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Whereas the sterols and fatty acid pro­file of olive oil are exam­ined to assure authen­tic­ity, other tests are aimed at assess­ing qual­ity and fresh­ness.

The free fatty acid level, per­ox­ide value and UV absorbency are the tra­di­tional tests used for this pur­pose. Two other tests that have been in use in the Northern European olive oil trade since at least 2006 mea­sure pyropheo­phytin (PPP) and dia­cyl­glyc­erols (DAGs).

Pyropheophytins (PPP) are chloro­phyll pig­ment break­down com­pounds from the ther­mal degra­da­tion of olive oil. Heat and long stor­age time break down chloro­phyll into pheo­phytins then into PPP. Used to indi­cate the pres­ence of adul­ter­ation with refined oil.

The PPP test mea­sures degra­da­tion prod­ucts of chloro­phyll in olive oil. This degra­da­tion of chloro­phylls to pyropheo­phytin was found to take place at a pre­dictable pace mak­ing it pos­si­ble to gain infor­ma­tion about the age of an olive oil. The rate at which the degra­da­tion occurs can be accel­er­ated by even short peri­ods at high tem­per­a­tures — such as those present dur­ing the deodor­iz­ing or soft col­umn refin­ing process — mak­ing it a use­ful indi­ca­tor of the pres­ence of deodor­ized olive oil as well as of the age of an oil.

The DAGs test mea­sures the pro­por­tion of two forms of dia­cyl­glyc­erol: 1,2 and 1,3. In oil freshly made from sound, good qual­ity olives, the preva­lent form of DAG is the 1,2 form, where the fatty acids are bonded to a glyc­erol mol­e­cule in the 1 and 2 posi­tions. The bond on the 2 posi­tion is weak and eas­ily bro­ken, lead­ing to the migra­tion of that 2 posi­tion fatty acid to the 3 posi­tion. This results in the much more sta­ble 1,3 DAG. This makes the ratio of 1,2 DAGs to the total DAGs a good indi­ca­tor of the qual­ity of the olive fruit and the pro­cess­ing. It is also an indi­ca­tor of the age of an oil, since the migra­tion from 1,2 to 1,3 DAGs takes place nat­u­rally as oil ages. Warmer stor­age tem­per­a­tures and higher free fatty acid lev­els will both accel­er­ate this process, but DAGs are not affected by the short expo­sure to high heat that is char­ac­ter­is­tic of deodor­iz­ing.

For more quick answers to your olive oil ques­tions, ask Ollie — a bot devel­oped by the Olive Oil Times Education Lab that uses arti­fi­cial intel­li­gence to help peo­ple learn more about olive oil.