The Effect of Different Wood Chips on Aging of Greek Syrah and Cabernet Sauvignon Wines

Over the past few years, I’ve covered the topic of oak and oak alternatives several times on this blog.  Many studies have examined the chemical and sensory differences of wine when exposed to different types of oak and other woods, as well as the difference in chemical and sensory attributes in wines kept in barrels versus wines exposed to oak barrel alternatives such as oak chips or oak extract.

The study presented today aimed to add to this wealth of knowledge, while adding different woods that have not yet been tested for chemical and organoleptic changes in wine, and compares the effects of the different woods on Greek wines, which to my knowledge has been covered very little (if at all).

Today’s study looked at a total of 11 different woods, and their chemical and sensory effects on two types of wine from Greece.  The goal of the study was simple—to examine the chemical and sensory differences between the wines when aged using different types of wood chips, and whether or not there were one or two

woods that performed significantly better than the others in terms of their chemical and sensory characteristics, which could ultimately be considered a “healthier” wine with greater levels of health-benefitting polyphenols.

Methods

Two wines were used in this analysis:  Syrah and Cabernet Sauvignon from the Greek appellation Messenikolas (Karditsa county).

The woods used for the wood chips came from 11 different forest and fruit tree species, including: 1) white oak (Quercus alba L.); 2) red oak (Quercus rubra L.); 3) Turkey oak (Quercus cerris L. var. cerris); 4) chestnut (Castanea sativa L.); 5) Bosnian pine (Pinus heldreichii Christ. var. leucodermis); 6) cherry (Prunus avium L.); 7) common juniper (Juniperus communis L.); 8) common walnut (Juglans regia L.); 9) white mulberry (Morus alba L.); 10) black locust (Robinia pseudoacacia L.); and finally 11) apricot (Prunus armeniaca L.).

Most of the woods came from Karditsa county in Greece, though the white mulberry came from Drama county, and Bosnian pine from Grevena county, while the red and white oak were imported (from exactly where was not made clear).

Wood samples were air-dried for three months, then cut into 1x1x1cm cube chips.  Wood chips were NOT toasted.

One to two chips were placed in 750mL of wine in glass bottles and stored for 20 days total.  All wines were stored at 75-80% humidity and 16-20^oC.  Bottles were shaken for three to five minutes every day during the 20 day aging period.  Wine samples were filtered and collected at 5, 10, and 20 days of aging for both chemical and sensory analyses.   Wines without aging with wood chips were used as controls.

Chemical analysis of all wine samples included: total polyphenols, resveratrol content, catechin content, antioxidant activity, and color.

Sensory analysis examined visual, taste, and aroma characteristics of the wines and was performed by two panelists with significant experience in evaluating sensory characteristics of red wine.

Results

• Total polyphenols varied depending upon the type of wood chip used.
  

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  • Higher polyphenol levels were noted with:  white oak, chestnut, cherry, white mulberry, black locust, and apricot woods.
• When 1 wood chip was used, there was a significant increase in polyphenol levels in all wines up until day 20 when the experiment ended.
• When 2 wood chips were used, polyphenols increased all the way through the experiment for the Syrah wines, however, for Cabernet Sauvignon wines, polyphenols increased until day 10, then proceeded to decrease until the end of the experiment at day 20.
  • The authors think this reaction may be due to the fact that with two wood chips there are more wood phenols present that react with the compounds in the wine, thus creating a sort of negative reaction ultimately leading to a decrease in total polyphenols.  This was not tested, but was conjecture by the authors.
• In Syrah, resveratrol content significantly increased during the 20 day aging experiment.
  • Resveratrol content increases were amplified by the use of chestnut and mulberry wood chips.
• In Cabernet Sauvignon, resveratrol levels were not stable and ranged in concentrations depending upon the type of wood chip used.
  • It was noted that resveratrol levels were doubled by day 20 when mulberry chips were used in Cabernet Sauvignon.
• In Syrah, catechin content significantly increased when wood chips were used up until day 10, then continued to decrease for most of the samples.
  • Catechin levels continued to increase until day 20 for Syrah wines exposed to mulberry and apricot wood chips.
• In Cabernet Sauvignon, catechin levels increased up until day 10 for all wine/wood samples.
  • Most wood chips resulted in a significant decrease in catechin levels between day 10 and day 20, with the exception of cherry and mulberry woods.
• In Syrah, antioxidant activity significantly increased over the 20 day aging period, with the highest antioxidant activity occurring when the mulberry wood chips were used.
• In Cabernet Sauvignon, antioxidant levels increased up until day 10 for all wine/wood samples, though between day 10 and 20 proceeded to show decreased antioxidant levels.
  • The highest antioxidant activity in Cabernet Sauvignon wines were found when black locust and apricot wood chips were used.
• Antioxidant activities in the wine samples were proportional to the total polyphenol content (as expected).

Sensory Analysis

• Prior to aging, Syrah wines were determined to be “satisfactory” (rejected < medium < satisfactory < good < very good < excellent < great).
  • Syrah wines exposed to white oak, chestnut, and black locust wood chips were improved in terms of their sensory characteristics to “good”.
  • Syrah wines exposed to apricot wood chips had the best sensory results, with an improvement to “very good”.
    • The score on the 20^th day was better than the score on the 10^th day.
• Prior to aging, Cabernet Sauvignon wines were determined to be “good” (rejected < medium < satisfactory < good < very good < excellent < great).
  • All wood chips improved the sensory characteristics of the Cabernet Sauvignon wines to “very good”.
  • Cabernet Sauvignon wines exposed to black locust and apricot wood chips had the best sensory results, with an improvement to “excellent”.
    • Scores decreased from the 10^th day to the 20^th day.
    • All wines showed increases in color throughout the experiment, with no notable differences between varietals or wood chip type.

Conclusions

Overall, this study showed that aging wine with different types of wood chips resulted in different chemical and sensory characteristics of the wines.  I am not at all surprised by this, as this has been shown many times over in other experiments.  What I found interesting were the “new” types of oak that I am less familiar with in the literature, particular apricot.  I haven’t really heard of anyone ever using apricot wood chips, and it was interesting to see how well it performed in both chemical and sensory improvements of both the Cabernet Sauvignon and Syrah wines.  Additionally, black locust, mulberry, and cherry woods all seemed to perform relatively well in terms of improving chemical and sensory characteristics of the wines.

Despite these results, I think they should be taken with a grain of salt.  The chemical analysis appears to be more sound, however, my beef is with the sensory analysis.   All wines were analyzed by TWO people.  Just two.  Yes, they may be “experts”, but I have a hard time accepting any reports of statistical significance when there were only two people tasting the wines.  To be more convincing, I would want to see a much larger cohort of panelists.  Think of two people who have different tastes in wine than you do—what if they were judging the wines in this experiment?  Would you be convinced that the wines aged with apricot or black locust chips actually tasted better than wines aged with white or red oak chips?  Adding more panelists won’t necessarily completely remove the “we have different tastes” factor, but it certainly helps.

My other issue with this study was the way in which the wines were aged with the chips.  Now, I am not a commercial winemaker, however, to the best of my knowledge I don’t believe anyone ages wine with oak chips by sticking a couple of chips directly into the bottle, then taking them out a couple weeks later.  While the results were interesting and perhaps enough to justify further experimentation, I would like to see it repeated using more realistic aging conditions.

Even though I did take issue with a couple of points in this study, I do think the concept was interesting and relevant to a growing wine industry that is looking for more individuality and variation in the wines produced for improving their sales in the growing market.  This study provides a decent starting point for the next set of experiments, which could allow winemakers to have another weapon in their arsenal of winemaking ingredients.

I’d love to hear what you all think about this study. Do you have any experience with any of these types of wood chips?  Please feel free to comment on anything related to this topic that comes to mind!

Source: Gortzi, O., Metaxa, X., Mantanis, G., and Lalas, S. 2013. Effect of artificial ageing using different wood chips on the antioxidant activity, resveratrol and catechin concentration, sensory properties and colour of two Greek red wines. Food Chemistry 141: 2887-2895.