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Research find­ings of a new chem­i­cal method to detect delib­er­ately com­pro­mised or inad­ver­tently adul­ter­ated extra vir­gin olive oil have been pub­lished by the UC Davis Olive Cen­ter.

Finan­cial incen­tives to adul­ter­ate extra vir­gin olive oil have long been known, but meth­ods to detect the dif­fer­ence between the real thing and a delib­er­ately com­pro­mised prod­uct, con­tain­ing other less expen­sive oils, are time-con­sum­ing and costly.

Now, the UC Davis researchers have devel­oped a more rapid and cost-effec­tive process to deter­mine the reli­a­bil­ity of a prod­uct bot­tled with an extra vir­gin olive oil label.

Selina Wang, research direc­tor of the UC Davis Olive Cen­ter, described the new process as involv­ing a faster, bet­ter and cheaper method than the mul­ti­ple stan­dard meth­ods in com­mon use for ana­lyz­ing olive oil purity.

“The method ana­lyzes tri­a­cyl­glyc­erol (TAG) pro­files in olive oil for poten­tial adul­ter­ants using ultra-high-per­for­mance liq­uid chro­matog­ra­phy (UHPLC) with charged aerosol detec­tion (CAD),” Wang said.

The UC Davis researchers used a UPHLC with a charged aerosol detec­tor loaned to the Olive Cen­ter by the man­u­fac­turer, Thermo Fisher Sci­en­tific.

“The method is more envi­ron­men­tal-friendly as it requires a sim­ple dilu­tion of the sam­ple rather than the sol­vents and chem­i­cals needed for exist­ing purity meth­ods,” Wang said.

She also said that the method could be auto­mated and does not require a chemist, thus allow­ing those with a UHPLC to run the method in-house.

The sophis­ti­cated screen­ing involves, ​“using as lit­tle as a tea­spoon of oil,” Wang said. The method is sen­si­tive and can detect 10 per­cent of an adul­ter­ant or greater.

“A key to the effi­ciency and effec­tive­ness of this new approach and use of tech­nol­ogy is expe­dit­ing extra vir­gin olive oil adul­ter­ation detec­tion by com­bin­ing TAG analy­sis with Prin­ci­pal Com­po­nent Analy­sis (PCA),” Wang said, adding that TAGS are the prin­ci­pal com­po­nent which makes up 90 per­cent of the com­pounds in edi­ble oils and each type of oil has its own char­ac­ter­is­tic TAG pro­file.

The UC Davis researchers deter­mined TAG pro­files for olive oil as well as for five com­mon extra vir­gin olive oil adul­ter­ants, includ­ing high-oleic sun­flower, high-oleic saf­flower, canola, soy­bean, and grape­seed oils.

These oils were cho­sen based on the like­li­hood of their usage in blend­ing with extra vir­gin olive oil. The researchers began screen­ing by using a UHPLC-CAD to quickly sep­a­rate and ana­lyze the TAGs in a vari­ety of pure oil sam­ples and oil blends.

Once TAGs were sep­a­rated, sim­i­lar­i­ties and dif­fer­ences between dif­fer­ent oils based on their TAG pro­files were ana­lyzed by PCA.

PCA is an estab­lished sta­tis­ti­cal tech­nique used to visu­al­ize the dif­fer­ences in sam­ples. The researchers were able to dif­fer­en­ti­ate the olive oil from the five extra vir­gin olive oil adul­ter­ants in their study, by using the dis­tinct TAG pro­file in dif­fer­ent oils.

“We were able to deter­mine TAG pro­files with­out much sam­ple prepa­ra­tion and build a PCA model to dif­fer­en­ti­ate oils; this is a time-effi­cient and cost-effec­tive method for detect­ing olive oil authen­tic­ity that can be uti­lized by the gov­ern­ment offi­cials and bulk buy­ers at var­i­ous food-con­trol­ling points,” Wang said.

“More research is needed to expand the TAG data­base with more oil types, more sam­ples within each type, mul­ti­ple adul­ter­ants, oils made from dif­fer­ent cul­ti­vars, geo­graph­i­cal loca­tions, cli­mate and such to bet­ter define clus­ters in the PCA thereby improv­ing the accu­racy of this approach,” she added.

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