Jbob04 said:
If you have to bleach canola oil to make it edible from the smell, I don't think that's something you want in your body. There is zero reason for anyone to use seed oils at home. I wish restaurants would get away from it but they won't since it's cheap.
Just FYI - the bleaching process doesn't involve bleach as in household bleach.
Bleaching refers to a process where the oil is passed through a filter containing natural or activated clays or carbons (that act as sorbents).
Most oils smell unpleasant and have a taste most people would not find acceptable. There are also a lot of undesirable things that have to be removed given that most oils come from a solid plant/seed and the desired product is a liquid.
Solvents that can be used to process the oil include water, organic acids (vinegar is an organic acid), and ethanol (yep, the same one you drink). Hexane can also be used, but there is no reason to scare people over that. It has a low toxicity and because of its low BP is easy to remove down to trace amounts or less. Hexane can also be used to extract other oils (ie, olive and avocado oil).
Other oils, including olive oil and avocado oil, can also be bleached. The process is necessary to produce a more shelf-stable product. Ever open an old container of oil that's been in the back of your pantry? It's gross, and that would happen a lot faster (creating more waste) if these oils weren't refined.