THE IMPACT OF ISO-ALPHA ACIDS ADDITIONS TO LIGHT BEER ON ELECTRON PARAMAGNETIC RESONANCE (EPR) AND FLAVOR STABILITIES PROFILES DURING AGING

R.T. Foster II
Extending the flavor stability of beer with modern day constraints of temperature exposure and time to retail is essential in insuring fresh beer flavor to the customer. Pilot brewing trials produced five packaged beers from a single American light brew. The control light beer (CW) was stored at 22.2°C and was compared against the four remaining beers which were: control light beer held at 4.4°C (CC), Divergan HM (DHM) treated light beer (T1), 5.1 ppm iso-alpha-acids (IAA) (T2) and 0.5 ppm iso-alpha-acids (T3) treated light beer, all held at 22.2°C for 13 weeks. DHM is an insoluble copolymer of polyvinyl-imidazole (PVI) and polyvinyl-polypyrrolidone (PVPP) (9:1) with good trace metal chelating strength. EPR and sensory profiles were developed over the 13 weeks of treatment at 22.2°C at fresh, 2-, 4-, 6-, 8-, 10-, and 13-week intervals to ascertain and compare sensory flavor stability and EPR metrics data. In addition, three other stabilities were measured, namely physical, foam, and microbiological along with other chemical profiles measuring trace metals, fatty acids, sulfur compounds, and polyphenols. The control light beer (CC) held at 4.4°C showed the best flavor stability via EPR and sensory profiles followed by the DHM treated beer (T1) which showed improved flavor stability because transition metals such as copper, iron, and manganese were effectively chelated by DHM and removed during filtration. The IAA dosed light beers T2 and T3 showed the opposite results with decreased flavor stability via EPR metrics and sensory profiles. The transition metals were not removed but actually increased in packaged beer probably because the IAA tests were dosed after filtration. IAA bound or chelated transition metals need to be removed in the beer filtration process in order to improve flavor stability by mitigation of the transition metals, which catalyze the Haber-Weiss and Fenton free radical oxidation reactions. Also, after 13 weeks of storage at 22.2°C, the non-pasteurized light warm treated control (CW), cold treated control (CC), and DHM treated (T1) showed microbiological instability from Lactobacillus brevis infection, whereas both the IAA dosed light beers, T2 and T3, showed no beer spoiling organism breakdown.
Foster II, R.T. (2009). THE IMPACT OF ISO-ALPHA ACIDS ADDITIONS TO LIGHT BEER ON ELECTRON PARAMAGNETIC RESONANCE (EPR) AND FLAVOR STABILITIES PROFILES DURING AGING. Acta Hortic. 848, 279-298
DOI: 10.17660/ActaHortic.2009.848.30
https://doi.org/10.17660/ActaHortic.2009.848.30
electron paramagnetic resonance, lagtime, T150, Super lagtime, x0, retardants, antioxidants, dx, oxidized beer flavour, iso-α acids (IAA), hop polyphenols, Divergan HM (DHM), polyvinyl-imidazole (PVI), polyvinyl-polypyrrolidone (PVPP), Lactobacillus brevis
English

Acta Horticulturae