Walnut Oil

Walnut oil is pressed from the walnut, Juglans regia, and is rich in polyunsaturated fat, chiefly linoleic acid at 58 percent and alpha-linolenic acid at 14 percent, along with oleic acid and saturated fat, plus tocopherol and phenolic compounds. It is made either by cold pressing, which yields less oil and costs more, or by expeller pressing with solvents followed by heating to about 400 degrees Fahrenheit to remove solvent residue, with more than 99 percent of United States walnut oil coming from California. Because heating dulls its flavor and can add bitterness, walnut oil is used mainly in cold preparations such as salad dressings, valued for its light color, delicate flavor and nutty character, though its high price limits how widely it is used compared with other oils.