The quality of wine and its aroma/flavor characteristics are directly related to its chemical composition. There are many factors that can influence the chemical composition of a wine, including grape variety, soil type, climate, and winemaking practices (just to name a few). Chemical composition, specifically the mineral content, is primarily of natural origin, influenced greatly by the geochemistry of the soil in which the vines grow. The concentrations of these minerals/metals are influenced by many factors, including the grape variety, type of soil, and climate conditions.
Mineral/metal composition in wine can also be influenced by natural plant defenses, viticulture management practices and the winemaking process. Studies have found that certain pesticides, fungicides, and fertilizers increase the amounts of arsenic (As), cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb), and zinc (Zn) in the soil, the vines grown in that soil, and the wine produced from the grapes of those vines. During the winemaking process, there is also opportunity for trace metal contamination, including the type of metal that the wine is exposed to along the way, the casks/barrels/pipes used in fermentation and storage, and the vessels used to store the wine in for aging purposes.
Since there are ample opportunities for metal contamination in wine, either through natural or anthropogenic sources, knowing the concentrations of these metals in the finished wine is of utmost importance for quality and health-related reasons.
In Croatia, several studies have found concentrations of some heavy metals in finished wines, including Cd, Cu, Pb, Zn, As, chromium (Cr), iron (Fe), nickel (Ni), and vanadium (V). Specific geographic origin of the wines may play a role in the concentrations of these various metals, however, few studies have sought to examine this aspect. In Croatia, the two largest grape growing regions are Slavonia and Istria, with Slavonia being the largest and producing the highest quality of wines. Grapes grown in the Slavonia region include Graševina, Pinot white, Traminac, Frankovka, Chardonnay, Rizvanac, Ružica, and Sauvignon. In Istria, the predominant grape variety grown is Malvazija Istarska, with other grape varieties grown much less often.
Studies have already established that Eastern Slavonia is a region in Croatia that is known for increased concentrations of arsenic in the water supply, which is a serious health hazard. Arsenic in this area comes from several sources, including natural geological formation, ore deposits, and mines, in addition to anthropogenic industrial activities. Groundwater in the region is used for human consumption and for agricultural irrigation practices. With some locations reaching arsenic concentrations of up to 600μg/L, water must first be treated and purified before it is fit for human consumption. However, water used for agricultural irrigation is known to remain untreated, thereby the foods and other products (in this case wine) created from agriculture may be contaminated and need be monitored and tested.
The study presented today sought to examine the mineral and metal content of Croatian wines, comparing wines created from grapes grown in known areas of high arsenic contamination with areas that have been historically uncontaminated.
All measurements were taken on a high resolution inductively coupled plasma sector field mass spectrometer.
14 brands of wine from three grape growing regions in Croatia were analyzed, including nine from Slavonia, three from Vojvodina, and two from Istria. For most of the brands, two bottles from the same vintage were analyzed. Both red and white wines were analyzed for the Slavonia and Istria regions, while only white wines were analyzed for the Vojvodina region. Nearly all the wines were stored in glass bottles with cork stoppers, with the exception of one wine from Istria that was purchased in bulk.
The following metals were measured and analyzed: Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, Ti, Tl, U, V, and Zn.
Data for the minimum contaminant level of toxic elements in wine is defined by the Croatian regulative for quality control of food and regulation for wine production. Wine standards were also given by the Office International de la Vigne et du Vin.
- For most of the wines, both bottles from the same vintage showed very similar results, though some brands showed greater differences in trace element concentrations between bottles (higher than 25% difference for some).
o For Traminac mirisavi, iron (Fe) differed between bottles.
o For Italijanski rizling, copper (Cu) differed between bottles.
o For Pinot sivi, selenium (Se) differed between bottles.
o For Traminac, titanium (Ti) differed between bottles.
o For Zweigelt, tin (Sn) differed between bottles.
o For Graševina, Muškat Ottonel, Teran, and Erdevički rajnski rizling, multiple elements differed between bottles.
§ All these variations between bottles could be due to differences in the winemaking process for each wine, or is a result of natural variation of certain elements.
- Average concentrations of elements in the studied wines decreased in the following order: Fe>Mn; Al>Zn>Sr; Cu>Ba>Ni; Pb>Cr>Ti; V>Li>Sn>As; Co>Se>Sb>Be>Cd>U; and Tl>Bi.
o Some elements showed little variation in concentrations from wine to wine (Ba, Cr, Co, Fe, Li, Mn, Ni, Se, Sr, Pb), while others showed a much greater variation from wine to wine (As, Cu, Sb, Tl).
- Most of the elements in this study fell in the range of concentrations found in other studies of Croatian wines, with the exception of cadmium (Cd), which was found to be higher than in previously reported studies and chromium (Cr) and manganese (Mn), which were found to be lower than reported studies.
- Arsenic concentrations reported were found to be similar to wines found in neighboring countries, with all levels remaining below the maximum contaminant level set by Croatian and O.I.V. laws and regulations.
o Regionally, significant differences were found for arsenic levels in wine in Slavonia and Vojvodina, when compared to wines from Istria.
§ The higher arsenic levels in Slavonia and Vojvodina wines are indicative of the known ground water contamination of arsenic in those areas.
- Aluminum (Al), arsenic (As), and beryllium (Be) were found at higher levels in wines from Vojvodina.
- Using a two-way ANOVA, elements could be divided into several groups in regards to their relatively concentrations in wines of different type and origin.
o Al, As, Be, Bi, Li, Pb, and Tl showed strong differences between regions, even after taking into consideration wine type.
§ For all those elements (except Tl), all were significantly higher in wines from Vojvodina.
o Cd, Cu, Fe, Ni, Sb, Sn, V, and Zn showed no significant differences between wine region or wine type.
o Ba, Cr, Se, and Sr were significantly different between wine type and wine region.
§ Vineyard soil and dust are possible sources of Ba and Sr in wine.
o Mn, Mo, and U were significantly different between wine type (red vs white), but were showed no significant differences between regions.
§ Regional differences are likely due to variation in soil geochemistry.
The results of this study indicate that wines are influenced not only by the mineral composition of the soil, but also the geochemistry of the water used in irrigation management. Starting with the knowledge that higher levels of arsenic contamination are present in certain regions of Croatia (i.e. Slavonia), the authors were able to confirm that the wines created from grapes grown in those same regions are also laden with higher levels of arsenic.
In regards to other elements, copper (Cu), molybdenum (Mo), antimony (Sb), and tin (Sn) have been found in atmospheric analyzes arising from anthropogenic sources such as vehicle emissions and wear and tear or mechanical structure on vehicles (i.e. brakes/brake lining, etc). These same elements were also found in the wines in this study, indicating another possible source of contamination in these study wines.
It is important to note, however, that the concentrations of all the elements analyzed in this study, including arsenic, were found to be below the maximum contaminant levels established by Croatian and O.I.V. laws and regulations. Variation in the concentrations of these elements appeared to be mostly region-specific, owing to the particular soil and water geochemistry of each region. Other elements measured, specifically Cu, Mo, Sb, and Sn, are strong indicators of anthropogenic contamination in the wines, which is likely due to vehicular emissions.
Overall, the elements analyzed in the wines from Croatia appear to be primarily natural in origin, reflecting regional soil and water geochemistry, with a smaller subset of elements arising from anthropogenic sources of environmental pollution such as industrial activities or other viticulture/winemaking practices.
One question I had after reading the results of this study was, even though the concentrations of heavy metals in these wines were below the accepted threshold levels according to law, what happens when there is long term exposure? Many heavy metals, including arsenic, cadmium, chromium, coppers, and lead (just to name a few), bioaccumulate in the environment, meaning that while small short-term exposure presents little to no danger, continual exposure to trace amounts accumulate in the system, resulting in the accumulation of high levels of the metal in the system and long-term damage.
Long-term exposure/bioaccumulation of some heavy metals may result in a wide variety of human health problems, including renal disease, lung disease/cancer, kidney damage, neurological damage, etc. If one consumes a wine naturally higher in certain trace heavy metals over a long period of time, does it bioaccumulate in the system and cause health problems down the road? Or, is the body able to rid itself of the metal faster than we have time to consume and accumulate it? I’d be curious to see a study on this, if determining cause and effect is even possible with this type of long-term study.
Though long-term studies should be performed to get a more complete view of the effect of arsenic and other heavy metal contamination in wines, this study shows that wine produced in regions of naturally higher heavy metal levels, while they do show increased concentrations in the wine itself, it does not appear to be at levels that are dangerous for human consumption for the short-term. Perhaps by treating the water used in irrigation, the levels of these heavy metals would be even lower, thereby reducing possible negative long-term effects with consumption over time.
I’d love to hear what you all think about this topic! Please feel free to comment below.
Source: Fiket, Z., Mikac, N., and Kniewald, G. 2011. Arsenic and other trace elements in wines of eastern Croatia. Food Chemistry 126: 941-947.
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!