Why should olive oil be kept in a cool, dark place and in a dark bottle if it's stable?

From: 
Shayne
Question: 

Why on the one hand olive oil is stated by many credible bodies to be "stable at high temperatures", yet packaging and storage stipulations state that it should be kept in a cool dark place, in a dark bottle? I'm sure there's a simple explanation for this apparent inconsistency.

Source: 
Olive Oil News
Answer: 

One issue is smoke point, the other is the tendency to oxidize, ie go rancid. Olive oil has a high smoke point so is "stable" to fry with.

All oils go rancid with heat, light and exposure to oxygen. Some are more prone to this, such as walnut, hazelnut and sesame oils which quickly go rancid and really should be kept in the refrigerator. Oils with low acidity and high antioxidants last longer on the shelf and tend to oxidize more slowly at high frying temperatures. A "stable" oil can be used 4-5 times. Extra Virgin Olive oil by definition has nothing added, high antioxidants and low acidity. Most seed oils such as corn, canola and safflower are inedible and unusable unless they are refined to remove acidity and have artificial antioxidants added to extend shelf life.

Even though Extra virgin olive oil and the seed oils are stable, they will go rancid if kept in a hot place in the light. I have thrown bottles of corn oil or sunflower seed oil in the garbage because they have passed their time. I have a real hard time keeping sesame oil beyond about 4 months even in a dark cool cabinet. A rancid oil might be fine for frying but I wouldn't want it on my salad.

One of the reasons that olive oil bottles make a bigger deal about this is because it can be 10 times more expensive and is supposed to have a flavor. Who cares if the canola oil is a little off, it didnt taste much to begin with and if it needs to be tossed, it's cheap to replace. Unfortunately, because it is a premium oil, I have heard of people keeping an expensive bottle of olive oil for years waiting for that special occasion, with unfortunate consequences.

Date: 
Monday, June 11, 2007

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