Issue link: https://read.dmtmag.com/i/491371
STiR tea & coffee industry international 49 Continued from pg. 47 Where do the flavors that develop when coffee is roasted come from? Leading work on the formation of taste active compounds in coffee was done by Thomas Hofmann and his research team at the TUM while various scien- tists elucidated many of the multi-step chemical reactions that happen during roasting, including Maillard reactions, Strecker reactions, caramelization, hy- drolyzation, and fragmentations. Scientists are still uncertain of what exactly happens during coffee flavor formation because of the complexity of such reactions and the fact that many resultant compounds are unstable. The recent International Conference on Coffee Science (ASIC) dedicated a full day to reports about recent research on the chemistry of roasting. Much of that presented used high tech tools to monitor on-line roasting. Whether such equipment will lead to precision tools for roasters or will only be used for scien- tific inquiry is an open question.The only certainty is that many researchers are now using improved approaches, and are applying these advanced analytical methodologies to further reveal some of the mysteries of coffee roasting. Three presentations at the ASIC conference aimed at getting a deeper understanding of the aroma formation during roasting: • Frédéric Mestdagh (Nestlé) presented a more basic scientific study to deepen our understanding of the kinetics of the chemical reactions taking place during roasting. His approach included analysis not only of the aroma compounds but also the pre-cursor material (i.e. the green bean). • Chahan Yeretzian's research group (ZHAW) connected proton-trans- fer-reaction-time of flight-mass spectrometry (PTR-ToF-MS) instruments to different types of roasting equipment to investigate how the airflow impacts the kinetics of aroma formation. • Ralf Zimmermann's research group (Uni Rostock) did a similar study but used resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry (REMPI/SPI-ToF-MS) to follow the aroma formation in the gas phase when using different varieties and roasting profiles. Zimmermann sug- gested using such instrumentation as a process optimization tool. The science experts at Nespresso who compiled this report strive to un- derstand how aroma and taste compounds contribute to the overall sensory profile of a coffee. This enables Nestlé to roast in a very precise way to create even more diversified coffees with unique sensory profiles for our consumers. Photo courtesy of Colombian Coffee Growers Federation Sources cited Blank, I., Sen A. and Grosch W. 1992b. "Potent odorants of the roasted powder and brew of Arabica coffee." Z. Lebensm. Unters. Forsch. 195: 239-45. Flament, Ivon. 2002. Coffee Flavor Chemistry. (West Sussex: Wiley) Glöss, Alexia. 2014. "C6: Application of on-line analysis of coffee roasting with ptr-tof-ms on industrial roasters: pros and cons." Research presented at the 2014 Association for Science and Information on Coffee, Armenia, Colombia, September 8-13. Grosch W. 2001. "Evaluation of the key odorants of foods by dilution experiments, aroma models and emis- sion." Chemical Senses 5:533-45. Kerler, Josef and Poisson, Luigi. 2011. "Molecular targets for new product development." New Food 6: 7-11. Mestdagh, Frédéric. 2014. "C4: Conversion of green coffee precursors into flavour during roasting of arabica and robusta coffees." Research presented at the 2014 Association for Science and Information on Coffee, Armenia, Colombia, Sept. 8-13. Zimmermann, Ralf. 2014. "C7: Photoionisation mass spectrometry for on-line analysis of the coffee roast- ing process and process control: a combined mass spectrometric and chemometrical approach." Research presented at the 2014 Association for Science and Information on Coffee, Armenia, Colombia, Sept. 8-13. Photo courtesy of Colombian Coffee Growers Federation Dynamics of flavor description Sensory scientists often prefer not to use industry experts on panels because many assume there is a bias towards judging quality rather than simply describing flavor. Given that food scientists and green buyers are not describing flavor from the same context or with the same vocabulary, how do product development teams communicate with green coffee buyers? On this point, Fernandez said, "What scien- tists need in order to do research about flavor is to describe flavor in the most objective possible way even though it's still a sensory method and it's still using human beings as assessors." According to Fernandez, some scientists are exploring ways to work with cuppers. He said, "[Cupping] has a number of advantages over [the other] scientific sensory methods, namely it's quick and it can be done by fewer people as long as they're experts." When this approach is taken, researchers also measure the behavior of experts as experts and to relate their outcome to the description of the sam- ple. Such strategies seem to work well for some transnational consumer product companies. Of teams at Nespresso, Rodriguez said: "[For] many years, we have [had] a close relation with our coffee buyers and we participate in most of our crucial activities as a team: Trip visits to origin to identify and select new coffees, quality audits to coffee warehouses, suppliers' reviews, tasting ses- sions in origins, tasting sessions for release in pro- duction [centers] and so on." At left, Felicia Tiller, manager at Rising Star Coffee in Little Italy, Cleveland, Ohio.