In a study of 19 top selling cocoa-containing and chocolate products on the US market, scientists found trans-resveratrol levels were highest in cocoa powders.
"This relationship suggests that both the stilbenes and the flavan-3-ols are associated with the brown cocoa particles in food formulation," report the researchers in the 30 August issue of Journal of Agricultural and Food Chemistry.
Adding that the "effects of food processing on levels of the stilbenes still need to be investigated".
Resveratrol is an antioxidant compound found in at least 72 species of plants, although science to date suggests that the primary dietary sources are grape and grape products, notably wine, and peanut products. Concentrations of resveratrol vary widely, even within a food source: for example, researchers have found that levels of the compound in wine tend to be higher in grapes grown in cooler climates.
Antioxidants, meanwhile, are understood to prevent cellular damage by preventing the formation of free radicals, atoms that are formed when oxygen interacts with certain molecules. These free radicals can, in turn, damage DNA and pave the way towards serious illness like cancer, other diseases, and outward signs of ageing.
Over the past few years, research into cocoa (Theobroma cacao L.), has detected a source of antioxidant compounds - most notably the flavan-3-ol polyphenol class - in this raw material, processed to make one of the most popular confectionery products around the globe.
For this latest study, conducted at US chocolate giant Hershey's Center for Health and Nutrition, scientists set out to further characterise the levels of trans-resveratrol and trans- piceid in a variety of cocoa-containing and chocolate foods, with the aim of relating these foods to other significant dietary sources of resveratrol, such as red wine and peanut products.
They investigated cocoa-powders, unsweetened baking chocolates, dark chocolates, milk chocolates and chocolate syrups.
The researchers, led by W. Jeffrey Hurst, found that cocoa powders contained the highest trans-resveratrol levels (an average of 1.85 micrograms per gram), followed by unsweetened baking chocolate (with an average of 1.24 micrograms per gram), semi-sweet chocolate chips, dark chocolate, milk chocolate and chocolate syrups.
"This places cocoa powder, dark chocolate, and baking chocolate in a relatively high position for foods that contain resveratrol," report the scientists.
They add that "on a per serving basis, cocoa-containing and chocolate products have less trans-resveratrol than red wine and grape juice but more than roasted peanuts".
Indeed, on an equal weight basis, cocoa powder had about half as much trans-resveratrol as the average Californian red wine.
Further, they concluded that amounts of trans-resveratrol, and trans-piceid, were closely correlated with the amount of non-fat cocoa solids (NFCS).
NFCS, the scientists explain, is a measure of the amount of brown cocoa 'particulates' in a product, and a direct result of the product formulation in the cocoa-containing products.
Source: Journal of Agricultural and Food ChemistryPublished online ahead of print, doi: 10.1021/jf801297w“Survey of the trans-Resveratrol and trans-Piceid Content of Cocoa-Containing and Chocolate Products”Authors: W.Jeffrey Hurst, J.A. Glinski, K.B. Miller, J. Apgar, M.H.Davey, D.A.Stuart