Alpha acids grow inside the flowers of Humulus lupulus (hop) plants. Eighty percent of the final bitter taste in beer come from alpha acids. Therefore, it is crucial that hop manufactures and beer brewers have knowledge of the exact percentage of alpha acids in a given batch of hops. Because alpha acids are not made synthetically and rather they come from a plant, every flower produces different amounts of alpha acids. This creates a need for a quantitative analysis of alpha acids before every batch of hops are put in wort during the brew process. Otherwise, each brew may produce changes in bitterness taste and a brewery will not be able to manufacture consistently tasting beer. Analytical methodologies for the extraction of alpha acids from hops are time consuming and impractical for a large brewery that supplies thousands of cases of beer every day.
Sarah has spent the 2011 summer quantitatively determining the alpha acids in hops. She is currently developing the most efficient method of alpha acid extraction using the ASE 200 Accelerated Solvent Extraction System made by Dionex Corporation (part of Thermo Fisher Scientific). After an efficient extraction method is created, HPLC (high performance liquid chromatography) will be used to separate and analyze the three alpha in given hop samples. Sarah is also studying the rate of hop acid isomerization as temperature increases from room temperature to 120 degrees Celsius. It is important for brewers to know the best temperature of the wort boil because they want to achieve the highest conversion of alpha acids into iso-alpha acids. Another analysis will determine the alpha acid content at a hop’s first stage of inflorescence maturity; the formation of its small hop cone; and finally, the full-grown hop cone. If time permits, a flavonoid uniquely found in hops called xanthohumol, which has been shown to be a powerful antioxidant and anticancer drug, will be analyzed.
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