Y. TAJIKA (1); (1) Asahi Breweries, Ltd., Suita, Japan
Yeast, Fermentation, and Microbiology
Thursday, June 5 - 10:00 a.m.-11:45 a.m.
Level 4, Red Lacquer Ballroom
Appropriate fermentation temperature is not the same for each brewery, and it depends on many factors, such as yeast strain, wort composition and beer type. Fermentation temperature for bottom-fermenting yeast is typically 9–12°C. Currently, high-gravity brewing is widely used, and higher fermentation temperature is often adopted to accelerate fermentation speed, even for bottom-fermenting yeast. High temperature is one effective way to increase fermentation speed, but the uptake of amino acids is also accelerated. The high consumption of amino acids leads to high production of higher alcohols and esters, which are produced from amino acids by yeast. So, it is difficult to adopt high-temperature fermentation when strong flavor is not required. Amino acids are classified into four groups based on the order of assimilation. The uptake of class A amino acids starts at the beginning of fermentation, and class C amino acids are utilized after the concentration of class A amino acids in wort becomes low. Yeast assimilates class B amino acids constantly during fermentation and does not assimilate class D; only proline is classified in this class. Higher alcohols and esters that strongly contribute to beer flavor include isobutanol, isoamyl alcohol, isoamyl acetate, phenethyl alcohol, and phenethyl acetate. These flavor compounds are produced by the metabolism of class B and C amino acids. So, it is expected that the production of these flavor compounds would be reduced by adding class A amino acids to wort, because high concentration of class A amino acids prevents the uptake of class B and C amino acids. In our tests, class A amino acids were added to wort, and fermentations were carried out. The concentrations of higher alcohols and esters after fermentation were measured. The results show that the addition of class A amino acids prevented higher alcohol and ester production in both normal- and high-temperature conditions. In the tasting test, samples were evaluated by trained sensory panels, and negative flavor was not found. The addition of class A amino acids was effective for controlling the flavor character of beer.
Yosuke Tajika obtained a master’s degree in the field of life science from Hokkaido University in 2004. He began employment with Asahi Breweries, Ltd. in 2004 as a technical staff member in the brewing section. After he working at the Ibaraki brewery in the product development section, he has been working in the R&D Promotion Office since September 2012.