Walnut trees grow in temperate zones throughout the world. Because they are used in so many dishes and are so popular, walnuts represent an important commercial crop. In the 18th century, while establishing Spanish missions there, Franciscan monks planted the English walnut tree in California, where a mild climate and deep fertile soil provided ideal growing conditions. California now provides 99 percent of this country’s supply of English walnuts, and two-thirds of the world’s supply.
Throughout the ages, the resemblance of the walnut to the human brain has been too much for would-be healers to resist. Here, in part, is a 17th-century walnut prescription: “The Kernel hath the very figure of the Brain, and therefore it is very profitable for the Brain, and resists poysons. For if the Kernel be bruised, and moystned with the quintessence of Wine, and laid upon the Crown of the Head, it comforts the brain and head mightily.”
What distinguishes walnuts from other nuts is that they contain alpha-linolenic acid (ALA), as does walnut oil. Not many foods are rich in ALA, which is a type of omega-3 fatty acid found in plant foods. In addition to walnuts, only canola oil, flaxseed oil, and soybean oil are high in ALA. Walnuts also contain other heart-healthy monounsaturated and polyunsaturated fats, as well as plant sterols.
For a full listing of nutrients, see English Walnuts in the National Nutrient Database.
Types of walnuts
Walnuts are available shelled and unshelled. Walnuts are also pressed for their oil. The most common type of walnut, the English walnut, is available year-round. Other types—black walnuts, butternuts, and heartnuts—are marketed on a very small scale, so you may find them only in farmers’ markets and some specialty food stores during the fall and early winter.
- Black walnuts: These walnuts have very tough, dark outer hulls and inner shells that are thicker than those of English walnuts. The shells have to be cracked under so much pressure that the nutmeats are usually crushed as a result. Black walnuts have a rather distinctive, cheese-like flavor that’s not to everyone’s taste, but aficionados of these walnuts will nevertheless go to great lengths to get their hands on them.
- Butternuts: Also called “white walnuts,” the nutmeats looks like the letter U, or a life preserver vest.
- English walnuts: Also called Persian walnuts, these are the walnuts that most people are familiar with. They are native to Asia and Europe though California is now the major world producer.
- Heartnuts: This Japanese walnut variety has a shell that looks like a flattened heart. It easily splits in two, releasing the whole nutmeat. Heartnuts are available on an extremely limited, and mostly local, commercial scale.
How to choose the best walnuts
When buying walnuts in the shell, look for undamaged shells with no tiny wormholes. Shake the nuts. Those that rattle or feel extra light may be withered or dried out inside.
When buying shelled walnuts, look for a freshness date on the jar, can, or bag. If visible, the nuts should be plump and uniform in size.
Buy nuts in bulk only if you are sure the store has a rapid turnover of their stock to ensure freshness. Check to see that the nuts are crisp. Don’t buy them if they are limp or rubbery, or if they smell musty or rancid. The high oil content in walnuts makes them susceptible to spoilage.
How to store walnuts
Walnuts are more perishable than other nuts because of their high polyunsaturated fat content, but can keep well if properly stored. In fact, in their shells, walnuts will keep for six months to a year if stored in a cool, dry place. Heat, humidity, and light will speed spoilage. For longer storage, keep them in the refrigerator or freezer.
Keep shelled walnuts in their original package until you are ready to use them. Store in a cupboard or other cool, dry place. They will stay fresh until the date marked on the package. If there is no date, count on them lasting for three to four months. Once the package is opened, wrap the nuts well and store them in the refrigerator or freezer. The nuts will stay fresh for six months in the refrigerator and for a year in the freezer.
If shelled walnuts seem a little soft but don’t smell rancid, freshen them by spreading them on a baking sheet and heating them in a very low oven (150°) for a few minutes.
How to shell and chop walnuts
English walnut shells split readily with the squeeze of a nutcracker, allowing the removal of whole nutmeats. Nut picks can be helpful, however, in teasing them out.
Black walnuts, on the other hand, have very tough, dark outer hulls, and the shells are rock hard. They usually have to be broken with a very hard hammer blow or in a vise. (Some people even resort to running over black walnuts with their car.) Because so much force must be used to break the shell, halves are virtually impossible to rescue—the meats have to be picked out in pieces with a nut pick.
Chop walnuts by hand with a sturdy chef’s knife. Chopping walnuts in a blender or food processor is hard to do without turning them into butter. If you want to try, process a small amount of walnuts at a time and pulse the machine on and off only once or twice.
If you’re finely grinding walnuts for a cake, process them with a small amount of the flour and proceed with the recipe.
Occasionally a recipe will direct you to remove the bitter walnut skin. To do this, drop shelled walnuts into boiling water and blanch for one minute. Drain, rinse under cold water, and rub the skin off. Place the nuts on a cookie sheet and bake at 350° for 10 minutes or until crisp.
6 ways to serve walnuts
1. Toss walnuts in any salad to add nutty flavor.
2. Crush walnuts and add them to a pie crust.
3. Stir walnuts into yogurt.
4. Add chopped walnuts to cookies and breads.
5. Add walnuts to cooked grains in a side dish or salad.
6. Substitute walnuts for pine nuts in a pesto.
Also see this recipe: Date and Walnut Bread.