Even Dark Glass Bottles Leave EVOO Susceptible to Oxidation, Study Finds

Extra virgin olive oil in dark glass bottles suffers significant degradation in supermarket-like conditions, researchers in Italy found.

Under certain conditions, glass bottles may hinder extra virgin olive oil’s resilience to oxidation, reduce its healthy properties and modify its flavour, according to new research out of Italy.

In the study, the researchers observed what happened to extra virgin olive oil over time when stored inside different kinds of bottles and packages.

When subjected to supermarket-like conditions for more than a few weeks, both green glass bottles and darkened bottles did not adequately protect their high-quality contents.

“The time has come to put some more effort into extra virgin olive oil packaging and protection while on sale or when shipped overseas,” said Maurizio Servili, co-author of the research and food science and technology professor at the University of Perugia.

In the study, the researchers exposed several samples of extra virgin olive oil to different conditions over time. The samples were bottled in green glass containers, ultraviolet-grade absorbing glass and multilayer plastic-coated paperboard aluminum foil.

They measured the chemical changes that took place within each oil, focusing on the modifications in the quantity and quality of its phenols, polyphenols, volatile compounds and sensory attributes.

The researchers also measured the specific alterations caused by chlorophyll.

“Chlorophyll is among the extra virgin olive oil components and plays a big role in modifying the quality profile of a bottle over time,” Servili told Olive Oil Times. “It does not happen with any other oil because it is practically absent in most other fats such as sunflower or soybeans seed oils.”

“Nowadays, it is unusual, but it once happened quite often, to spot on a supermarket shelf an extra virgin olive oil bottle turned somewhat orange,” he added, explaining that this happened because traditional glass bottles let the light through and triggered chlorophyll. More

Read the research article Overall quality evolution of extra virgin olive oil exposed to light for 10 months in different containers here