Whether you’re deep frying or pan frying a fish, the oil you use must have a high enough smoke point -- the temperature at which the oil starts to smoke and release impurities -- to hold up under this high-heat cooking method. You might also want to consider the nutrition content of the oil and its ability to cook the fish without interfering with the flavor.
The most common type of cooking oil, vegetable oil comes in varieties such as corn, canola and a blend of different vegetables. Most vegetable oils are polyunsaturated fats (with the exception of canola oil, a monounsaturated fat), which means they can help lower cholesterol levels. Its neutral flavor and high smoke point, 450 degrees Fahrenheit for corn, allows it to cook at high temperatures without compromising the flavor of the fish.
As the name implies, nut oil comes from nuts like peanuts, cashews and almonds. Nut oils typically have high smoke points -- 440 degrees F for peanut oil -- making it suitable for deep frying or pan frying fish. These monounsaturated fats can also help lower cholesterol levels. Depending on the type of nut, the oil can have subtle to mild taste and smell, which may or may not be desirable depending on your recipe.
Different types of olive oil come with varying smoke points (typically around 400 to 450 degrees F). Another type of monounsaturated fat, olive oil can be classified as extra-virgin, light, pure or refined.
Olive oil works for a quick pan fry, but it is not recommended for any deep frying. Extra-virgin olive oil has a smoke point of 320 degrees F and should not be used for any prolonged frying. Virgin olive oil and extra-light olive oil have smoke points higher than 400 degrees F and work for any type of pan frying.
Seed oils come from seeds that include sesame, coconut and sunflower. Seed oils have a heavy flavor that can transfer to the fish. They have medium to high smoke points (coconut at 350 degrees F and sesame at 410 degrees F) and can be polyunsaturated or saturated fats. Saturated fats like coconut oil can cause high cholesterol and are not recommended for frying fish. For frying a fish, it's better to go with seed oils that have higher smoke points and are monounsaturated or polyunsaturated fats.
Refined and Unrefined Oils
You must also keep in mind whether you're buying unrefined or refined oil for your fish frying needs. The difference is that unrefined oils are just oils extracted from whatever source it came from, be it vegetable or olive, and bottled without any processing. Unrefined oils have a strong taste and odor as a result of this. They also have lower smoke points, between 220 degrees F and 330 degrees F, making them inadequate for any prolonged frying.
Refined oils, however, undergo a process to remove any substances that can cause unwanted colors or flavors from appearing in the oils. Most refined oils have high smoke points in the 400 degrees F range.