Technical Session 14: Yeast II Session
Takeshi Kawakubo, Company
Co-author(s): Kentaro Iwasaki, Yuichiro Mese, Nobuyuki Hayashi, and Hiroyuki Yoshimoto, Kirin Brewery Company, Japan
ABSTRACT: In 2011, low-malt beer comprised approximately
20% of Japan’s alcohol market. Compared to normal beer wort, low-malt
beer wort contains less non-sugar nutrients, such as amino acids,
minerals, and vitamins. It has been reported that yeast metabolism is
negatively affected by insufficient non-sugar nutrients, thus reducing
fermentability and the production of fermentation by-products. To make
high quality beer, it is important to control the balance of sugar and
non-sugar nutrition concentrations. However, the relationship between
the concentration of non-sugar nutrients and yeast metabolism remains
unclear. The purpose of this study was to elucidate the relationship
between the concentration of non-sugar nutrients, especially vitamins
and minerals, and yeast metabolism and their effects on fermentability
and beer quality. To investigate the effects of low concentrations of
non-sugar nutrients on fermentation and beer flavor, we performed
fermentation tests using a synthetic medium or a low-malt beer wort with
adjusted concentrations of several minerals and vitamins. As a result,
insufficient fermentation and increased pyruvate production above the
threshold limit were observed in the fermentation with a low
concentration of some minerals and vitamins. This increase in the
pyruvate concentration resulted in an unbalanced, acidic flavor.
Moreover, this tendency was enhanced with increased repitching. In these
experiments, potassium and thiamine concentrations were found to have
important roles in yeast fermentation performance. To monitor the
physiological state of yeast cropped from this fermentation test, we
estimated intracellular metabolite concentrations using capillary
electrophoresis time-of-flight mass spectrometry (CE-TOFMS). The
CE-TOFMS analysis revealed that the organic acid metabolism of this
yeast differed from that of normal yeast cropped from all-malt beer
fermentation. It is assumed that this difference in yeast metabolism is
the cause of the insufficient fermentation and increased pyruvate
production. These data suggest that such nutrients as potassium and
thiamine have important effects on fermentability and beer flavor,
especially during the production of low-malt beer.
Takeshi
Kawakubo graduated in 2009 from the Department of Agriculture at Kyoto
University in Japan. He began his career in yeast technology development
in the Brewing Technology Development Centre at Kirin Brewery Company,
Limited.
VIEW PRESENTATION 47
