North Central College - Naperville, IL

John Willis earns Outstanding Major in Chemistry Award

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John Willis
John Willis

John Willis was awarded the 2011 Outstanding Major in Chemistry Award during Honors Day May 17 at North Central College.

Willis is a graduating senior majoring in chemistry. At North Central, Willis tutored students in chemistry and presented research at the National Conference for Undergraduate Research (NCUR). He also conducted summer research at the College and participated in the Summer Undergraduate Research Colloquium (SURC).

He participated in a Biology-Chemistry Interdisciplinary Seminar, presenting research about the chemistry of brewing beer. His abstract from the seminar read as follows:

"Brewing beer is one of the world’s oldest biochemical practices, yet the specific properties of yeasts used to produce the beer and its flavor compounds still aren’t well understood. Organic esters are one of the most important flavor compounds in beer; however, their volatility makes traditional analysis techniques difficult. Solid phase microextraction (SPME) in conjunction with gas chromatography-mass spectrometry (GC-MS) analysis has proved to be reliable for the analysis of these esters, allowing us to record a beer’s unique ‘ester profile’ which can then be compared to the profiles of beer brewed under different conditions or with different yeast strains. We’ve used genetically altered Saccharomyces cerevisiae strains to potentially affect ester synthesis during anabolic metabolism to brew beer. The ester profile of each beer was then determined using SPME followed by GC-MS analysis. For this study, fifteen different esters were analyzed in beers brewed with different yeasts to determine variation. Additionally, alcohol content was measured using nuclear magnetic resonance (NMR) spectroscopy to determine the effect of the yeast strain on alcohol production. We found that our 2 modified strains had unique profiles to each other, but were both similar to our unmodified strain. Alcohol contents in our modified strains were all approximately 2%. We also used an ale yeast strain from a brewery for comparison purposes, which had a unique, and simpler, ester profile and taste, along with having much higher alcohol content under similar brewing conditions. This research will be extended to include observations of the beer at 5 and 10 months in cool isolation to determine the effect of aging on taste and ester profile once the compounds have more time to interact. This research could eventually affect large scale brewing practices by using different yeast strains as opposed to different ingredients to alter the taste of beer."