There is probably no other single factor more responsible for the degradation of olive oil than improper packaging and storage. Olive oil is highly perishable and breaks down when exposed to ultra violet light. Never store olive oil in clear plastic or glass containers for a prolonged period of time. In addition, olive oil oxidizes when exposed to air. The larger the surface area exposure the more rapid oxidation occurs. Once an olive oil container is opened the natural breakdown and increase in peroxide values is accelerated, creating rancid oil. Partially filled containers deteriorate much more rapidly.
On your next trip to the gourmet store, notice that nearly all high-quality olive oil is packaged in UV protected packages. Olive oil will soften in flavor and intensity if exposed to light for a prolonged period of time. If the olive oil is to be consumed in a short period of time (one to two weeks), then repacking or decanting into clear glass will not noticeably harm the oil if stored in the dark. Avoid olive oil that is packed and displayed on store shelves in unprotected containers.
Over 98% of the olive oil sold in the United States has traveled via ocean freight from the Mediterranean and may have been in the bottle for months before it makes the thirty-to-sixty-day crossing to the United States. It may be months longer before that oil makes its way to the retail outlet where it is finally purchased. This is particularly troublesome when it comes to the more expensive slow moving oils that sit for months in distribution. The problem is compounded by the fact that these same expensive oils are generally not used quickly but left partially used in cupboards for prolonged periods of time. Once the oil is exposed to air and light deterioration is accelerated. It is a fact that much of the olive oil consumed in the United States is rancid before it is completely consumed. It is also true that a significant portion of olive oil sold in the United States is rancid before it is even purchased and would fail to pass a grading test if it had to be retested.
Many consumers do not actually taste the olive oil before they use it. Olive oil is a spice. Taste and smell the oil before you use it. If the olive oil has so much as a hint of rancidity, return it. Avoid olive oils that do not have a clear packaging date. Avoid oils that have been in the bottle or container for more than six months. Oils packed in clear unprotected containers will deteriorate much more rapidly than UV protected ones. It is preferable to purchase oil packed from bulk stocks stored in the United States under optimum conditions. Olive oil properly stored in bulk tends to age less rapidly and will retain its original characteristics longer. When it comes to high quality olive oil, fresher is always better.
This article has been republished with permission from Delizia.