Oak aging is a very common practice in winemaking, particularly in wines destined for a higher quality designation. In general, with oak aging (and other wood aging, for that matter), the contact between the wine and the wood promotes an influx of compounds into the wine which often has a positive influence on the complexity of the wine, as well as the intensity of the nose and palate. Even more important, the small pores within the wood influence the rate of oxygen diffusion into the aging wine, with has a significant effect on color stabilization, as well as the phenolic composition of the finished beverage.
Let’s focus on color for a bit (or, well, for the remainder of this post). The color of wine can tell you many things, including its age, how it may have been stored, and also its potential overall quality. Color in wine comes primarily from its anthocyanin content, which originates from the skins of grapes. In red wine, the skins of the grapes remain in contact with the must (unfermented wine) for a period of time, which is known as maceration, which extracts more and more anthocyanins (among a barrage of other compounds) the longer the skins sit with the juice.
Once these anthocyanins are extracted from the skins into the grape must, their concentrations decrease over time due to several chemical reactions, including polymerization, oxidation, precipitation, as well as absorption by yeast. Some of the by-products of these chemical reactions between anthocyanins and other compounds in the wine can provide a greater resistance to bisulphite bleaching and pH changes, which is important in regards to the sensory characteristics of the finished wine.
What does wood aging and color have to do with one another?
As I mentioned just previously, anthocyanins can react with other compounds in the wine, which can alter color, in addition to other quality factors in the beverage. Since aging in wood barrels ads an influx of wood-related compounds into the wine, these can interact with anthocyanins and ultimately change the color and overall quality of the finished wine.
What type of wood are you talking about, anyway?
To date, most of the studies examining the influence of wood aging on wine have focused on French and American oak barrels, which are undoubtedly the two most common types of wood used in this type of aging. These types of barrels have been used for generations, and are the traditional woods of choice when aging wine or other distilled beverages. However, more and more alternatives to the traditional French and American oak barrels are being used, partly for variety, but more importantly for cost-savings. These alternatives include chestnut, acacia, cherry, and ash (to name a few); all of which cost markedly less than traditional French or American oak barrels, and also give unique sensory characteristics to the finished wine which are becoming more desirable among consumers.
Cherry wood, in particular, has been found to contribute to the complexity of wine, by significantly increasing the cherry and red fruit notes to the wine, as well as increase the overall acceptance of the wine. Studies have shown that cherry wood promotes a more oxidative environment for the wine, which suggests a shorter aging period lest one be left with a wine that suffers from too much oxygen exposure (which is not good!).
The study published last year in the Journal of Agricultural and Food Chemistry, the results of which I will present shortly, aimed to take this known information regarding cherry wood aging and anthocyanins and examined the impact of cherry wood aging on the oxidative changes of color and pigment in red wines. In a nutshell, they wanted to know how does cherry wood aging affect the color of the red wine, and how does it compare to red wine aged in more traditional French oak barrels?
How did they do it?
The red wine used for this study was 80% Sangiovese and 20% Merlot from the 2008 vintage by Marchesi de Frescobaldi in Tuscany, Italy (Sieci, to be more specific). Wines followed a traditional vinification protocol, including 20 days of maceration (skin contact with must). After alcoholic fermentation, the wines underwent spontaneous malolactic fermentation.
The barrels used were two 225L medium toasted barriques of French oak and cherry wood, as well as a larger 1000L cask made of cherry wood with light toasting. All aging conditions were performed in triplicate. Barriques and casks were made with staves that had been seasoned for 24 months. A 1000L stainless steel tank was used as a control.
An aging length of 4 months was chosen, due to the nature of the experiment. This experiment was testing anthocyanin changes over time, so the experiment was carried out long enough so that the total anthocyanins would significantly decrease or disappear all together. This magic number turned out to be 4 months. It is important to note that even though the anthocyanin content significantly decreases during this time, the sensory contribution of the cherry wood does not decrease during this time period.
General enological parameters (titratable acidity, pH, etc), dissolved oxygen, pigment, and color were measured for all wines using various analytical techniques.
What did they find?
- The authors found many results in this study, but I’ll just share a few of them for space considerations. Please feel free to ask if you’re wondering about any particular result that I may not have mentioned.
- Dissolved oxygen stabilization was a function of the wood surface-to-wine volume ratio, with the smaller casks (225L) having a higher dissolution rate than the larger casks (1000L).
- Dissolved oxygen levels were similar in wines aged in French oak barrels than cherry wood casks.
- During the first month of aging, wine in cherry wood casks showed a higher SO2 reduction trend than in French oak casks.
o In wines aged in cherry wood casks, the free SO2 levels were lowest, compared to the French oak casks.
- Total phenolic content was similar between wines aged in cherry wood versus wines aged in French oak casks.
o This result contrasts another study that found a significant decrease in polyphenols in cherry wood-aged wines after 3 months of aging. The researches cite differences in experimental methods as a possible explanation of this discrepancy.
- Tannins increased for all wines in all aging conditions.
- Wines aged in cherry wood saw faster reductions in anthocyanins than wines aged in French oak.
o The total pigment in the larger casks (1000L) was twice that of the smaller casks (225L).
- After 4 months of aging, wines aged in cherry wood casks had the lowest percentage of acylated anthocyanins compared with all other storage treatments.
- Wines aged in cherry wood casks showed large variations in the pigment profile of the wines at any given point in the aging process, indicating that wines aged in cherry wood casks may more significantly change from the initial anthocyanin content present in the wine than wines aged in other wood casks.
- Cherry wood aging promoted the highest levels of adduct formation over time compared with other aging conditions.
- Wines aged in cherry wood had the highest levels of color intensity compared to wines aged in other conditions.
- After 2 months, wines aged in cherry wood possessed deeper colors, as well as a “redder” tint than the other aging conditions.
o After 2 more months, this redness decreased in shade, resulting in all wines sharing similar coloring regardless of aging condition.
- French oak barrels did not contribute to wine color as much as cherry wood barrels.
What does this all mean?
According to the results of this study, the use of cherry wood barrels/casks in the aging of wine significantly influenced the color and pigment of red wine (in this case, Sangiovese/Merlot blend). Also, the anthocyanin content of wines was affected by the type of wood used for aging, with the cherry wood barrels/casks losing nearly all ρ-coumaroylated pigments by the end of the 4 month experimental aging period. According to the authors (and I agree), more work needs to be done to explore this result further: by examining the role of wood porosity and/or phenolic composition of cherry wood.Due to the significant decrease in anthocyanins and pigments by the end of the 4 month aging period, it is recommended that wines aged in cherry wood barrels/casks are kept for relatively short periods of time or if longer age times are more feasible, then the use of larger barrels with lower wood-surface to wine-volume ratios should be utilized.
Of course, wines aged in cherry oak barrels with yield wines with a different aroma/flavor profile than wines aged in traditional oak barrels, so the decision to choose one type of barrel over another should not be simply based on anthocyanin content alone, as discussed in this post. One must take into consideration all the differences between wines aged in alternative wood barrels and traditional oak barrels (including economic differences) before jumping to any conclusions as to which barrel is right for them or their winery.
I’d also be curious to see how cherry wood aging affects other wines, including both red and white wines. Will we see the same results? Will some wines age better in cherry wood barrels than others?What do you all think of cherry wood to age wine?Have you ever tasted a wine aged in cherry wood barrels? I have to admit, I have not, but I would certainly be interested in trying one to compare between that and the more traditional aging methods.I’d love to hear what you all think of this topic! Please feel free to comment below! (Note: If you do not see the comments section, be sure you are in the post URL and not just on the main page)Source: Chinnici, F., Natali, N., Sonni, F., Bellachioma, A., Riponi, C. 2011. Comparative changes in color features and pigment composition of red wines aged in oak and cherry wood casks. Journal of Agricultural and Food Chemistry 59: 6575-6582
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!