Program Book - Master Brewers Association of the Americas

P-78
Liquid phase primary dissolved oxygen calibration for package
analyzers
CHRIS NIMPTSCH (1), Ken Page (2)
(1) Profamo Inc., Sarasota, FL; (2) Headmaster Ltd., Bramshill,
United Kingdom
GEM-F calibrator systems offer the beverage industry the ideal
solution to that elusive target—a practical and reproducible means
of presenting both portable and package analyzers with clean
liquid samples containing accurate, known DO levels. Because this
is performed rapidly and economically using an on-site facility,
Headmaster maintains it is a more powerful QA tool than schemes
using “reference can” batches, which rely on statistical processing
of results from many individual samples. GEM’s two series-operated
gas/liquid contactors give a stable permeable 2.8 m 2 interface
between counter-flowing gas and water. Pressure and flow rates are
fixed to deliver a stable >99.99% saturation of outlet water with the
inlet gas. This property of the contactor system is ensured by builtin
design redundancy and can be confirmed using feed gas which
is oxygen-free or has a known oxygen concentration. The output
liquid DO level is therefore always defined, using the O 2 solubility
algorithm, by outlet water temperature, feed gas pressure, and
oxygen concentration in the internally-blended feed gas. Operating
at constant pressure and gas concentrations, GEM computes
and displays temperature-corrected DO levels using proprietary
circuitry. The systems are justifiably described as calibrators
because all process parameters can be checked independently with
calibrated instruments so that displayed and actual DO values can
be compared. DO levels are chosen to suit product applications,
recognizing analyzer characteristics and practical tolerances in
the calibrator’s key parameters (gas O 2 %, temperature, pressure).
Typically, 150–300 ppb (5 ppb tolerance) is used for low DO
products such as beers and ca. 750 ppb (10 ppb tolerance) for wines.
F-format systems include interface units enabling Headmaster’s reusable
sample bottles (SB) to be pre-purged with the same gas and
to the same pressure used in the calibrator’s contactors, so filling is
at constant DO level and results in a known total package gas level.
SB is designed for filling to a head-space of either 10 ml or 1 ml:
the latter is useful if QA focuses on package liquid DO and if filling
and sampling temperatures are different. Left in air, the bottles are
valid calibration samples (+/–5 ppb DO) provided they are sampled
within 2 or 3 hours of filling. For situations involving longer
delays, O 2 ingress through the closure and connectors is avoided
by holding SBs in sealable outer housings purged to 1% O 2 . These
protected SBs, shipped from another calibrator facility, provide for
independent validation of the analyzer and calibrator.
Chris Nimptsch received a B.S. degree in physiology from McGill
University in Montreal, Canada, in 1981 and obtained a bachelor
of civil and common laws degree from the University of Ottawa in
1985. He worked as a litigation and real estate attorney in Montreal
for eight years before coming to his senses and starting his career in
the brewing industry. He completed a concise course in brewing at the
Siebel Institute in 1994.
P-79
The oxidative capacity of rosemarinic acid and a catalase/
superoxide dismutase mimetic using an adapted europium
tetracycline based hydrogen peroxide assay
PETER ROGERS (1), Ryan Hyland (2), Vincent Higgins (2)
(1) Fosters Group Ltd., Abbotsford, Australia; (2) University of
Western Sydney, Campbelltown, Australia
We describe the application of a novel fluorescence method to
measure hydrogen peroxide levels in beer. The method can be
used as a diagnostic tool in predictive beer ageing tests. It can
also be used to determine the effects of hop varieties, malt, and
emerging processing aids, like rosemary extract, on reactive oxygen
suppressive character. It is based on the behavior of europium
tetracycline complex (EuTC). EuTC is naturally fluorescent, but
when bound to peroxide the fluorescence yield increases by 15
times or more, with a detection limit around 1 micromolar. The
method is cheap and reliable and capable of formatting with 96 well
plates. It requires a fluorimeter, but these are generally cheaper
than the instruments required to perform the luminol-based
chemiluminescence peroxide assay. The EuTC-based peroxide assay
was used to compare the effects of herbal extracts, extracts from
different hop varieties, and fractionated malt extracts on peroxide
accumulation during ageing at elevated temperatures. This enabled
us to compare the equivalent ‘reductive character’ of these fractions
with respect to sulfite. Trials with rosemary extracts show that the
rosemary could replace exogenous sulfite addition without affecting
quality profiles for a range of different beer types. Sulfite oxidizes
peroxide to water and oxygen, and in the process is converted to
sulfate. However the extracts work differently. They possess catalase
and superoxide dismutase activity. Classically catalase coverts
peroxide to water and oxygen. Superoxide dismutase converts the
super-anion to peroxide which in the presence of the catalase is
transformed into water and oxygen. Superoxide requires an electron
donor, and polyphenols in the beer could provide these reducing
substrates. The activity is heat stable, so the activities are not due
to classic protein-based enzymology. Small molecules with catalytic
properties have been described as mimetics. Molecules with
enzyme-like activity are small and usually heat stable. Salens are
one such example; they are crescent shaped heterocyclic molecules
which can bind a metal ion, often manganese, in the cleft. We
were able to show that these molecules have both SOD activity and
also catalase activity using the EuTC assay. And, that the activity
operates in a beer matrix. In theory salen can break down peroxide
indefinitely without any supporting reductive substrate. This is quite
unlike the terminal role of sulfite. It acts as a reactant to destroy
peroxide. It seems inevitable that developments being reported for
anti-oxidant, therapeutic mimetics will spill over into the food and
beverage industries. Our results show how these products could
manage quality and improve shelf life. The EuTC assay can be used
to assay product, improve process quality and guide innovation.
Peter Rogers is national manager of research within the Foster’s
Group’s Consumer and Category Solutions section. He deals with
strategic issues, part risk, part invention, and part new opportunity.
He is an adjunct professor at RMIT and Griffith universities. He
graduated from the Australian National University and was
involved in pioneering work on yeast mitochondrial genetics.
In keeping with his view of self as practical and empirical, he
moved progressively to biochemical value adding. He worked as a
postdoctoral fellow in Goettingen, before joining Griffith University.
He combined fundamental research with value adding in central
Queensland, the heart of cattle country. He worked at one time with
BHP, BHP Billiton these days, and prophetically, as it happened,
with steel pull-ring-tab cans. He received the Eric Kneen Memorial
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