After analyzing the oils during both production and packaging, Baianos team found that antioxidant activity remained unchanged throughout the first three months of storage. However, by the six-month mark, most of the oils had lost about 40 percent of their antioxidant properties.
Diekman expressed little surprise with the findings.
"Although this might surprise a lot of people who would expect that if something stays sealed it will not lose nutritional value, antioxidants are very fragile," she noted. "And, of course, in general, it is well known that when we look at plant foods as a whole, the nutritional value is best the fresher it is."
"So, the message here is that when we go shopping, we need to think about the quantity of produce and fresh foods that we buy," Diekman advised. "This is true whether we're talking about the actual food -- for example, olives -- or whether it is the olive oil derived from the food. The question should be: 'Can you use it within a reasonable period of time?' Because from a nutritional standpoint, big quantities may not be a real dollar savings, when you look at the loss of nutritional value that will occur over time."
Diekman also suggested that consumers should generally favor tinted containers over clear ones, to protect antioxidant, vitamins and minerals from exposure to the sun. In that regard, the authors of the Italian study specifically noted that extra virgin olive oil should ideally be stored in small glass bottles placed in a dark setting at room temperatures ranging from 68 degrees to 77 degrees Fahrenheit.
For more on antioxidants, visit the U.S. National Library of Medicine.
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