Kelly Decorde of the University of Montpelier in France, part of the European research team, said processing the fruit into juice has the potential to increase the bioavailability of the naturally-occurring compounds and anti-oxidants found in the whole fruit.

The study, published in Molecular Nutrition and Food Research, said aortic plaque was evaluated to determine the effectiveness in decreasing plaque that is associated with atherosclerosis -- or "hardening" of the arteries caused by multiple plaques within the arteries.

"This study demonstrates that processing apples and purple grapes into juice modifies the protective effect of their phenolics against diet induced oxidative stress and early atherosclerosis in hypercholesterolemic hamsters," the researchers said in a statement.

"These results show for the first time that long-term consumption of anti-oxidants supplied by apples and purple grapes, especially phenolic compounds, prevents the development of atherosclerosis in hamsters, and that the processing can have a major impact on the potential health effects of a product."