Recent evidence has suggested that moderate consumption of red wine results in a decreased risk of cardiovascular disease. This is attributed to the antioxidant effect of the polyphenolic compounds in red wines. The major antioxidant in red wines – resveratrol – is a stilbene shown to have anticancer effects.
However, wines have also been shown to be contaminated with ochratoxin A (OTA), a mycotoxin that is widespread in foodstuffs including cereals, coffee, walnuts, milk, and pork meat. The European Scientific Committee for Food defines OTA as “a mycotoxin having carcinogenic, nephrotoxic, teratogenic, immunotoxic, and probably neurotoxic effects.” Attempts have been made to clarify what level of OTA consumption is safe, with estimates ranging from 0.5-10 μg kg (parts per billion).
This study examines 15 different red wines – five table wines, four Controlled Denomination of Origin (Denominazione di origine controllata, or DOC), and six organic wines. Researchers (Micelli et al., 2003) looked at the levels of polyphenolic compounds, resveratrol, antioxidant activity, and ochratoxin A (OTA) contamination.
Organic and DOC wines were found to have significantly higher levels of total polyphenols. DOC wines had the greatest total polyphenols, averaging 2,148 mg/liter (parts per million). An organic wine was shown to have the highest total polyphenols of all 15 varieties studied, 2,540 mg per liter, 30% higher than the average total polyphenols in table wines.
Resveratrol and antioxidant activity were both were found to be highest in the organic wines. In terms of resveratrol levels, the organic wines averaged 1.69 mg per liter (parts per million), while DOC and Table wines averaged 1.16 and 1.18 mg per liter respectively. The organic wines tested were found to have the greatest antioxidant activity, averaging 13.6 percent (percentage of β-carotene protection against oxidation). Table wines had on average 50 percent less antioxidant activity than organic and DOC wines.
Of the three types of wine, only the organic wines showed a significant difference in OTA contamination. OTA contamination in six organic wines averaged 0.14 μg per liter (parts per billion), while the four DOC wines averaged 0.45 μg per liter and the five table wines were 0.38 μg per liter.
This study found that among 15 varieties of red wine, organic wines had the greatest concentrations of antioxidant activity and of the key antioxidant resveratrol. An organic wine also was found to have the highest level of total polyphenols. Contamination of the mycotoxin OTA was over three times higher in conventionally grown DOC varieties compared to organic wines, and the OTA levels in table wines were 2.5 times higher that organic red wines.
The study found that the combination of farming practices used by organic grape growers reduced the risk of mycotoxin formation, through an as yet unidentified mechanism. Two possible explanations are discussed:
- Lower levels of nitrogen in organic systems tends to reduce fungal growth; and
- Generally higher levels of antioxidants in organic grapes protects fruit from mycotoxin-forming fungi.
Source: “Polyphenols, resveratrol, antioxidant activity, and ochratoxin A contamination in red table wines, Controlled Denomination of Origin (COD) wines and wines obtained from organic farming.”
Authors: Antonio Micelli, Carmine Negro, Luca Tommasi and Pietro de Leo, Journal of Wine Research, Volume 14, Number 2-3, December 2003.