Natural Olive Oil Preservative as Effective as Synthetic Ones

A new study has found that adding tomato peel extracts to refined olive oil increases the pro­duc­t’s shelf life.

Researchers from the University of Sfax and Ayachi Group Industry in Tunisia com­pared the sta­bi­liz­ing effects of adding ole­o­resin and syn­thetic antiox­i­dants to the oils.

When olive oil is refined some of its nat­ural antiox­i­dants are par­tially elim­i­nated and there­fore must be sup­ple­mented in order to pre­vent the oil from spoil­ing. Olive oil must be refined when the qual­ity is too low to be safely con­sumed. According to the International Olive Council, more than 50 per­cent of olive oil pro­duced in the Mediterranean region is refined.

The group of researchers found that ole­o­resin had com­pet­i­tive antiox­i­dant prop­er­ties with­out the health risks asso­ci­ated with the syn­thetic antiox­i­dants.

Oleoresin is a lycopene-rich extract from tomato peels. Up until a cer­tain point, the com­pound pro­tects olive oil against oxi­da­tion, a process which spoils the oil. The study found that 250 μg/g (micro­grams of ole­o­resin per gram of oil) is the opti­mal ratio.

“The pro­tec­tive effect of tomato peel ole­o­resin (TPO) against the pri­mary oxi­da­tion of these refined oils was sig­nif­i­cantly cor­re­lated to their lycopene con­tents,” Noureddine Allouche, one of the researchers involved with the study wrote in the report. ​“Hence, it can be con­cluded that lycopene rich-TPO is endowed with a com­pet­i­tive free rad­i­cal scav­eng­ing capac­ity with that of syn­thetic antiox­i­dants.”

The syn­thetic antiox­i­dants buty­lated hydrox­yanisole (BHA) and buty­lated hydrox­y­toluene (BHT) were com­pared with TPO in the study. Both of these syn­thetic antiox­i­dants have been labeled as human car­cino­gens. BHA is banned in sev­eral European Union (EU) coun­tries, Japan and California, while reg­u­la­tors from the United States and sev­eral European coun­tries allow small amounts BHT in food prod­ucts.

TPO is a nat­u­rally occur­ring antiox­i­dant that cap­tures free rad­i­cals and helps to pre­vent lipid oxi­da­tion in olive oil, while it is being trans­ported and stored.

However, in con­cen­tra­tions of more than 1000 μg/g, the extract’s effec­tive­ness begins to wane after week 11.

TPO and other nat­ural antiox­i­dants have dis­played proox­ida­tive prop­er­ties at high con­cen­tra­tions and under high oxy­gen ten­sion in foods and emul­sions.

The study also found that TPO’s effec­tive­ness at all con­cen­tra­tions decreases, but does not entirely fade after week 19.

“TPO com­po­nents and mainly carotenoids, e.g. lycopene, were expected to act as pow­er­ful antiox­i­dants pre­vent­ing the oxida­tive reac­tions occur­ring within [refined olive oils].” Allouche wrote. ​“However, for long stor­age peri­ods, carotenoids may have acted as proox­i­dant agents.”

In spite of this, the study con­cluded that using TPO as a preser­v­a­tive is still prefer­able to the syn­thetic antiox­i­dant alter­na­tives.

“TPO extracts from tomato indus­trial byprod­ucts can be used as an effec­tive dietary sta­bi­lizer of [refined olive oil] instead of the syn­thetic preser­v­a­tives, against the oxi­da­tion reac­tions dur­ing long stor­age,” Allouche wrote.

The study, which was funded by the EU, comes at a time of ris­ing pop­u­lar­ity for ole­o­resins on the con­ti­nent. According to the Dutch Center for the Promotion of Imports (CBI), demand for ole­o­resin has increased in many EU and European Free Trade Association coun­tries.

One of the rea­sons for the increase cited by the CBI is the sub­sti­tu­tion of nat­ural ingre­di­ents for syn­thetic ones that is tak­ing place across Europe.

Increasingly health con­scious con­sumers are also look­ing for nat­u­rally pre­served food in the United States, which is already the sec­ond largest importer of olive oil.

“More American con­sumers are jump­ing on the ​‘free-from’ and seek­ing out more nat­ural or less processed foods,” Judie Bizzozero, a man­ag­ing edi­tor at the Natural Products Insider Magazine, said.

“Interestingly, 71 per­cent of ​‘free-from’ con­sumers are look­ing for preser­v­a­tive-free claims on food and bev­er­age label, which opens the door for inno­va­tion in the area of nat­ural antiox­i­dants as food preser­v­a­tives.”

• Science Direct


• CBI