­tion of polyphe­nols in olive oil,” Stojkovič said. ​“In pre­vi­ous years, for exam­ple, we had about ten per­cent oleo­can­thal, and this year, we man­aged to get more than 60 per­cent of all polyphe­nols.”

Over the past five years, the qual­ity of his high-polyphe­nol extra vir­gin olive oils has been cor­rob­o­rated at Aristoleo, a Greek com­pe­ti­tion spe­cial­iz­ing in high-polyphe­nol olive oil.

“I sent the first sam­ple of my oil to that com­pe­ti­tion five years ago and won the high­est prize,” Stojkovič said. ​“It was a con­fir­ma­tion that I am on the right path.”

Along with the health ben­e­fits and awards, Stojkovič’s extra vir­gin olive oil is increas­ingly val­ued in haute gas­tron­omy. Chef Jérôme Banctel uses it at Le Gabriel restau­rant in Paris, which has 3 Michelin stars.

With his QQLYN brand, Stojkovič intends to enter the 2025 NYIOOC World Olive Oil Competition, the world’s most pres­ti­gious olive oil qual­ity qual­ity con­test.

He hopes an award at the NYIOOC will help him estab­lish a part­ner­ship with a large American com­pany spe­cial­iz­ing in dis­trib­ut­ing high-phe­no­lic olive oils.

Despite the addi­tional cost, Stojkovič believes demand for high-polyphe­nol extra vir­gin olive oils will con­tinue to rise in the United States.

“The cost of pro­duc­ing extra vir­gin olive oil from green olives is dou­ble, maybe even triple [that of ripe olives],” he said. ​“Oil yield is lower. For exam­ple, Istarska bjel­ica, one of the ear­lier vari­eties we pro­duced this year’s first oil, had some­where between eight and ten per­cent oil yield.”

“In September, we will pick all other vari­eties as well,” Stojkovič added. ​“Oil yield will be slightly higher. However, when we cal­cu­lated the pro­duc­tion costs of this first oil, they were between €40 and €50 per liter, so the final price cor­re­sponds to that.”

While some high-phe­no­lic extra vir­gin olive oils retail for €150 to €500 per liter, Stojkovič said his prices will be lower. Still, he is con­vinced that demand for this mar­ket seg­ment will grow, encour­ag­ing pro­duc­ers to opt for an early har­vest in Slovenia and other coun­tries that can­not com­pete with Spain, Italy or Greece in quan­tity. Slovenia pro­duces between 800 and 2,000 tons of olive oil annu­ally.