Source: http://www.beercollege.net/wp-content/uploads/2010/12/20070320_asimov.jpg

Wines aged in oak barrels are traditionally a favored style of wine for consumers. With oak aging comes a change in color, structure, and aroma, as a result of reactions between the phenolic compounds in the wine and the oxygen and other compounds extracted from the oak. Though this style is very popular among consumers, it can be very expensive and time consuming.

One of the major costs in producing commercial wine is the cost of the barrel in which the wine is fermented and aged. With oak barrels pushing $1000 per barrel (or higher), the expenses add up very quickly. Stainless steel tanks have become a significantly less expensive alternative in the long run for winemaking, however, the style of wine produced from such a vessel is different than the style of wine produced from an oak barrel.

One alternative that is gaining popularity in the United States is the use of oak chips in stainless steel tanks. In addition to using oak chips, scientists have found that micro-oxygenation techniques are also required to produce a comparable style to oak-aged wines, since stainless steel tanks do not possess oxygen transfer capabilities as oak barrels do. Even with the need to purchase a micro-oxygenation system and oak chips, the money and time savings for the winery may be well worth it.

What about the wine produced using this alternative method? Are there any differences between the finished wine produced this way and the finished wine produced in the traditional oak barrel method?

Chemical Composition

Studies have found that the type of grape and the vintage will have significant effects on the chemical composition of a finished wine, therefore making blanket comparisons of oak chips versus oak barrels problematic. Only after taking these other influential variables into consideration, can a true comparison be made.

According to a study by Ortega-Heras et al, 2010, it was found that for both Mencía and Tinta del País red wines that were aged with oak chips, a color and chemical composition similar to that of wines aged in oak barrels for three months was observed, but not for wines aged for longer periods of time. The main compounds that were found to differ between oak barrel aged red wines and oak chip aged red wines were total and polymeric anthocyanins, acetylated and glucoside anthocyanins, and pigments from direct condensation of anthocyanin-flavonol.

What this result means is that the biggest difference between red wines aged in oak barrels and red wines aged with oak chips relates to the levels of anthocyanin compounds in the finished wine (i.e. color characteristics). In regards to timing, the results of this and other studies have found that wines aged in oak chips show the most similar color and phenolic/chemical composition to that of oak barrel aged wines when aged for a short period of time (roughly three months).

So far, studies have found significant differences between wines aged in oak barrels and wines aged with oak chips when aged for longer periods of time. However, at shorter aging times (i.e. three months), it is possible to produce a wine using oak chips that is chemically very similar to wines aged in oak barrels. The results from these studies therefore indicate that the use of oak chips may be a good alternative to the use of oak barrels if the goal is to produce a younger wine with more delicate oak characteristics.

Sensory Characteristics

Studies have shown that the use of oak chips in wine does have an effect on the sensory characteristics of the finished wine when compared to wine aged in traditional oak barrels. For example, in a study investigating the sensory characteristics of white wine aged in oak barrels versus using oak chips, Afonzo (2002) found that oak chips were found to produce a greater intensity of oak aromas (i.e. coconut and vanilla) and a greater taste impact (i.e. bitterness and astringency). According to this and other studies, it is possible that as a result of higher surface area ratios, more oak lactones may be extracted out of the oak chips and incorporated as oak aromas in the wine than those extracted and incorporated from traditional oak barrels.

Does the type and size of oak chips matter?

According to studies, the use of oak chips changes the sensory characteristics of the finished wine by increasing oak aromas. What about different types of oak chips? Are there differences between American oak and French oak chips? The short answer is yes.

Geographic Origin

One study by Rodríguez-Bencomo et al (2009) examined the chemical composition of wines macerated with Spanish, American, and French oak chips. In general, they showed that there were significant differences in chemical composition of the three oak types in the finished wines. The wines made with Spanish oak chips contained higher levels of furanic aldehydes and eugenol, while wines made with American oak chips contained higher levels of cis-whiskey-lactone, vanillin, and methyl-vanillate. The study also found that Spanish and French oak chips produced wines with similar levels of oak volatile compounds, the two of which were different than the wines from the American oak chips. The take-home message from this experiment is that oak chips from different geographical locations will produce wines with different chemical profiles.

When comparing American oak chips versus Hungarian oak chips, Guchu et al (2006) found that chemical and sensory characteristics were comparable. One small difference between the two oak types in this experiment was that American oak chips produced wines with a greater “woody” sensation than wines produced from Hungarian oak chips. This was confirmed both in the chemical and sensory analyses.

Toasting

As with oak barrels, different levels of toasting of oak chips appear to change both the chemical and sensory characteristics of the finished wine. The study by Guchu et al (2006) found that wines treated with toasted oak chips were generally more astringent and bitter than non-toasted oak chips, and that there was greater body, oak, and ripe fruit tones. According to this study, the toasting of the oak chips appeared to have significantly more influence on the chemical composition and sensory characteristics of the finished wine than the geographical origin of the chips.

Length of contact time

While examining the effect of contact time of oak chips on red wines, Cano-López et al (2008) found that the length of time in contact with the wine had significant influence on aroma quality. According to their results, aroma quality hit a peak at 6 months of contact, and showed a decrease between 6 and 9 months of contact. Fruity character peaked at 6 months, whereas vanilla, wood, spicy, and other oak aroma characteristics peaked at 3 months.

Size of chips

Cano-López et al (2008), in addition to contact time, also examined the size of oak chips and evaluated whether or not different chip sizes influences the sensory characteristics of the finished wines. As it turns out, they found no significant differences in fruity, spicy, herbaceous, and horsy characters of the wines made from different sized oak chips. The highest aromatic intensity was found in the wines made from oak cubes, whereas the highest aroma quality scores were found in the wines made from the oak shavings.

Several studies have found that smaller sized chips can absorb the wine much faster and more completely. This absorption better helps facilitate the aromatic diffusion of wood compounds into the aging wine. Other studies have found that smaller chips are most combustible, thereby after toasting, more toast-related compounds are formed and better incorporated into the wine. After a certain size (less than 0.5mm), the oak chip is too small, allowing evapotranspiration of oak character into the air, thus lessening the overall quality of the wine.

Consumer preferences

Consumer preferences often change with time and trends, and preferences for wine are no different. Historically, consumers have held a high appreciation for wine aged in oak barrels. While it is now legal in many countries to produce wine using oak chips, very few studies have been done on how consumers perceive and accept wine created in this method, and how their purchase intention may change based on this knowledge.

A study by Perez-Magariño et al (2010) found that when given information regarding the use of oak chips on a label, 55% of respondents would not buy the wine and would only consider purchasing the wine if they had a chance to taste it first and found it not unpleasant. However, after a sensory analysis using wines made with oak chips versus wine made with oak barrels, those same respondents could not ascertain any difference in quality between the wines.

Conclusions

The overall take-away from this article should be that using oak chips in stainless steel tanks (preferably with a micro-oxygenation system) is an acceptable alternative to using more expensive oak barrels for the fermentation and aging of wines. Though it may not seem that wines aged for longer periods of time will retain similar quality characteristics, wines aged with oak chips for a shorter period of time (3-6 months) should produce a wine very much comparable to a short-aged wine in traditional oak barrel.

In regards to type of chips, toasting, and size of chips, the choice of which to use is a matter or personal taste. None of the options created an inferior style of wine, though all contributed different chemical and sensory characteristics to the wine. Are you looking to create a wine with more intense oak flavor and strong smoky characteristics? Then maybe go with American oak chips with higher toasting levels and in the size of shavings. Are you looking to create a more delicately oaked wine? Then maybe go with French oak chips that are untoasted and the size of cubes.

Overall, provided the oak chips are not exposed to the wine for too long (i.e. longer than 6 months for some wines), the finished product is one that is comparable in quality to wines aged for similar lengths of time in traditional oak barrels. With enough education for the consumers purchasing the wine, using oak chips in stainless steel tanks is a great alternative to using traditional oak barrels, which will leave consumers happy and results in overall financial savings for the winery.

About The Author
Rebecca Yeamans

Becca Yeamans is the owner/writer of the science-based wine blog, The Academic Wino, as well as the Tasting Room Manager at a vineyard in central Virginia. With a Bachelor of Science in Biology and a Master of Science in Environmental Science, her solid background in science and research allows her to approach wine blogging with a unique style that is both informative to those in the industry, and entertaining for those simply wishing to learn.

Tags: , , , , , , , , , , ,
Posted in Blog, Latest News | No Comments »