Vegetable Oils and Their Use for Frying: A Review of Their Compositional Differences and Degradation

This review provides an overview of the main vegetable oils of different botanical origin and composition that can be used for frying worldwide (olive and extra-virgin olive oil, high-oleic sunflower oil, rapeseed oil, peanut oil, rice bran oil, sunflower oil, corn oil, soybean oil, cottonseed oil, palm oil, palm kernel oil and coconut oil) and their degradation during this process. It is well known that during this culinary technique, oil's major and minor components degrade throughout different reactions, mainly thermoxidation, polymerization and, to a lesser extent, hydrolysis. If severe high temperatures are employed, isomerization to trans fatty acyl chains and cyclization are also possible. The factors conditioning frying medium degradation are addressed, including oil composition (unsaturation degree, fatty acyl chain length and "free" fatty acid content, and presence of beneficial and detrimental minor components), together with frying conditions and food characteristics. Likewise, this review also tackles how the frying oil and other processing conditions may impact on fried food quality (oil absorption, texture, flavor and color). Finally, potential health implications of fried food consumption are briefly reviewed.