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Seeds and Nuts - Walnuts (Juglans)

Updated on September 11, 2011
Walnuts: green, pickled and mature
Walnuts: green, pickled and mature

Nutritional Information

Walnuts have a high oil content, being especially rich in linoleic acid, an essential polyunsaturated fatty acid. Because of their large amount of polyunsaturated oil they are prone to rancidity.


The walnut is the fruit of the walnut tree (Juglans species). It has a smooth outer green husk, or "chuck", which splits open when the nuts are ripe for harvesting. The walnut has a creamy-brown round shell, which is formed in distinct halves, encasing two deeply ridged lobes of 'butterfly'-shaped, light brown kernel, with creamy-white, mild-flavored flesh. When mature, the outer shells have hardened and are easily cracked. Immature nuts are sometimes picked before the outer shell has hardened (see more in Preparation and Use below).

The Greeks described the walnut as 'karyon' (kara meaning head) because it looked like the convolutions of the human brain.

Origin and History

The walnut is related to the hickory nut and the pecan nut. There are 21 different kinds of walnut, scattered from the Mediterranean to eastern China and from North America to the Andes in South America. They vary from the white butternut to the yellow-brown Persian walnut and the dark brown or black walnut. The yellow-brown Persian walnut is the most popular.

The Persians used walnuts for barter and the Romans and Greeks, who called it 'the Persian nut', dedicated the walnut to Diana, whose feasts were held under walnut trees. The Persian walnut was introduced into Italy before Christianity but did not reach England until the sixteenth century.

British settlers planted them in Virginia and Massachusetts (hence the name English walnut as the Persian walnut is better known in the United States) but they did not grow well. Later settlers discovered that the climate in Oregon and California was best for the trees. Today, California produces virtually all commercially-grown walnuts in the United States. In France, Europe's main walnut producer, the Titmouse variety has a shell so thin that a bird can break the shell and eat the nut. A huskless variety grows in China.

Buying and Storage

Buy walnuts in the shell, preferably, as they are fresher. Store in a cool place or in the refrigerator for up to 6 months. When buying shelled walnuts, choose airtight packages or cans and store after opening in an airtight glass jar in the refrigerator.

Preparation and Use

Remove shells from walnuts with a nutcracker or a clean hammer. They may be eaten from the hand as a snack or halved, chopped or ground and used in cooking. Walnut halves may be added to salads, fruit desserts and fruit cakes. Chopped walnuts are good in stuffings, pressed into cream cheese, in buns, breads and cakes, and are an essential ingredient of waldorf salad. Ground walnuts can be added to pastry and cookies, fruit tarts and confectionery. Immature or 'green' walnuts are suitable for pickling in vinegar, which turns them black. They are also used to make walnut ketchup.


Walnuts are crushed to extract walnut oil, which is prized for use in salad dressings as well as cooking. Walnut kernels are canned.

To Remover Bitterness from Walnuts

Fresh walnuts are wonderfully sweet, and there is no need to remove their skins. However, other walnuts are likely to have some bitterness in their skins. To remove this, put the shelled walnuts into a bowl and cover them with boiling water. Leave for 10 minutes, then drain the nuts and rub them really hard in a clean tea towel. Spread the nuts on a paper-lined baking tray and dry in an oven set at 250° F (120° C) for 10-15 minutes.

The nutritional information provided on this page has been prepared using Australian metric weights and measures. For conversion to weights and measures appropriate for your country click here.


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