Muscadines (Vitis rotundifolia) are a grapevine species native to the present-day southeastern United States that has been extensively cultivated since the 16th Century. Its recognized range in the United States extends from New York south to Florida, and west to Missouri, Kansas, Arkansas, Oklahoma and Texas. They are well adapted to their native warm and humid climate; they need fewer chilling hours than better known varieties and they thrive on summer heat.
The muscadine berries range from bronze to dark purple to black in color when ripe. They have skin sufficiently tough that eating the raw fruit often involves biting a small hole in the skin to suck out the pulp inside. Muscadines are not only eaten fresh, but also are used in making wine, juice, and jelly.
Muscadine grapes are rich sources of polyphenols and other nutrients studied for their potential health benefits. Reports have indicated that muscadine grapes may contain high concentrations of resveratrol — a polyphenol with reported beneficial health effects — and that wines produced from these grapes, both red and white, may contain more than 40 mg/L of resveratrol. However, subsequent studies have found no or little resveratrol in different varieties of muscadine grapes.
Unlike most cultivated grapevines, many muscadine cultivars are pistillate, requiring a pollenizer to set fruit. A few, however, such as 'Carlos' and 'Noble', are perfect-flowered, produce fruit with their own pollen, and may also pollinate pistillate cultivars.
Cultivars include Black Beauty, Carlos, Cowart, Fry, Granny Val, Ison, James, Jumbo, Magnolia, Nesbitt, Summit, Supreme. Produced by the University of Florida, the cultivar, 'Southern Home', contains both muscadine and subgenus Vitis in its background.
Crops can be started in 3-5 years. Commercial yields of 3–7 tonnes per hectare (8-18 tons per acre) are possible. Muscadines grow best in fertile sandy loam and alluvial soils. They grow wild in well-drained bottom lands that are not subject to extended drought or waterlogging. They are also resistant to pests and diseases, including Pierce's disease, which can destroy other grape species. Muscadine is one of the grape species most resistant to Phylloxera, an insect that can kill roots of grapevines.
While not one of the most widely marketed varietals produced, the visibility of muscadine wine has benefited from the discovery that it appears to provide greater amounts of antioxidants than many better-known red wines. In particular, muscadine wines (both red and white) contain over five times more resveratrol than ordinary red wines: more than 40 mg/L compared to between 0.2 and 5.8 mg/L.
Because grape vines synthesize resveratrol as a defense, it has been claimed in sales literature that the use of pesticides greatly reduces the grape's resveratrol content; however, scientific studies either find no correlation between pesticide use and resveratrol, or find that pesticide use has only a weak effect.
Although muscadine-derived products are sold as source of resveratrol, they have become eclipsed by knotweed, a cheaper and more concentrated source. Muscadine grape seeds and skins contain high concentratons of antioxidants. Often grape derivatives are included in supplements for the sake of appearance, with knotweed supplying the bulk of the resveratrol.
Resveratrol is produced by many plants, apparently due to its antifungal properties. It is found in widely varying amounts in grapes (primarily the skins). Ordinary non-muscadine red wine contains between 0.2 and 5.8 mg/L, depending on the grape variety, while white wine has much less - the reason being that red wine is fermented with the skins, allowing the wine to absorb the resveratrol, whereas white wine is fermented after the skin has been removed. Wines produced from muscadine grapes, both red and white, may contain more than 40 mg/L.
In grapes, resveratrol is found primarily in the skin and seeds. This is particularly true for muscadine grapes, whose skin and seeds have been reported to have about one hundred times the concentration as the pulp. The amount found in grape skins also varies with the grape cultivar, its geographic origin, and exposure to fungal infection. The amount of fermentation time a wine spends in contact with grape skins is an important determinant of its resveratrol content. According to "Le Blanc et al., 2006", muscadine table wines contain between 9 and 32 mg/L of cis resveratrol and between 5 and 13 mg/L trans resveratrol.
Several studies have detected substantial amounts of resveratrol in Muscadine berries and seeds. Concentrations for the berries without seeds have been reported to range from 3 to 24 ppm (parts per million) in dried samples. Containing an average of 43 ppm, the high seed concentration of resveratrol could be significant during muscadine wine making when the fermenting wine is in contact with seeds. Muscadine pomace, the solids left after pressing, contained 18 to 84 ppm in dried samples. A purée made from the pomace with the seeds removed contained 10 to 62 ppm. Muscadine wine was reported to have from 0.7 to 2 mg/L resveratrol for red wines and 0.3 to 1 mg/L resveratrol for white wine. For juices, resveratrol was found in concentrations ranging from 3 to 13 mg/L. While initial reports have indicated that muscadine grapes could contain high concentrations of resveratrol, subsequent studies have found no or little resveratrol in different varieties of muscadine grapes.
Other muscadine polyphenols include:
Interestingly, the rank order of total phenolic content among muscadine components was found to be seeds >> skins > leaves >> pulp.