Walnut oil

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Walnut oil
Walnut oil made from roasted nuts
Raw material plant (noun)

Real walnut ( Juglans regia ); also from the black walnut (SN) ( Juglans nigra )

origin

Seeds (kernels)

colour

pale greenish yellow to straw yellow (cold pressed); greenish (hot-pressed)

ingredients
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
properties
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
Cetane number 33.6
Manufacturing and Consumption
Most important production countries China , Iran , USA, Turkey
use Edible oil , industry

Opened walnut with a core
"Persian walnuts" ( Juglans regia )
General chemical structure of walnut oil, a triglyceride : (R 1 , R 2 and R 3 are alkyl or alkenyl radicals with mostly an odd number of carbon atoms), depending on the type of fatty acid bound (linoleic acid, linolenic acid, palmitic acid, lauric acid, myristic acid etc. )

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.

Manufacturing

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.

For cooking

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 .

Use (technical)

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.

Individual evidence

  1. ^ Josef Schormüller : Handbuch der Lebensmittelchemie. Volume 4: Fette und Lipide (Lipoids) , Springer, 1969, ISBN 978-3-662-23548-5 , p. 75.
  2. ↑ a b G. P. Savage et al .: Fatty acid and tocopherol contents and oxidative stability of walnut oils. In: J. Am. Oil Chem. Soc. 76, 1999, p. 1059, doi : 10.1007 / s11746-999-0204-2 .
  3. ↑ a b Bavarian State Ministry for State Development and Environmental Issues: Vegetable oil- powered combined heat and power plants. Part 2, 2002, online (PDF; 1.35 MB), lfu.bayern.de, accessed on April 30, 2017.
  4. ↑ a b c d e f g h i Sabine Krist: Lexicon of vegetable fats and oils. Springer, 2008, ISBN 978-3-211-75606-5 , pp. 459-462, doi : 10.1007 / 978-3-211-75607-2_23 .
  5. ↑ a b c d e f g NIIR Board: Modern Technology Of Oils, Fats & Its Derivatives. 2nd Edition, Asia Pacific Business Press, 2013, ISBN 978-81-7833-085-3 , p. 116.
  6. ↑ a b c d e f g D. K. Salunkhe, SS Kadam: Handbook of Fruit Science and Technology. Marcel Dekker, 1995, ISBN 0-8247-9643-8 , p. 529.
  7. ↑ G. Uzunova, M. Perifanova-Nemska u. a .: Chemical composition of Walnut Oil from Fruits on different years old branches. In: Bulgarian Journal of Agricultural Science. 21 (3), 2015, 494–497, online (PDF; 675 kB), at agrojournal.org, accessed on May 8, 2017.
  8. ↑ Linda J. Harris: Improving the safety and quality of nuts. Woodhead, 2013, ISBN 978-0-85709-748-4 , p. 206.
  9. ^ Jan CJ Bart, Emanuele Gucciardi, Stefano Cavallaro: Biolubricants: Science and Technology. Woodhead, 2013, ISBN 978-0-85709-263-2 , p. 150.
  10. ↑ Ibrahim Dincer, Calin Zamfirescu: Sustainable Energy Systems and Applications. Springer, 2011, ISBN 978-0-387-95860-6 , p. 184.
  11. ^ Forest Gregg: SVO. New Society, 2008, ISBN 978-0-86571-612-4 , p. 47.
  12. ↑ FAO statistics 2014 .
  13. ↑ walnut oil. Retrieved September 28, 2016 .
  14. ↑ Production and origin of walnut oil. Retrieved September 27, 2016 .
  15. ↑ a b Ralf Buchholz: Bring nature to wood . In: HolzWerken . No. 1 . Vincentz, 2010, p. 30-33 .