Canola oil and corn oil are sometimes mistaken for the same product although they are made from different plants and have discernible taste differences. Here is a little background on these commonly used vegetable oils and how they compare to each other in terms of taste and nutrition.
Canola oil is made from rapeseed, an oilseed plant that has been cultivated since ancient times as a fuel source. In the 1970's, Canadian plant scientists came out with a genetically modified version of rapeseed that produces an oil with a different nutritional profile and much less erucic acid than oil derived from the naturally occurring plant. The resulting oil was dubbed "Canola" which stands for "Canadian oil, low acid".
Canola oil is commonly used in frying, but only with medium frying temperatures, about 450 degrees F. It is also used for marinades, salad dressings, margarine, in recipes that call for vegetable oil, and to grease cake pans and cookie sheets. Non-food uses for canola oil include animal feed, industrial lubricants, biofuels, candles, lipsticks, and newspaper inks.
Corn oil is made from corn germ by a combination of mechanical pressing and solvent extraction. (The germ is the solid part of a corn kernel - it is essentially a seed). It is one of the most common cooking oils, where its high smoke point makes it ideal as a frying oil. It is also used in margarines and in recipes that call for vegetable oil. Non-cooking uses include biodiesel, soap, salve, paint, inks, textiles, nitroglycerin, and insecticides.
Corn oil is generally less expensive than other types of oil although its price has increased in recent years as the demand for corn for ethanol and food products has grown.
Corn oil and canola oil both have a relatively neutral taste compared to oils like olive oil with canola oil being milder tasting than corn oil. Corn oil tends to impart a slight roasted corn taste to foods made from it at room temperature - such as mayonnaise - that some people find offensive. However, this same corn taste enhances the flavor of certain cooked foods such as popcorn and French fries.
When canola oil is heated to high temperatures such as during deep-frying, the unsaturated fatty acids in the oil break down and take on a subtle fishy taste that some people find disagreeable. Corn oil does not produce this fishy taste.
Canola oil is considered one of the healthiest of the cooking oils because of its low saturated fat (about 7%) and high monounsaturated fat (63%) content. It is a healthier oil than corn oil which is relatively low in terms of unhealthy saturated fat (12%) but lower in healthful polyunsaturated fats (28%) and omega-3 fatty acids. Only flaxseed oil surpasses canola oil in its content of cardio-protective omega-3 fatty acids. Some studies have also indicated that canola oil may have inhibitory effects on breast cancer although further research is needed.