In cooking, fats used are typically differentiated by whether they are liquid or solid at room temperature, with liquids referred to as oils and solids referred to as lard or shortening. Cooking oil, then, refers to fat in its liquid form. Unsaturated fats like those sourced from plants are liquid at room temperature, while saturated fats like those found in animal foods are largely solid at room temperature. Exceptions include palm and coconut oil, which are semisolid plant oils comprising both kinds of fat. Therefore, cooking oil always comes from plants, with the most popular varieties including olive oil, canola oil, corn oil, and soybean oil, as well as the aforementioned palm and coconut oils.
Studies of the benefits of unsaturated fat consumption paired with the growing awareness of the health concerns presented by a diet rich in animal fat have led to the widespread use of plant oils for cooking as an alternative to butter and lard. Among the most popular are vegetable oil and olive oil. An oil labeled simply as vegetable oil is typically a blend of plant oils ® largely soybean oil ® and while its ratio of monounsaturated, polyunsaturated, and saturated fatty acids may vary, it is roughly 85 percent unsaturated fat. Olive oil is valued for its high ratio of unsaturated to saturated fats, with approximately 73 of every 100 grams coming from monounsaturated fat, 11 from polyunsaturated fat, and 14 from saturated fat. By contrast butter is nearly 63 percent saturated fat.
Canola oil, corn oil, and sunflower oils are other common varieties of cooking oil, ranging from 84 percent unsaturated fat in the case of sunflower oil to 94 percent in the case of canola oil. Canola oil in particular is widely used for baking and frying. Derived from the rapeseed plant, it is the third most sourced cooking oil, with the soybean oil used in common vegetable oil and palm oil coming in first and second.
Other oils that vary widely in their fat content remain popular in many parts of the world. Palm oil and coconut oil, both semisolid oils sourced from the palm tree, are mostly made up of saturated fat and remain everyday ingredients in tropical regions in South America, Africa, and Southeast Asia. Both are also commonly used in commercial food production as a preservative, as their high saturated-fat content delays rancidity. Peanut oil, by contrast, is 82 percent unsaturated fat and is a staple in Asian cooking, as is sesame oil, another cooking oil made up of mostly unsaturated fat.
Since one cooking oil may respond differently to heat than another, it is recommended that attention be paid to the cooking method when selecting the oil. Those with higher smoke points like avocado, canola, corn, and peanut oils are more tolerant of high temperatures and therefore are better suited to frying. Oils with lower smoke points like extra virgin olive oil, on the other hand, are better suited to lower temperature cooking and dressing salads.