What are trans fatty acids primarily formed from?

Trans fatty acids are primarily formed from the process of partial hydrogenation of vegetable oils. During this industrial process, hydrogen is added to oil, which alters its chemical structure and creates trans fats. These fats are typically found in partially hydrogenated oils, which are used extensively in food manufacturing to improve the shelf life and texture of products.

Unlike naturally occurring fatty acids found in some animal fats, trans fats are mostly a result of human processing. This is why the choice that indicates partially hydrogenated oils is accurate, as it directly represents the primary source for trans fatty acids in the food supply.

Natural fermentation processes refer to the way certain foods may develop flavors or textures but do not produce significant amounts of trans fats. While certain animal fats contain small amounts of naturally occurring trans fats, they are not the primary source in the diet. Fried foods may contain trans fats if they are prepared with partially hydrogenated oils, but they are not a direct source in the same way that the oils themselves are. Thus, the best answer is the one highlighting partially hydrogenated oils.