Researchers Investigate Olive Powder as Food Ingredient

The pro­duc­tion of dried olive pow­der has long been pro­posed to reduce waste in the table olive indus­try.

However, dry­ing meth­ods have been asso­ci­ated with poorer nutri­tional pro­files. New research sug­gests that freeze-dry­ing can yield prod­ucts with sig­nif­i­cantly higher phe­no­lic con­tent.

According to the International Olive Council, more than three mil­lion kilo­grams of table olives were pro­duced glob­ally dur­ing the 2022/23 crop year, and pro­duc­tion lev­els con­tinue to rise.

As a result of this pro­duc­tion, more than 150,000 kilo­grams of waste is gen­er­ated, approx­i­mately three to five per­cent of which com­prises olives that fail to meet qual­ity stan­dards due to their size, visual defects or mechan­i­cal dam­age.

Although a great deal of progress has been made in recent years in trans­form­ing olive waste into prod­ucts such as bio­fuel, build­ing insu­la­tion and even super­ca­pac­i­tors, these appli­ca­tions are derived from olive pits.

Despite their high nutri­tional value, the edi­ble dis­cards are gen­er­ally dis­posed of as fer­til­izer or ani­mal feed.

A new study pub­lished in the jour­nal LWT explores the poten­tial of using table olive indus­try dis­cards as a raw mate­r­ial for cre­at­ing table olive pow­der with nutri­tion­ally sig­nif­i­cant lev­els of sub­stances such as oleic acid, fiber, vit­a­mins and phe­no­lic com­pounds.

By con­vert­ing fruit waste into pow­der, the authors hope to enhance sus­tain­abil­ity and reduce waste in the indus­try.

The researchers stud­ied two types of dis­cards, green pit­ted olives and anchovy-stuffed olives, pro­vided by a Spanish table olive pro­ducer.

The dis­carded olives under­went con­vec­tive dry­ing at two dif­fer­ent tem­per­a­tures (50 ºC and 70 ºC) and freeze-dry­ing to pro­duce pow­der sam­ples. Then, the researchers assessed each dry­ing method’s effects on the pow­ders’ nutri­tional com­po­si­tion, antiox­i­dant activ­ity and lipid oxi­da­tion.

Analyses revealed that all pow­ders retained high lev­els of fiber, lipids and pro­tein, although their exact com­po­si­tion depended more on the type of raw mate­r­ial than on the dry­ing process.

Anchovy-stuffed olive pow­ders con­tained higher pro­tein and ash (min­er­als such as sodium, potas­sium, iron and cal­cium) con­tent but lower fiber and lipid lev­els than pit­ted olive pow­ders.

The authors also note that these pow­ders required longer dry­ing times due to higher ini­tial mois­ture con­tent. They added that this pro­longed dry­ing process might con­tribute to sub­tle dif­fer­ences in the pow­ders’ final com­po­si­tion and phys­i­cal prop­er­ties.

The phe­no­lic con­tent, a key mea­sure of bioac­tive prop­er­ties, was high­est in freeze-dried pow­ders, with val­ues exceed­ing 2,500 mg GAE/kg (mil­ligrams of gal­lic acid equiv­a­lents per kilo­gram).

Convective dry­ing, espe­cially at 70 ºC, resulted in sig­nif­i­cant losses of up to 70 per­cent of phe­no­lic com­pounds. This reduc­tion aligns with pre­vi­ous find­ings that high tem­per­a­tures degrade many bioac­tive com­pounds. Freeze-dried sam­ples also main­tained bet­ter antiox­i­dant activ­ity, sug­gest­ing their poten­tial as a source of nat­ural antiox­i­dants.

Moisture con­tent in all pow­ders was reduced to below 2.54 per­cent, ensur­ing long shelf life and resis­tance to micro­bial spoilage.

Lipid oxi­da­tion, mea­sured using per­ox­ide and thio­bar­bi­turic acid indices, was low­est in freeze-dried pow­ders, indi­cat­ing bet­ter sta­bil­ity against ran­cid­ity, another key fac­tor in main­tain­ing qual­ity over time.

Anchovy-stuffed pow­ders exhib­ited higher oxi­da­tion lev­els due to their fish paste con­tent, which con­tains polyun­sat­u­rated fatty acids prone to oxi­da­tion. Nevertheless, the over­all lipid qual­ity of these pow­ders remained within accept­able lim­its, sug­gest­ing their suit­abil­ity for use in food for­mu­la­tions.

In addi­tion to nutri­tional and func­tional prop­er­ties, the study noted vis­i­ble changes in the pow­ders’ appear­ance depend­ing on the dry­ing method.

Convective dry­ing caused brown­ing, reduced light­ness and altered color indices, par­tic­u­larly at higher tem­per­a­tures. Freeze-dried pow­ders retained a more vibrant and con­sis­tent color, which may be more desir­able for com­mer­cial appli­ca­tions in which sen­sory qual­i­ties are val­ued along­side nutri­tional prop­er­ties.

The study con­cluded that freeze-dry­ing is the opti­mal method for pro­duc­ing high-qual­ity olive pow­der due to its abil­ity to pre­serve phe­no­lic con­tent, antiox­i­dant capac­ity and sen­sory qual­i­ties.

However, con­vec­tive dry­ing remains viable for indus­tries that pri­or­i­tize cost-effec­tive­ness and shorter pro­cess­ing times.

The researchers hope their work will pro­vide a foun­da­tion for scal­ing pro­duc­tion and inte­grat­ing table olive pow­der into food for­mu­la­tions such as baked goods, sea­son­ings or health sup­ple­ments.