In the spirit of the upcoming New Year, we’ll focus the next few blog posts on sparkling wine/Champagne!
There are several different methods for producing sparkling wine, including the traditional method and the Charmat method. The traditional method, also known as méthode champenoise when referring to Champagne winemaking, incorporates the use of a bottle as the vessel for secondary fermentation, whilethe Charmat method employs a large tank for the secondary fermentation process.
For each method, the process starts with a still base wine which undergoes secondary fermentation. Typically, sugars and yeasts are added to the base wine in order to jump start the secondary fermentation process. Secondary fermentation takes place within a sealed vessel (e.g. bottle, tank, etc) in order to keep the carbon dioxide fermentation by-product within the wine for the characteristic sparkling wine bubbles rather than letting it escape into the atmosphere.
After secondary fermentation in complete, the sparkling wines are then aged on their lees (i.e. dead yeasts and other materials in the wine) for a few days to several months, depending upon the method employed and type of wine desired. During this aging process, many chemical reactions take place, most notably the autolysis of yeasts. Briefly, the autolysis of yeasts is when the yeasts are broken apart thus exposing the wine to the various components of the yeast cells, including but not limited to cell walls, peptides, amino acids, and proteins.
The autolysis of yeasts is considered to be very important in regards to the final composition and quality of the finished sparkling wine. The compounds released into the wine can influence the aroma, flavor, and mouthfeel, as well as the “foaminess” of the bubbles. The length of time the wine ages on the lees and thus the length of time the wine is exposed to yeasts undergoing autolysis affects on the overall quality of the finished wine, though since longer aging time equates to larger monetary investments, it is in the best financial interest of the winery to try and speed up this process without losing the benefits of the long aging process.
One way to speed up the autolysis of yeast process that has been examined in the past is the addition of various yeast components to the wine. What is less known is how the addition of these components change the quality of the finished wine in regards to antioxidant capacity. While the information regarding the antioxidant capacity of still wines is well known, it is much less known how changing in the composition of sparkling wine affects antioxidant capacity and overall quality of wine.
Those few studies that have been done on antioxidant capacity and sparkling wine have shown that role of phenolic compounds on antioxidant capacity isgreater in sparkling wines produced in the traditional method compared with sparkling wines produced in the Charmat method. Other studies have found that other by-products of the autolysis process, including the polysaccharides β-glucanase and yeast cell wall fragments, also influence the antioxidant capacity of sparkling wines.
The purpose of the study today was to investigate the antioxidant capacity of sparkling wines when supplemented with by-products of yeast autolysis, yeast cell wall fragments, mannoproteins, and β-glucanases. Information gathered from these results may help sparkling wine makers decide if and how they wish to treat their wines in order to optimize the contact time with the lees, potentially saving money and increasing overall sparkling wine quality.
The experimental wines were created at the experimental wine cellar of the Agricultural Engineering College using Verdejo grapes. Grapes were grown and harvested from the experimental vineyard of the Agriculture Technology Institute of Castilla y León in Valladolid, Spain in 2008.
The base wine was created using traditional white winemaking processes. The enological parameters of the base wine were: 11.2% alcohol, 0.23g/L volatile acidity, 9.6g/L total acidity, 3.53 pH, 25mg/L free sulfur dioxide, 53mg/L total sulfur dioxide, and 1.7g/L reducing sugars.
Sparkling wine was created using the traditional method. Added to the base wine was 22.3g/L of sugar (sucrose), Saccharomyces bayanus yeasts, and a clarificant. Sparkling wine was aged on the lees for 9 months and was then riddled and disgorged. Before bottling, wines were topped off with dosage liquor.
The 5 treatments in this study were: 1) addition of B-glucanases; 2) addition of autolysated yeasts; 3) addition of yeast cell walls; 4) addition of purified mannoproteins; and 5) control with nothing added. Three bottles of each wine were analyzed. Each assay (test) was run in triplicate.
Antioxidant capacity was analyzed using three methods: DPHH radical-scavenging method; FRAP assay; and Hydroxyl radical scavenging activity. Also measured were: total proteins, neutral polysaccharides, total polyphenols, total hydroxycinnamates, and total flavonoids.
- The addition of all the treatments increased the antioxidant capacity of the sparkling wines.
- According to the DPPH assay, the addition of the mannoproteins elicited the highest increase in antioxidant capacity and the control the lowest.
- According to the DPPH assay, the addition of β-glucanases, autolysated yeasts, and yeast cell walls increased antioxidant capacity by 24.1%. The addition to mannoproteins increased antioxidant capacity by 27.5%.
- According to the FRAP assay, just as with the DPPH assay, the addition of the mannoproteins elicited the highest increase in antioxidant capacity and the control the lowest.
- Those wines with higher antioxidant capacities also had higher reducing capacities.
- Those wines with greater levels of neutral polysaccharides and total proteins had higher antioxidant capacities and hydroxyl scavengers.
- There were no significant correlations between polyphenol families, hydrocinnamic esters, total flavonols and antioxidant capacity.
- The authors attribute this to some research that suggests not all polyphenols have high antioxidant capacities, and perhaps more of the polyphenols in these experimental sparkling wines were higher in those polyphenols with low antioxidant capacities.
- There were positive and significant correlations between total polyphenols and hydroxycinnamic esters and flavonols.
- Mathematical modeling and principle components analysis found that neutral polysaccharides and proteins play an important role in the antioxidant capacity of sparkling wines.
According to the results of this study, the antioxidant capacity of sparkling wines is increased when the wine is treated with β-glucanase, mannoproteins, or other yeast autolysis compounds. The greatest response was found with the addition of the mannoproteins, with these proteins being responsible for the greatest increase in antioxidant capacity. The results also showed that neutralpolysaccharides and total proteins had the most influence on antioxidant capacity when treated with the aforementioned compounds. A result the authors did not anticipate was the fact that they did not see any correlation between phenolic families and antioxidant capacity.
The results of this study indicate that by adding mannoproteins, B-glucanase, or other yeast autolysis compounds, the antioxidant capacity of the wine is increased, thus suggesting that the length of time required for wine aging to achieve the same wine quality may be reduced. I would be curious to know how much time the treatment actually reduces, and if the time saved is significant enough to justify the practice.
I would also be curious to know how the addition of these or similar compounds affect antioxidant capacity in sparkling wines made from other production methods (i.e. Charmat method, etc). Would we see the same increase in antioxidant capacity? Or does it depend upon which sparkling wine production method one employs?
Research into individual polyphenols may be of interest as well, to determine which polyphenols in particular have influence on the antioxidant capacity of sparkling wines, and also which do not.
I’d love to hear what you all think about this research. Is there anything else you would have liked to have seen performed that was not? What other questions (if any) does this raise for you? Please feel free to leave any comments you may have!
Source: Rodriguez-Nogales, J.M., Fernández-Fernández, E., Gómez, M., Vila-Crespo, J. 2012. Antioxidant properties of sparkling wines produced with β-glucanases and commercial yeast preparations. Journal of Food Science 77(9): C1005-C1010.