Hop aroma and harvest maturity

Technical Session 01: Hops I Session
Daniel C Sharp, Oregon State University, Corvallis, OR USA
Co-author(s): Yanping Qian, Shaun Townsend, and Thomas Shellhammer, Oregon State University, Corvallis, OR, USA

ABSTRACT: Hop chemical composition changes, in particular aroma development, during plant maturation are part of a rapid and dynamic process that requires a comprehensive, in-depth chemical and sensory analysis to maximize characteristics of interest to brewers. The complex aroma chemistry associated with hops in beer has been a confounding variable for practical brewers, and a deeper understanding of hop aroma development during cultivation is needed. This presentation discusses results and conclusions from a two-year study and compares these results with other studies that have examined location and harvest time and their effect on brewing quality. The effect of harvest date and location on and a variety of key chemical components of Willamette and Cascade hops were investigated for the 2010 and 2011 growing seasons. Hops were harvested at three time points within a 3-week interval (early, normal, and late), from three different farms in the Willamette Valley, Oregon, and then analyzed for moisture, hop acids content, total oil content, and essential oil composition. The response of analytes was dependent on the variety being examined, its location within the Willamette Valley, as well as the time of harvest. Hop acids did not change appreciably during plant maturation, while hop oil content increased hyperbolically to a plateau as the hops aged on the bine. Increases in oil quantity were strongly correlated (r > 0.80) with increases in alpha-pinene, beta-pinene, myrcene, limonene, methyl heptanoate, linalool, and eudesmol concentrations. Growing location within the Willamette Valley had a significant effect on oil concentrations for each variety at each time point, thus suggesting that individual grower practices and local environmental influence hop chemical composition.

Daniel Sharp is a master’s student in the Food and Fermentation Science program at Oregon State University. His research is currently focused on hop studies being conducted in Thomas Shellhammer’s lab. Daniel’s primary area of study is the aroma compounds in hops and beer. Prior to joining the Food Science program at OSU, Daniel earned a B.A. degree in both Spanish and adventure leadership at the University of Oregon. After graduation he lived and worked in South America, first as a mountain guide in Venezuela and later as a brewer at the Center of the World Brewery, Ecuador’s only microbrewery at the time.