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A study of factors affecting the extraction of flavor when dry hopping beer

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dc.contributor.advisor Shellhammer, Thomas
dc.creator Wolfe, Peter Harold
dc.date.accessioned 2012-10-03T16:21:44Z
dc.date.available 2012-10-03T16:21:44Z
dc.date.copyright 2012-08-07
dc.date.issued 2012-08-07
dc.identifier.uri http://hdl.handle.net/1957/34093
dc.description Graduation date: 2013 en_US
dc.description.abstract This work set out to examine the methodologies of dry hopping, compare different hop materials, and look at the extraction behavior of different types of hop compounds. This work consists of two discrete studies, where the first study informed the design of the second. The first study measured the concentrations of hop aroma compounds extracted from Cascade hops during dry hopping using a model beer system devoid of malt, yeast aromas, and hops. Cascade hops pelletized by four different processors yielded different particle size distributions and pellet densities. These pellets were dosed into a degassed medium (water, 6% v/v ethanol, pH 4.2) and the hop aroma extraction was measured periodically over a one week period. Solid phase micro-extraction (SPME) followed by gas chromatography (GC-FID) was used to analyze the levels of aroma compounds in the extraction medium. Variation in the hop pellet physical properties did not significantly impact the extraction rate of hop volatiles such as linalool, geraniol, limonene and myrcene with one exception. One treatment showed an increased absolute concentration of geraniol. Separately, dry hop aroma extraction was measured over a short time (1 day) at room temperature in an unhopped beer using small-scale (1L), stirred vessels. Irrespective of the hop form (whole or pellet), the concentrations of hydrocarbon terpenes peaked between 3 and 6 hours and subsequently declined, while the concentrations of terpene alcohols continued to increase throughout the 24 hour dry hop extraction. The rate of hop aroma extraction did not appear to be significantly influenced by hop pellet properties and occurred rather rapidly regardless of the hop form. The second study examined the extraction of hop aroma compounds during a pilot brewery scale (~4hL) dry hop treatment. Dry hop treatments consisted of whole cone hops and pellet hops (Cascade cultivar, 2011 harvest) which were dosed into cylindroconical vessels which were either stirred with a pump or left quiescent. Samples were taken for GC-FID and HPLC analysis as well as sensory evaluation at various time points between 30 minutes and 12 days. Polyphenol and alpha acid extraction was highest in a stirred system dosed with pellets. Hop aroma compound extraction was also the highest in the stirred system utilizing pellet hops. The sensory panel rated the stirred pellet samples as having the highest hop aroma, bitterness, and astringency. The results showed that hop flavor from dry hopping can be readily achieved with much shorter contact time than the current 4-12 day industry practice. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Brewing en_US
dc.subject.lcsh Beer -- Flavor and odor en_US
dc.subject.lcsh Hops -- Sensory evaluation en_US
dc.title A study of factors affecting the extraction of flavor when dry hopping beer en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Food Science and Technology en_US
dc.degree.level Master's en_US
dc.degree.discipline Agricultural Sciences en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Qian, Michael
dc.contributor.committeemember Townsend, Shaun
dc.contributor.committeemember Gable, Kevin
dc.description.peerreview no en_us


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