Walnut oil is oil extracted from walnuts, Juglans regia . The oil contains polyunsaturated fatty acids, monounsaturated fatty acids, and saturated fats. [1] [2] [3]
According to gas chromatographic and HPLC analysis, virgin walnut oil consists of linoleic acid (60–62%). It also contains many phenolc compounds including γ-tocopherol, tanins, and flavanoids. Several of these exhibit antioxidant properties. [2] According to another source, 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%). [1]
Walnuts typically contain high concentrations of phenolics including ellagic acid. [4]
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. [5] 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. [5]
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 °F (200 °C). Both methods produce food-grade culinary oils. Walnut oil, like all nut, seed and vegetable oils can turn rancid.
Over 99% of walnut oil sold in the US is produced in California. [6]
Linoleic acid, the major component of walnut oil, is a "drying oil", which means that in air it polymerizes, forming strong but flexible films, useful in oil paints and varnishes. [7] 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.
Some woodworkers favour walnut oil as a finish for implements that will come in contact with food, such as wooden bowls, because of its safety. Rancidity is not an issue because walnut oil dries when applied to wood in a thin coating. People who mix oil and 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. [8]
A triglyceride is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates as well as vegetable fat. They are also present in the blood to enable the bidirectional transference of adipose fat and blood glucose from the liver and are a major component of human skin oils.
α-Linolenic acid, also known as alpha-linolenic acid (ALA), is an n−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, walnuts, chia, hemp, and many common vegetable oils.
Walnut trees are any species of tree in the plant genus Juglans, the type genus of the family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, 10–40 metres (33–131 ft) tall, with pinnate leaves 200–900 millimetres (7.9–35.4 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya), but not the hickories (Carya) in the same family.
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of edible plants. Like animal fats, vegetable fats are mixtures of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fats from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of plants. In common usage, vegetable oil may refer exclusively to vegetable fats which are liquid at room temperature. Vegetable oils are usually edible.
Coconut oil is an edible oil derived from the kernels, meat, and milk of the coconut palm fruit. Coconut oil is a white solid fat below around 25 °C (77 °F), and a clear thin liquid oil at higher temperatures. Unrefined varieties have a distinct coconut aroma. Coconut oil is used as a food oil, and in industrial applications for cosmetics and detergent production. The oil is rich in medium-chain fatty acids.
A saturated fat is a type of fat in which the fatty acid chains have all single bonds between the carbon atoms. A fat known as a glyceride is made of two kinds of smaller molecules: a short glycerol backbone and fatty acids that each contain a long linear or branched chain of carbon (C) atoms. Along the chain, some carbon atoms are linked by single bonds (-C-C-) and others are linked by double bonds (-C=C-). A double bond along the carbon chain can react with a pair of hydrogen atoms to change into a single -C-C- bond, with each H atom now bonded to one of the two C atoms. Glyceride fats without any carbon chain double bonds are called saturated because they are "saturated with" hydrogen atoms, having no double bonds available to react with more hydrogen.
Linseed oil, also known as flaxseed oil or flax oil, is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant. The oil is obtained by pressing, sometimes followed by solvent extraction.
Hemp oil is oil obtained by pressing hemp seeds. Cold pressed, unrefined hemp oil is dark to clear light green in color, with a nutty flavor. The darker the color, the grassier the flavour. It should not be confused with hash oil, a tetrahydrocannabinol-containing oil made from the Cannabis flower.
Grape seed oil is a vegetable oil derived from the seeds of grapes. Grape seeds are a winemaking by-product, and oil made from the seeds is commonly used as an edible oil.
Cottonseed oil is cooking oil from the seeds of cotton plants of various species, mainly Gossypium hirsutum and Gossypium herbaceum, that are grown for cotton fiber, animal feed, and oil.
A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature. The oil hardens through a chemical reaction in which the components crosslink by the action of oxygen. Drying oils are a key component of oil paint and some varnishes. Some commonly used drying oils include linseed oil, tung oil, poppy seed oil, perilla oil, castor oil and walnut oil. The use of natural drying oils has declined over the past several decades, as they have been replaced by alkyd resins and other binders.
Linoleic acid (LA) is an organic compound with the formula HOOC(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are cis. It is a fatty acid sometimes denoted 18:2 (n−6) or 18:2 cis-9,12. A linoleate is a salt or ester of this acid.
Sesame oil is an edible vegetable oil derived from sesame seeds. The oil is one of the earliest-known crop-based oils. Worldwide mass modern production is limited due to the inefficient manual harvesting process required to extract the oil. Oil made from raw seeds, which may or may not be cold-pressed, is used as a cooking oil. Oil made from toasted seeds is used for its distinctive nutty aroma and taste, although it may be unsuitable for frying, which makes it taste burnt and bitter.
In biochemistry and nutrition, a monounsaturated fat is a fat that contains a monounsaturated fatty acid (MUFA), a subclass of fatty acid characterized by having a double bond in the fatty acid chain with all of the remaining carbon atoms being single-bonded. By contrast, polyunsaturated fatty acids (PUFAs) have more than one double bond.
Corn oil or maize oil (British) is oil extracted from the germ of corn (maize). Its main use is in cooking, where its high smoke point makes refined corn oil a valuable frying oil. It is also a key ingredient in some margarines. Corn oil is generally less expensive than most other types of vegetable oils.
Soybean oil is a vegetable oil extracted from the seeds of the soybean. It is one of the most widely consumed cooking oils and the second most consumed vegetable oil. As a drying oil, processed soybean oil is also used as a base for printing inks and oil paints.
Sunflower oil is the non-volatile oil pressed from the seeds of the sunflower. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient.
In biochemistry and nutrition, a polyunsaturated fat is a fat that contains a polyunsaturated fatty acid, which is a subclass of fatty acid characterized by a backbone with two or more carbon–carbon double bonds. Some polyunsaturated fatty acids are essentials. Polyunsaturated fatty acids are precursors to and are derived from polyunsaturated fats, which include drying oils.
Pistachio oil is a pressed oil, extracted from the fruit of Pistacia vera, the pistachio nut.
Cooking oil is a plant or animal liquid fat used in frying, baking, and other types of cooking. Oil allows higher cooking temperatures than water, making cooking faster and more flavorful, while likewise distributing heat, reducing burning and uneven cooking. It sometimes imparts its own flavor. Cooking oil is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips.