Question: A local natural foods store recently held a seminar on cooking oils. The talk favored olive oil over alternatives, but it said that when you open any bottle of cooking oil, such as corn, safflower, canola or peanut, the oxygen in the air immediately begins spoiling the oil. They said this was a “hidden cause of disease.” They advised refrigerating all cooking oils after opening. However, product labels make no mention of any need to refrigerate. What do you recommend?
DR. BLONZ: It is true that air gets in when you open the bottle, and the oxygen in the air participates in the oxidation reactions associated with spoilage. However, it’s a slow process under normal conditions, and there is no evidence to fear that your oil, or your body, is at risk.
You can keep oils at room temperature, but you should follow some simple guidelines: Keep oils out of the sunlight and away from heat. And always keep the container sealed when not in use. Avoid buying amounts in sizes greater than you typically use in three to four months.
There’s no problem with storing oil in the refrigerator, but if you decide to go that route, be sure to have a tight seal on the container to keep the oil from picking up any undesirable refrigerator odors. Some oils may become cloudy when refrigerated, but this disappears when they return to room temperature.
Oils can go rancid if they are mistreated or stored in the wrong way. Rancidity does occur when an oil reacts with oxygen, and aside from giving foods an “off” taste, the consumption of oxidized oil does represent a health risk. The greater the degree of unsaturation (double bonds), the greater the tendency to oxidize. Omega-3 oils, such as flax or fish oil, have more double bonds than other oils, so they are very susceptible to spoilage. This helps explain the nasty aroma of fish left at room temperature for an extended period of time."Use caution when storing olive oil" - DR. BLONZ advices,