Aroma potential of oak battens prepared from decommissioned oak barrels

Factors in Modulating the Potential Aromas of Oak Whisky Barrels: Origin, Toasting, and Charring

In this study, the effects of origin (Chinese, France, and America), intensity of toasting, and degree of charring on the volatiles of oak whisky barrels were comprehensively investigated via liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS) combined with multivariate statistical analysis. Results of principal component analysis (PCA) showed that the main oak-derived volatiles in oak were more influenced by origin and toasting than by charring. French oak had a higher content of volatile compounds than the other two origins, and this difference decreased with toasting and charring. The process of toasting and charring was important for the release of volatile compounds from oak. The content of most oak-derived volatiles increased with deeper toasting intensity, and the degree of charring promoted or inhibited the release of oak-derived volatiles. The volatile components in oak blocks were affected by the two-factor interaction of toasting and charring. Continuing the process of the charring of oak at a certain level of toasting may have an enhancing or diminishing effect on the content of different volatile compounds, depending on the circumstances.

Chemo-sensory characterization of aroma active compounds of native oak wood in relation to their geographical origins

Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

Sanitization of Oak Barrels for Wine-A Review

Oak barrels form an integral part of wine production, especially that of high-quality wines where they are implemented as fermentation and aging vessels. Insufficient cleaning and sanitization of barrels can result in microbial spoilage which may have a detrimental impact on wine quality. To date, no review has been published on the various sanitization methods for wine barrels. The objective of this review is to provide an overview of the sanitization methods used in wineries from conventional techniques like the use of sulfur dioxide and steam to alternative and new approaches using ozone and high-power ultrasound. The methods' efficacies are outlined in terms of their ability to eradicate spoilage microorganisms such as Brettanomyces and acetic or lactic acid bacteria. Furthermore, their advantages and drawbacks are described together with their influence on physicochemical properties of the wood. Finally, limitations in existing knowledge are discussed and areas that merit further research are identified.