Presence of Sugar in Sparkling Wines May Affect Resveratrol Content and Antioxidant Capacity

With the new year arriving in a couple of days, what better than to finish off 2011 with an article discussing sparkling wine! 

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As many of you know, sparkling wine is created when a still wine undergoes an enclosed secondary fermentation, thus trapping the CO2 bubbles inside.  There are four ways of creating this effect; including simple carbon dioxide injection, Metodo Charmat (Charmat method), méthode champenoise (traditional method), and finally, the transfer method.  All four methods are frequently used, though the method used in the study reviewed today is the Charmat method.  Briefly, with the Charmat method, the wine undergoes secondary fermentation in large bulk tanks and is bottled under pressure.  This method is frequently used for Prosecco and Asti, and results in smaller, long-lasting bubbles.

Sparkling wines have variable chemical compositions, which depend on many factors including the variety of the grape, how well the grape grew and ripened, the quality of the base wine, the type of yeast used, and how long the wine took to mature.  In regards to human health, sparkling wine has been shown to have similar cardiovascular health benefits attributed to resveratrol (and other polyphenols) as still red wine, which this blog discussed in its’ very first blog post (where you may find here). 

With sparkling wines comes a variety of sugar levels as well, depending on the style desired.  From Brut to Doux, sparkling wine comes in completely dry forms to very sweet forms.  Some studies have shown that sugar levels in wine may influence certain chemical reactions, including polyphenol concentrations and antioxidant activity.

The article reviewed today, which was published in 2010 in the journal Redox Report, the authors goal was to examine how resveratrol and other polyphenols/antioxidants change with changing sugar levels in sparkling wine.

Methods

Sparkling wine using the Charmat method was made by Möet Hennessy do Brasil – Vinhos e Destilados, with grapes grown in the region of Garibaldi in Serra Gaucha, Brazil (2006 vintage).  The base wine was a blend of Chardonnay (10%), Italic Riesling (42%), and Pinot Noir (48%).  Base wines were stored in stainless steel tanks prior to secondary fermentation.  The yeast used during secondary fermentation was Saccharomyces bayanus.  At bottling, a liqueur d’expédition created from the same base wine, SO2, and different levels of sugar were added (10, 20, 30, 40, 50, 60, and 70 g/l).

The following enological parameters were measured and analyzed: alcohol content, total acidity, pressure, volatile acidity, pH, free and total SO2, dry extract and reduced dry extract concentration, ascorbic acid, and sugar.

Also measured were: total polyphenols, total hydroxycinnamates, trans-resveratrol, trans-piceid, antioxidant activity, DPPH radical scavenging activity, potential CAT and/or SOD activities, and β-glucosidase activity.

Results

  •       The enological parameters measured indicated that the grapes were healthy and good vinification practices were used.
  •       Enological parameter values were found to be within legal ranges set by Brazilian and International legislation.
  •       There were nochanges in polyphenol concentrations at sugar levels of 10, 20, and 30g/l.

o   However, as sugar levels increased from 40 to 70g/l, concentrations of all phenolic groups decreased.

§  The authors suggest this result may be due to the esterification reactions between glucose molecules and the hydroxyl groups of certain polyphenols.

§  To summarize this result, polyphenol levels were negatively correlated with sugar concentration.

  •       The addition of sugar decreased the concentrations of both trans-resveratrol and trans-piceid for sugar concentrations up to 40g/l for trans-piceid, and 30g/l for trans-resveratrol.

o   Increasing the concentration of sugar after 40 and 30g/l, the concentrations of trans-resveratrol and trans-piceid did not decrease, but remained constant.

§  Overall, trans-resveratrol was negatively correlated with sugar content.

§  Overall, trans-piceid was positively correlated with sugar content.

·         The authors suggest these results occurred because of a possible conversion and reversible reaction of aglycones into their glycosylate derivatives.

  •       There were no changes in the antioxidant activities of CAD-like and SOD-like complexes due to sweetness.

o   The authors claim this is the first time these antioxidants have been studied in sparkling wine.

o   There was a positive correlation between sugar content and SOD-like activity.

§  The authors speculated this may be due to sugars’ ability to act as scavengers of hydroxyl radicals.

  •       There were no changes in the β-glucosidase activity relative to different sugar concentrations in sparkling wines.

Conclusions

Overall, the authors claim that sparkling wines’ ability to scavenge for free radicals shows the potential benefit against oxidative stress when consuming these wines in moderation.  Also, the addition of sugar in sparkling wines does not significantly alter the antioxidant activity of or important polyphenol concentrations of sparkling wine. 

In regards to resveratrol content, there appeared to be some decreases in wines with lower sugar content, while maintaining constant levels in wines with higher sugar concentrations.  The authors speculated the higher acidity in the lower sugar wines may have had some impact on this result, though they do not provide any other evidence to support it.  Therefore, this ultimately means that sparkling wines with higher sugar concentrations have greater levels of health-benefitting resveratrol, whereas drier sparkling wines may show a reduction in the concentration of resveratrol.  Based on this study alone, I am not 100% convinced this is true, since some of their results are opposite of the results of other studies.

The authors also claim that the results show that demi-sec Charmat sparkling wines may be efficient antioxidants in human diets, and aid in promoting a healthy lifestyle regardless of sugar content, since wines with lower sugar content may not contain the same level of resveratrol as the higher sugar wines.  However, one must keep in mind that consumption should remain at most moderate, as too much consumption of wine with higher sugar levels could cause negative health issues that are commonly associated with too much sugar intake.

Since this study is the first of its’ kind, naturally more work need be done to determine if these results are repeatable and convincing.  However, if the authors’ claims are correct, then it can be safely said that sparkling wines produced in the Charmat method with higher sugar concentrations do not show reduced health benefits when in the presence of higher sugar concentrations.

Happy New Year, everyone! 

Source: Stefenon, C.A., Bonesi, C.dM., Marzarotto, V., Barnabé, D., Agostini, F., Perin, J., Serafini, L.A., Vanderlinde, R. 2010. Sugar levels in Charmat sparkling wines can affect the quality and resveratrol levels. Redox Report 15(6): 243-249.

DOI: 10.1179/135100010×12826446921626

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!

2 comments for “Presence of Sugar in Sparkling Wines May Affect Resveratrol Content and Antioxidant Capacity

  1. WineKnurd
    January 3, 2012 at 1:35 am

    Living up to my handle, I am not sure how these potential esterifications can occur, from "as sugar levels increased from 40 to 70g/l, concentrations of all phenolic groups decreased. The authors suggest this result may be due to the esterification reactions between glucose molecules and the hydroxyl groups of certain polyphenols." If this were the case, no wine would ever be made, because glucose would be esterified rather than fermented, in the presence of yeast. Oh well enough wineknurding for now :)

  2. January 3, 2012 at 1:51 am

    To tell you the truth, I think the authors may have been struggling to come up with explanations for some of their results. I don't think this is the strongest paper (it's published in a journal I'm not that familiar with, but I suppose that doesn't necessarily mean anything), and that more work should be done to see if 1) these results are repeatable and 2) there are more solid explanations for what may be occurring in the system.

    Keep up the good wineknurdin' ;)

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