Watermelon Science, Size and Surprising Uses

(View the original article on the N.C. Research Campus website.)

Once, people wanted big watermelons with lots of seeds.

“Now,” explained Penelope Perkins-Veazie, PhD, postharvest physiologist with N.C. State University’s Plants for Human Health Institute at the N.C. Research Campus, “there are personal-size watermelons in the produce section, and, today, most U.S. melons are seedless.”

Perkins-Veazie has researched watermelon fruit for 15 years working closely with the National Watermelon Association and the National Watermelon Promotion Board. As consumer demand creates a larger market for smaller watermelons, she envisions an apple-like variety with a thin, edible skin that fits in the palm of a hand and has the same familiar flavor, crunch and nutrition.

Such a watermelon, Perkins-Veazie feels, could be a bonanza for growers and consumers because it would be both a novelty and easier to carry on the go. Eating watermelon isn’t the only use she sees for this popular fruit.

Delicious, Nutritious and Useful

Collaborating with scientists at the Appalachian State University Human Performance Laboratory at the N.C. Research Campus and in Boone, N.C., Perkins-Veazie’s recent research studies found that watermelon puree is equivalent to a commercial sports drink in terms of reducing the effects of extensive exercise (manuscript in preparation).

As part of the same collaboration, they are also studying the use of watermelon as a sunscreen. In another partnership, she and scientists in South Carolina are studying the anti-viral properties of watermelon.

Watermelon is the subject of so much research because it is an important crop economically and nutritionally. The fruit is grown in 44 out of 50 American states as well as numerous countries around the world. North Carolina is ranked ninth in U.S. production. Nutritionally, the melon has no fat and is packed with vitamins A and C, potassium and the phytonutrients citrulline and lycopene, all in only 43 calories per cup.

Yet, watermelon has its challenges. A part of the cucurbitaceae plant family (Citrullus lanatus), it is closely related to cucumber, squash and pumpkin. Unlike its cousins, it is best served fresh and does not cook or freeze well.

“Watermelon doesn’t have many ways to be fed to people,” Perkins-Veazie said. “So as a postharvest physiologist, I am looking at fresh cut or juice, for example, and finding out what happens when they are prepared and how long before they go bad, a lot of practical considerations.”

Phyto-Benefits

The nutritional benefits of watermelon and its potential use as a sunscreen or sports drink tie into another area of Perkins-Veazie research. She has studied lycopene and citruline, both of which are phytonutrients or secondary compounds in plants that benefit human health. Lycopene is an antioxidant that gives watermelon its red color. Research shows that lycopene consumption reduces the risk of heart attack and some cancers.

Perkins-Veazie began researching lycopene in 1999 when she was at the U.S. Department of Agriculture in Oklahoma. She and her colleagues were some of the first scientists to quantify the lycopene content among numerous watermelon varieties. They discovered that lycopene levels in watermelon are equivalent to that of raw tomatoes.

Tomatoes were once thought to have the highest levels. They also proved that lycopene in watermelon is bioavailable to the human body, and that lycopene amounts vary across watermelon varieties and growing conditions. Seedless varieties consistently have the highest quantities.

After several years of working with lycopene, Perkins-Veazie became interested in citrulline, which is a non-essential amino acid that coexists with the essential amino acid arginine. In the body, citrulline is converted into arginine via the nitric oxide system. Arginine plays a role in cell division, healing and the removal of ammonia from the body. Consuming citrulline is shown by some research studies to lower blood pressure and blood sugar levels.

“Citulline and agrinine, it is difficult to pry the two apart. So citrulline wasn’t studied much in the methodology,” she said. “We started looking at that and teamed up with a chemist so we can figure out how much was in watermelon. It became apparent that lycopene was secondary to citrulline in health benefits.”

Teaming up with colleagues in Florida, Perkins-Veazie participated in a study that showed citrulline can help lower blood pressure.

Beyond Watermelon

Perkins-Veazie’s research extends beyond watermelon. She works with raspberry, black raspberry, blackberry, muscadine, peach and strawberry growers on improving varieties, studying storage life and phytonutrient content. She can see the day when growers have blackberries that have an identifiable aroma like other berries and fruits in the produce section.

She is experimenting with the use of phytosanitizers that can be sprayed on berries in the field to eliminate bacteria and other pathogens to extend shelf-life. She is also involved with research that is leading to new methods to detect and eliminate pathogens on tomatoes while they are still in the field or in packing houses.

She is part of a team with researchers from the University of Tennessee that developed an organic wash system for cantaloupes. In Western North Carolina, she is partnering with growers to develop pumpkin and winter squash varieties that can boost agro-tourism to supplement the Christmas tree industry.

“It is all about consumer demand,” she said. “The biggest challenge of my job is coming up with niche products and approaches that will help stabilize a commodity for growers.”

Products that help watermelon to berry growers succeed and make fruits and vegetables more accessible, desirable, nutritious and safe for consumers.

Writer: Jennifer Woodford, N.C. Research Campus