` To Filter or Not Filter? Well, it Depends. - Olive Oil Times

To Filter or Not Filter? Well, it Depends.

Oct. 13, 2015
Olive Oil Times Staff

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Filtered or non-fil­tered? Cloudy or Clear? Asked how they pre­fer their olive oil, peo­ple tend to be in one camp or the other, for rea­sons they’re not quite sure of and often with lit­tle basis in facts.

Producers of extra vir­gin olive oil weigh the impli­ca­tions of fil­ter­ing on the qual­ity of their prod­uct through its shelf life and the often diver­gent pref­er­ences of their cus­tomers.

With the aim of bring­ing a lit­tle clar­ity to the fil­ter-or-no-fil­ter ques­tion, researchers at the University of California at Davis Olive Center set out to review the sci­en­tific evi­dence on the effects of fil­tra­tion. What they found in a report released today, is that, while each option has its pros and cons, the answer remains a lit­tle murky.

The effects of fil­tra­tion depend on the chem­i­cal and sen­sory pro­files, qual­ity of the ini­tial oil, the type of fil­ter aid and sys­tem, and stor­age con­di­tions.- UC Davis Olive Center

To make olive oil, olives are washed and crushed into a paste that is stirred (or, malaxed) before being pressed, or spun in a cen­trifuge. What’s left after remov­ing the water is unfil­tered olive oil.

Those lit­tle bits float­ing around include pieces of olives, water and enzymes that make the oil cloudy in appear­ance. Some peo­ple find unfil­tered olive oil to be more fla­vor­ful. Others look at the omi­nous sed­i­ment at the bot­tom of the bot­tle and think the oil has gone bad.


Filtering the oil removes the sus­pended solids, result­ing in a clearer appear­ance. But it might also remove some of the healthy phe­no­lic com­pounds and actu­ally decrease the shelf life of the oil, depend­ing on the type of fil­ter used.

The sus­pended solids con­tain water and enzymes that impair oil sta­bil­ity, increase fer­men­ta­tion and degrade the oil’s sen­sory qual­ity,” the Davis researchers found. By remov­ing these solids, fil­tered oil has less water activ­ity, clearer appear­ance, less green color, and no deposits in the stor­age con­tainer.”

On the other hand, the lit­er­a­ture also shows that fil­tra­tion can have neg­a­tive impacts on a vari­ety of para­me­ters.”

So which is bet­ter? Filter or unfil­tered? As it turns out, the Davis team dis­cov­ered, research sug­gests the effect of fil­tra­tion depends on the chem­i­cal and sen­sory pro­files, qual­ity of the ini­tial oil, the type of fil­ter aid and sys­tem, and stor­age con­di­tions.”

Which means pro­duc­ers need to take those fac­tors and the myr­iad of other mov­ing parts of olive oil pro­duc­tion into con­sid­er­a­tion to deter­mine which fil­tra­tion tech­nolo­gies, if any, will yield the best results.

As for the rest of us, it could just remain a mat­ter of per­sonal taste.

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