Natalie Nienaber (1); (1) Stone Brewing, Escondido, CA, U.S.A.
Analytical
Poster
In an effort to help improve shelf stability and the understanding of
how detrimental iron is to the stability of beer, iron concentrations
were analyzed at several key points in the production process. Raw
materials used for brewing, including malt, hops, water and yeast, are
the main sources for metal ions in beer. However, packaging equipment
and materials could also be a source of iron. The majority of iron
research published focuses on lagers and other traditional beer styles;
however, it is important to gain information for the current craft beer
market. After reaching out to several other craft breweries and
analyzing iron levels in finished beer, we were able to determine a
benchmark for iron as 0.040 mg/L. Average iron concentrations throughout
several crucial brewing steps for 13 styles of beer were determined
using ASBC Approved Method Beer-18C, iron analysis by ferrozine. Wort
samples contained a higher concentration of iron compared to chilled
pre-filtered beer for all beer styles evaluated in this test. More
specifically, the West Coast-style IPA had iron concentrations of 0.082
mg/L in the wort and 0.040 mg/L in the chilled pre-filtered beer sample.
Iron concentrations decrease during the brewing process and are lost to
spent grains, trub and yeast (any significant amount of iron is toxic
and mutagenic to yeast). For the American strong ale, the wort and
post-filtered samples had iron levels double that of the IPA, which
indicates malt ingredients play a critical role in iron levels. Previous
research suggests certain filtration medium can increase iron content.
There was no significant difference in average iron concentrations
between pre- and post-filtered beer, which indicates the filter medium,
Harborlite, does not add additional iron into any beer style analyzed.
Additionally, we were able to determine there is little to no iron
pickup in the beer from the crowns, therefore, the lining on the inside
of the crown is adequate at preventing iron from leaching into the beer.
To further understand how iron may affect beer over time, a
shelf-stability study is currently being conducted for several styles of
craft beer. The iron concentrations are measured in freshly bottled
beer and then again after 90 days stored at cold temperature. Future
research is going to focus on styles of beer that contain iron levels
above the accepted benchmark values, such as the American strong ale,
hoppy pale ale and black IPA.
Natalie Nienaber received her B.S. degree in chemistry from Miami
University in Oxford, OH, and graduated as an ACS certified chemist. She
then went on to receive her M.S. degree in food science and technology
from The Ohio State University. In March 2012, Natalie successfully
defended her master’s thesis and continued to work with the university
after graduation. She also has three publications in scientific
journals, including The Journal of Organic Chemistry, Food Chemistry and Journal of the American Oil Chemists’ Society.
Natalie placed first in the master’s division of the 2011 OVIFT Poster
Competition and placed second in the Quality Assurance Division at the
national IFT competition in 2012 for her work on authenticating
high-value ingredients using ATR-IR spectroscopy and multivariate
analysis. She began employment at Stone Brewing Co. in February 2014 as a
quality assurance assistant working in the analytical, microbiology and
sensory labs. Natalie has seen been working as a technician primarily
in the analytical chemistry lab with a focus on iron, TBI and gluten
analysis and recently began focusing on double seam analysis for the new
can line. She is also in the process of applying to become a TTB
certified chemist for export.
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