Researchers Show How Crushing Speed Affects Yield and Quality

Quality parameters were unaltered by crushing speed, but extraction efficiency and chlorophylls content increased with faster hammer mill rotor speed in a continuous industrial process.

Oct. 10, 2017
By Olive Oil Times Staff

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Researchers have ana­lyzed how mod­i­fy­ing the ham­mer mill rotor speed affects the extrac­tion effi­ciency, qual­ity, phe­no­lics, volatiles and sen­sory pro­file of olive oils from super-high-den­sity planted Arbosana olives processed in an indus­trial facility. 

The study, Impact of indus­trial ham­mer mill rotor speed on extrac­tion effi­ciency and qual­ity of extra vir­gin olive oil, will be pub­lished in the March 2018 jour­nal Food Chemistry.

The team included Selina Wang and Juan Polari of the University of California at Davis; David Garcí-Aguirre of Corto Olive Co.; and Lucía Olmo-Garcia and Alegría Carrasco-Pancorbo of the University of Granada.

The results revealed that qual­ity para­me­ters such as free fatty acid­ity (FFA), per­ox­ide value (PV), UV absorbances, dia­clyg­lyc­erols (DAGs) and Pyropheophytins (PPP) were unal­tered by crush­ing speed, but extrac­tion effi­ciency and chloro­phylls con­tent increased lin­early with faster ham­mer mill rotor speed in a con­tin­u­ous indus­trial process. 

Quantitative val­ues of total phe­nols and some indi­vid­ual phe­no­lic com­pounds, such as 3,4‑DHPEA-EDA and p‑HPEA-EDA, increased with rotor speed. Similarly, the level of triter­penic com­pounds, such as oleano­lic acid and maslinic, increased sig­nif­i­cantly when higher crush­ing speeds were applied.

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This is not only the first study on the effect of ham­mer mill speed in the indus­trial scale olive oil pro­cess­ing facil­ity but the first peer-reviewed arti­cle on olive oil pro­cess­ing pub­lished from a U.S. insti­tu­tion,” said Wang. It also show­cased the col­lab­o­ra­tion between acad­e­mia and indus­try” to iden­tify a rel­a­tively minor pro­duc­tion adjust­ment that pro­duc­ers can employ to improve yield along with cer­tain aspects of EVOO quality.

When asked why the ham­mer speed led to higher phe­nol lev­els in the research, Wang said her team hypoth­e­sized that the esca­lated cut­ting action on the olive fruit poten­tially released more phe­no­lic com­pounds result­ing in higher lev­els in the oil by decreas­ing the oil droplets diam­e­ter, aug­ment­ing the oil/water emul­sion inter­phase area and facil­i­tat­ing the mass trans­fer of phe­nols to the lipid phase after the action of β‑glucosidase.”

Higher lev­els of phe­no­lic com­pounds would increase the shelf life of an oil and lead to greater health ben­e­fits to consumers.


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