`How Heat, Light and Oxygen Harm Olive Oil - Olive Oil Times
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How Heat, Light and Oxygen Harm Olive Oil

By Julie Butler
May. 22, 2012 14:24 UTC

Researcher Jamie Ayton at the Australian Oils Research Laboratory

A three-year study by Australian sci­en­tists con­firms that oxy­gen, light and heat are indeed among extra vir­gin olive oil’s worst ene­mies.

The study also pro­vides the best avail­able guid­ance for gaug­ing the shelf life and use-by date for olive oils, Jamie Ayton, Rodney J. Mailer and Kerrie Graham state in their report.

The bot­tom line in The Effect of Storage Conditions on Extra Virgin Olive Oil Quality (PDF)” is that olive oil should be stored at cool tem­per­a­tures, away from light and with­out expo­sure to oxy­gen.

Not just in the short term, but through­out the life of the oil, which includes dur­ing the trans­port, stor­age and mar­ket­ing of the oil, as well as when the oil has reached its final destination…the con­sumer” they say.

Otherwise, the olive oil can dete­ri­o­rate so much that it can no longer be clas­si­fied as extra vir­gin olive oil, at a huge expense to grow­ers.”

Test results

The study found that high stor­age tem­per­a­ture and oxy­gen expo­sure neg­a­tively affect the sen­sory pro­file of olive oils. Over time at higher tem­per­a­tures, the com­pounds that cause pleas­ant fla­vors and aro­mas in olive oil change and instead cause unpleas­ant ones. Rancidity devel­ops sooner and free fatty acid lev­els rise faster.

Similarly, when exposed to oxy­gen, ran­cid­ity starts to develop and olive oil’s sen­sory prop­er­ties quickly and sig­nif­i­cantly decline.

Exposure to light causes a sub­stan­tial loss of antiox­i­dants, espe­cially toco­pherols, and an increase in ran­cid­ity com­pared to oil stored in the dark.

Meanwhile, all three affect — though to dif­fer­ent degrees — an oil’s colour. This is impor­tant as the first sen­sory’ assess­ment a con­sumer makes is by assess­ing the colour of the oil they are going to pur­chase” the report says..

Study method

Funded by Australia’s Rural Industries Research and Development Corporation (RIRDC) and the Australian Olive Association, the inten­sive research tracked nine Australian EVOOs over three years, using 882 bot­tles of olive oil.

  • To test the effect of tem­per­a­ture, sam­ples were stored at 15°C, 22°C and 37°C.
  • To test for oxy­gen expo­sure, some were stored with the bot­tle lid only loosely attached and 10 mL of oil was removed each month to ensure the head space in the bot­tle con­tained oxy­gen.
  • To test for light expo­sure, sam­ples were stored in clear bot­tles exposed to sun­light and flu­o­res­cent light.
  • Chemical para­me­ters for oxi­da­tion and age­ing, and the sen­sory char­ac­ter­is­tics of the oils, were analysed every three months.


Lead researcher Jamie Ayton, an edi­ble oils chemist at the New South Wales Department of Primary Industries Australian Oils Research Laboratory, in Wagga Wagga, spoke to Olive Oil Times about the project.

Is there any aver­age shelf life for olive oil? Taking your research into account, how could a pro­ducer cal­cu­late a best-before or use-by date for their olive oil?

Many fac­tors affect the shelf life of an olive oil, such as the ini­tial oil matrix as well as the con­di­tions the oils are stored under. Oils which have low total polyphe­nols lev­els and high lev­els of polyun­sat­u­rated fatty acids will have a shorter shelf life than those which are more robust (i.e. high polyphe­nols and low polyun­sat­u­rated fatty acid con­tent).

As you can see from the results in our report, there is no blan­ket” state­ment which can apply to all oils. The gen­eral indus­try view is that oils which are more than 18 – 24 months old are reach­ing the outer lim­its of their shelf life. Having said that, some of the oils in our project were still clas­si­fied as EVOO after 36 months under rea­son­able” stor­age con­di­tions.

After the oil has dete­ri­o­rated, there are no health impli­ca­tions with using it, it is just that it may no longer be clas­si­fied as EVOO accord­ing to stan­dards cri­te­ria (IOC or AS5264-2011).

What should shops and con­sumers do?

Retailers should ensure that tem­per­a­ture is reg­u­lated suf­fi­ciently. I would sug­gest less than 25 degrees C would be prefer­able. Oils should also have min­i­mal expo­sure to light and radi­ant heat from lights in super­mar­kets.

Prior to this, ware­hous­ing and trans­port con­di­tions should be man­aged in order to have the min­i­mum impact on the oil.

Consumers should fol­low sim­i­lar advice. The oil should be stored in the dark at cool tem­per­a­tures, for exam­ple at the back of a kitchen cup­board — not on the win­dowsill or near the stove top. Once the bot­tle is opened, expo­sure to oxy­gen will occur, there­fore the oil should be used quickly, while still fresh.


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