Researchers Find Ways to Reduce Acrylamide in Table Olives

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A recent study con­ducted by Extremadura’s provin­cial gov­ern­ment in Spain has iden­ti­fied some strate­gies to mit­i­gate the pres­ence of acry­lamide dur­ing the indus­trial pro­cess­ing of black olives.

Acrylamide is a com­pound found in car­bo­hy­drate-rich foods after being heated. The International Agency for Research on Cancer con­sid­ers the com­pound car­cino­genic.

According to the researchers, acry­lamide gen­er­a­tion in table olives is evi­dent in larger quan­ti­ties in Californian-style black ripe olives. The com­pound devel­ops as a result of oxi­da­tion after ther­mal ster­il­iza­tion occurs dur­ing the table olive pro­duc­tion process.

The amount of acry­lamide in table olives is depen­dent on many fac­tors such as how olives are processed, ther­mal ster­il­iza­tion con­di­tions, pack­ag­ing meth­ods that may or may not involve the use of brine and cook­ing.

The researchers con­ducted their study using Hojiblanca olives, a com­mon Spanish vari­ety with an inter­me­di­ary level of acry­lamide con­tent.

By chang­ing dif­fer­ent phases of the pro­duc­tion process – olive mat­u­ra­tion stage, length of stor­age period and type of wash­ing treat­ment – the researchers were able to lower lev­els of acry­lamide and thus improve the qual­ity of the table olives.

“Applying these mit­i­ga­tion mea­sures at indus­trial scale, black table olives con­sumers will intake a sig­ni­fica­tively minor quan­tity of this toxic com­pound,” Daniel Martín-Vertedor and Antonio Fernández, the two lead researchers on the project, told Olive Oil Times.

“Therefore, this type of table olive elab­o­ra­tion can be more present in the human diet, tak­ing advan­tage of the ben­e­fits of table olives,” they added.

The researchers used olives har­vested at two dif­fer­ent points of mat­u­ra­tion: the green and yel­low-green stages. Olives har­vested at the yel­low-green mat­u­ra­tion stage – when they are one step closer to verai­son – had higher lev­els of acry­lamides.

Furthermore, green olives stored for 21 months pre­sented the low­est acry­lamide lev­els. Acrylamide lev­els also low­ered by 18 per­cent when the olives were sprayed with water before rins­ing. Washing the olives with water heated to 25 ºC for 40 min­utes also led to a 36-per­cent reduc­tion in the chem­i­cal.

However, fol­low­ing treat­ment with lye, which is com­monly used to remove the com­pound respon­si­ble for the bit­ter taste of table olives, acry­lamide lev­els increased. Pitted olives retained the low­est lev­els of the chem­i­cal, fol­lowed by unpit­ted olives and sliced olives.

The researchers fur­ther found that table olives canned in brine with higher con­cen­tra­tions of salt after the pro­duc­tion process also increased the acry­lamide con­tent. However, this was not observed in olives stored in other liq­uids.

“The study pro­vides dif­fer­ent strate­gies that, with­out impos­ing any addi­tional cost in its man­u­fac­ture, upgrade the pro­cess­ing of Californian-style black ripe olives by remov­ing acry­lamide from the final prod­uct and, con­se­quently, tak­ing care of the con­sumer’s health and diet,” Martín-Vertedor and Fernández said.

The two researchers added that the impact of pack­ag­ing on acry­lamide con­tent was a sep­a­rate vari­able that requires fur­ther study to under­stand bet­ter.

“Both in the process and the com­mer­cial­iza­tion, the pack­ag­ing is a steady fac­tor in the acry­lamide for­ma­tion as can be seen in the results of the arti­cle,” Martín-Vertedor and Fernández said. ​“There will be a future study in which the con­tainer is eval­u­ated as another pos­si­ble vari­able in the acry­lamide gen­er­a­tion.”

In a 2019 study, the two researchers found that the addi­tion of phe­no­lic com­pounds, includ­ing hydrox­y­ty­rosol, and olive leaf extract before the ster­il­iza­tion stage also decreased the acry­lamide con­tent from the final prod­uct.

Martín-Vertedor con­cluded that lim­its on the amount of acry­lamide present in table olives should be estab­lished. Baseline lev­els of the com­pound in Hojiblanca olives mea­sure at 254 micro­grams per kilo­gram but are nearly dou­ble that in Manzanilla de Sevilla.

“We con­sider that the min­i­mum lev­els of acry­lamide in table olives mar­keted should be set at val­ues closer to 300 micro­grams per kilo­gram, thus guar­an­tee­ing the health of table olive con­sumers at an inter­na­tional level,” he said.

• Journal of Food Composition and Analysis
• Food Control