Siebert, K. J., Cornell University, Geneva, NY, USA
Technical Session 6: Sensory
Tuesday, June 06, 2017
1:45–3:30 p.m.
Everglades Ballroom
People can directly sense the appearance (color, clarity and foam) and flavor (smell, taste and mouthfeel) properties of beer. These, however, are subjective observations that differ between and within individuals and are poor in precision and accuracy. It is of interest to consider how and how well analytical methods represent human perceptions. Color can be assessed using a color comparator or a light absorbance measurement. Although the latter employs only a single wavelength or wavelength band, it gives a reasonably good agreement with perception, except for red and hazy beers. Measuring light scattering at a 90° angle gives good agreement with human perceptions of turbidity. Strongly colored samples cause underestimation of haze by humans and instruments. Foam measurements involving pouring from a container are problematic as they are influenced by carbon dioxide content and container geometry. Methods involving piercing a container remove the second effect. Methods involving degassing and then foaming up (e.g., Rudin head retention value) remove both. Taste involves 5–7 senses (sweet, sour, salty, bitter, umami, likely oleogustus and maybe starch) on the tongue. Some efforts have been made to develop an “electronic tongue,” but these have not produced a good representation of the human senses. Smell (olfaction) includes many perceptions made when volatile compounds reach the olfactory epithelium. Gas chromatography (GC) has been used to measure volatile compounds, but no known GC detector even approximates the response of the human nose. Using an actual nose, as in GC-olfactometry, is more successful, but laborious. Efforts have been made to develop an “electronic nose”; although an “electronic nose” produces a pattern of responses like the nose, it does not produce comparable results. Efforts have been made to develop sensors for some of the chemesthetic (mouthfeel) sensations. Simple temperature measurements should work well for the physical hot and cold sensations, but not those produced by substances such as capsaicin or menthol. A sensor has been reported for astringency. Smoothness is, at least, to some extent the lack of astringency.
Karl Siebert received a Ph.D. degree in biochemistry from Penn State in 1970. He then joined the Stroh Brewery Company in Detroit, MI, where he spent 18 years and held positions ranging from research associate to director of research. In 1990, he joined Cornell University as professor of biochemistry in the Department of Food Science, where he continued to work on beverages, particularly beer, until he retired in 2015. He received two MBAA Presidential Awards, and with his colleague, Penny Lynn, received the Eric Kneen Memorial Award (for the best paper in the Journal of the ASBC in the prior year) three times. He received the ASBC Award of Distinction in 1999 and the MBAA Award of Merit in 2011. Karl is active as a consultant in beverage technology and chemometrics.
