White sediment in bottom of bottle of Canola oil

[barbitu8]

http://www.ehow.com/how_8632532_prevent-oil-rancidity.html This link refers to polyunsaturated oils, but this refers to all unsaturated oils: Can You Get Sick From Eating Rancid Oil? | livestrong

Olive oil contains both poly- and mono- unsaturated, but more unsaturated.

[barbitu8]

Not that it matters to anyone but me, but I buy half a gallon of pure virgin olive oil (cold-pressed, no heat involved in its extraction) from Costco and use a little for frying, sauteeing, and a lot when I roast chicken. Because I don’t want to continually baste chicken, I use a lot and wrap it in foil so it won’t splatter.

[Michael63129]

@Cheshire_Human

Some do, most don’t. Animal fats are likely to do so, which is why butter goes bad if you leave it out too long. Most vegetable oils are the wrong type of fat to go rancid rapidly. Hence my sesame oil that’s not gone bad in a decade of room temp storage.

It has to do with the saturation of the fat molecule, but I don’t remember what kind of saturated or unsaturated fat goes rancid. If they don’t refrigerate it at the store, you don’t need to, either, unless the package says ‘refrigerate after opening’.

The rapid rancidity of butter likely has more to do with the milk proteins (think of how fast milk spoils when left out) and other molecules it contains, including significant amounts of water to fuel microbial growth, than its fat content or composition (note that saturated fat doesn’t go rancid easily, although significant amounts of unsaturated fat are present in butter).

[barbitu8]

@barbitu8

Chow Down | ehow This link refers to polyunsaturated oils, but this refers to all unsaturated oils: Can You Get Sick From Eating Rancid Oil? | livestrong

Olive oil contains both poly- and mono- unsaturated, but more unsaturated.

I meant “more monounsaturated.”