A few weeks ago, a reader (Christine M.) asked the following question in a comment on one of my posts (“Noble Rot Affects the Aromatic Composition and Quality of Amarone Wine”): “it has been hinted to me that noble rot wines might contain significant beneficial health effects – just anecdotal information, not scientific…if you have any knowledge of people deriving benefit from drinking these wines, I would love to hear it – whether scientific or anecdotal.” After a bit of digging, I was able to find one article that I thought would shed some light on her question. It’s a little older than the articles I usually review on this blog, however, it was still published within the last 6 years, and is the most relevant article I could find to answer her question as directly as I could. I hope Christine M. is reading!
Certain polyphenols in wine have been linked to increased health benefits, most notably, resveratrol. It has been found to inhibit the oxidation of LDL cholesterol, the dioxygenase activity of lipoxygenase, and also platelet aggregation. In addition to these inhibitory properties, resveratrol is also known for its’ beneficial anti-inflammatory properties. Resveratrol can exist in several forms, trans-resveratrol, cis-resveratrol, and its glucosidic form, piceid. There are several other important polyphenols in wine that also serve beneficial roles in humans, however resveratrol is the one most often studied.
Different winemaking techniques can change the amount of resveratrol in the finished wine, as well as the variety of grape and growing conditions. It has been shown that clarifying and filtering wine leads to decreases in resveratrol and piceid levels, however extended maceration techniques increases the levels of these compounds. Certain diseases affecting grapes, specifically Botrytis cinerea (grey mold; Noble Rot) have been shown to lead to decreases in resveratrol content in grapes (and thus the finished wine), which is caused by B. cinerea generating a lactase-like enzyme that effectively oxidizes resveratrol and other stilbenic compounds.
There are three commonly known types of wine in the world that are made from Botrytis cinerea-infected grapes, including Tokaji Aszú (from Hungary), Sauternes (from France), and German quality wines with “Prädikat Auslese, Beerenauslese, Eiswein, and Trockenbeerenauslese”.
In the study presented today, the authors aimed to determine if the presence of Botrytis cinerea in the vineyard leads to decreased levels of resveratrol in some Hungarian and German wines (see styles above), and to compare different wines with varying levels of Botrytis cinerea exposure and undergoing different winemaking techniques in regards to their resveratrol and piceid levels, as well as their total phenolic content and antioxidative capacity. By knowing these values, it can be inferred if wines made from Botrytis cinerea-infected grapes contain health beneficial side effects for humans.
18 wines from Hungary and 15 wines from Germany were studied. The wines came from a variety of sources, and represented the entire spectrum of Tokaj and German wines with “Prädikat Auslese, Beerenauslese, Eiswein, and Trockenbeerenauslese”.
HPLC was used to measure resveratrol and picied. Total polyphenols were determined using the Folin-Ciocalteu method. Finally, antioxidative capacity was determined using the TEAC-test.
- Trans-picied levels ranged from not detectable to 1.8mg/L, with a mean of 0.6mg/L.
- Cis-picied levels ranged from not detectable to 6.6mg/L, with a mean of 1.4mg/L.
- Trans-resveratrol and cis-resveratrol levels ranged from not detectable to 0.4mg/L, with a mean of 0.03mg/L.
- Total resveratrol levels ranged from not detectable to 7.8mg/L, with a mean of 2.5mg/L.
- Trans-picied levels ranged from not detectable to 3.4mg/L, with a mean of 0.4mg/L.
- Cis-picied levels ranged from not detectable to 2.9mg/L, with a mean of 0.4mg/L.
- Trans-resveratrol levels ranged from not detectable to 0.5mg/L, with a mean of 0.1mg/L.
- Cis-resveratrol levels ranged from not detectable to 0.6mg/L, with a mean of 0.04mg/L.
- Mean total resveratrol was 0.9mg/L.
- The majority of German wines had low levels of resveratrol.
o Levels of resveratrol in Hungarian wines were higher than levels in German wines.
§ This result is likely due to differences in winemaking techniques. For the German wines (with the exception of “Trockenbeerenauslese” which uses Botrytised grapes only), both healthy and Botrytised grapes are pressed together. For the Hungarian wines, there is typically much longer skin contact time with the juice, thereby facilitating better extraction of resveratrol into the finished wine.
- Comparing “normal” wines from Germany, German wines made from Botrytised grapes had lower levels of resveratrol and picied.
o Ex: Resveratrol levels in a typical German Riesling (of standard quality) are between 0.5 and 4.4mg/L, with a mean of 2.1mg/L (compared to 0.9mg/L in the wine made from Botrytised grapes).
§ The decreased levels of resveratrol in wines made from Botrytised grapes are possibly due to the ability of Botyritis cinerea to oxidize resveratrol into its metabolites.
§ Though the physical process of shriveling of grapes caused by Botrytis cinerea infections could concentrate the contents of the grapes, the oxidation of resveratrol by B. cinerea would negate any potential increases in concentration due to lower surface to volume ratios.
§ Due to higher skin contact time for Hungarian wines, even though resveratrol is being oxidized by B. cinerea, the longer skin contact may help in the extraction of resveratrol before oxidation is complete, thus potentially explaining why resveratrol levels in Hungarian wines are higher than in German wines.
- Compared to un-botritised wines from other regions of the world, levels of resveratrol in all wines studied were relatively low.
o Botrytised grapes lead to wines with decreased resveratrol levels when compared to wines made from “normal” or un-botrytised grapes.
- Botrytised wines from Hungary had very high levels of total polyphenols: levels ranged from 537mg/L to 1725mg/L, with a mean of 886mg/L.
- Botrytised wines from Germany had lower levels of total polyphenols than Hungarian wines (presumably due to much shorter skin contact): levels ranged from 248mg/L to 747mg/L, with a mean of 441mg/L.
- Compared with “normal” or un-botrytised wines, both Hungarian and German botrytised wines had total polyphenol values that were very high.
- Antioxidant capacity (TEAC) levels for German wines ranged from 0.6mmol/L to 2.8mmol/L, with a mean of 1.4mmol/L.
- TEAC levels for Hungarian wines ranged from 1.1mmol/L to 10.8mmol/L, with a mean of 4.2mmol/L.
o This is due to their higher total polyphenol levels.
- Compared to “normal” or un-botryitised wines, the antioxidant levels for both German and Hungarian (but particularly, Hungarian) botrytised wines were very high.
o To the authors’ knowledge, no white wine has ever been reported to have higher than 5mmol/L TEAC values (some of the Hungarian botrytised wines were double that!). Values over 10mmol/L have only been found in red wines.
When comparing German botrytised wines with Hungarian botrytised wines, the results of this study found that Hungarian wines had higher levels of resveratrol, due to increased skin contact time and therefore greater extraction of the compound. However, resveratrol levels of both wines were lower than “normal” wines.
On the other hand, total polyphenol content and antioxidative capacity of both German and Hungarian wines were higher than “normal” German wines, particularly the Hungarian wines. Interestingly, the antioxidative capacity of some of the botrytised Hungarian wines were at the same levels as “normal” red wines, which has never been recorded in the literature for a white wine.
Even though resveratrol levels were lower, the fact that health-benefitting total polyphenols and antioxidative capacities for botrytised wines (particularly Hungarian botrytised wines) indicates that there may be significant health benefits for humans consuming these wines. Since some of the values were comparable to that of red wines, theoretically consuming some of these botrytised wines would provide the same health benefits as a red wine. However, clinical research would need to be performed to confirm this, but it’s likely that some increased health benefit to consumers would be noted.
I’d love to hear your thoughts on this topic! Please feel free to comment below (unauthorized HTML tags will be deleted)!
Source: Nikfardjam, M.S.P., László, G., and Dietrich, H. 2006. Resveratrol-derivatives and antioxidative capacity in wines made from botrytized grapes. Food Chemistry 96: 74-79.
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!