Walnut oil is oil extracted from walnuts, Juglans regia. The oil contains polyunsaturated fatty acids, monounsaturated fatty acids, and saturated fats. Walnut oil is composed largely of polyunsaturated fatty acids (72% of total fats), particularly alpha-linolenic acid (14%) and linoleic acid (58%), oleic acid (13%), and saturated fats (9%). Walnut oil is edible and is generally used less than other oils in food preparation, often due to high pricing. It is light-coloured and delicate in flavour and scent, with a nutty quality. Although chefs sometimes use walnut oil for pan-frying, most avoid walnut oil for high-temperature cooking because heating tends to reduce the oil's flavour and produce a slight bitterness. Walnut oil is preferred in cold dishes such as salad dressings. Cold-pressed walnut oil is typically more expensive due to the loss of a higher percentage of the oil. Refined walnut oil is expeller-pressed and saturated with solvent to extract the highest percentage of oil available in the nut meat. The solvents are subsequently eliminated by heating the mixture to around 200 °C. Both methods produce food-grade culinary oils. Walnut oil, like all nut, seed and vegetable oils can turn rancid.