Refrigerate ripe tomatoes to inactivate enzymes that continue to soften the fruit by dis-
solving pectins in its cell walls. Fully ripe tomatoes should be used within two or three days.
Preparing This Food
Remove and discard all leaves and stalks. Wash the tomatoes under cool running water, then
slice and serve. Or peel the tomatoes by plunging them into boiling water, then transferring
them on a slotted spoon into a bowl of cold water. The change in temperature damages a
layer of cells just under the skin so that the skin slips off easily.
To get rid of the seeds, cut the tomato in half across the middle and squeeze the halves
gently, cut side down, over a bowl. The seeds should pop out easily.
What Happens When You Cook This Food
When a tomato is heated the soluble pectins in its cell walls dissolve and the flesh of the tomato
turns mushy. But the seeds and peel, which are stiffened with insoluble cellulose and lignin,
stay hard. This is useful if you are baking or broiling a tomato (the peel will act as a natural
“cup”) but not if you are making a soup or stew. If you add an unpeeled tomato to the dish the
peel will split, separate from the tomato flesh, and curl up into hard little balls or strips.
Vitamin C is sensitive to heat. A cooked tomato has less vitamin C than a fresh one,
but it has the same amount of vitamin A because carotenoid pigments are impervious to the
heat of normal cooking.
How Other Kinds of Processing Affect This Food
Artificial ripening. Tomatoes are available all year round. In the summer, when they can be
picked close to the market and have less distance to travel, they are picked vine-ripened. In
the winter, when they have to travel farther, they are picked while the skin is still a bit green
so they will not spoil on the way to market. On the vine, in shipping, or in your kitchen,
tomatoes produce ethylene, a natural ripening agent that triggers the change from green
to red skin. In winter, if the tomatoes are still green when they reach the market, they are
sprayed with ethylene—which turns them red. These tomatoes are called hard-ripened (as
opposed to vine-ripened). You cannot soften hard-ripened tomatoes by storing them at room
temperature. They should be refrigerated to keep them from rotting.
Juice. Since 2000, following several deaths attributed to unpasteurized apple juice contami-
nated with E. coli O157:H7, the FDA has required that all juices sold in the United States be
pasteurized to inactivate harmful organisms such as bacteria and mold.
Canning. Most canned tomatoes are salted. Unless otherwise labeled, they should be con-
sidered high-sodium foods. NOTE: The botulinum organism whose toxin causes botulism
thrives in an airless, nonacid environment like the inside of a vegetable can. Because tomatoes
are an acid food, many people assume that canned tomatoes will not support the growth of
Tomatoes