State of Science :: Nutritional Quality
Weather Conditions Account for Higher Levels of Anthocyanins in Conventional Syrah Grapes Compared to Organically Grown
Anthocyanins are naturally occurring polyphenols that cause the red to blue colors in fruit and vegetables. They are found in grape skins and red wines and have recently been shown to have potential antioxidant and other health benefits. Some studies have shown a difference in polyphenol concentrations of crops grown using organic or conventional practices; but this study was the first to look at grapes in particular.
This study found that the anthocyanin concentrations were very high for both organic and conventional Syrah grape plots. However, they found that "conventionally grown grapes showed a significantly higher content of total anthocyanins compared to that found in the organic cultivation."
Due to the absence of synthetic pesticides, "organically grown plants are usually exposed to different forms of stress, which induce accumulation of phenolic compounds." This study, however, found this not to be the case. The researchers felt this may be explained by the fact that the growing season in 2002 when this study was conducted was very hot and dry, causing a weaker pathogen pressure on the plants than usual. During this exceptionally hot and dry season, "chemical stress accompanying conventional production probably overtook biotic stress such as pest pressure, finally resulting in a higher anthocyanin content in grape skin."
Further studies are needed to help clarify the effect organic and conventional growing practices have on the anthocyanin concentration in grapes and other crops.
Source: "Comparison of the anthocyanin composition during ripening of Syrah grapes grown using organic or conventional agricultural practices."
Authors: Mayline Abert Vian, Valerie Tomao, Phillipe Olivier Coulomb, Jean Michel Lacombe, and Olivier Dangles, Journal of Agricultural Food and Chemistry, Volume 54, Number 15, pp 5230-5235, 2006.