Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Kevin A Schug

Abstract

There has been an increased interest in the “craft” alcohol industry in recent years. Contrary to larger corporations that focus on standardizing their recipes for mass production, these small, independent businesses can experiment with ingredients and procedures to create unique and flavorful products. Beer and whiskey in particular have seen a surge in popularity, indicating the public may be interested in a deeper understanding of these beverages and their flavors on the chemical level. Brewing and distilling rely heavily on chemistry to perform the proper procedures to obtain the desired product, and to understand the interactions of the various ingredients. However, these modern craft beers and whiskies tend to have more intricate flavors than their mass-produced counterparts, making their chemical profiles potentially even more complex. Therefore, advanced analytical techniques are desirable to obtain a more complete view of these popular beverages. Three studies were conducted using mass spectrometry methods for beer and whiskey flavor analysis. First, a collection of 32 craft beers covering 5 styles were analyzed in a targeted fashion using liquid chromatography quadrupole time-of-flight mass spectrometry to determine if they could be distinguished based solely on the presence or relative content of iso-α-acids and phenolic compounds. These two classes of compounds were selected due to their influence on beer flavor and stability. The optimized method successfully separated and quantified the monitored analytes using high resolution multiple reaction monitoring. While a few compounds were found to be unique to a style, such as vanillin in stout beers and a higher iso-α-acid content in India pale ales, it was determined that the targeted analytes were not sufficient to confidently distinguish the styles. Therefore, the second study analyzed the same set of beers using untargeted and multivariate techniques to determine which compounds were the most influential in differentiating beer styles. Unsupervised principal component analysis provided visualization of the variance in the 5 styles, confirming that there were indeed differences between them on the chemical level. Further multivariate analysis resulted in a list of possible formulas for the most influential metabolites, and their identities were predicted. Finally, a third study was conducted to develop a headspace solid phase microextraction gas chromatography mass spectrometry method to simultaneously identify and quantify compounds which cause off-flavors in whiskey. Some of the major contributors to whiskey off-flavors include 2,4,6-trichloroanisole and geosmin, which impart moldy and musty tastes. These compounds, along with two other haloanisoles, were separated and quantified in ten different whiskey samples using the optimized method. The application of these advanced analytical methods could potentially enhance quality control practices and product marketability in the alcohol industry.

Keywords

Liquid chromatography, Gas chromatography, Mass spectrometry, Targeted chromatography, Untargeted chromatography, Beer, Whiskey, Quality control, Multiple reaction monitoring

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Included in

Chemistry Commons

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