Matthew McCarroll (1),
Kelly Bender (1), Marika Josephson (2), Katherin Strain (1), Lucas A.
Rose (1); (1) Southern Illinois University, Carbondale, IL, U.S.A.; (2)
Scratch Brewing Company, Ava, IL, U.S.A.
Yeast, Fermentation, and Microbiology
Poster
Recently there has been a reemergence of the use of local wild yeast
and bacteria in beer fermentations. While some groups have begun to
examine the identity and evolution of micro-flora in the fermentation of
traditional sour lambic and American coolship ale styles of beer, less
work has been done to examine the use of mixed wild cultures in beers
that are not traditional, slow-fermented sour beers. Following a working
observation that wort formulation and brewing conditions affect the
expression of yeast and bacterial characteristics in the finished beer,
we set out to systematically determine the effect of IBU level on the
evolution of micro-flora during primary fermentation. Mixed yeast and
bacteria cultures were obtained from three breweries in three distinct
regions of the United States. Beer for this study was produced on a
pilot system at the Fermentation Science Institute using standard
brewing methods and materials. Each of the three mixed cultures was used
to ferment a replicate of the same wort at three different IBU values
(0, 10 and 25) under identical conditions, in addition to a control beer
using a pure yeast strain. The finished beers were then evaluated by
instrumental and organoleptic analysis to identify differences in yeast
expression, especially with regard to ester formation and sour
character. Samples of the cultures were collected prior to and after
completion of primary fermentation for each of the three brewery
cultures and were submitted to genetic analysis. Results of the genetic
analysis will be used to examine and quantify the micro-flora population
variations through fermentation and will be examined for correlation
with IBU level and identified expressions of yeast character in the
finished beers.
Matthew E. McCarroll received his B.A. and B.S. degrees in
chemistry and interdisciplinary studies from Appalachian State
University in 1994. He then pursued graduate studies at the University
of Idaho, where he received his Ph.D. degree in 1998. He then spent two
years as a postdoctoral associate at Louisiana State University. In 2000
he joined the faculty at Southern Illinois University as an assistant
professor and was promoted through the ranks to professor. Since 2013
Matthew has served as director of the Fermentation Science Institute at
Southern Illinois University.
