|Raw material plant (noun)|
pale greenish yellow to straw yellow (cold pressed); greenish (hot-pressed)
|Oleic acid||12.7–22.2% (SN: 28–35.6%)|
|Linoleic acid||55.3–64.3% (SN: 48.6–51%)|
|Linolenic acid||10.3-16.2% (SN: 5-7.4%)|
|Palmitic acid||5–8% (SN: 3.4–11%)|
|More fatty acids||Stearic acid 1.7-2.9% (SN: 1.8-5%)|
|Other ingredients||Tocopherol up to 567 mg / kg|
|density||0.92-0.924 kg / l|
|viscosity||= 30.7 mm 2 / s at 40 ° C|
|Oxidation stability||3.9-7.8 h|
|Melting point||−28 ° C|
|Smoke point||160 ° C (unrefined); 205 ° C (refined)|
|Flash point||326 ° C|
|Iodine number||141-158.5 (SN: 135-141)|
|Saponification number||188-194.5 (SN: 190-193.5)|
|Calorific value||39.5 MJ / kg|
|Manufacturing and Consumption|
|Most important production countries||China , Iran , USA, Turkey|
|use||Edible oil , industry|
Walnut oil is a high-quality vegetable oil made from ripe, partially roasted seeds of walnuts ( juglans ). It is from pale greenish yellow to straw yellow in color, relatively thin, has an intense, nutty taste and is characterized by a particularly high content of triglycerides of unsaturated fatty acids . It has a limited shelf life, even when refrigerated.
The highest quality walnut oil is obtained by cold pressing with subsequent filtration . After the nuts have been peeled and chopped, the oil is slowly pressed out of the nuts under pressure. With multiple filtration , unwanted impurities and suspended particles are separated. This gentle process, at below 40 ° C, preserves the valuable ingredients.
The oil obtained by hot pressing or extraction with an organic solvent is inferior from a nutritional point of view compared to the cold-pressed oil. After the solvent was removed by re-heating, is also here a refining of the oil. Refining is necessary because larger amounts of bitter substances get into the oil during extraction . Heating reduces the oil's volume and taste, making it usable.
In hot pressing , the oil is obtained through a very high supply of heat. Subsequent refining removes unwanted substances from the oil. The end product is a tasteless and odorless oil that has a relatively long shelf life. A lot of nutrients are lost due to the high heat.
Due to its smoke point of 160 ° C (unrefined), walnut oil can also be heated, but not used for frying or deep-frying . It is therefore more suitable for cold cuisine, it is popular in French cuisine .
Refined walnut oil is also used in oil painting . It is characterized by its low viscosity, high pigment absorption capacity, relatively quick drying and a low tendency to yellowing with a simultaneous gloss of the surface. Walnut oil is still indispensable today, especially for strongly siccative pigments.
Refined walnut oil is used to treat wooden surfaces, particularly in the Anglo-American region; It is important to have a very smooth wooden surface before the first application. The first layer of the oil is applied with the grain and the supernatant is absorbed after a few hours. The following one or two layers are applied across the grain. The oil film has hardened after 24 hours. The treatment does not lead to permanent protection of the wood, it wears off and must then be repeated.
Due to the long drying time and the periodically repeated application, treatment with walnut oil is mostly only used for wooden surfaces that come into contact with food, e.g. B. kitchen countertops and cutting boards, but especially for untreated wooden toys .
Mixing the walnut oil with real turpentine , by no means turpentine substitute , leads to a deeper penetration of the seal into the wood, but also removes the harmlessness with regard to contact with food.
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