Program Book - Master Brewers Association of the Americas

P-212
Investigation of a floatation process in the respect of oxygen
consumption by yeast and ester control
TAKU IRIE (1), Wataru Hatsumi (2), Yuichi Nakamura (3)
(1) Ibaraki R&D Promotion Office, Production Technology Center,
Asahi Breweries, Ltd., Moriya, Japan; (2) Production Technology
Development Section, Nagoya Brewery, Asahi Breweries, Ltd.,
Nagoya, Japan; (3) Nishinomiya R&D Promotion Office, Production
Technology Center, Asahi Breweries, Ltd., Nishinomiya, Japan
We use a flotation process with a dedicated tank for cold break
removal. This method, however, involves tank cleaning after each
brew and, consequently, results in considerable costs for rinse water,
energy, and detergent among other things. Therefore, we considered
the possibility of a brewing method that allows the omission of
the floatation tank without compromising product quality. A test
brew using a pilot plant revealed that cold break removal had little
influence on any of the values in the analysis or on flavor quality,
such as bitterness and astringency. On the other hand, in a fullscale
brewery test brew without a flotation tank, a larger amount of
acetate esters was produced than when the conventional brewing
method was used. Following this result, an additional test was
performed in which the wort aeration rate was increased to increase
the amount of oxygen available for consumption by the yeast. As a
result, the amount of product esters decreased, and the flavor quality
remained equivalent to the quality obtained by the conventional
method. When aerated wort is allowed to settle in a flotation tank,
a sufficient amount of oxygen can be stably supplied to the yeast for
each brew batch. On the other hand, in full-scale brewing where a
fermentation tank is filled with several brew batches, when aerated
wort is newly poured into the fermentation tank, the oxygen in the
wort will also be consumed by the yeast in the pre-existing wort
in the fermentation tank. Consequently, the amount of oxygen
available for consumption by the yeast (especially that available for
yeast added later) is expected to decrease and result in the increased
production of acetate esters. We found the possibility that the
flotation process could be involved in the control of ester levels. If
we manage to suppress the production of esters by increasing the
amount of oxygen consumption by the yeast, we would be able to
omit this process. This is one example that our pursuit of efficiency
resulted in finding a clue for technology development.
Taku Irie was born in 1975. He received a M.S. degree in engineering
from the University of Tokyo in 2000 and began working for Asahi
Breweries, Ltd.. He worked in the Packaging Section in the Suita
brewery from 2000 to 2001 and Hukushima brewery from 2001 to
2005. Since October 2005, he has been working at the Ibaraki R&D
Promotion Office, Production Technology Center, and since January
2007, he has been in charge of the technological development of
brewing.
P-213
Dried yeast: Impact of dehydration and rehydration on
brewing yeast cell organelle integrity
DAVID JENKINS (1), Christopher Powell (2), Katherine Smart (1)
(1) University of Nottingham, Loughborough, United Kingdom; (2)
Lallemand Inc., Montreal, QC, Canada
As a consequence of drying, yeast cells are susceptible to damage,
which primarily occurs due to water loss. Associated effects can
include cell wall crenellation, cytoplasmic crowding, DNA supercoiling,
membrane disruption, phase transitions and ultimately
cell death. Although the dehydrated phenotype has been well
characterized, the sequence of events that cause damage to the
cell have not been effectively investigated. To address this we have
studied the impact of dehydration and rehydration on three key
attributes that are critical to brewing yeast quality and performance
at the onset of fermentation: viability, genome stability and
plasma membrane integrity and function. In the current study,
the impact of dehydration on the stability of the brewing yeast
genome (including both chromosomal and mitochondrial DNA) was
established by analyzing restriction fragment length polymorphisms
and chromosome length polymorphisms in dried and rehydrated
populations, in addition to laboratory grown cells. Plasma
membrane integrity and functionality (fluidity, H+ATPase activity
and composition) were also investigated using fluorimetry and
proton efflux evaluations.
David Jenkins received a B.S. degree in applied biology from the
University of Cardiff (United Kingdom) in 2006. He is currently
working toward a Ph.D. degree at the University of Nottingham
(United Kingdom), with his research focusing on improving the
viability of dried yeast for alcoholic beverage and bioethanol
production.
169