Walnut oil is oil extracted from English walnuts (also known as Persian walnuts). Each 100.0g of oil provides about 63.3g polyunsaturated fatty acids, 22.8g monounsaturated fats, and 9.1g saturated fats. It contains no cholesterol. It is about 22.2% monosaturated oleic acid, an omega-9 fatty acid, 52.9% linoleic acid, an essential polyunsaturated omega-6 fatty acid, and 10.4% alpha linolenic acid, which supplies the body with needed omega-3 fatty acids, another form of polyunsaturated fatty acid essential to human nutrition.
A cup of California roasted walnut oil
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; heating tends to reduce the oil's flavour & nutritive value and to produce a slight bitterness. In addition cooking rapidly destroys the oil's antioxidants. Walnut oil is at its most valuable in cold dishes such as salad dressings, where it lends its flavour to best advantage.
Over 99% of walnut oil sold in the USA is produced in California. There are also producers in France, Australia and New Zealand.
There are two types of walnut oil commercially available: cold pressed, and refined. 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 400 degrees F. Both methods produce food grade culinary oils. However, cold pressing preserves more of the nutrients and flavour.
Walnut oil was one of the most important oils used by Renaissance painters. Its short drying time and lack of yellow tint make it a good oil paint base thinner and brush cleaner. However, some practitioners consider walnut oil paint film to be inferior to linseed oil paint film. Walnut oil, like all nut seed and vegetable oils will rancidify and rancidification is accelerated by heat, light, and oxygen. Instead of walnut oil, many artists and stores sell linseed oil, poppyseed oil, and safflower oil as replacements.
Some woodworkers favour walnut oil as a finish for implements that will come in contact with food, such as cutting boards and wooden bowls because of their belief in its safety. People who mix oil & wax to formulate wood finishes value walnut oil as an ingredient because of the edibility of both ingredients. The oil typically is combined with beeswax in a mixture of 1/3 oil to 2/3 beeswax. Others will use mineral oil or its other name butcher block oil. Even though mineral oil is a petroleum based product it is inert and is also used as a laxative.