Program Book - Master Brewers Association of the Americas

O-35
A survey and explanation for the variation in the levels
of diastatic power enzymes that indicate potential malt
fermentability
EVAN EVANS (1), Chengdao Li (2), Jason Eglinton (3)
(1) TIAR, University of Tasmania, Hobart, Australia; (2)
Department of Agriculture, Perth, Australia; (3) University of
Adelaide, Adelaide, Australia
In this study over 1000 commercial malting samples from Australia
and internationally, primarily malted in 2005 and 2006, were
analyzed for their levels of the DP enzymes α-amylase, β-amylase and
limit dextrinase. The survey showed that there was more variation
within the varieties for DP and DP enzymes than between varieties.
The data was evaluated, and a micro malting experiment was
conducted to ascertain if the wide range of malt qualities observed
were the result of customer specifications, environmental conditions
under which the barley was grown, variety or malting practices. The
evaluation of malt used by two breweries over the course of a year
suggested that the conventional brewery customer specifications for
variety, KI and DP are somewhat successful in constraining potential
fermentability variation. The conditions under which barley for
malting was grown were also plausible factors that could explain
the observed differences in DP enzyme levels. However, micromalting
barley sourced from different regions showed that malting
conditions had a strong influence on the malt levels of α-amylase
and limit dextrinase. Combined, the observations and conclusions
of this study further support our previous recommendations that
the routine measurement of the individual DP enzymes would most
likely improve the consistency and predictability of the potential
fermentability of malt supplied to brewers. The manuscript for this
potential presentation was submitted for publication to the Journal
of the American Society of Brewing Chemists in December 2007.
Evan Evans graduated with a B. Agr. Sc. (Hon.) degree in 1986,
followed by a Ph.D. degree in 1990, both at the University of
Melbourne. In 1992, he joined the University of Adelaide, where he
developed his interest in malting barley and brewing. Recently he
relocated to the University of Tasmania, where his brewing research
interests continue to be in improving malt quality to improve beer
quality and the efficiency of the brewing process. Dr. Evans is
currently serving on the IBD Awards Committee and is a member of
the editorial boards for the Journal of Institute of Brewing and the
Journal of the American Society of Brewing Chemists. In 2005, Dr.
Evans was made a Fellow of the Institute of Brewing & Distilling.
82
O-36
Ethanol and sucrose interaction cross-products and influence
on specific gravity
JAMES HACKBARTH (1), Peter Takacs (2)
(1) The Gambrinus Company, San Antonio, TX; (2) The Spoetzl
Brewery Inc., Shiner, TX
In 1830 the French chemist M. Emile Tabarie introduced the
hydrometer, and a procedure for boiling off wine spirits in an
uncovered vessel. The alcohol concentration in the wine was backcalculated
based on the difference in specific gravity between the
wine SG and the residue SGE brought back to its original volume.
The Tabarie equation: SGA = SG – SGE + 1, and his patented
apparatus relied on tables used to convert SGA to alcohol % by
volume in the virtual distillate and hence the wine. Today direct
measurements of alcohol which utilize gas or membrane sensors or
NIR spectroscopy no longer depend on specific gravity to measure
alcohol. But Tabarie’s equations remain essential for inferring real
extract or estimating apparent extract/SG when only alcohol and
extract are known. Water, alcohol, and polysaccharides participate
in intermolecular hydrogen bonding due to the dipole-dipole
attractions between hydroxyl groups. Tables which convert SGA
to ethanol and SGE to sucrose concentrations account for single
aqueous-solute relationships, but do not consider ethanol-sucrose
interactions or the disruptive effects that a second solute has on the
remaining intermolecular forces. To elucidate these interactions
a series of 124 sucrose and ethanol solutions with a combined
weight up to 35% were measured in triplicate for SG and RI. OLS
regression and cross products of SGA and SGE were used to model
the difference between the experimental SG’s and a gravimetric
Tabarie. Adj.R2 = 0.9994, SE = 4.4E-5, n = 124. For a solution of
5% ethanol and 5% sucrose by weight, the model is lower than the
Tabarie by mass –2.4E-4 and higher than the Tabarie by volume
+1.0E-4. Additional trials using beer distillation products confirmed
the model. It was also determined that the scale refractive index was
simply a linear combination of the component ethanol and sucrose
SRI’s. Adj.R2 = 0.9993, SE = 1.5, n = 70. Collaborative data from
LGC/BAPS and ASBC/BACK indicates that sucrose SRI’s modeling
real extract were 2.9% lower, and ethanol SRI’s modeling beer
alcohol were 4.3% lower and 7.6% lower then the measured beer
SRI’s for LGC and ASBC respectively.
Jim Hackbarth served in the U.S. Air Force as a nuclear weapons
specialist from 1966 to 1970. He then used the GI Bill to complete a
M.S. degree in chemistry at the University of Illinois Chicago, with
research in x-ray crystallography. His first career path was as a
research pharmacologist at Abbott Laboratories in North Chicago in
the field of QSAR (quantitative structure activity relationships). In
1976 Jim moved back home to Milwaukee, WI, to join the Jos. Schlitz
Brewing Co. as a research chemist. Jim has been on the corporate
brewing staff for Schlitz, Stroh, and now The Gambrinus Company
and is currently manager of brewing development, physical chemist
in San Antonio, TX.