Walnut oil is oil extracted from walnuts.
Walnut oil is not used as extensively as other oils in food preparation due to cost. It is light-coloured and delicate in flavour and scent, with a surprisingly nutty quality. Although sometimes used for pan frying, most chefs do not use walnut oil for high temperature cooking, as heating can remove some of the oil's flavour and produce a slight bitterness; instead it is used primarily as an ingredient in cold dishes such as salad dressings, where its flavour more easily comes through. In addition, the antioxidants present in the oil are easily destroyed in cooking. Most walnut oil is produced in France, though there are also producers in Australia, New Zealand and California.
Walnut oil was one of the most important and vital oils used by Renaissance painters. Its quickness of drying and lack of yellow tint make it a good oil paint thinner and brush cleaner. However, the paint film it produces is often considered inferior to that of linseed oil.
Commercially, walnut oil has become harder to find; demand is often low, and stock can become rancid if kept improperly. Instead of walnut oil many artists and stores sell linseed oil, poppyseed oil, and safflower oil as replacements.
On the other hand, walnut oil is favoured by some woodworkers as a finish for implements that will come in contact with food, such as cutting boards and wooden bowls.