The University of Ioannina.

Extra vir­gin olive oil pack­aged in bag-in-box con­tain­ers retained its qual­ity for longer peri­ods of time and under harsher con­di­tions than extra vir­gin olive oil stored in tin-plated steel con­tain­ers, accord­ing to a recent study from the University of Ioannina, in Greece.

“Statistical analy­sis showed that sam­ples pack­aged both in tin-plated steel and in bag-in-box con­tain­ers were affected by stor­age tem­per­a­ture but those stored in bag-in-box con­tain­ers were less affected,” the researchers wrote in the study.

The main prac­ti­cal impli­ca­tion is that the bag-in-box con­tainer pro­vides excel­lent pro­tec­tion to olive oil from both light and oxy­gen.- Michael Kontominas, pro­fes­sor at University of Ioannina

The researchers found that olive oil stored in bag-in-box con­tain­ers main­tained its extra vir­gin clas­si­fi­ca­tion for the entire 120 day trial when stored at room tem­per­a­ture (71.6 degrees Fahrenheit) and had a 100 day shelf-life when stored at abuse tem­per­a­tures (98.6 degrees Fahrenheit).

The olive oil sam­ples stored in the tin-plated steel con­tain­ers could no longer rank as extra vir­gin after 80 days of stor­age at room tem­per­a­ture and only 60 days of stor­age at abuse tem­per­a­tures.

See more: Olive Oil Research News

“The main prac­ti­cal impli­ca­tion is that the bag-in-box con­tainer pro­vides excel­lent pro­tec­tion to olive oil from both light and oxy­gen, as there is no head­space filled with air at any time dur­ing its use,” Michael Kontominas, the lead author of the study and a pro­fes­sor at the University of Ioannina, told Olive Oil Times.

“This is bet­ter pro­tec­tion than that pro­vided by tin-plated steel and most prob­a­bly by dark-col­ored glass, which remains to be proven,” he added.

Kontominas and his research team took four sam­ples of Koroneiki extra vir­gin olive oil har­vested in the exact same man­ner and placed two sam­ples in the tin-plated steel con­tain­ers and placed the other two sam­ples in bag-in-box con­tain­ers. One of each of these sam­ples was stored at 71.6 degrees Fahrenheit and the other of each was stored at 98.6 degrees Fahrenheit.

“Experimental con­di­tions cho­sen [the oils stored at room tem­per­a­ture] are those sim­i­lar to super­mar­ket stor­age con­di­tions,” Kontominas said. “The abuse tem­per­a­ture of 98.6 degrees Fahrenheit was cho­sen to sim­u­late mostly home tem­per­a­ture con­di­tions encoun­tered dur­ing the sum­mer months in the Mediterranean area.”

These abuse tem­per­a­tures are also fre­quently expe­ri­enced by olive oil being trans­ported in non-air con­di­tioned trucks and ship­ping con­tain­ers dur­ing sum­mer months.

During the exper­i­ment, Kontominas and his research team tested sev­eral extra vir­gin olive oil qual­ity para­me­ters every 20 days: free acid­ity, per­ox­ide value and two absorp­tion coef­fi­cients.

The oleic acid con­tent of the oils increased at vary­ing rates over time, with a more rapid increase tak­ing place at higher tem­per­a­tures and in the tin-plated steel con­tain­ers. As acid­ity rises above 0.8 per­cent, olive oil can no longer be qual­i­fied as extra vir­gin.

The olive oil sam­ples con­tained in bag-in-box con­tain­ers did not exceed the 0.8‑percent acid­ity thresh­old at room tem­per­a­ture over the 120-day test period and only did so in the abuse stor­age con­di­tions after 100 days. The sam­ples con­tained in tin-plated steel con­tain­ers reached the max­i­mum acid­ity thresh­old after 100 days at room tem­per­a­ture and 80 days in abuse stor­age con­di­tions.

Regarding per­ox­ide val­ues, another mea­sure of extra vir­gin olive oil qual­ity, three of the four sam­ples remained within the para­me­ters nec­es­sary to qual­ify as extra vir­gin with the excep­tion of the sam­ple stored in tin-plated steel at abuse tem­per­a­tures.

The same pat­tern held true when the researchers mea­sured the absorp­tion coef­fi­cients of the sam­ples – a mea­sure of how much ultra­vi­o­let light the oil can absorb before los­ing its extra vir­gin qual­i­fi­ca­tion. Only sam­ples stored in tin-plated steel con­tain­ers at abuse tem­per­a­tures exceeded the para­me­ters for extra vir­gin olive oils, which hap­pened after the 60-day mark.

“It is obvi­ous that at abuse tem­per­a­tures the bag-in-box con­tainer proved supe­rior to the tin can as doc­u­mented by all four olive oil qual­ity para­me­ter val­ues,” the researchers wrote in the study.

“Abuse stor­age tem­per­a­tures and the exces­sive pres­ence of oxy­gen, as a result of the head­space cre­ated in the tin-plated con­tainer after each sam­pling, resulted in a more rapid dete­ri­o­ra­tion of oil qual­ity for the sam­ples stored in tin-plated steel con­tain­ers as the pres­ence of oxy­gen enhances oxi­da­tion,” they wrote.

Kontominas said that he was not sur­prised by any of these results. In fact, they con­firmed what he had assumed, which was that bag-in-box con­tain­ers are supe­rior to other ones.

“I expected some kind of a pos­i­tive effect of the bag-in-box pack­age on olive oil qual­ity reten­tion given the absence of oxy­gen within the pack­age, some­thing that can­not be avoided in dark-col­ored glass or tin-plated steel con­tain­ers with repeated removal of olive oil from the pack­age over time,” he said.

Kontominas and the research team are already in the process of repeat­ing the exper­i­ment again with dark-col­ored glass bot­tles. Once they have these results, the team will move on to deter­min­ing the effect of low ver­sus high phe­no­lic olive oil con­tent on prod­uct qual­ity reten­tion dur­ing stor­age.



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