Technical Session 16: Yeast III Session
Takuya Hashimoto, Suntory Liquors Limited, Osaka, Japan
Co-author(s): Taichi Maruhashi, Yutaka Yamaguchi, Yoshinori Hida, and Kaneo Oka, Suntory Liquors Limited, Osaka, Japan
ABSTRACT: Amino acids in the wort, measured as free amino
nitrogen (FAN), are extracted during the mashing process and are
essential nutrients for sufficient fermentation performance. Too low a
level of amino acids causes incomplete fermentation due to insufficient
nutrition of the yeast, but too high a level remaining in the finished
beer may negatively affect sensory variables such as foam quality.
Therefore, for good fermentation, it is necessary to ensure the
appropriate quantity of amino acids in the wort. In this study, we
investigated the influence of fermentation conditions that differed in
the amount of amino acids in the wort with most variables held constant.
We made the wort at 12.0°P with 115, 160, and 230 mg/L of FAN and
fermented. This showed that the more FAN in the wort, the more isoamyl
acetate was produced. We analyzed the relationship between the quantity
of this ester and the amount of the amino acids valine and leucine,
which are biosynthetic precursors of isoamyl acetate. As expected, in
the wort with low FAN content, valine and leucine were depleted during
fermentation, inhibiting the formation of isoamyl acetate. The uptake of
amino acids involved in yeast metabolism during fermentation is also
connected with the generation of sulfur compounds, so the quantity of
FAN also correlated with the quantities of hydrogen sulfide (H2S) and sulfur dioxide (SO2).
Thus, the FAN utilized by the yeast during fermentation was confirmed
to be an important factor determining the quality of the beer. In
conclusion, in addition to being an essential yeast nutrient for
fermentation, FAN in the wort is involved in the biosynthesis of a
number of fermentation by-products. In particular, we found that the
quantity of isoamyl acetate can be controlled. This suggests that the
adjustment of FAN is a factor that can control the flavor of the beer.
Hashimoto graduated with a master’s of engineering degree from Osaka
University in 2009. He has worked for three years in the Beer
Development Department of Suntory Liquors Limited.
VIEW PRESENTATION 55