By Jeremy Appleton, ND, CNS
Healthnotes Newswire (September 7, 2006)—Storing your watermelon in a cool, but not cold, place could make it a healthier snack. New research has found significant gains in the carotenoid content of watermelons stored at 69.8°F (21°C) compared with fresh watermelons and those stored at lower temperatures.
“Red-fleshed watermelon contains significant amounts of lycopene, a carotenoid pigment that is a highly efficient free radical scavenger,” said Penelope Perkins-Veazie, a plant physiologist with the US Department of Agriculture (USDA) and lead author of the study. “Compared to fresh fruit, watermelons stored at 69.8°F (21°C) gained 11 to 40% in lycopene and 50 to 139% in beta-carotene.”
Lycopene, beta-carotene, and other carotenoids are powerful antioxidants. Consuming lycopene-rich tomatoes and tomato-containing foods and beverages has been linked with a reduced incidence of cardiovascular disease and some types of cancer. Lycopene also protects the skin from damage caused by exposure to ultraviolet light and may improve male fertility. The carotenoid content of watermelons is similar to that of tomatoes.
In the new research, which was published in the Journal of Agricultural and Food Chemistry, researchers at USDA stored samples of three different types of watermelon (open-pollinated seeded, hybrid seeded, and seedless) for 14 days at three different cool temperatures: 41°F (5°C), 55.4°F (13°C), and 69.8°F (21°C). (Most kitchen refrigerators are set between 35 and 40°F (1.67° and 4.45°C.) They compared these watermelons with fresh watermelons for signs of ripeness (rind thickness, pH, color, soluble solids) as well as for content of several carotenoids.
The fruit stored at 69.8°F (21°C) had increased signs of ripeness compared with fresh fruit and fruit stored at lower temperatures. This ripeness appears to have contributed to an increase in lycopene (by far the major carotenoid in watermelon), as well as beta-carotene and other carotenoids.
“Lycopene content of watermelon varies from one cultivar to another,” said Dr. Perkins-Veazie. “Seedless types of watermelon tend to have more lycopene, averaging more than 50 mcg per gram of fresh weight.”
For those wishing to get more lycopene in their diet, this is good news. Keeping a fresh watermelon around for a week or two to ripen in a cool spot appears to make it that much healthier. Other sources of lycopene include red grapefruit and guava.
(J Agric Food Chem 2006; 54;5868–74)
Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.
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