Hydrogenation
There are two kinds of hydrogenation. The first one is the kind we’re all familiar with, where a polyunsaturated fat is purposefully converted to a trans fat. This is the kind that requires mentioning on the label. The second kind is when the conversion to a trans fat occurs as a ’side effect’ of some other process. For example, canola oil has a wretched smell in its native state and requires deodorization to be fit for selling. This deodorization process creates trans fats. These trans fats are not reflected on the label. For this reason, I avoid canola oil or foods made with it if I can.