The influence of additives on beer stability investigated by EPR spectroscopy.
In thermally-accelerated aging followed by EPR spectroscopy of beer samples of various stabilities, free radical 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPOL) was shown to be an effective indicator of the breakdown of a sample's stability, comparable to the commonly used spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN). Both indicators were then employed to investigate the influence of additives on beer stability. The addition of L-ascorbic acid (ASC) to the beer samples accelerated the radical processes and a lower stability was found. DL-alpha-tocopherol (alpha-TOC) did not influence beer stability significantly (probably due to its limited solubility). Na2SO3, described as a very effective stabilizer in experiments with the PBN spin trap, was found not to be effective using the TEMPOL indicator. This is probably due to inhibition in the formation of spin adducts or their degradation by Na2SO3.
Brezová
Vlasta
V
Department of Physical Chemistry, Faculty of Chemical Technology, Slovak Technical University, Bratislava, Slovak Republic. brezova@cvtstu.cvt.stuba.sk
Polovka
Martin
M
Stasko
Andrej
A
D001205:Ascorbic Acid / Q000737:chemistry / Q000494:pharmacology; D001515:Beer; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005503:Food Additives / Q000737:chemistry*; D007202:Indicators and Reagents / Q000494:pharmacology*; D013113:Spin Labels; D013431:Sulfates / Q000737:chemistry; D013997:Time Factors; D014810:Vitamin E / Q000737:chemistry; D024502:alpha-Tocopherol / Q000737:chemistry
D003497:Cyclic N-Oxides; D005503:Food Additives; D007202:Indicators and Reagents; D013113:Spin Labels; D013431:Sulfates; C012036:sodium sulfate; D014810:Vitamin E; D024502:alpha-Tocopherol; D001205:Ascorbic Acid; C001803:tempol