The team of scientists, based at the University of Arkansas, said that the method – which is based on a technique called subcritical water processing – is not only more environmentally friendly than traditional extraction with solvents, but also increases the efficiency of extraction and produces antioxidant compounds that are smaller and are more effectively adsorbed in the body.
Dr Jerry King, professor of chemical engineering at the University of Arkansas, who led the project, said that the goal is to use grape skins left from making wine and juice “to get a value-added food supplement product.”
Whilst wine and grape juice are known to contain natural antioxidants, including and the powerful antioxidant resveratrol, up to 50% remain in the waste material left behind when the skins, stems and seeds are filtered.
King and his team said that the process could one day be used to create ingredients for health foods and supplements from the grape waste by-products of the wine and juice industries – adding that the US alone is estimated to produce 15 million tons of grape waste.
“These are valuable components that don’t go into the juice or wine," said King, who noted there is great commercial interest in developing new technologies to extract functional ingredients from industrial waste.
The research team initially received $350,000 over four years from the U.S. Department of Agriculture as part of an interdepartmental collaboration to employ a method using pressurized water to extract the antioxidants.
In the past four years, they worked to optimize the extraction method which involves a process of continuous extraction that allows for high flow rates of heated high-pressure water, thus allowing it to remain liquid at high temperatures and act as an extraction solvent.
The researchers said that the method helps to stop the break-down of antioxidants at high temperatures, thus minimising degradation and maximising efficiency.