The New Complete Book of Food

 0The New Complete Book of Food

Diets That May Restrict or Exclude This Food

Antiflatulence diet

Low-fiber diet

Buying This Food

Look for: Firm, clean shallots; yellow, white, or red onions with smooth, dry, crisp skin

free of any black mold spots. Leeks and green onions should have crisp green tops and clean

white bulbs.

Avoid: Onions that are sprouting or soft or whose skin is wet—all signs of internal decay.

Storing This Food

Store shallots and red, yellow, and white onions in a cool cabinet room or root cellar where

the temperature is 60°F or lower and there is plenty of circulating air to keep the onions dry

and prevent them from sprouting. Properly stored, onions should stay fresh for three to four

weeks; at 55°F they may retain all their vitamin C for as long as six months.

Cut the roots from green onions, scallions, and leeks; trim off any damaged tops; and

refrigerate the vegetables in a tightly closed plastic bag. Check daily and remove tops that

have wilted.

Preparing This Food

When you cut into an onion, you tear its cell walls and release a sulfur compound called pro-

panethial-S-oxide that floats up into the air. The chemical, identified in 1985 by researchers

at the University of St. Louis (Missouri), turns into sulfuric acid when it comes into contact

with water, which is why it stings if it gets into your eyes. You can prevent this by slicing

fresh onions under running water, diluting the propanethial-S-oxide before it can float up

into the air.

Another way to inactivate propanethial-S-oxide is to chill the onion in the refrigerator

for an hour or so before you slice it. The cold temperature slows the movement of the atoms

in the sulfur compound so that they do not float up into the air around your eyes.

To peel the brown papery outer skin from an onion or a shallot, heat the vegetable in

boiling water, then lift it out with a slotted spoon and put it in cold water. The skin should

come off easily.

What Happens When You Cook This Food

Heat converts an onion’s sulfurous flavor and aroma compounds into sugars, which is why

cooked onions taste sweet. When you “brown” onions, the sugars and amino acids on their