Building a Better Walnut

The resemblance of a shelled walnut to the human brain is uncanny, almost creepy. Europeans of the 16th and 17th centuries ascribed meaning to this likeness, prescribing walnuts for the treatment of head ailments and emotional unrest. Students in some Asian cultures still munch on walnuts when studying for exams. Hey, it doesn’t hurt to cover all the angles.

The link between brains and walnuts is especially appropriate these days, because some of the most energetic horticultural minds at UC Davis are working hard to help improve the yield, meat ratio and pest resistance of this popular food.

Using both university land and private orchards for their studies, the professors are trotting out watermark sensors and infrared thermometer guns in the quest for a better walnut. They use a photodiode light sensor array to measure how much sunlight particular leaves are getting each minute of the day, which tells them how they should be pruning the trees. They’ve got a contraption that looks like a rugged baby carriage but really is a mobile radar unit for measuring soil density and moisture. On the conveyor belt at high-end processing plants, a laser reads the light density of each passing nut; when it senses a dark (undesirable) specimen, it alerts another machine that knocks the ugly fruit off the belt with a blast of air.

Walnuts are big business. California produces 99% of the nation’s--and two-thirds of the world’s--commercial walnuts, a yearly volume that adds up to 246,000 tons and translates to about $300 million in sales.

Production isn’t likely to diminish now that the walnut has been nutritionally rehabilitated. Remember when nuts were bad for you? Now consumers have started to ignore overall fat content and focus instead on the various categories of fat. Nuts are fairly low in the bad saturated fats. And walnuts, in particular, are high in the good polyunsaturated fats, the source of trendy omega-3 fatty acids. A handful of walnuts a day is enough to satisfy requirements for alpha-linolenic acid, as recently formulated by the National Academy’s Institute of Medicine. Walnuts also happen to be the best single source of antioxidants after rose hips, which aren’t very appealing when sprinkled on ice cream.

The most logical reason for the healthy sales of California walnuts, however, is the food’s versatility as a cooking ingredient. Walnut bars, walnut brownies and walnut bread need no introduction. The nuts can be crunchy complements to salads and stir fry and anything involving cheese, and they shine with linguine and caramelized onions, or in warm lamb salad with Roquefort. My wife has taken to replacing pine nuts with walnuts in her pesto.

But if ground-penetrating radar units are helping to improve our walnuts, the key in the kitchen might be simplicity. Here’s my advice: roast some salty-spicy walnuts, eat them whole, and consider yourself brainy.

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Roasted Cayenne Walnuts

Serves 4

2 1/2 tablespoons unsalted butter

1 1/2 tablespoons chopped rosemary (or 2 teaspoons dried)

1/2 teaspoon salt

1/2 teaspoon cayenne pepper

2 cups walnuts

Melt butter and add rosemary, salt and cayenne. Stir mixture and pour over walnuts, tossing until coated. Bake nuts on a cookie sheet for 10 minutes at 300 degrees, or until you no longer can taste rawness.