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ASBC Program

Session: Posters: Sensory II

P-33 - Determining the Absolute Thresholds of Iron (III) Sulfate (Fe2(SO4)3) and Iron (III) Chloride (FeCl3) in Non-alcoholic Beer

Thursday, August 14, 2025
4:30pm - 5:15pm PDT
Location: Sinatra Ballroom Foyer
Abstract: The market for highly hopped beer styles (e.g., IPA, IPL, NEIPA) has sharply increased in the last ten years, achieving ~40% of the production. These beer styles commonly use dry-hopping methods, which led to an increase of over 50% in average hop usage in beer and aroma hops production and usage. Previous research showed that lager beers had an iron content in the range of 10.9-28.7 µg/L and ales between 11.0-40.4 µg/L. the hop industry grew with aroma hop production taking the lead in production. The addition of hops also increases the mineral content of the beer and could potentially bring metallic off-flavors to the final product. Therefore, the goal of this study was to evaluate if the ranges of iron detected in beer could impart metallic flavor to the beverage. An absolute sensory threshold was conducted using a triangle test in ascending order of concentration with positive and negative control given to the participants for identification of the taste according to ASBC Sensory Analysis 9 with 23 participants over the age of 21. The final concentrations ranges were 20-579 µg/L for iron (III) chloride (FeCl3) and 32-428 µg/L iron (III) sulfate (Fe2(SO4)3). The solutions were prepared by adding 2 mL of iron (III) solution or deionized water into a 355-mL non-alcoholic beer (0.0% ABV), recapping, and flipping the bottle for homogenization. The beers were poured into graduated plastic cups and filled to 2 fl. oz (28 mL) and served at room temperature. The tests were set up that one bottle would contain the added iron while the other two had added water. The results obtained from this study showed that the iron threshold in non-alcoholic beer is similar to the threshold in water (42-498 µg/L) with iron chloride and iron sulfate ranging from 47-818 µg/L and 76-585 µg/L, respectively. In conclusion, the absolute threshold for iron in beer is above the levels detected in lager and ale beers. Therefore, metallic taste in beer may be caused by other factors, such as other ions, volatiles, and/or synergistic effect thereof. Future studies should focus on the absolute threshold of other metals (e.g., manganese) or combination of metals that could lead to metallic taste to aid brewers in identifying possible causes for this off-flavor in beer.