`Promising Results for New Test for Pesticide Residues in Olive Oil

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Promising Results for New Test for Pesticide Residues in Olive Oil

Dec. 10, 2012
Julie Butler

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What appears to be a new, cheap and fast way to detect insec­ti­cide residues in olive oil is the focus of joint research by French and Moroc­can sci­en­tists.

Agro­chem­i­cal residues remain highly toxic and com­pro­mise the qual­ity of olive oil

They say biosen­sors they have devel­oped show promise as a more effi­cient way to detect organophos­phate pes­ti­cides com­monly used on olive trees, par­tic­u­larly malathion, dimethoate and methi­dathion.

Chro­matog­ra­phy has tra­di­tion­ally been used for pes­ti­cide analy­sis in lab­o­ra­to­ries. It is reli­able and pre­cise but also time con­sum­ing and requires expen­sive instru­men­ta­tion and highly-trained staff, the researchers say in a research arti­cle to be pub­lished in April in the peer-reviewed Food Con­trol jour­nal.

Mean­while biosen­sors — using a liv­ing organ­ism or bio­log­i­cal mol­e­cules such as enzymes to detect the pres­ence of chem­i­cals — have been devel­oped for pes­ti­cide detec­tion and are gen­er­ally low-cost, com­pact and sim­ple in design.

The elec­tric eel plays a part

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Led by Prof. Thierry Noguer, the team of researchers from the Uni­ver­si­ties of Per­pig­nan in France and of Ibn Zohr in Morocco is eval­u­at­ing the use of amper­o­met­ric biosen­sors, which can detect pes­ti­cides via changes in elec­tric cur­rent. Specif­i­cally, they are using an enzyme from elec­tric eels — acetyl­cholinesterase (AChE) – which is entrapped using a method known as the sol-gel process.

In their paper, Sol-gel immo­bi­liza­tion of acetyl­cholinesterase for the deter­mi­na­tion of organophos­phate pes­ti­cides in olive oil with biosen­sors”, they said that they tested the via­bil­ity of the method on the detec­tion of insec­ti­cides from extra vir­gin olive oil spiked with known quan­ti­ties of the oxi­dized forms of malathion, dimethoate and methi­dathion.

They had checked no other insec­ti­cide was already in the olive oil, which was organic and bought in a super­mar­ket.

The analy­sis of the spiked olive oil sam­ples achieved nearly 100 per­cent recov­ery of insec­ti­cides from the spiked sam­ples and showed a good cor­re­la­tion with results obtained via con­ven­tional meth­ods, they wrote, con­clud­ing that a cheap, fast and sim­ple amper­o­met­ric biosen­sor” had been devel­oped.

The lim­its of detec­tion of the devel­oped devices were very com­pat­i­ble with the max­i­mum residue limit tol­er­ated by inter­na­tional reg­u­la­tions” they wrote.

Why detec­tion is impor­tant

Insec­ti­cides, mainly organophos­phates, are widely used on olive trees to con­trol fruit fly, the researchers said in the paper‘s intro­duc­tion.

These chem­i­cals allow crop pro­tec­tion of olive trees, how­ever their residues detected in the oil and fruits are a major risk for con­sumer health.”

There­fore, both the Euro­pean Union and the Codex Ali­men­ta­r­ius Commission…have estab­lished max­i­mum pes­ti­cide residue lim­its (MRLs) for olives and olive oil.”

In another paper, they said that while agro­chem­i­cals improve olive yield, they still remain highly toxic and com­pro­mise the qual­ity of olive oil.”

The major­ity of these pes­ti­cides are lipophilic and are able to remain in the oil for extended peri­ods of time.”

Reg­u­lar mon­i­tor­ing and detec­tion of these chem­i­cals are essen­tial for con­sumer pro­tec­tion” they wrote.

But Noguer told Olive Oil Times the group‘s aim was not to eval­u­ate the qual­ity of olive oils, rather to pro­vide tools for check­ing them.

However…we did not find pes­ti­cides in con­cen­tra­tions higher than the MRLs in the tested sam­ples” he said.

About fifty cents per test

Asked if the biosen­sors had dis­ad­van­tages, he said that gen­er­ally it was their rel­a­tive insta­bil­ity, due to the use of a bio­log­i­cal ele­ment — an enzyme — which made fre­quent change of the elec­trode nec­es­sary.

How­ever this rel­a­tive draw­back is bal­anced by the very low cost of the mea­sure­ment” he said.

The esti­mated cost of one test using a biosen­sor is about €0.50, which fac­tors in fab­ri­ca­tion of the biosen­sor and the analy­sis. But they are not yet on sale.

A start-up com­pany is being cre­ated to develop some of our biosen­sors. The main bar­rier to their devel­op­ment is the lack of mar­ket. The only widely used biosen­sor is the one for glu­cose, used by mil­lions of dia­betic peo­ple.”

Future work

The group is now devel­op­ing biosen­sors using new poly­mers — instead of the eel enzyme AChE — for the detec­tion of other insec­ti­cides used on olive trees.

We hope these devices will be bet­ter adapted to wide uti­liza­tion by non-qual­i­fied end users and will be finally autho­rized as con­trol tools by reg­u­lat­ing author­i­ties” Noguer said.

Fund­ing

The research fell within the frame of the bilat­eral Hubert Curien Vol­u­bilis Pro­gramme (France-Morocco) Asso­ci­a­tion bio­cap­teur-matéri­aux à empreinte molécu­laire pour la détec­tion des insec­ti­cides util­isés sur l’o­livier”. It was co-financed by the IMAGES lab­o­ra­tory at the Uni­ver­sity of Per­pig­nan Via Domi­tia.

Team mem­bers

Uni­ver­sity of Per­pig­nan Via Domi­tia, France (IMAGES lab­o­ra­tory): Thierry Noguer, Pro­fes­sor; Régis Rouil­lon, Pro­fes­sor, Uni­ver­sity Insti­tute of Tech­nol­ogy of Per­pig­nan; Georges Istam­boulié, PhD

Uni­ver­sity Ibn Zohr, Agadir (Morocco): Ihya Ait-Ichou, Pro­fes­sor; Elhabib Ait-Addi, Pro­fes­sor

PhD Stu­dents (co-tutelle): Najwa Ben Oujji; Idriss Bakas



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