Juglans regia L. - Juglandaceae - (Persian, English, common) walnut, Echte Walnuss, Walnuß

Large deciduous tree, native to Europe and Asia.
„The male flowers are in drooping catkins 5-10 cm long, and the female flowers are terminal, in clusters of two to five, ripening in the autumn into a fruit with a green, semifleshy husk and a brown, corrugated nut.“

The leaves (walnut leaf, Juglandis folium) and the fruit husks (Juglandis fructus cortex) are used as astringend and diarrhoeal. „The value of walnut leaf to treat skin orders is mainly ascribed to the tannins (astringent, anti-inflammatory, antimicrobial) but also to juglone and germacrene D, all of which have antimicrobial activity.“
[Medicinal Plants of the World. Ben-Erik Van Wyk and Michael Wink, Pretoria 2004, 183]

„[Walnuts] are ripe when the green fleshy sheath is split open, loosen the nuts from the shell, and falling to the ground. Usually, the nuts are shaken from the trees, swept into rows, collected and brought to first cleaning and subsequent drying.“

Main volatile compounds identified from walnut headspace via GS-MS were myrcene (13%), farnesene (13%), limonene (9%), (E)-ocimene (8%), caryophyllene (8%), caryophyllene oxide (4%) and sabinene (4%).
[Response to walnut olfactory and visual cues by the parasitic wasp Diachasmimorpha juglandis., Henneman, M.L., Dyreson, E.G., Takabayashi, J., Raguso, R.A., Journal of chemical ecology, Vol.28(11), 2002, 2221-2244]

„The aroma volatiles of walnuts from three different geographical locations were studied. Over 110 compounds were identified in the headspace volatiles, many for the first time as walnut components. Walnuts from China and the Ukraine contained high levels of lipid-derived volatiles, in particular hexanal, pentanal, 1-hexanol and 1-pentanol from linoleic acid breakdown, and 1-penten-3-ol from α-linolenic acid breakdown. Chilean walnuts, however, contained high levels of alkylbenzenes of molecular weight 120, with the lipid-derived aldehydes and alcohols present at much lower levels than in the other two walnut samples.“
[Analysis of the headspace aroma compounds of walnuts (Juglans regia L.)., Elmore, J.S., Nisyrios, I., Mottram, D.S., Flavour and fragrance journal, Vol.20(5), 2005, 501-506]

Walnut oil is obtained from the seeds (of unripe nuts picked from the tree) by hydraulic pressing and is rich in polyunsaturated fatty acids.
„Similar to olive oils, in walnut oils the most abundant group of volatiles was the aldehydes and hydrocarbons. n-Pentane (8.84-19.46%) was the principal component in all varieties, followed by 2,4-decadienal and nonanal. Unlike olive oils, the walnut oil contained significantly higher amounts of pentanal and hexanal. Other aldehydes and alcohols were produced and formed an important fraction of volatiles in walnut oil of the variety Criolla. Furthermore, 2-hexanone, 2-pentylfuran, and 2-octylfuran were present only in this variety.“
[A multivariate study of the relationship between fatty acids and volatile flavor components in olive and walnut oils., Torres, M.M., Martínez, M.L., Maestri, D.M., Journal of the American Oil Chemists' Society, Vol.82(2), 2005, 105-110]

Important volatiles of walnut oils (pressed from roasted walnuts) were typical roasting products like furfural (1.3-12.5%), 2-methylpyrazine (0.6-1.8%), dimethylpyrazines (0.3-2.2%), furfurylalcohol (0.5-3.3%), furthermore acetic acid (18.6-42.2%), hexanal (6.6-31.8%), and (E)-2-hexenal (tr-0.4%).
[Bail, Stefanie, et al. „Characterization of volatile compounds and triacylglycerol profiles of nut oils using SPME‐GC‐MS and MALDI‐TOF‐MS.“ European journal of lipid science and technology 111.2 (2009): 170-182]

„The chemical composition of volatile extract of Pakistani cultivar of walnut [ground nuts] was investigated using Gas Chromatography-Mass Spectrometery (GC-MS) analysis… Some volatiles e.g. α-thujene, sabinene, p-cymene, 1,8-cineol, linalool, myrtenal, pinocarveol, verbenol, myrtenol, p-cymen-8-ol, isobutyl cyanide and benzyl alcohol have already been reported from walnut while the remaining constituents namely α-cadinol, α-bisabolol, isopulegol, carvacrol, estragol, globulol, viridiflorol, nerolidol, and neo-iso-3-thujanol are reported for the first time from this species.“
[Investigation on the volatile constituents of Juglans regia and their in vitro antioxidant potential., Abbasi, M.A., Raza, A., Riaz, T., Shahzadi, T., Aziz-ur-Rehman, J.M., Shahwar, D., Ahmad, N., In Proceedings Royal Society Queensland, Vol.47, 2010, 137-41]

„A total of 10 aroma-active compounds of OAVs ≥ 1 were identified in raw walnut, among which (E)-2-nonenal showed the highest OAV, and octanal, hexanal, and nonanal were also contributive to the flavor of raw walnut. In roasted walnut, 20 aroma-active compounds (OAVs ≥ 1) were obtained, and (E,E)-2,4-decadienal, 1-octen-3-ol and pyrazines were the characteristic flavor sources of roasted walnut.“
[Liu, Bing, et al. „Characterization of Predominant Aroma Components in Raw and Roasted Walnut (Juglans regia L.).“ Food Analytical Methods 15.3 (2022): 717-727]


„Fresh kernels of the walnut tree (Juglans regia L.) show a characteristic and pleasant aroma, the molecular basis of which was unknown. The application of an aroma extract dilution analysis resulted in 50 odor-active compounds. Among them, 37 had not been reported as fresh walnut kernel volatiles before, including the two odorants with the highest flavor dilution factors, namely, fenugreek-like smelling 3-hydroxy-4,5-dimethylfuran-2(5H)-one (sotolon) and oatmeal-like smelling (2E,4E,6Z)-nona-2,4,6-trienal. Quantitations revealed 17 odorants with concentrations in the walnuts that exceeded their odor threshold concentrations. Aroma reconstitution and omission experiments finally showed that the characteristic aroma of fresh walnuts is best represented by a binary mixture of sotolon and (2E,4E,6Z)-nona-2,4,6-trienal. Of both, the natural concentration was ∼10 μg/kg. Further sensory studies showed that the walnut character is intensified when their concentrations are in parallel increased to ∼100 μg/kg. This finding may guide the future breeding of new walnut cultivars with improved aroma.“
[Stübner, Christine A., and Martin Steinhaus. „Sotolon and (2E,4E,6Z)-Nona-2,4,6-trienal Are the Key Compounds in the Aroma of Walnuts.“ Journal of Agricultural and Food Chemistry 71.18 (2023): 7099-7108]

The main volatile component of walnut leaves was germacrene D (0.5ppm). Other major volatiles identified include caryophyllene, (E)-β-ocimene, β-pinene, and limonene.
[Buttery, Ron G., et al. „Identification of germacrene D in walnut and fig leaf volatiles.“ Journal of Agricultural and Food Chemistry 34.5 (1986): 820-822]

Kohl, F.G., Die officinellen Pflanzen der Pharmacopoea Germanica, t. 29 (1891-1895)

Juglans regia
© Rolf Marschner (2006),

juglans_regia_l.txt · Zuletzt geändert: 2023/09/21 09:04 von andreas