Plums
Plums have moderate amounts of dietary fiber and a little vitamin A. They are a good source of vitamin C.
One fresh plum (21/8-inch diameter) has one gram dietary fiber, 228 IU vitamin A (10 percent of the RDA for a woman, 8 percent of the RDA for a man), and 6 mg vitamin C (8 percent of the RDA for a woman, 7 percent of the RDA for a man).
Like apple seeds, apricot pits, and peach pits, the seed inside a plum pit contains amygdalin, a naturally occurring cyanide compound (see apples).
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Fresh and ripe, with the peel.
Look for: Firm, brightly colored fruit that are slightly soft to the touch, yielding a bit when you press them with your finger.
Comparing Varieties of Plums
Damson Dark skin and flesh (for preserves only)
Friar Dark red skin, deep yellow flesh
Greengage Green yellow skin and yellow flesh
Italian (“prune” plums) Small, oval, with blue purple skin and firm golden flesh
Laroda Large; yellow skin with a red blush and yellow flesh
Red beauty Bright red skin, firm yellow flesh
Santa Rosa Red purple skin, yellow flesh (very tart)
Store firm plums at room temperature. Plums have no stored starch to convert to sugars, so they won’t get sweeter after they are picked, but they will soften as their pectic enzymes dissolve some of the pectin stiffening their cell walls. When the plums are soft enough, refrigerate them to stop the enzyme action.
Wash and serve fresh plums or split them, remove the pit, and slice the plums for fruit salad. Plums can be stewed in the skin; if you prefer them skinless, put them in boiling water for a few minutes, then lift them out with a slotted spoon and plunge them into cold water. The hot water will damage a layer of cells under the skin, the plum will swell, and its skin will split and peel off easily.
When you cook a plum, its water-soluble pectins and hemicellulose will dissolve and the flesh will soften. Cooking may also change the color of red, purple, or blue red plums containing anthocyanin pigments that are sensitive to acids or bases (alkalis). The colors get more intensely red or purple in acids (lemon juice) and less so in bases (baking soda). Cooking plums (which are acid) in an aluminum pot can create acid/metal compounds that discolor either the pot or the plum.
Drying. See prunes.
False-positive test for carcinoid tumors. Carcinoid tumors, tumors that may arise from tissues of the endocrine or gastrointestinal systems, secrete serotonin, a chemical that makes blood vessels expand or contract. Because serotonin is excreted in urine, these tumors are diagnosed by measuring the serotonin levels in the patient’s urine. Plums contain large amounts of serotonin. Eating plums in the 72 hours before the test might give a false-positive result, suggesting that you have an endocrine tumor when in fact you do not. (Other foods rich in serotonin include avocados, bananas, eggplant, pineapple, tomatoes, and walnuts.)
