WASHINGTON (Reuters) -- That ice-cold watermelon may be refreshing, but it can be less nutritious than watermelon served at room temperature, U.S. Department of Agriculture scientists reported on Wednesday.
Watermelons stored at room temperature deliver more nutrients than refrigerated or freshly picked melons, they reported in the Journal of Agricultural and Food Chemistry.
Penelope Perkins-Veazie and Julie Collins of the USDA's South Central Agricultural Research Laboratory in Lane, Oklahoma, looked specifically at carotenoids -- antioxidants that can counter the damage caused by sun, chemicals and day-to-day living.
Watermelon is rich in lycopene, an antioxidant that makes watermelons and tomatoes red and may help prevent heart disease and some cancers.
Perkins-Veazie and Collins tested several popular varieties of watermelon stored for 14 days at 70 F, 55 F and 41 F.
Whole watermelons stored at 70 degrees Fahrenheit, which is about room temperature in air-conditioned buildings, had substantially more nutrients, they reported.
Compared with freshly picked fruit, watermelon stored at 70 F gained up to 40 percent more lycopene and 50 percent to 139 percent extra beta-carotene, which the body converts to vitamin A.
"All watermelons used in our study had been selected by commercial growers as fully ripe when harvested," the researchers wrote.
They said their findings showed that watermelons continue to produce these nutrients after they are picked and that chilling slows this process.
"The usual shelf life for watermelons is 14 to 21 days at 13 degrees Celsius (55 F) after harvest," the researchers wrote.
At refrigerated temperatures, such as 41 F, watermelon starts to decay and develop lesions after a week, they noted.