`New Testing Method Simplifies Elemental Analysis of EVOO Samples - Olive Oil Times
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New Testing Method Simplifies Elemental Analysis of EVOO Samples

By Paolo DeAndreis
May. 18, 2021 09:07 UTC

Researchers in Italy have devel­oped a new method to accu­rately iden­tify 45 dif­fer­ent chem­i­cal ele­ments in extra vir­gin olive oil.

According to the paper pub­lished in the jour­nal Food Chemistry, researchers iden­ti­fied the best approach to ana­lyze each ele­ment and dra­mat­i­cally reduced the risks of faulty analy­sis due to sam­ple manip­u­la­tion (the phys­i­cal move­ment of sam­ples from one con­tainer to another) and dilu­tion.

Extra vir­gin olive oil ele­ments present sev­eral dif­fer­ences from other veg­etable oils, which have been used to adul­ter­ate extra vir­gin olive oil.- Maria Luisa Astolfi , researcher, Sapienza University of Rome

The research also paves the way for new stud­ies on the spe­cific char­ac­ter­is­tics of each ana­lyzed extra vir­gin olive oil, includ­ing the deter­mi­na­tion of geo­graph­i­cal ori­gin and anti-coun­ter­feit­ing activ­i­ties, among oth­ers.

Self-financed by a team of four Italian sci­en­tists, the new study eval­u­ates how dif­fer­ent sam­ple pre-treat­ment meth­ods can be applied to dis­tinct ele­ments, which is the best to use for each ele­ment and what out­come may be expected.

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“The ele­men­tal con­tent in olive oils is chal­leng­ing to study,” Maria Luisa Astolfi, a researcher at the Sapienza University of Rome’s chem­istry depart­ment and one of the authors of the study, told Olive Oil Times. ​“Their matrix is com­plex and char­ac­ter­ized by high vis­cos­ity and organic con­tent; more­over, some ele­ments are present in extra vir­gin olive oils at very low con­cen­tra­tion level.”

The sci­en­tists ran­domly chose 24 extra vir­gin olive oils from dif­fer­ent brands and con­tain­ers sold in sev­eral super­mar­kets in Rome for their exper­i­ments.

The researchers’ goal was to eval­u­ate meth­ods to detect known ele­ments and explore extra vir­gin olive oil com­po­si­tion.

“We focused our research on look­ing for a very high num­ber of ele­ments within extra vir­gin olive oil,” Astolfi said. ​“Forty-five is a num­ber that derives from pre­vi­ous stud­ies and tra­di­tional con­tent analy­sis. To those ele­ments, we added the search for traces no one has ever looked for, to inves­ti­gate their pres­ence and their quan­ti­ties.”

For this rea­son, the researchers com­pared dif­fer­ent ana­lyt­i­cal approaches that allowed a more accu­rate eval­u­a­tion of extra vir­gin olive oil com­po­si­tion.

By using ICP-MS (induc­tively cou­pled plasma mass spec­trom­e­try), researchers were able to achieve accu­rate and repro­ducible results with low detec­tion lim­its for the ana­lyzed trace ele­ments.

At the same time, the use of this ana­lyt­i­cal tech­nique and the research on how to apply it on extra vir­gin olive oil sam­ples effec­tively led the researchers to reduce both sam­ple dilu­tion oper­a­tions and manip­u­la­tion.

“The way sam­ples are treated is the main obsta­cle for researchers, since there lies the rea­son analy­sis might fail,” Astolfi said. ​“For instance, the dilu­tion to which an overly acidic solu­tion must be sub­ject to be ana­lyzed by ICP-MS and the trans­fer of sam­ple from one test tube to another are oper­a­tions that can com­pro­mise the result by con­t­a­m­i­nat­ing the sam­ple or los­ing the traces for which you are look­ing.”

Researchers went through sev­eral sam­ple treat­ments and digest­ing solu­tions, which are used to ana­lyze the sam­ples, try­ing to find a com­pro­mise between the method of analy­sis required for each ele­ment and the time needed to exe­cute it.

In some cases, dilu­tion oper­a­tions were avoided by iden­ti­fy­ing and apply­ing a spe­cific solu­tion of diluted nitric acid and hydro­gen per­ox­ide.

“That is an exam­ple of a solu­tion that, once in con­tact with the sam­ple, does not need to be diluted to fall under the max­i­mum acid­ity level that an ICP-MS can tol­er­ate,” Astolfi said. ​“That also means that the sam­ple does not have to pass from one test tube to another, sig­nif­i­cantly reduc­ing manip­u­la­tion. Working time is also con­sid­er­ably reduced.”

The researchers detected nor­mal quan­ti­ties of arsenic, cop­per, iron and lead in the extra vir­gin olive oil sam­ples, all of which are com­monly screened for. Meanwhile, researchers also detected cal­cium, cobalt, cop­per, mag­ne­sium, man­ganese and nickel in trace amounts. These six ele­ments, along with iron, are known to impact the taste and oxida­tive sta­bil­ity of extra vir­gin olive oil.

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“Furthermore, we also wanted to have a look at other ele­ments to deter­mine a more com­plete pro­file of extra vir­gin olive oil,” Astolfi said.

By get­ting a com­plete pic­ture of all the ele­ments present in a sam­ple, sci­en­tists can bet­ter deter­mine the geo­graphic ori­gin of the olive oils.

“The tree absorbs ele­ments from the ground, which then are present in the fruit. This can tell us a lot about the land of ori­gin,” Astolfi said. ​“Previous research also looked for track­ing ele­ments. We inched closer to under­stand­ing which ele­ments can give us that infor­ma­tion.”

However, not all ele­ments can be eval­u­ated with the same pro­ce­dure.

“If we take bar­ium, phos­pho­rus, sil­ver or tin, for instance, we could not use the new method because they need other reagent mix­tures, vol­umes and times for sam­ple extrac­tion or diges­tion,” Astolfi said. ​“The main chal­lenge is find­ing the most appro­pri­ate oil pre-treat­ment method for many dif­fer­ent ele­ments.”

She added that bar­ium, chromium, sil­ver or tin need to be digested in a warmed-up solu­tion and will not be accu­rately mea­sured with ultra­sonic extrac­tion.

“With the new method, we can assess the pro­file of 45 dif­fer­ent ele­ments and, with the com­par­i­son of the other meth­ods of analy­sis, our research might help to iden­tify which method best fits for any chem­i­cal ele­ment we are look­ing for,” Astolfi said.

Beyond the pos­si­bil­ity of more accu­rately deter­min­ing the province of olive oil and under­stand­ing its con­tents, new meth­ods may also help crack­down on coun­ter­feit and extra vir­gin olive oil adul­ter­ation.

“Extra vir­gin olive oil ele­ments present sev­eral dif­fer­ences from other veg­etable oils, such as seed oils, which in the past have been used to adul­ter­ate extra vir­gin olive oil before their dis­tri­b­u­tion on the mar­ket,” Astolfi said. ​“Differences lie in which ele­ments are present and their den­sity.”

New research is ongo­ing to inves­ti­gate the dif­fer­ences between organic and non-organic extra vir­gin olive oil and under­stand what dif­fer­en­ti­ates Italian and non-Italian extra vir­gin olive oils.

“Many oppor­tu­ni­ties come up because of this new method,” Astolfi said. ​“We are cur­rently inves­ti­gat­ing sam­ples com­ing from all over Italy, taken by local agribusi­ness active in their ter­ri­to­ries, to iden­tify their ori­gin and tell us about their dif­fer­ences, what are their spe­cific char­ac­ter­is­tics and so on.”

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