Preserving and Storing Olive Oil
All oils, especially extra-virgin olive oils and other unrefined oils, are best kept away from heat and light.
At the mill, the oil produced has to be stored for a relatively long period until it is sold. The best storage tanks are made of materials to protect the oil from air and light, and are kept at relatively constant temperatures. The oil should be kept indoors in covered stainless steel tanks or steel-plated tanks lined with epoxy or similar safe resins.
However, if the tanks are stored outdoors, they should be coated with an external lining to prevent extreme changes in temperature. In all cases, the tanks should have slanted or conical bottoms that allow for drainage of accumulated impurities. All oils intended for human consumption are prepared under proper hygienic conditions and packed in metal cans and tins lined with suitable varnishes, and in glass bottles.
The containers have to be filled to at least 90% capacity so that no harmful air pockets are left. Each container bears a label stating both the generic and the specific designation of the oil, its acidity level expressed in degrees, its net content expressed in weight or volume, the name of the bottler, manufacturer or distributor, and the country of origin.
Extra-virgin olive oil is at its best when it is just pressed because this is when its organoleptic characteristics are most distinct, and the oil’s flavor is most intense. Olive oil should be consumed as quickly as possible or it will start oxidizing and consequently decline in quality and taste.
The oxidation curve is sharper for mild olive oil, meaning that once bottled, it will remain palatable for less time. All olive oil will inevitably become rancid over time, but the process can take up to three years; fruity-spicy olive oil stays good the longest. At home, to preserve the freshness of your precious bottle of extra-virgin olive oil for as long as possible, store it in a cool, dark spot; the ideal spot would be a cabinet far from the stove.
Olive oil can be refrigerated but it solidifies, so it should be taken out a few minutes to return to room temperature before use. Tinted glass, porcelain, or stainless steel are the best materials for containers; oil should never be stored in plastic or in reactive metals.