Date of Award
Master of Science
Simioan Petrovan, Timothy Rials, David Harper
The stipulations from the government of the United States require whisky distillers to use a new, charred oak barrel for maturation of the spirit. The amount of money spent on new oak accounts for almost 60% of the price for the finished spirit. Determining the amount of virgin wood, wood not affected by the maturation process, which remains in the stave, could reduce the costs for the production of certain spirits.
Thermal treatment to the wood before maturation creates some of the compounds attributing to the flavor and color of the spirit. Utilizing pressure, temperature, and humidity differences from season to season allows the distiller to create a spirit that reflects the standards of the final product. However, these differences also cause to increase the variability observed in the samples
Multiple methods were tested to determine the amount of virgin wood remaining in the stave. Analysis was performed on the surface of the stave using near infrared (NIR) spectroscopy and on the extract with high performance liquid chromatography (HPLC) and multivariate analysis (MVA). The NIR approah did not yield an amount of virgin wood, but instead showed the drastic modification of the stave from charring and charring process.
A univariate and multivariate approach were used on the HPLC extract. Analysis using nonparametric tests coupled with a univariate approach, a consistent amount of virgin wood could not be determined.
A multivariate approach was implored to find the limit of virgin wood remaining in the stave. By analysis of the HPLC chromatograms using principal component analysis coupled with the Wilcoxon Rank-Sum test, the amount of virgin wood remaining after maturation could be calculated.
Another issue facing spirit distillers is the natural variation of compounds specific to the spirit in the wood. Determining the amount of “spirit specific” compounds naturally present in the wood and available for maturation will allow for distillers to engineer casks to certain standards. Analysis of near infrared spectra obtained on the milled staves before extraction and correlation with quantified results from the HPLC chromatograms using a partial least squares regression (PLSR), predictive models were generated for certain spirit specific compounds.
Wolff, John Powers, "Determination of Virgin Wood Remaining in a Cask after Maturation and Predictive Modeling for Spirit Specific Compounds. " Master's Thesis, University of Tennessee, 2008.