Soaking muscadine grape seeds or skins in an enzyme solution can boost antioxidants extracted from the fruit, creating possible new uses for grape leftovers according to a University of Florida study.
The study was published in the February online edition of the journal Food Chemistry and is scheduled for its print edition in August.
Winemakers typically dispose of grape seeds and skins after production, study co-author Maurice Marshall, a University of Florida and Institute of Food and Agricultural Sciences food science and nutrition professor, said in a news release.
But researchers found that cellulase, pectinase and glucosidase from the seeds and skins increase antioxidant activity. Possible new uses for what’s been regarded a waste product include food additives or nutritional supplements.
Changmou Xu, a doctoral student in food science and nutrition, led the study under Marshall’s advisement. Researchers ground muscadine skin or seeds to a powder and extracted phenolics by soaking the powder in an enzyme solution.
Xu and other researchers hoped that by treating grape skins and seeds with enzymes that break down cell walls, they could make it easier to extract phenolic compounds.
But the enzymes actually decreased the phenolics from the discarded material. That was the downside, Marshall said. The upside was that enzyme hydrolysis — a form of digestion — can release more antioxidants.
“You got less phenolics, but you improve their antioxidant activity,” he said.
Muscadine grapes are grown in Florida. Their thick skin accounts for about 40% of the fruit’s weight. That skin gives the grape natural resistance to disease, fungi and insects, as well as storing many antioxidants, according to the study.
Grape phenolics serve as anti-inflammatory agents, Marshall said, and can reduce the risk of certain cancers as well as high blood pressure and heart disease.
Currently the food industry uses synthetic antioxidants as a preservative. Synthetic antioxidants also preserve fats and oils in cosmetics and pharmaceuticals. But the phenolics extracted during the University of Florida study are natural antioxidants.
Besides Xu and Marshall, authors included Yavuz Yagiz; Wlodzimierz Borejsza-Wysocki; Milena Ramirez-Rodrigues; and Jiang Lu, professor of viticultural sciences at Florida A&M University.