Y. NORO (1), A. Murakami (1), J. Furukawa (2), Y. Kawasaki (1), R. Ota (1);
(1) Kirin Brewery Company, Limited, Yokohama, Japan; (2) Kirin Brewery Company, Limited, Okayama, Japan
There have been many studies on selective adsorption of nonpolar substances by viable brewing yeast. Besides viable brewing yeast, we have found that nonviable dry brewing yeast also has the same characteristic. Viable brewing yeast adsorbs nonpolar substances selectively. Therefore, hop derived polar substances such as myrcene and humulene, resin-like aroma substances, are adsorbed to a greater extent compared to less polar substances such as linalool and geraniol, floral and/or fruity aroma substances. This is one of the reasons for favorable modification of hop aroma during beer fermentation. With this selectivity of viable brewing yeast, hop flavors have been developed by bringing viable brewing yeast into contact with hop oil. However, the method requires control of fermentation. Furthermore, alcohol is produced and as a result, it could not be used for non-alcohol beverage products, such as alcohol-free beers. Therefore, the objective of the study was to find a suitable, easy to handle and non-alcohol producing adsorbent which is a substitute for viable brewing yeast. In a first experiment, activated carbon and synthesized adsorbent were added to hop oil respectively. Both results showed no selectivity in adsorption. Not only myrcene and humulene, but also linalool and geraniol were more than 90% adsorbed. In the second experiment, non-viable dried brewing yeast was put into contact with hop oil. The yeast is a by-product of beer and is produced by drying yeast from beer at a temperature higher than 100°C. Because of its high content of nutrients, such as amino acids and minerals, it is used in cattle feed or dietary supplement for humans or lipid membranes of the yeast are used as materials for medical capsules. Recent studies revealed its function as biosorbent. For example, it adsorbs iron ions, odor inducing factors, from red wine or cadmium ions from wastewater to prevent water pollution. Therefore, we have investigated its selectivity of adsorption to hop derived resin-like aroma substances. The result of the experiment showed a selectivity similar to viable brewing yeast. Myrcene and humulene were adsorbed at 90% and 85%, respectively. On the other hand, adsorption of linalool was 20% and of geraniol was 35%. No alcohol was produced. Therefore, we have identified nonviable dry brewing yeast as a suitable biosorbent for producing hop flavors.
Yoko Noro worked for Kirin Brewery Company Limited after receiving a master’s degree in agricultural science from Kyoto University in 2009. She worked in the Brewing Department of the Sendai brewery for 3 years as an assistant manager and then entered the Brewing Technology Development Center, where she conducted research on hop aroma. Since 2013, owing to reorganization, she has been working for the Research and Development Division in Kirin Brewery Company, Limited, with the same hop theme.