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Walnuts

 

Walnuts (genus Juglans) are plants in the family Juglandaceae. They are deciduous trees, 10鈥40 meters tall (about 30鈥130 ft), with pinnate leaves 200鈥900 millimetres long (7鈥35 in), with 5鈥25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya) but not the hickories (Carya) in the same family.

The 21 species in the genus range across the north temperate Old World from southeast Europe east to Japan, and more widely in the New World from southeast Canada west to California and south to Argentina. The Latin name, Juglans, derives from Jupiter glans, "Jupiter's acorn": figuratively, a nut fit for a god.

The word walnut derives from Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign" (wealh is akin to the terms Welsh and Vlach; see *Walha and History of the term Vlach).[1] The walnut was so called because it was introduced from Gaul and Italy. The Latin name for the walnut was nux Gallica, "Gallic nut".

Classification

The genus Juglans is divided into four sections:

 

l  Sect. Juglans. Leaves large (20鈥45 cm) with 5鈥9 broad leaflets, hairless, margins entire. Wood hard. Southeast Europe to central Asia.

l  Sect. Rhysocaryon. Leaves large (20鈥50 cm) with 11鈥23 slender leaflets, finely pubescent, margins serrated. Wood hard. North America, South America.

l  Sect. Cardiocaryon. Leaves very large (40鈥90 cm) with 11鈥19 broad leaflets, softly downy, margins serrated. Wood soft. Fruits borne in racemes of up to 20. Nuts have thick shells. Northeast Asia.

l  Sect. Trachycaryon. Leaves very large (40鈥90 cm) with 11鈥19 broad leaflets, softly downy, margins serrated. Wood soft. Fruits borne in clusters of 2-3. Nuts have a thick, rough shell bearing distinct, sharp ridges. Eastern North America.

Nuts and Kernels

Inside of a common walnut nut with green outer layer visible in the top left corner;

The nut kernels of all the species are edible, but the walnuts most commonly available in shops are from the Persian walnut, the only species which has a large nut and thin shell; black walnut species are more difficult to crack and remove from the shell. One horticultural form selected for thin nut shells and hardiness in temperate zones is sometimes known as the 'Carpathian' walnut. The nuts are rich in oil, and are widely eaten both fresh and in cookery. Walnut oil is expensive and consequently is used sparingly; most often in salad dressing. Walnuts are also an excellent source of omega-3 fatty acids, and have been shown as helpful in lowering cholesterol. Due to the high unsaturated fat content of the oil, English walnuts need to be kept dry and refrigerated to store well; in warm conditions they become rancid in a few weeks, particularly after shelling. An extreme example of rancidity is Oil paint, which has often employed walnut oil as an effective binding medium, known for its clear, glossy consistency and non-toxicity.

Two-thirds of the world export market and 99% of the US commercial production of English walnuts is grown in California's Central Valley and in Coastal Valleys, from Redding in the north to Bakersfield in the south. Of the more than 30 varieties of J. regia grown there, Chandler and Hartley account for over half of total production.In California commercial production, the Hinds' black walnut (J. hindsii) and the hybrid between J. hindsii and J. regia, Juglans x Paradox, are widely used as rootstocks for J. regia cultivars because of their resistance to Phytophthora and to a very limited degree, the oak root fungus. However, trees grafted on these rootstocks often succumb to black line.

 

Common Walnuts

In some countries immature nuts in their husks are preserved in vinegar. In England these are called "pickled walnuts" and this is one of the major uses for fresh nuts from the small scale plantings. In Armenian cuisine, walnuts are preserved in sugar syrup and eaten whole. In Italy, liqueurs called Nocino and Nocello are flavoured with walnuts, while Salsa di Noci ("Walnut Sauce") is a pasta sauce originating from Liguria. In Georgia, walnuts are ground along with other ingredients to make walnut sauce.

Walnuts are heavily used in India. In Jammu, India it is used widely as a prasad (offering) to Mother Goddess Vaisnav Devi and, generally, as a dry food in the season of festivals such as Diwali.

According to one commercial source which did not identify which of the seventeen or so black walnut species was being described, [7]"One ounce of black walnut has 16.7 grams of total fat and .57 grams of omega 3's. One ounce of English walnuts has 18.5 grams of total fat and 2.6 grams of omega 3's."

Manos and Stone studied the composition of seed oils from several species of the Rhoipteleaceae and Juglandaceae and found that the nut oils were generally more unsaturated from species which grow in the Temperate zone and more saturated for species which grow in the Tropical zone.[8]. In the northerly-growing section Trachycaryon, J. cinerea oil was reported to contain 15% linolenate (the report did not specify whether the linolenate was the alpha ( n-3) or gamma (n-6) isomer, or perhaps a mixture), 2% of saturated palmitate, and a maximum concentration of 71% linoleate. In the section Juglans, J. regia nut oil was found to contain from 10% to 11% linolenate, 6% to 7% palmitate, and a maximum concentration of linoleate (62% to 68%). In the section Cardiocaryon, the nut oils of J. ailantifolia and J. mandshurica were reported to contain (respectively) 7% and 5% of linolenate, 2% of palmitate, and maximum concentrations of 74% and 79% linoleate. Within the section Rhysocaryon, the nut oils of the U.S. native black walnuts J. microcarpa and J. nigra were reported to contain (respectively) 7% and 3% linolenate, 4% and 3% palmitate, and 70% and 69% linoleate. The remaining results for black walnuts were: J. australis contained 2% linolenate, 7% palmitate, and 61% linoleate; J. boliviana contained 4% linolenate, 4% palmitate, and 70% linoleate; J. hirsuta contained 2% linolenate, 5% palmitate, and 75% linoleate; J. mollis contained 0% linolenate, 5% palmitate, 46% linoleate, and 49% oleate; J. neotropica contained 3% linolenate, 5% palmitate, and 50% linoleate; and J. olanchana contained only a trace of linolenate, 9% palmitate, and 73% linoleate;