Kirkpatrick, K. R.1 and Shellhammer, T. H.1, (1)Oregon State University, Corvallis, OR, USA
Poster
With the increasing trend of greater dry-hopping rates, the impact hop compounds have on beer flavor and beer quality becomes more important, but it is not entirely understood. Experiments carried out at OSU suggest that residual enzymatic power of hops can be transferred to dry-hopped beer and, in turn, influence the composition of its fermentable and nonfermentable carbohydrates. Fully attenuated and packaged American lager beer was dry-hopped at a rate of 10 g/L with pelletized Cascade hops, dosed with 1 million cells/mL of ale yeast, and incubated at 20°C. Real extract of the treated beer declined significantly within several days, with a drop of 1°P RE after 5 days, which when fermented is equivalent to the production of an additional 2.5% (v/v) of CO2 and an additional 0.5% (v/v) of alcohol. Further analysis of the carbohydrate profile via HPLC of dry-hopped beer in a yeast-free beer stabilized with sodium azide indicated an increase in appreciable levels of glucose and maltose in beer incubated with pelletized Cascade hops. Over a period of 1 week, glucose steadily increased to 15-fold its original concentration, and maltose increased by threefold compared to an unhopped control. The residual enzymatic activity of hops in beers containing active yeast may result in excessive build-up of CO2 in packaged beer, which represents a safety hazard, along with alcohol contents that are out of specification.
Kaylyn Kirkpatrick is a graduate student in the Oregon State University Brewing Science Laboratory under the mentorship of Dr. Thomas Shellhammer. She obtained her B.S. degree in biochemistry from Colorado State University in 2013 and was awarded a Diploma in Brewing through the Institute of Brewing & Distilling in 2016. Her research focuses on the effects of hop and yeast interactions on beer fermentation and flavor.
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