M-32: A practical approach to controlling the formation of <i>trans</i>-2 nonenal and sensory perception of papery off-notes in packaged beer, a six sigma approach

E. J. SAMP (1), M. Eurich (1), T. Horner (1), R. Ortiz (2), R. T. Foster (1); (1) MillerCoors, Golden, CO, U.S.A.; (2) MillerCoors, Milwaukee, WI, U.S.A.

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The formation of trans-2 nonenal, (E)-2-nonenal, in packaged beer during shelf life is one parameter that brewers seek to control as this aldehyde imparts undesirable papery off-notes. One mechanism generally accepted by brewers is that flavor-inactive bound forms of trans-2 nonenal produced in brewhouse operations survive in packaged beer, and free trans-2 nonenal is liberated during its shelf life, where it is eventually perceived organoleptically. In utilizing a structured problem-solving approach to assist in the control of both free and bound trans-2 nonenal, a cross-functional team followed the define-measure-analyze-improve-control (DMAIC) process to uncover practical brewing factors that influence the formation of trans-2 nonenal. Both wort and beer samples were analyzed using headspace solid-phase microextraction on fiber derivatization in combination with GCMS for both free and bound forms of trans-2 nonenal. Through a series of experiments it was determined that some practical factors can influence (P < 0.05) the formation of trans-2 nonenal in wort, such as mash-in pH, mash-in temperature, whirlpool stand time, wort boiling time, and timing when hops are added, whereas other factors tested (P > 0.05) were deemed not significant (sparge water temperature, number of lauter tun deep bed rakes, and sweet wort clarity). In a series of confirmation experiments with the significant factors optimized, we were successful in reducing wort trans-2 nonenal levels by 75%, with concomitant improvements (P < 0.01) in papery off-note sensory scores at 8 weeks of ambient (24°C) storage. However, the sensory results in the confirmation trial were still deemed too high, leading us to also question the masking effects of other compounds in beer. Using a full factorial design, dimethyl sulfide and iso-amyl acetate were added to stale, “papery” beer, and the test runs were evaluated by our sensory panels. Both compounds exhibited a masking effect (P < 0.05), and we suspect the interaction between these two compounds may also be important. Thus, controlling the formation of papery off-notes in beer can be viewed as having multiple avenues to drive improvements—all of which must be considered when addressing papery off-notes.

Eric Johann Samp graduated with a Ph.D. degree in applied statistics from the University of Northern Colorado in 1994 after completing an M.S. degree in manufacturing systems from Southern Illinois University in 1991. He also completed an M.S. degree in brewing and distilling from Heriot-Watt University in 2009. He is a three-time recipient of the ASBC Eric Kneen Memorial Award. Eric serves on the editorial review boards for the MBAA Technical Quarterly, ASBC Journal, and JIB. He has held numerous positions in both quality assurance and brewing research and development with Coors, MolsonCoors, and MillerCoors over the past 18 years. Eric is a certified lean six sigma master black belt and is also a certified quality engineer, certified manager of quality/organizational excellence, and diploma brewer. He is currently employed with MillerCoors in the corporate QA team as a quality engineer/senior statistician.

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