89. Determination of iron concentrations in beer through key steps in the brewing and packaging processes using iron analysis by ferrozine

Natalie Nienaber (1); (1) Stone Brewing, Escondido, CA, U.S.A.


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.