Preparing Blueberries

Rinse the berries under cool running water, then drain them and pick them over carefully to remove all stems, leaves, and hard (immature) or soft (over-ripe) berries.

What Happens When You Cook Blueberries

Cooking destroys some of the vitamin C in fresh blueberries and lets water-soluble B vitamins leach out. Cooked berries are likely to be mushy because heat dissolves the pectin inside.

Blueberries may also change color when cooked. The berries are colored with blue anthocyanin pigments. Ordinarily, anthocyanin-pigmented fruits and vegetables turn reddish in acids (lemon juice, vinegar) and deeper blue in bases (baking soda). But blueberries also contain yellow pigments (anthoxanthins). In a basic (alkaline) environments, as in a batter with too much baking soda, the yellow and blue pigments will combine, turning the blueberries greenish blue. Adding lemon juice to a blueberry pie stabilizes these pigments; it is a practical way to keep the berries a deep, dark reddish blue.

How Other Kinds of Processing Affect Blueberries

Canning and freezing. The intense heat used in canning the fruit or in blanching it before freezing reduces the vitamin C content of blueberries by half.

Medical Uses and/or Benefits of Blueberries

Reduced risk of heart disease, cancer, decline of brain function, and other diseases of aging. Antioxidants, such as vitamin C, prevent free radicals, fragments of molecules, from hooking up with other fragments to produce compounds that damage body cells and may cause heart disease, cancer, memory loss, and other conditions associated with aging or damaged cells.

In 1996, researchers at the USDA Jean Mayer Human Nutrition Research Center on Aging at Tufts University (Boston) showed that, ounce for ounce, blueberries, spinach, and strawberries were the most potent antioxidants of 40 foods tested.

In a second series of studies the following year, the scientists fed aging rats a diet of chow alone or chow plus extract of blueberries, strawberries, or spinach. In the end, the diet with added blueberry extract was most effective in slowing oxygen-related changes. NOTE: The antioxidant ranking of these foods may vary depending on growing conditions, season, and other variables.

Urinary antiseptic. A 1991 study at the Weizmann Institute of Science (Israel) suggests that blueberries, like CRANBERRIES, contain a compound that inhibits the ability of Escherichia coli, a bacteria commonly linked to urinary infections, to stick to the wall of the bladder. If it cannot cling to cell walls, the bacteria will not cause an infection. This discovery lends some support to folk medicine, but how the berries work, how well they work, or in what "dosages" remains to be proven.

Adverse Effects Associated with Blueberries

Allergic reaction. Hives and angiodemea (swelling of the face, lips, and eyes) are common allergic responses to berries, virtually all of which have been reported to trigger these reactions. According to the Merck Manual, berries are one of the 12 foods most likely to trigger classic food allergy symptoms. The others are chocolate, corn, eggs, fish, legumes (peas, lima beans, peanuts, soybeans), milk, nuts, peaches, pork, shellfish, and wheat.