RESEARCH HYBRID BARREL French Oak Heads and American Oak Staves Dr. Jennifer Newton and Terry Nolan www.worldcooperage.com
ABSTRACT Oak barrels were manufactured using French oak heads and American oak staves. Four such barrels were produced along with four American oak barrels and four French oak barrels. Chardonnay was produced sur lie and left in contact with the oak for six months. The wine from each set of barrels was blended and tested for sensory and chemical analysis. Chemical analysis conducted eight months after bottling found the Hybrid barrel produced wine with characteristics of both French and American oak. It contained more oak lactones than the French oaked wine and more oak tannins than the American oaked wine. Its aromatic oak aldehydes also fell in between the French and American samples. Sensory differences were difficult to judge. This may have been due to the long time, 4 months, in bottle. INTRODUCTION Due to the physiological structure of French oak, a large portion of the tree cannot be used to make barrels. French oak has only a small amount of tyloses, which means that its staves are prone to leaking. Coopers have overcome this drawback of French oak by splitting the staves along the grain. However, this cutting method leaves a large amount of short pieces unsuitable for stave production but useable for making barrel heads. French Oak Head American Oak Staves American oak contains sufficient amount of tyloses to allow it to be sawn. This leads to far less waste and greater yield for American oak, just one of the reasons why American oak is less expensive. To maximize the use of American and French oak, we put the extra French oak heads onto American staves to build a Hybrid barrel. This created a barrel with 5% French oak and 75% American oak. To study the influence this combination barrel had on wine, Benziger Family Winery produced barrel fermented Chardonnay in it alongside all-french and all-american barrels. MATERIALS AND METHODS Chardonnay grapes from Bryton Vineyards, Carneros were crushed on September, 997. Prior to fermenting lb / 000 gal Bentonite, / lb / 000 gal DAP, / lb / 000 gal Nutrex were added. Fermentation was carried out using Cote de Blanc yeast, lbs / 000 gals and it lasted 5 days. During fermentation, lb / 000 gal more DAP was added. At the end of fermentation 45 ppm KMBS was added. Wine was filled into barrels 4 were American oak, 4 were French oak and 4 were American oak staves with French oak ends. Wine was matured for 6 months.
RESULTS Table : Harvest data of juice Total acidity 5.5 g/l Brix.8 B ph 3.44 Solids 5% The four barrels from each set were mixed to make three composite wine samples: French, American and Hybrid. The composite wine samples were analyzed for wood extractives, smoke components and wine phenolics. The chemical analysis is given in Table 3. Table : Wine analysis as of December, 997 59 Gallon Alcohol 4. % v/v Total acidity 6. g/l Volatile acidity 0.46 g/l Free sulfur dioxide 30 ppm Total sulfur dioxide 73 ppm ph 3.6 Residual sugar 0.5 % Table 3: Chemical analysis of finished wine Gallic acid.03.79.8 Hydroxy methyl furfural.8.4 Furfural 5.9 4.5 6.8 5-methyl furfural 0.43 4 0.74 Vanillic acid 0.6 0.39 0.36 Syringic acid.3.6.37 Ellagic acid.7.8.66 Vanillin 0.39 0.44 0.4 Syringaldehyde 0.34 0.37 0.4 Coniferaldehyde 0.0 0.05 0.03 Sinapaldehyde 0.03 0.03 0.04 Trans-lactone 0.04 0.034 0.346 Cis-lactone 0.73 0.37 0.870 Myricetin 0.03 0.0 0.06 Quercetin 0.3 0.48 0.39 Dihydroxybenzoic acid 0.94 0.97 0.9 Catechin 6.07 5. 5.36 Epicatechin 0.96.85 9 Chlorogenic acid 3.99 4.6 4.5 Caffaeic acid.89 3.44 3.03 Phenol 0.8 0.3 0.7 Guaiacol 0.36.06.4 M/P-cresol.69 3.9 3.83 O-cresol.6.03.8 4-methyl guaiacol 0 0 0 4-ethyl phenol 0 0.04 0 4-ethyl guaiacol 0 0 0 3
Figure is a bar graph comparing the lignin degradation products of the three wines. Lignin degradation products are aromatic aldehydes extracted from seasoned and toasted oak barrels. They should give the wine a sweet, rich, vanillin flavor. The wine matured in the 00% American oak barrel had the most lignin degradation products. However, the Hybrid barrels produced wine with the most vanillin. Vanillin is the most flavor active of the lignin degradation compounds. Figure : Lignin degradation products in wine matured in French, American and Hybrid barrels 3.0 mg/l.0.0 Sinapaldehyde Coniferaldehyde Syringaldehyde Vanillin Syringic acid Vanillic acid 0.0 Figure shows the tannin hydrolysis products. Tannins in oak are co-polymers of gallic or ellagic acids with sugars (mostly glucose), and therefore are called gallitannins and ellagitannins. French oak can contain ten times more tannins than American oak. It is not surprising that the wine matured in the French oak barrel contained the most oak non-flavanoids, namely gallic and ellagic acid. The American oaked wine contained the least. Figure : Tannin content of wines matured in French, American and Hybrid barrels mg/l 5.0 4.5 4.0 3.5 3.0.0.0 0.0 Ellagic acid Gallic acid 4
Figure 3 shows the lactones in the wine. These compounds are responsible for the woody, coconut, oaky aroma of barrel aged wines. The cis isomer is ten times more flavor active than the trans isomer, and is more abundant in American oak than French. The French oak barrel produced wine with the least total oak lactones, and the wine made in the Hybrid barrel did not have significantly more. The American oaked wine contained the most oak lactones. Figure 3: Lactone content of wines matured in French, American and Hybrid barrels 0.6 mg/l 0.4 0.3 0. 0. cis - lactone trans-lactone 0 The smoke compounds and sugar caramelization products were highest in the Hybrid barrel (see Table ). This would be caused by an inconsistency in toasting amongst the set. The Hybrid barrels may have received a higher toast than the others, thus producing more sugar caramelization products and smoke phenolics. In March 999 a sensory panel assessed the wine using quantitative descriptive analysis. The results are presented below. Figure 4: Sensory profile for French barrel Figure 5: Sensory profile for Hybrid barrel Figure 6: Sensory profile for American barrel astringent rich complexity TIA vanilla astringent rich complexity TIA vanilla astringent rich complexity TIA vanilla bitter toasty bitter toasty bitter toasty sweet smoky sweet smoky sweet smoky sulfury fruity sulfury fruity sulfury fruity 5
The preference was solidly for the American oaked wine in this tasting with the French oaked wine being least preferred. The wine made in the American barrel was the most intense, indicated by its high TIA score. It also scored high in vanillin and smoky aromas. However, its overall score for fruitiness was lower than the other two samples. The Hybrid and French oak barrels produced subtler more astringent wines. The astringency could be due to their higher tannin content. At the 4th International Barrel Symposium, delegates tasted the wines. Comments on sensory perception and preference scores were taken. Table 4 gives a summary of the tasting. Table 4: Results from the 4th International Barrel Symposium tasting Preference American Oak Barrel 40% French Oak Barrel 9% Hybrid Oak Barrel 3% No clear preference was decided at the Symposium. Additionally the sensory profiling did not find any statistically significant differences amongst the samples. This may have been due to the wine being in bottle for over a year. The bottle aging had softened the wine and dulled the oak species influence on flavor. CONCLUSION A study into the influence of a Hybrid American/French oak barrel (75:5 ratio) on wine was carried out. It was found the wine produced in the Hybrid barrel took characteristics from both species of oak. It had a higher tannin content but less oak lactone than the American oaked wine. Its aromatic oak aldehydes also fell in between the all-french and all-american levels. Similarly, the quantitative descriptive analysis described the wine as a blend. An economical choice appears to be available to add up to 5% French oak character into wine without purchasing an entire French oak barrel. 6