> Refined vegetable oils are deceptive. You can’t tell a rogue from a saint. They all pretty much look alike. They have been purified, deodorized, and stripped of all taste and character. When the oil begins to go rancid, it does not affect the smell or flavor.12 You can eat a very rancid, highly oxidized oil and not even detect any difference, especially if the oil is combined with other foods as it normally is. The only time rancid oils produce an offensive smell and flavor is when they contain impurities such proteins or plant pigments. Free radicals attack these impurities and transform them into putrid-smelling substances. An oil that has been minimally processed and still contains some of its natural plant substances is more likely to produce an offensive smell than a highly processed and purified oil. You can eat rancid oil without realizing it.