B. BUFFIN (1), T. Shellhammer (2), V. Algazzali (3), N. Bird (1);
(1) Kalsec Inc., Kalamazoo, MI, U.S.A.; (2) Oregon State University, Corvallis, OR, U.S.A.; (3) John I. Haas, Yakima, WA, U.S.A.
The use by brewers of pre-isomerized and reduced advanced hop products, such as dihydro-(r)-iso-α acids (Rho), tetrahydro-iso-α acids (Tetra), and hexahydro-iso-α acids (Hexa), continues to increase. Given the potential for each of these to impart different relative bitterness to beer, as well as the previously unexplored variance associated with the starting material and the manufacturing process involved, a study was undertaken to better assess how various hop acid products impact beer flavor and bitterness. Reduced hop acid products and starting materials evaluated included α-acid derived, β-acid derived, and iso-α-acid derived Tetra; α-acid and β-acid derived Hexa; and α-acid and iso-α-acid derived Rho. Each of the eight different reduced iso-α-acid products was individually dosed into unhopped lager beer and evaluated using two different trained sensory panels. The samples were rated on eight attributes: citrus, paper, medicinal, astringent, vegetative, metallic, peak bitterness intensity, and duration of bitterness. Through replicated descriptive analysis testing, the panels found significant differences between the different classes of advanced hop acids. For example, univariate and multivariate analyses of the descriptive data suggest that large differences exist between Rho, Hexa, and Tetra in lager beer while only subtle differences exist within the Tetra treatments. Surprisingly, the Tetra samples that exhibited the greatest differences in sensory scores were the most similar in terms of analog composition, suggesting that the relative concentrations of individual analogs (e.g., co-tetrahydro-iso-α acids) are not a valid predictor of sensory bitterness quality. Replicated triangle testing also found no differences within Hexa nor within Tetra treatments. While solubility and other physical differences can exist, generating Tetra from hop α-acids, iso-α-acids, or β-acids will produce a product of similar bitterness quality. Details of the product syntheses, brewing and dosing, analytical analysis, sensory analysis, and data processing will be discussed.
Brian Buffin is the director of corporate discovery, analysis, and quality for Kalsec, Inc., a leader in the supply of advanced hop products to the brewing industry. Brian holds Ph.D. and M.S. degrees in organometallic chemistry from the University of Utah and a B.S. degree in chemistry from Calvin College. After working in the diatomaceous earth industry for World Minerals/Celite, he spent more than 13 years in professorships at academic institutions before joining Kalsec in 2008. Brian has been active in the area of hops research for more than 7 years.