As a child, you may have wondered why the grapes in the fruit bowl didn't taste much like grape juice or grape candy and sodas. That's because commercial grape juice gets its flavor from dark, thick-skinned grapes, rather than the sweeter and milder-flavored varieties grown for eating. White grape juice, a newer product, is made from a green-skinned variety of grapes.
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Commercial Grape Juice
Ripe grapes are high in naturally occurring sugars, and the powdery coating on their skins contains yeast, so it's no surprise that freshly crushed grape juice ferments readily. After all, this is the characteristic that distinguishes grapes as the ideal fruit for wine. However, wine isn't always the desired result. The story of unfermented grape juice in American commerce begins in 1869 with Dr. Thomas Welch, a tee-totaling dentist who wanted to make non-alcoholic Communion wine for his church. Welch's son Charles promoted the juice successfully at the 1893 World's Fair in Chicago, and their grape juice became a national brand.
Purple Grape Juice
Most purple grape juice is made from the Concord grape, though juice from wine grapes is used as filler in some brands. Concord is a variety native to America and parts of Canada, which produces small berrylike fruit with a distinctive flavor and aroma. A 2007 British study, reported in the "Journal of Agriculture and Food Chemistry," determined that purple Concord grape juice was the fruit juice richest in anthocyanins and polyphenols, two groups of complex organic chemicals with potentially far-reaching health benefits. Aside from these phytochemicals, purple grape juice is also an excellent source of vitamin C and also contains the mineral phosphorus.
White Grape Juice
White grape juice is typically manufactured from green-skinned grapes. Niagara grapes, a cousin of the Concord, are used for their flavor, and juice from white wine grapes is used as a lower-cost filler in some brands. White grape juice lacks the array of phytochemicals found in purple grapes, but it is still a refreshing and healthy beverage with high vitamin C content. A 1992 study published in the "Journal of Pediatrics" also demonstrated that white grape juice was the most digestible for infants and was the best choice as a baby's first fruit juice. Numerous other studies have shown comparable results.
Both white and purple grape juice are an excellent source of vitamin C, with a single 8-ounce glass providing a full day's allowance. That same glass of juice counts as two servings of fruit for nutritional purposes. For medical researchers, the high level of antioxidant phytochemicals in purple grape juice makes it worth further appraisal. Several small-scale studies, collated on the website of the Grape Science Center, have shown that purple grape juice might have a favorable impact on cardiovascular health, the human immune system and the brain's cognitive functions.