From en.wikipedia.org:
[Nut of any tree of the genus Juglans] [walnuts as food] [date=January 2023]
[date=September 2024]
right A WALNUT is the edible seed of any tree of the genus _Juglans_ (family
Juglandaceae), particularly the Persian or English walnut, _Juglans regia_.
They are accessory fruit because the outer covering of the fruit is
technically an involucre and thus not morphologically part of the carpel; this
means it cannot be a drupe but is instead a drupe-like nut.
After full ripening, the shell is discarded, and the kernel is eaten. Nuts of
the eastern black walnut (_Juglans nigra_) and butternuts (_Juglans cinerea_)
are less commonly consumed.
** Description
Walnuts are the round, single-seed stone fruits of the walnut tree. They
ripen between September and November in the northern hemisphere. The brown,
wrinkly walnut shell is enclosed in a husk.[1] Shells of walnuts commercially
available usually have two segments (but three or four-segment shells can also
form). During the bumming process, the husk becomes brittle and the shell
hard. The shell encloses the kernel or meat, which is usually in two halves
separated by a membranous partition.<ref name="GKH" /> The seed kernels –
commonly available as shelled walnuts – are enclosed in a brown seed coat
which contains antioxidants. The antioxidants protect the oil-rich seed from
atmospheric oxygen, preventing rancidity.<ref name="wde1" />
Walnut trees are late to grow leaves, typically not doing so until more than
halfway through the spring.
*** Chemistry
Walnut hulls contain diverse phytochemicals, such as polyphenols, that stain
hands and can cause skin irritation. Seven phenolic compounds, including
ferulic acid, vanillic acid, coumaric acid, syringic acid, myricetin, and
juglone, were identified in walnut husks; juglone had concentrations of 2–4%
fresh weight.[2]
Walnuts also contain the ellagitannin, pedunculagin.[3] Regiolone has been
isolated with juglone, betulinic acid and sitosterol from the stem bark of _J.
regia_.[4]
** Species
The three species of walnuts most commonly grown for their seeds are the
Persian (or English) walnut (_J. regia_), originating from Iran, the black
walnut (_J. nigra_) – native to eastern North America – and the Japanese
walnut, also known as the heartnut (_J. ailantifolia_).[5] Other species
include _J. californica_, the California black walnut (often used as a
rootstock for commercial propagation of _J. regia_), _J. cinerea_
(butternuts), and _J. major_, the Arizona walnut. Other sources list _J.
californica californica_ as native to southern California, and _Juglans
californica hindsii_, or just _J. hindsii_, as native to northern California;
in at least one case, these are given as "geographic variants" instead of
subspecies (Botanica).[date=January 2021]
Numerous walnut cultivars have been developed commercially, which are nearly
all hybrids of the Persian walnut.[6]
** Cultivation
*** History
During the Byzantine era, the walnut was also known by the name "royal
nut".[7] An article on walnut tree cultivation in the Iberian Peninsula is
included in Ibn al-'Awwam's 12th-century _Book on Agriculture_.[8]
The _wal_ element in the name is Germanic and means _foreign_, especially in
the sense of _Latin_ or _non-Germanic_. Compare, for example, Wales,
Walloons, Wallachia. The _wal_ element is present in other Germanic-language
words for the same nut, such as: German [de], Dutch [nl], Danish [da], and
Swedish [sv].
*** Storage
Walnuts, like other tree nuts, must be processed and stored properly. Poor
storage makes walnuts susceptible to insect and fungal mold infestations; the
latter produces aflatoxin – a potent carcinogen. A batch that contains
mold-infested walnuts should be entirely discarded.[9]
The ideal temperature for the extended storage of walnuts is [-3] with low
humidity for industrial and home storage. However, such refrigeration
technologies are unavailable in developing countries where walnuts are
produced in large quantities; walnuts are best stored below [25] with low
humidity.. Temperatures above [30] and humidity levels above 70 percent can
lead to rapid and high spoilage losses. Above 75 percent humidity threshold,
fungal molds that release aflatoxin can form.<ref name="wde1" />[10]
*** Cultivars
{{columns-list|colwidth=12em|
- Ashley
- Chandler [11]
- Cisco <ref name="Cultivar" />
- Dawson <ref name="Cultivar" />
- Eureka <ref name="Cultivar" />
- Feradam
- Ferbel
- Ferjean
- Fernette <ref name="Cultivar" />
- Fernor
- Ferouette
- Forde <ref name="Cultivar" />
- Franquette <ref name="Cultivar" />
- Grandjean [12]
- Germisara
- Gillet <ref name="Cultivar" />
- Hansen
- Hartley <ref name="Cultivar" />
- Howard <ref name="Cultivar" />
- Hu
- Ivanhoe [13]
- Jupanesti
- Lara
- Livermore
- Marbot
- Mayette [14]
- Meylanaise <ref name="ReferenceA" />
- Paradox
- Parisienne
- Payne <ref name="Cultivar" />
- Poe <ref name="Cultivar" />
- Robert Livermore <ref name="Cultivar" />
- Rita
- Ronde de Montignac
- Royal
- Serr <ref name="Cultivar" />
- Sexton <ref name="Cultivar" />
- Solano <ref name="Cultivar" />
- Sunland <ref name="Cultivar" />
- Tehama <ref name="Cultivar" />
- Tulare <ref name="Cultivar" />
- Valcor
- Vina <ref name="Cultivar" />
- Wilson's Wonder
- Yolo
}}
** Production
{| class="wikitable" style="float:right; width:12em; text-align:center;" |+
Walnut production – 2022 ! scope="col" | Country ! scope="col" |
<small>millions of tonnes</small> |- | [CHN] || 1.40 |- | [USA] || 0.68 |- |
[IRN] || 0.36 |- | [TUR] || 0.34 |- | [MEX] || 0.18 |- | WORLD || 3.9 |- |
colspan="2" |<small>Source: FAOSTAT of the United Nations[15]</small> |}
In 2022, world production of walnuts (in shell) was 3.9 million tonnes, with
China contributing 36% of the total (table). Other significant producers (in
the order of decreasing harvest) were the United States, Iran, and Turkey.<ref
name=faostat/>
** Nutrition
{{Nutritional value | name = Walnut, English | image = Whole Walnut Kernel.jpg
| image_size = 100px | caption = Walnut kernel, halves | serving_size = 100
grams | kJ = 2738 | carbs = 13.71 g | fat = 65.21 g | protein = 15.23 g |
sugars = 2.61 g | satfat = 6.126 g | transfat = | monofat = 8.933 g | polyfat
= 47.174 g | omega3fat = 9 g | omega6fat = 38 g | fiber = 6.7 g | starch =
0.06 g | water = 4.07 g | calcium_mg = 98 | iron_mg = 2.91 | phosphorus_mg =
346 | magnesium_mg = 158 | manganese_mg = 3.414 | sodium_mg = 2 | potassium_mg
= 441 | zinc_mg = 3.09 | vitA_ug = 1 | vitA_iu = 20 | betacarotene_ug = 12 |
lutein_ug = 9 | thiamin_mg = 0.341 | riboflavin_mg = 0.15 | niacin_mg = 1.125
| pantothenic_mg = 0.570 | vitB6_mg = 0.537 | folate_ug = 98 | vitB12_ug = 0 |
vitC_mg = 1.3 | vitE_mg = 0.7 | vitK_ug = 2.7 | note = Link to Full USDA
Database Entry (see https://fdc.nal.usda.gov/food-details/2346394/nutrients)
}}
English (or Persian) walnuts without shells are 4% water, 15% protein, 65%
fat, and 14% carbohydrates, including 7% dietary fiber (table). In a
reference amount of [100], walnuts provide [654] and rich contents (20% or
more of the Daily Value, DV) of several dietary minerals, particularly
manganese at 148% DV, along with significant amounts of B vitamins (table).
Unlike most nuts, which are high in monounsaturated fatty acids, walnut oil is
composed largely of polyunsaturated fatty acids (72% of total fats),
particularly alpha-linolenic acid (14%) and linoleic acid (58%), although it
does contain oleic acid as 13% of total fats (table source).
*** Health claims
In 2004, the US Food and Drug Administration (FDA) provided a qualified health
claim allowing products containing walnuts to state: "Supportive but not
conclusive research shows that eating [1.5] per day of walnuts, as part of a
low saturated fat and low cholesterol diet and not resulting in increased
caloric intake, may reduce the risk of coronary heart disease."[16] At the
same time, the agency refused to authorize the claim that "Diets including
walnuts can reduce the risk of heart disease"[17] and in 2010, it sent a
warning letter to Diamond Foods stating there is "not sufficient evidence to
identify a biologically active substance in walnuts that reduces the risk of
coronary heart disease."[18]
In 2011, a scientific panel for the European Food Safety Authority recommended
a health claim that "Walnuts contribute to the improvement of
endothelium-dependent vasodilation" at a daily intake of [30]; it also found
that a cause and effect relationship did not exist between consuming walnuts
and reduction of blood LDL-cholesterol levels.[19] The recommended health
claim was later authorized by the European Commission.[20]
*** Research
A 2020 systematic review assessing the effect of walnut supplementation on
blood pressure found insufficient evidence to support walnut consumption as a
blood pressure-lowering strategy.[21]
[2021], the relationship between walnut consumption and cognitive health is
inconclusive.[22]
** Allergic potential
[Tree nut allergy] Walnuts are among several tree nuts having potential to
cause allergic reactions when eaten or if their oils contact the skin.[23][24]
Lifetime walnut allergies occur in about 0.4% of the population in Europe and
the United States,<ref name=allergy/> although regional prevalence may vary
according to availability of walnut products and consumption amounts.<ref
name=allergy/> The prevalence of walnut and other nut allergies may be as high
as 5% in American children.<ref name=treenut/>
Proteins implicated as allergens in walnut and tree nut allergic reactions
include lipid transfer protein, 2S albumin, vicilin, legumin, and
oleosin.[25][26]
Symptoms of a walnut allergic reaction are abdominal pain, cramps, nausea,
vomiting, difficulty swallowing, itching, shortness of breath, and potentially
anaphylaxis, which may be fatal.<ref name=treenut/>[27] Walnuts are considered
to be a priority food allergen in Canada.<ref name=canada/> Emergency
treatment for anaphylaxis includes an injection of epinephrine, while milder
symtoms are treated with an antihistamine.<ref name=canada/> An allergic
reaction to walnuts is best avoided by not eating or touching walnut
products.<ref name=treenut/><ref name=canada/> Walnut allergy is usually
lifelong and there is no cure.<ref name=treenut/><ref name=canada/>
Walnut allergy appears to have cross-reactivity with the allergies to pecans,
cashews, and other tree nuts.<ref name=borres/><ref name=wein/><ref
name=canada/>
** Uses
*** Culinary
Walnut meats are available in two forms: in their shells or de-shelled. Due
to processing, the meats may be whole, halved, or in smaller portions. All
walnuts can be eaten on their own (raw, toasted, or pickled), or as part of a
mix such as muesli, or as an ingredient of a dish: e.g. walnut soup, walnut
pie, walnut coffee cake, banana cake, brownie, fudge. Walnuts are often
candied or pickled. Pickled walnuts that are the whole fruit can be savory or
sweet depending on the preserving solution.
Walnuts may be used as an ingredient in other foodstuffs. Walnut is an
important ingredient in baklava, Circassian chicken, potica (a traditional
festive pastry from Slovenia), satsivi (chicken in walnut sauce), tarator (a
summer soup in Bulgarian cuisine), and poultry or meat ball stew from Iranian
cuisine.
Walnuts are also popular as an ice cream topping, and walnut pieces are used
as a garnish on some foods.[28]
Nocino is a liqueur made from unripe green walnuts steeped in alcohol with
syrup added.
Walnut oil is available commercially and is chiefly used as a food ingredient,
particularly in salad dressings. It has a low smoke point, which limits its
use for frying.[29][30]
*** Inks and dyes
[Walnut ink] Walnut husks can be used to make durable ink for writing and
drawing. It is thought to have been used by artists including Leonardo da
Vinci and Rembrandt.[31]
Walnut husk pigments are used as a brown dye for fabric[32] and were used in
classical Rome and medieval Europe for dyeing hair.[33]
*** Cleaning
The US Army once used ground walnut shells for abrasive blasting to clean
aviation parts because of low cost and low abrasive qualities. However, an
investigation of a fatal Boeing CH-47 Chinook helicopter crash (11 September
1982, in Mannheim, Germany) revealed that walnut shell grit had clogged an oil
port, leading to the accident and the discontinuation of walnut shells as a
cleaning agent.[34]
Commercially, crushed walnut shells are still used outside of aviation for
low-abrasive, less-toxic cleaning and blasting applications.[35] In the oil
and gas industry, deep bed filters of ground walnut shell are used for
"polishing" (filtering) oily contaminates from water.[36]
*** Cat litter
At least two companies, LitterMaid and Naturally Fresh, make cat litter from
ground walnut shells.[37][38] Advantages cited over conventional clay litter
include environmental sustainability of using what would otherwise be a waste
product, superior natural biodegradability, and odor control as good or better
than clay litter.[39] Disadvantages include the possibility of allergic
reactions among humans and cats.[40]
*** Folk medicine
Walnuts have been listed as one of the 38 substances used to prepare Bach
flower remedies,[41] a herbal remedy promoted in folk medicine practices for
its supposed effect on health. According to Cancer Research UK, "there is no
scientific evidence to prove that flower remedies can control, cure or prevent
any type of disease, including cancer".[42]
** In culture
Large, symmetrically shaped, and sometimes intricately carved walnut shells
(mainly from _J. hopeiensis_) are valued collectibles in China where they are
rotated in hand as a plaything or as decoration. They are also an investment
and status symbol, with some carvings having high monetary value if
unique.[43] Pairs of walnuts are sometimes sold in their green husks for a
form of gambling known as _du qing pi_.[44]
** Gallery
<gallery> File:Juglans regia 2009 G2.jpg|Common walnut in growth
File:California Blackwalnut.jpg|California black walnut in growth File:Juglans
regia polyploid fruit bottom.jpg|A three-segment shell which occurs rarely
File:Noix3coquilles.jpg|Walnut in shell and a nutcracker utensil used to break
the shell File:Benutzung eines Nussknackers.gif|Video of cracking a walnut
File:Walnuts no shell.jpg|Walnut meats File:Gozinaki with walnuts.jpg|Georgian
snack Gozinaki made from roasted walnuts and honey File:Applesauce walnut
coffee cake.jpg|Applesauce coffee cake garnished with walnuts File:A Pair Of
Chnese Collectible Walnuts.jpg|Walnuts as collectibles File:Walnut
murabba.jpg|Murabba made from young walnuts </gallery>
** See also
- Pickled walnuts
** References
[reflist]
** Further reading
- [last=Ramos ]
- [last=Smith ]
** External links
[walnut] [Walnuts] [Cookbook]
- [38394]
[Nuts] * Category:Edible nuts and seeds Category:Fruit trees + Category:Plant
dyes Category:Symbols of California