Researchers Identify New Markers to Detect Fraud in Refined Oils

A group of researchers includ­ing Nadia Mulinacci, Lorenzo Cecchi, Marzia Innocenti and Fabrizio Melani (University of Florence), Marzia Migliorini (PromoFirenze) and Lanfranco Conte (University of Udine) were con­duct­ing a study on mix­tures of vir­gin oils and rec­ti­fied olive oils when they noticed some­thing unusual.

“As often hap­pens, this research was born quite by chance after an obser­va­tion in a study we were car­ry­ing out on lig­nans, which are among the ele­ments that char­ac­ter­ize the minor com­po­nents of olive oil,” Nadia Mulinacci told Olive Oil Times.

The lig­nans are a group of phy­to­chem­i­cals wide­spread in plants, belong­ing to the class of phy­toe­stro­gens and ben­e­fi­cial for human health. Nevertheless, as the report reads, ​“although their quan­tity in olive oils is com­pa­ra­ble to other classes of phe­no­lic com­pounds, they were dis­cov­ered ten years after the first stud­ies appeared on the oleu­ropein deriv­a­tives.” Moreover, they are ​“the most abun­dant phe­no­lic com­pounds after sec­oiri­doids in vir­gin olive oils and their con­cen­tra­tion mainly depends on the cul­ti­var, while the milling process does not affect their amount in a sig­nif­i­cant man­ner.”

During the study, besides two typ­i­cal lig­nans which are present in vari­able quan­ti­ties, the researchers noticed the pres­ence of other mol­e­cules with the same weight and sim­i­lar struc­ture, which they had never seen before. ​“This intrigued us and we hypoth­e­sized that they may have been caused by the refin­ing process,” Mulinacci explained. ​“Nevertheless, we did not know which step caused this trans­for­ma­tion.”

At this point, they ana­lyzed three sets of rec­ti­fied oils with inter­me­di­ate sam­ples and found that a typ­i­cally applied pro­ce­dure, that is the pas­sage through active earth, or so-called bleach­ing, (i.e. the fil­tra­tion of olive oils through mate­ri­als that absorbs a series of unwanted com­pounds, includ­ing part of lig­nans and phe­no­lic sub­stances), induces the for­ma­tion of some iso­bars (iso­baric forms of nat­ural (+)-pinoresinol and (+)-1-ace­toxypinoresinol).

Molecular dynamic sim­u­la­tion helped to iden­tify the most prob­a­ble chem­i­cal struc­tures cor­re­spond­ing to these new iso­bars, with data in agree­ment with the chro­mato­graphic find­ings. According to results, the iden­ti­fi­ca­tion of these com­pounds can there­fore be help­ful to reveal if a refined olive oil is added to a vir­gin olive oil, as in the case of adul­ter­ations.

“This is an addi­tional tool at the dis­posal of pro­duc­ers and ana­lysts respon­si­ble for the qual­ity con­trol of olive oil,” Mulinacci added. ​“For years now, our research group has been work­ing to enhance the qual­ity of extra vir­gin olive oils through the devel­op­ment of appro­pri­ate ana­lyt­i­cal meth­ods, and this work con­tributes to the ana­lyt­i­cal equip­ment needed to com­bat frauds.”