Date of Award

Summer 8-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food and Nutrition Sciences

Advisor

Brian Perkins

Second Committee Member

Jason Bolton

Third Committee Member

Jennifer Perry

Abstract

For many years the only beer that was commercially available in the United States were simple lagers and ales made primarily of barley (and other cereals), water, hops, and yeast. These beer varieties were simple and quick to produce with high levels of consistency. In the last 30 years the rise in craft and microbreweries have dramatically changed the landscape of brewing and beer. As smaller breweries rose in popularity so did the use of unique ingredients such as vegetables, fruits, herbs, meat, etc. along with higher gravity mashes and long barrel aging times. All these ingredients have a profound effect on the chemical makeup of a beer, adding a variety of organic acids, antimicrobials, amino acids, etc. These compounds become important when examining the influences of what may be the most important ingredient in beer (and all alcoholic beverages), yeast.

Yeast, specifically Saccharomyces yeast (though many other genera are capable of this), consume simple carbohydrates within the unfermented beer and produce carbon dioxide and alcohol. While these fermentation biproducts are the most well-known compounds produced by yeast, there are many others. During development (log phase) and times of stress/carbohydrate starvation, yeast can often consume proteins and amino acids and produce biogenic amines. Biogenic amines (BA’s) are small nitrogenous bases produced through the enzymatic decarboxylation of amino acids by living organisms. Examples of biogenic amines include histamine, serotonin, tyramine, and spermine (though many others exist). These compounds are important and powerful signaling molecules used by every living creature on Earth. While endogenous biogenic amines produced within the body are critical to survival, exogenous biogenic amines in a consumed food product can be highly dangerous; biogenic amines can cause a variety of symptoms ranging from headaches to hyper/hypotension to pseudo-anaphylaxis. While all living things create these compounds, the levels in most food products are too low to cause any symptoms: The only products with potentially dangerous levels of biogenic amines are fermented foods as bacteria and fungi used to make these products can also produce biogenic amines.

While the biogenic amine content in certain fermented foods like cheese, sausages, and lacto-fermented vegetables has been well studied, formation of biogenic amines in beer remains largely under-examined. The three main objectives of this research were: 1., to perform an extensive review of the literature to ascertain analytical methods, types, levels, and sources of biogenic amines in beer, 2., to develop a quick and effective high performance liquid chromatography (HPLC) method to examine the biogenic amine content in beer, and 3., use this HPLC method to test a variety of commercial beer sample to examine what effect (if any) these new microbrewery recipes had on the biogenic amine profile of the final beverage.

Method development focused primarily on the tagging of BA’s using the Waters AccQ Rapid Amine Tag (AccQ Tag Ultra, 2014) and analysis using an Agilent Organic Acids column. In total, more than 17 HPLC methodologies were tested and only one effectively resolved a mixed amine standard solution.

Despite this successful test using a mixed standard, no mobile phase adjustment was able to effectively separate biogenic amines from interfering compounds (free amino acids or other nitrogenous compounds) in a beer sample. It was ultimately decided that moving forward, an effective extraction method, involving sample cleanup and capable of separating biogenic amines from highly soluble peptides and amino acids would be necessary for successful analysis.

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