An Onionology

Nothing is simple anymore, not even buying an onion. This spring, depending on the exact time and place you’re shopping, you may have to consult an atlas before picking one. Maui, Hawaii; Vidalia, Ga.; Walla Walla, Wash.; Southeast Texas and California’s Imperial Valley all grow sweet onions.

But in fact--except for the Walla Walla--they are all more or less the same onion, hybrids of the Granex or its related Grano variety. (The Walla Walla, a totally different onion, was brought from Corsica at about the turn of the century.)

The differences are more due to soil, climate and cultivation than they are to the nature of the onion itself. Indeed, there may be as much variation among onions of the same region grown in different fields as there is among onions of different regions.

And when you get right down to it, onions aren’t really sweet. More accurately, they are mild. It all has to do with the relative amounts of pungency and sugar in the onion, says Doyle Smittle, a horticulture professor at the University of Georgia who helped refine the Vidalia onion.

“Let’s say I take your finger and squeeze it between my thumb and forefinger and at the same time I drop an 8-pound sledgehammer on your foot,” says Smittle. “If it misses your foot, you still realize how hard I’m squeezing your finger. But if it hits your foot, you don’t care. In onions, the sledgehammer is pungency, the sugar is squeezing your finger. If you bite into a pungent onion, you don’t care how sweet it is, you just want to get it out of your mouth. If you bite into an extremely mild onion . . . it tastes good anyway”--regardless of the actual sugar content.

In fact, ordinary yellow storage onions, sold at rock-bottom prices in any grocery store, are higher in sugar than any of the so-called sweet onions. It’s just that the pungency is also much higher (they’re bred that way--the sulfuric acid also acts as a fungicide).

For cooking, you’re better off using cheaper onions, since sulfuric acid compounds go away. “A person is crazy to waste good money using a Vidalia onion in a meat loaf,” Smittle says. “It’s like using a Rolls Royce to go mud-bogging in.”

Chemical analyses actually show a lower level of enzyme activity in sweet onions, too, which equates to less onion flavor.

But Keith Mayberry, farm advisor for the University of California at the Holtsville Agricultural Center, says that the onion he helped develop, the California Sweet Imperial, is good for a certain kind of cooking. Because of the mild growing season in the Imperial Valley, he says, his onions develop thicker rings that make “truly outstanding onion rings. They have never been beaten in any contest.”

April is the beginning of the sweet onion season. Texas 1015s (they are usually planted beginning Oct. 15), Sweet Imperials and Vidalias are all in season from April to June. Because of their higher latitude, Walla Walla Sweets come into season in June and August. Mauis are available year-round.

But, cautions Smittle, don’t buy a bunch of the first sweets you see. “As an onion ripens, the sugar increases and the pungency decreases,” he says. “The only advantage to the early onions is that they’re better than the storage onions you’ve been eating all winter. The first ones on the market are just not as good as the ones that have served their time. Normally I don’t buy too many. I know the good ones are coming later.”