DAVIS, Calif. — Pop quiz: What nut was beloved by the Romans, has fascinated artists through the centuries, and is produced predominantly by one state of these United States?
Answer: Walnuts. The Romans willingly paid dearly for this flavorful nut and threw them at weddings, for fertility. The convoluted shape of the walnut kernel, resembling the human brain, in its tan wrinkled shell has captivated artists. And the state of California supplies 99 percent of U.S. walnuts and the majority of the world supply.
Walnuts have a history that's even more ancient than the Romans, dating back to prehistoric times. Today they are used in cuisines around the world, particularly for baked goods and confections.
These days, with the focus on good fats and bad fats in our diet, the walnut has come into fashion with those who see it as an easy way to stock up on those good fats. This year the Walnut Marketing Board dubbed the walnut the "Mega Nut" to highlight its polyunsaturated fats, a source of heart-healthy omega-3 fatty acids.
(One ounce of walnuts, about 14 walnuts halves, contains 190 calories, 4 grams of protein, 2 grams of fiber, 0 cholesterol, 1.5 grams saturated fat, 2.5 grams monounsaturated and 13 grams polyunsaturated fat, according to the USDA.)
The marketing board recently sponsored a two-day gathering with industry experts, growers and researchers to give visitors a behind-the-scenes look at walnuts.
The two major species of walnuts in the United States are the English or Persian walnut, which originated in Persia and was brought here from Europe, and the black walnut, native to the United States.
English walnuts were first planted in Southern California about 1770 by the Spanish Mission fathers," explained Gail McGranahan, a pomologist at the University of California at Davis. (The "English" refers to the English merchant marines who transported the nuts for world trade.)
The temperate climate and nutrient-rich soil in California's Central Valley attracted growers and helped the industry thrive. Walnut trees are now cultivated in a 370-mile region, primarily in the San Joaquin and Sacramento valleys. Now there are more than 5,000 growers and 50 processors in the state, producing a yearly average of 300,000 tons of walnuts.
The black walnut, though edible and historically a staple of American Indians, is not used commercially for food because of its hard shell and small nutmeat yield. The Eastern American black walnut, found east of the Rocky Mountains, is grown for its wood. Walnut wood is prized for furniture — in particular burled walnut, used as a veneer and for dashboards in luxury cars.
The Northern California black walnut is so hardy that its roots are used as rootstock, and U.C.-Davis scientists demonstrated how English nut varieties are grafted onto the roots of black walnut trees. There are some 37 varieties, hybrids of the English or Persian walnut, in the United States.
Walnut trees can produce fruit for up to a century and bear their first fruit within 5 to 7 years of planting. Because it takes so long to realize a profit, California growers are mostly multigenerational family farms (which can diversify with other crops while waiting for profits) as opposed to corporations seeking quick profits.
The following recipes were developed by two California chefs for the Walnut Marketing Board.
There are two entrees — walnut-crusted pork tenderloin with a maple syrup sauce, and walnut-crusted halibut with a soy honey sauce. There is also a dish prepared from Belgian endive with Roquefort, walnut and dried cranberries, that could be served as a salad or hors d'oeuvre.
BELGIAN ENDIVE WITH ROQUEFORT, WALNUTS AND CRANBERRIES
4 heads Belgium endive
1/4 cup cranberries, dried
1/2 cup walnuts, coarsely chopped
4 ounces Roquefort cheese (about 1 cup), lightly crumbled
1/2 cup Roquefort Dressing (recipe follows)
Trim the base of the endive using a diagonal cut, then separate the leaves. Toss the cranberries, nuts and Roquefort together in a bowl, being careful not to break up the Roquefort too much. Spoon the mixture into the endive leaves and garnish with the watercress.
For advance preparation: Fill the endive leaves up to 3 hours before serving, cover and chill. Garnish just before serving. Drizzle with Roquefort Dressing, as desired.
ROQUEFORT DRESSING
1/4 cup Roquefort cheese, crumbled
3/4 cup mayonnaise
1/3 cup buttermilk
Juice of 2 limes
1/2 teaspoon Worcestershire sauce
1/8 teaspoon cayenne pepper
1 tablespoon red wine vinegar
Pinch black pepper
Melt Roquefort cheese in the oven or in a pan on top of the stove, being very careful not to scorch. Let cool. In a bowl, combine the melted cheese, mayonnaise, buttermilk, lime juice, Worcestershire sauce, cayenne, red wine vinegar and black pepper; mix well until all ingredients are combined. If desired, add more Roquefort cheese to taste, for an even more intense flavor. Makes 4 servings.
Nutrition information per serving: 355 cal., 11 g pro., 34 g carbo., 18 g fiber, 20 mg chol., 520 mg sodium, 22 g total fat (4 g saturated fat) Recipe from chef David Vartanian of The Vintage Press restaurant, Visalia, Calif., for the Walnut Marketing Board
WALNUT-CRUSTED HALIBUT WITH HONEY SOY SAUCE
1/4 cup flour
Pinch of salt and pepper
2 cups clover honey
1/3 cup soy sauce
Four 6-ounce Alaskan halibut fillets
2 eggs lightly beaten with 1 tablespoon water
1 1/2 cups walnuts, toasted, chopped
1 tablespoon olive oil
Preheat the oven to 375 F.
Stir a pinch of salt and pepper into the flour and reserve in a shallow dish. Whisk together the honey and soy sauce and reserve in another dish.
Dip the halibut fillets in the flour, coating thoroughly and shaking gently to remove any excess. Next dip them in the beaten egg wash, draining off any excess; then immediately roll them in the walnuts to coat. Reserve for 5 minutes to allow the coating to "set."
Heat the olive oil in an ovenproof skillet large enough to hold the fillets, and add the fish. Cook on one side until golden brown, flip carefully and put it immediately into the oven for 5 minutes, or until cooked through.
Arrange on a plate and drizzle with the reserved honey-soy sauce. Makes 4 servings.
Nutrition information per serving: 1,104 cal., 50 g pro., 149 g carbo., 3 g fiber, 160 mg chol., 1,937 mg sodium, 39 g total fat (5 g saturated fat) Recipe from chef Joey Kistler of The Cutting Horse Restaurant, San Juan Bautista, Calif., for the Walnut Marketing Board
WALNUT-CRUSTED PORK TENDERLOIN
1/2 cup flour
1/2 teaspoon salt
1/2 teaspoon pepper, freshly ground
1 pound pork tenderloin, cleaned and trimmed
2 eggs beaten with 1 tablespoon water
1 1/2 cups walnuts, chopped
3 tablespoons olive oil
Maple Syrup Sauce (recipe follows)
Toss together the flour, salt and pepper. Cut the tenderloin into two equal portions. Roll the tenderloin in the flour, shaking to remove excess. Dip the tenderloin in the beaten egg wash and roll to coat thoroughly. Drain off excess. Roll the coated tenderloin in the crushed walnuts, pressing gently to secure the crust. Set aside for 5 minutes for the coating to "set."
Heat the olive oil in a heavy-bottomed pan. Add the tenderloin pieces and sear well on all sides.
Add 1 to 1 1/2 cups of the warm Maple Syrup Sauce and cook over medium heat, turning the tenderloins often to coat with sauce and keep the crust from burning. The sauce will reduce to a thick glaze; add more if necessary to keep the desired consistency. When the pork is just pink in the center, remove from the pan and reserve.
Reduce the sauce if necessary to get a thick glaze.
Slice the pork on the diagonal and arrange on 4 plates. Drizzle with the thick, glazed sauce. Makes 4 servings.
Nutrition information per serving (without Maple Syrup Sauce): 630 cal., 35 g pro., 19 g carbo., 370 mg sodium, 48 g total fat (7 g saturated fat) Recipe from chef Joey Kistler of The Cutting Horse Restaurant, San Juan Bautista, Calif., for the Walnut Marketing Board
MAPLE SYRUP WALNUT SAUCE
3/4 cup walnuts, toasted
2 cups maple syrup
1/3 cup red wine vinegar
2 teaspoons fresh thyme
Add all ingredients to a small pot, bring to a boil and set aside. Serve warm with Walnut-Crusted Pork Tenderloin. Makes 4 servings.
Nutrition information per serving: 562 cal., 6 g pro., 111 g carbo., 1 g fiber, 0 mg chol., 17 mg sodium, 14 g total fat (1 g saturated fat). Recipe from chef Joey Kistler of The Cutting Horse Restaurant, San Juan Bautista, Calif., for the Walnut Marketing Board.