34. Assessing the role of four key process variables in the dry-hopping of beer

Christian Holbrook (1); (1) New Belgium Brewing Company, Fort Collins, CO, U.S.A.

Technical Session 10: Dry Hopping
Monday, August 15  •  9:45–11:30 a.m.
Tower Building, Second Level, Grand Ballroom

The practice of dry-hopping beer after fermentation for the purpose of imparting the character of the raw hop to the beer is a common process in the craft brewing industry. Significant impacts to the industry include the cost and availability of desirable aroma hops to breweries as the consumer demand for India pale ale (IPA) styles and other hop forward beers continues to grow. Type 90 (T90) hop pellets are one of the most common hop products among craft brewers used for dry-hopping beer, and there also is growing interest in custom-made hop pellets designed specifically for dry-hopping of beer. This work set out to examine the influence of four variables on the dry-hop process and the effect of each variable, or combination of variables, on the transfer of terpene compounds into beer during dry-hopping. Beer temperature (°C), beer alcohol concentration (%ABV), hop pellet type (T90 or custom E90 pellets of Cascade hops), and hop dosing rate (g/hL) were evaluated in a designed bench-scale experiment under controlled conditions. Solid-phase microextraction (SPME) followed by gas chromatography with mass spectrometry (GC/MS) was used to analyze the concentrations of myrcene, linalool, caryophyllene, and humulene in the trials. These terpenes were selected due to their significance as key aroma and flavor components of our flagship IPA, which served as the model beer for all experiments. Statistical analysis of the GC/MS results was utilized to determine which factors and combinations of factors are significant drivers (P ≤ 0.05) of terpene compound concentration and variability in dry-hopped beer. This study then took key findings from the laboratory-scale work and applied them to production-scale (1,400 hL) dry-hop trials to evaluate if the results carried over with the increase in scale. Analysis of terpene compound concentrations in beer by GC/MS, and sensory analysis of beer was used to determine key differences in production-scale trials. Opportunities for efficiency improvements in dry-hopping were assessed, and resulting process changes will be discussed.

Christian Holbrook received an M.S. degree in brewing science from the University of Nottingham in 2015. He began employment in the brewing industry with Fitger’s Brewhouse in Duluth, MN, in 1999 and has worked in various production roles with Kona Brewing Company and, since 2003, with New Belgium Brewing Company. Since June 2010 he has worked in the role of quality manager for brewing ingredients, with a supporting role in technical brewing quality at New Belgium. He also serves in various roles on behalf of New Belgium in the American Malting Barley Association, the Brewing & Malting Barley Research Institute, the Hop Research Council and the Hop Quality Group.