BCOJ Symposium: Technology for the Future Session
Masahide Sato, Sapporo Breweries Ltd., Shizuoka, Japan
Co-authors: Atsushi Tanigawa, Sapporo Breweries Ltd., Shizuoka,
Japan; Takeshi Arai, Sapporo Breweries Ltd., Oita, Japan; Tatsuro
Shigyo, Sapporo Breweries Ltd., Shizuoka, Japan
ABSTRACT: In Japan, beer-flavored beverages brewed with no malt
have been available since 2003. The raw materials used in beer-flavored
beverages with no or less malt compared with regular beer generally
contain fewer nutrients than malt, which sometimes leads to sluggish
fermentation and the production of off-flavors. In this paper, we review
our studies on the effects of insufficient nutrients on off-flavor
compound production, propagation, and fermentation of yeast. Among the
off-flavors, sulfur-containing compounds, such as hydrogen sulfide (H
2S),
are of particular interest for many brewing scientists and brewers,
because they have an unpleasant flavor and very low threshold. We have
extensively studied the production of hydrogen sulfide (H
2S) and its precursor, sulfite (SO
2),
during fermentation in lager yeast. Upon the addition trials of three
concentrations of methionine, we found that five genes (
MET3,
MET5,
MET10,
MET6, and
CYS4)
were regulated by our microarray analysis system. Further gene
expression analyses revealed that the gene expression balance of
MET3 and
MET10 led to the production of a higher level of sulfite (SO
2) in the lager yeast. We also found that metabolism from SO
2 to H
2S by yeast occurred depending on the pH value during the secondary fermentation. The amount of H
2S
was higher at the lower pH value during secondary fermentation.
Furthermore, in order to reduce the risks in brewing new products, we
investigated the possible production of other off-flavors that might be
important in brewing new raw materials. During the investigation, we
detected several off-flavors that are different from sulfur-containing
compounds. GC-MS-olfactometry analysis revealed that one of these
flavors was indole. In brewing, indole has been recognized as an
off-flavor and is thought to be produced by microorganism contamination
during fermentation. It has not been reported that brewing yeasts
produce indole during fermentation. We concluded that the lack of
vitamin B
6 in wort led to the accumulation of indole in yeast
due to the inhibition of tryptophan synthase reaction. Further study on
the fermentation and propagation of yeast in the case of nutrient
deficiency also shows that the lack of inositol induces a strange
budding. In reviewing both of these findings, we discuss the essential
combination of nutrients for brewing in order to reduce the risk of
off-flavors and poor fermentation and propagation.
Masahide Sato
is a general manager for Frontier Laboratories of Value Creation Sapporo
Breweries, Ltd. He joined Brewing Research Laboratories Sapporo
Breweries, Ltd. in 1990 after receiving an M.S. degree in applied
microbiology from Tohoku University, Japan. From 1990 to 2008 he studied
the genetic instability of flocculation of lager yeast and the sulfur
amino acid metabolism of lager yeast. In 2002 he received a Ph.D. degree
in applied microbiology from Tohoku University, Japan. In 2008 he moved
to the Shizuoka brewery, in 2009 to the Kyushu Hita brewery (present
name), and in 2010 to his present position.
VIEW PRESENTATION S-4
