Oak Aging Research Articles

SENSORY DESCRIPTIVE ANALYSIS OF A RED WINE AGED WITH OAK CHIPS IN STAINLESS STEEL TANKS OR USED BARRELS: EFFECT OF THE CONTACT TIME AND SIZE OF THE OAK CHIPS

ABSTRACT The influence of adding oak chips to a wine stored either in a stainless steel tank or in used barrels was assessed by sensory analysis, using descriptive analysis as well as triangular tests to determine whether differences between the samples could be clearly perceived. Both the size of the oak chips and the length of contact time were studied. The results were also compared with the scores reached by wines aged in new oak barrels. The sensory analyses showed that when the wines were aged in tanks, the effect of adding oak chips was readily appreciated by the panelists and the differences were clearer than when the panelist had to differentiate wines aged in used barrels, with or without chips. Also, the panelists were able to clearly differentiate between wines aged in new barrels and those aged in tanks and in contact with wood chips. When the wood pieces were added to used barrels, the differences between the resulting wine and that aged in new barrels, although smaller, were still perceived, the latter reaching higher scores in the sensory analysis. PRACTICAL APPLICATIONSAging wines in barrels improves their quality and contributes to their organoleptic characteristics. After a period of oak barrel maturation, the wines are enriched in aromatic substances, the color is more stable and mouthfeel complexity is improved. However, barrels are expensive, take up a lot of space in the winery and their lifetime is not very long. Therefore, alternatives have been developed in order to simplify the aging process while ensuring that the wood‐originated volatiles are released into the wine. One of these techniques consists of the addition of small pieces of wood, commonly known as oak chips, to the wine kept in stainless steel tanks or used barrels. These alternatives to oak aging were not a legal practice in European Union (EU) countries until last October when the EU approved the use of pieces of oak wood in winemaking and the designation and presentation of wine so treated. The rapid spread of these techniques makes it necessary to carry out studies to assess the influence of oak chips on the chemical and sensory characteristics of wines and to evaluate the differences with the traditional oak aging systems.

Retrospective land cover/land use change trajectories as drivers behind the local distribution and abundance patterns of oaks in south-western Finland

Valuable cultural landscapes are challenging to sustain. They are usually rare and reflect unique histories of nature–human interactions. We have studied the influence of environmental factors on the present distribution, age and abundance of oaks in a unique forest site in south-western Finland. The Landscape Change Trajectory Analysis (LCTA) approach was tested to improve management strategies at a local level. We used geospatial analysis in GIS on existing data from a recent forest inventory, a multi-temporal land cover/land use analysis, and a digital elevation model. The results show that mature Pendunculate oaks ( Quercus robur) are restricted to the eastern parts of Ruissalo island and their present abundance patterns can be linked with change trajectories as opposed to physical conditions. While the prevailing strategy of strict protection seems to lead to an increasing amount of dead wood, the lack of management hampers the regeneration of oaks. We suggest four principles for future management of these sites that could be applied throughout the hemiboreal region of Europe with similar historical development: (1) management regimes should be spatially explicit in terms of land cover history instead of treating valuable oak biotopes as one homogenous unit; (2) management units should be determined by biotope dynamics and development rather than present status and distribution; (3) management should allow strict protection of sites with long duration of protection and high abundance of decaying oak wood to support biodiversity; (4) alternative management regimes should be introduced in sites with high potential for re-establishment of light-abundant favourable conditions.

The use of oak chips during the ageing of a red wine in stainless steel tanks or used barrels: effect of the contact time and size of the oak chips on aroma compounds

Background and Aims: This paper reports the influence of adding oak chips to a wine being aged either in stainless steel tanks or in used barrels on aroma compounds, comparing these wines with those aged in new barrels. Both the size of the oak chips and the length of contact time were considered. Methods and Results: Aroma compounds were analysed by gas chromatography–mass spectrometry to determine the differences in these compounds between the samples. The results showed that chips release aroma compounds into wine very rapidly, an effect that was clearly seen when they were added to the wines stored in tanks. The wines aged in new barrels continued to extract aroma compounds for a longer time, and higher concentrations were reached in these wines for most aroma compounds. Wines in used barrels with added oak chips behaved in an intermediate manner. Conclusions: Although overall quality is better in wines matured in new barrels, the use of oak chips could be considered a good choice for producing short-aged wines and for reusing used barrels under good sanitary conditions. Significance of the Study: The rapid spread of technique alternatives to oak ageing justifies studies to assess the influence of oak chips on the chemical characteristics of wines and to evaluate any differences from traditional oak ageing systems.

Changes in the color components and phenolic content of red wines from Vitis vinifera L. Cv. “Tempranillo” during vinification and aging

Changes in phenolics and color components during vinification and aging of Tempranillo wines were studied. Different phenolics display different diffusion into the must, and with the exception of proanthocyanidins and acetyl-glucoside anthocyanins, with maximum concentration at the end of postmaceration, the rest of the unacylated and coumarated anthocyanins, monomeric flavanols, and hydroxycinnamic acids reached their maximum at the end of alcoholic fermentation. This resulted in a significant increase in both wine color and stable color, mainly due to the formation of copigmentation complexes, although polymeric pigment formation was also important. Malolactic fermentation produced a significant decrease in flavonoid content while nonflavonoid concentrations were maintained, prompting a considerable loss in wine color, despite the dramatic increase in bisulfite-stable color. Wine oak aging did not produce any significant change in the studied parameters, while bottle aging reduced the level of monomeric anthocyanins and flavanols, and hydroxycinnamic acids. However, wine color remained stable due to a significant increase in stable color. Polymerization reactions of anthocyanins prevailed over pigment degradation reactions, and copigmentation was still relevant after 2 years of bottle aging.

Statistical differentiation of wines of different geographic origin and aged in barrel according to some volatile components and ethylphenols

The purpose of this paper was to study the effect of wine composition and geographical origin on the accumulation of volatile compounds in barrel-aged wines. Therefore, 267 wines belonging to different origin appellations were analysed. In order to analyse the data, a multivariate statistical technique was applied, that can be quite useful in creating an overall view of the problem in which multiple variables are analysed. Statistical analysis gave four significant factors, accounting for 84.12% of the variance. These factors summarise the information of a group of variables closely correlated to each other. Factor 1 grouped together oak lactones and eugenol, so it was associated with oak barrel type and with toasting of barrels. Factor 2 was associated with ethylphenols, related to wine quality diminution. Factor 3 grouped together guaiacol, furfural, and 5-methylfurfural, and was thus associated with wood thermal degradation; factor 4 was associated with the cis/ trans ratio, related to oak origin. Whereas geographical origin of wines affected the accumulation of volatile compounds, the cis/ trans ratio was only affected by oak barrel type. Among the tested parameters, alcoholic degree was the enological parameter that had the greatest effect on the accumulation of volatile compounds in wines. Oak lactones were the compounds that were present in all wines, so they could be used as oak ageing indicators.

Effect of Winemaking Practices on Color Indexes and Selected Bioactive Phenolics of Aglianico Wine

Phenolic compounds are responsible for the sensory properties of wine as well as the properties beneficial to human health. The objective of this study was to establish the effect of the use of SO2 and pectolitic enzymes in the prefermentative phase, maceration time, and oak aging on color, anthocyanins, tannins, (+)-catechin, (-)-epicatechin, rutin, trans-resveratrol, and quercetin content of Aglianico wine. Color indexes and phenolics were analyzed by HPLC and spectrophotometric methods. The addition of SO2 and pectolitic enzymes before fermentation caused an increase in color intensity, color stability, total phenolics, anthocyanins, (+)-catechin, (-)-epicatechin rutin, trans-resveratrol, and quercetin content in Aglianico wine. Longer maceration times gave wines richer in total phenolics and with better chromatic characteristics. Storage in oak caused a decrease in anthocyanins, (+)-catechin, (-)-epicatechin, trans-resveratrol, and quercetin content but an increase in total phenolic content, and a stabilizing effect on color also occurred.

Influence of Micro-Oxygenation Treatment before Oak Aging on Phenolic Compounds Composition, Astringency, and Color of Red Wine

Micro-oxygenation is usually applied to red wines as a cheaper alternative to oak aging. It has been suggested, however, that micro-oxygenation can also be used to complement oak aging in order to improve the quality of very astringent and herbaceous red wines. In this paper we study how applying the micro-oxygenation technique before oak aging affects the composition and quality of astringent red wines. When this technique is applied prior to oak aging, the wines have a slightly less intense red color and significantly higher levels of combined and free anthocyanins and ethyl-bridged anthocyanin-flavanol pigments. On the other hand, no differences in other newly formed pigments are found. Applying micro-oxygenation before oak aging does not affect the total proanthocyanidin concentration, but it produces wines with a slightly (though significantly) higher mean degree of proanthocyanidin polymerization and a drastically lower astringency. These wines also present a clearer impact of wood aromas.

Chemical Markers for Tracking the Sensory Contribution of Production Stages in Muscat Wine Distillates

ABSTRACT:The main sensory contribution of each post‐fermentation production stage of muscat wine distillates can be tracked by following the concentration of just 1 corresponding chemical marker. Matching sample clusters of sensory and chemical data by using principal components analysis (PCA) revealed potential chemical markers. The data used in this study correspond to 12 sensory attributes that showed significant differences among products (P < 0.05) and concentrations of 23 volatile compounds of 14 distillate fractions and 15 finished Piscos. Artificial fruit attribute, characteristic of the head fraction (FR1) can be tracked with esters. Linalool, main odor attribute of the 1st part of the heart (FR2) can be tracked with linalool molecule. The 2nd part of the heart (FR3) can be tracked with octanoic acid, decanoic acid, furfural and ethyl lactate, accounting for tails attribute. In blended and aged finished products, chemical markers accounting for the effects of distillate fractions were similar but not identical to the markers from samples obtained from the purely distilled samples. Chemical markers for FR1 are ethyl hexanoate, ethyl octanoate, ethyl decanoate. Differentiation between FR1 and FR2 is less evident than in the purely distilled samples due to the linalool and artificial fruit attribute correlation. Chemical markers for FR2, therefore, include linalool and esters ethyl hexanoate, ethyl octanoate, and ethyl decanoate. The blending of the 2nd part of the heart (FR3) can be tracked with 2‐phenylethanol, ethyl lactate, and decanoic acid. Oak aging was tracked with eugenol and whisky lactones, while 5‐hydroxy‐methyl‐2‐furfural accounted for added caramel.

Influence of the Presence of the Lees during Oak Ageing on Colour and Phenolic Compounds Composition of Red Wine

Oak ageing of red wine in the presence of lees is currently a procedure that is being introduced in most wineries. This work analysed the influence of this technique on colour and phenolic compounds of two red wines, one with a low ageing potential (low anthocyanin and proanthocyanidin concentration) and the other one with a high ageing potential (high anthocyanin and proanthocyanidin concentration). Wines, after six months of ageing in new American oak barrels, were analysed and tasted by expert panellists. In general terms, ageing in the presence of lees presented the disadvantage of producing wines with a slightly less intense colour and with lower proanthocyanidin concentration. However, the advantages were that wines presented a colour slightly less evolved towards yellowish nuances, a non-negligible diminution of their astringency and an increase in the mouthfeel perception.

Diversity and specificity of ectomycorrhizal fungi retrieved from an old‐growth Mediterranean forest dominated by Quercus ilex

We analysed the ectomycorrhizal (ECM) fungal diversity in a Mediterranean old-growth Quercus ilex forest stand from Corsica (France), where Arbutus unedo was the only other ECM host. On a 6400 m2 stand, we investigated whether oak age and host species shaped below-ground ECM diversity. Ectomycorrhizas were collected under Q. ilex individuals of various ages (1 yr seedlings; 3-10 yr saplings; old trees) and A. unedo. They were typed by ITS-RFLP analysis and identified by match to RFLP patterns of fruitbodies, or by sequencing. A diversity of 140 taxa was found among 558 ectomycorrhizas, with many rare taxa. Cenococcum geophilum dominated (35% of ECMs), as well as Russulaceae, Cortinariaceae and Thelephoraceae. Fungal species richness was comparable above and below ground, but the two levels exhibited < 20% overlap in fungal species composition. Quercus ilex age did not strongly shape ECM diversity. The two ECM hosts, A. unedo and Q. ilex, tended to share few ECM species (< 15% of the ECM diversity). Implications for oak forest dynamics are discussed.

Evolution of sugars in cider brandy aged in oak barrels: a contribution to its characterization.

A chemometric study was carried out to typify cider brandies according to the type of wood employed in the maturation process and their aging time. Monosaccharides, previously derivatized with p-aminobenzoic ethyl ester, were analyzed using a reversed-phase high-performance liquid chromatographic method. Univariate data treatment was not sufficient to enable differentiation of the classes of cider brandies on the basis of wood type and maturation time. Two linear combinations of original variables, ascertained by principal components analysis, provided an adequate data structurization. A mathematical decision rule was established to classify cider brandies with prediction capacities of 92 and 97% using an LDA method and Bayesian analysis, respectively. The use of the PLS algorithm allowed the authors to differentiate cider brandies according to the age and type of oak used in the aging process.

Identification of 2,3-Dihydroxy-1-guaiacylpropan-1-one in Brandies

We have purified and identified a new phenolic compound in brandies aged in wood. Spectral structural analysis by HPLC-DAD suggested that the unknown compound corresponded to a 3-methoxy-4-hydroxybenzoic ketone with an aliphatic chain containing hydroxyl groups. 1H NMR analysis confirmed its structure as 2,3-dihydroxy-1-guaiacylpropan-1-one. Concentration of this ketone in brandies is related to the genuine aging of these beverages in oak and, therefore, to their market value. Keywords: Aromatic aldehydes; brandies; oak aging; lignin breakdown

Effect of Storage at Elevated Temperatures on Aroma of Chardonnay Wines

The effect of elevated temperatures during storage on wine aroma was determined for commercial Chardonnay wines with and without oak aging. A significant difference in aroma was detected between the control wine (held at 5°C) and the unoaked (94-U) and oaked (94-O) 1994 wines, after they were held at 40°C for five and seven days, respectively. The 1993 oak-aged wine (93-O) was more resistant to the storage treatment, with a significant difference produced only after nine days at 40°C. After five to nine days of heated storage, only very small decreases in glycosyl glucose (GG) level were observed, suggesting that the initial changes affecting aroma were not a result of hydrolysis of glycosides. To characterize the changes in aroma produced by heating, wines stored at 40°C for 0, 15, 30, and 45 days were profiled by descriptive analysis using trained judges. Upon heating of all wines (93-O, 94-O, 94-U), the intensity of floral and fruity notes decreased, while aromas associated with oak and aging increased: honey, butter/vanilla, oak, tea/tobacco and rubber. The first 15 days of heating resulted in significant increases in the honey, rubber and tea/tobacco attributes and decreases in citrus, tropical fruit, green apple and floral aromas. Increasing the storage time to 30 days resulted in a further decrease in fruity aromas and increase in honey, rubber, tea/tobacco, butter/vanilla, and oak. Few further changes in aroma occurred when storage was extended to 45 days. Although larger decreases in GG concentration occurred upon heating for 15 to 45 days, no consistent relation between GG and the attributes was found.

Determination of the natural mortality age of an holm oak ( Quercus ilex L.) stand in Corsica (Mediterranean Island)

Determination of old forest stand age and forestry history is problematic due to the difficulties which arise in obtaining core samples from trees. In the present paper, the natural mortality age and forestry history of a Corsican holm oak stand are estimated using the methods described below. Firstly, the correlation between stem age estimated from healthy stump count in fellings and stem diameter is determined using a second order polynomial equation. Secondly, the distribution of stand diameter classes is analyzed by the Bhattacharya (1967) method. This method allows the identification of cohorts as well as the estimation of cohort mean diameters and theoretical tree count numbers. Using cohort mean diameters, we are able to estimate their age and discuss stand forestry history. Finally, the analysis of thirty broken stumps originating from senescent holm oak natural falls, is used to determine the mean natural mortality age of trees based on their mean diameter. This natural mortality is estimated to occur at 170±46 years of age. The causes of holm oak mortality and the capacity of old stumps to renew the ecosystem are discussed in order to contribute to the conservation and management of these woodland communities.

Barrel-to-Barrel Variation of Volatile Oak Extractives in Barrel-Fermented Chardonnay

Barrel-to-barrel variation in barrel-fermented wines was measured by determining the concentrations of seven volatile oak extractives — furfural, 5-methylfurfural, furfuryl alcohol, guaiacol, <i>cis</i>-ß-methyl-γ-octalactone, <i>trans</i>-ß-methyl-γ-octalactone, and syringol — in individual barrels of four 10-barrel lots, two French and two American oak — of barrel-fermented Chardonnay after seven months of oak aging. Within individual commercial production lots, the variance of individual compounds averaged 27% and ranged from 15% to 40% as measured by the percentage of standard deviation with respect to the mean. Statistical analysis of the data showed that an experiment with four barrels per lot would yield chemical levels within 30% of the barrel population (a specific barrel type from a specific producer) while a 10-barrel lot would be within 20% and a 39-barrel lot would be within 10%. However, the use of one barrel could yield chemical levels more than 50% different from the population.

Crown Class Transition Rates of Maturing Northern Red Oak (Quercus rubra L.)

Abstract Crown classes and diameters of 704 northern red oaks on medium quality sites were measured at 10-yr intervals between 1927-1987. Nominal age of northern red oaks at the beginning of the study was 25 yr. Mortality rates between ages 25-55 and between ages 55-85 decreased with each increase in crown class (i.e., mortality of dominant is &amp;lt; codominant is &amp;lt; intermediate is &amp;lt; suppressed). Ascension rates into higher crown classes increased with each increase in crown class between ages 25-55 and between ages 55-85. Mortality rates of dominant, codominant, and intermediate trees were higher between ages 55-85 than between ages 25-55. The cause of the increased mortality was likely periodic episodes of defoliation which began after age 55. Within several diameter classes at age 25, survival through age 55 and the proportion found in upper canopy at age 55 increased with crown class. Mortality rates between ages 25-55 were lower for the largest northern red oak in a sprout clump than for lesser sprouts and for those trees which were not part of a sprout clump. There was no significant difference in canopy position transition rates between ages 55-85 for the largest red oaks in a sprout clump and those trees which were not part of a sprout clump. However, mortality rates between ages 55-85 of lesser trees in a sprout clump were significantly higher than for either the largest sprout in a clump or for those trees which were not part of a sprout clump. Survival of suppressed and intermediate 25-yr-old red oak was negatively related to the number of oaks in dominant and codominant crown classes. Crown class can be a powerful tool for determining the future status of maturing northern red oaks in southern New England. For. Sci. 40(2): 221-237.

Comparison of Actual and Predicted Blue Oak Age Structures

There is increasing interest in understanding the role of management on the current lack of blue oak (Quercus douglasii H. & A.) recruitment on California foothill rangelands. Age structure analysis has been suggested to relate when and how much recruitment occurred under past management as an indication of current management effects on recruitment. Previous estimates of blue oak age structure were based on unquantified correlations between age and diameter. Using regression analysis we found that diameter at breast height (DBH) accounted for 42-71% of the variation in tree age at 2 sites. Actual age structures were significantly different than age structures predicted from all regression equations at both sites. We suggest that the use of age structures to infer the role of management on blue oak population dynamics requires direct age measurement.

The Botanical History of the 'Sindian' and the Age of Abraham's Oak

The Botanical History of the 'Sindian' and the Age of Abraham's Oak

Age of Oaks

Age of Oaks

Age of the oak

Age of the oak