Reatividade de iso-α-ácidos e seus derivados hidrogenados frente ao radical 1-hidroxietila: implicações na perda de qualidade sensorial da cerveja

摘要: ABSTRACT The iso-acids are the main responsible constituents for bitter taste of beer, they easily degraded during aging and light exposed process, specially transdiastereoisomer. 1-hydroxyethyl radical is major produced beer process. present work describes reactivity towards as probed by spin-trapping technique detected electron paramagnetic resonance (EPR) mass spectrometry (ESI-(+)-MS/MS). It was observed that both diastereoisomers cisand trans-iso-acids in presence with apparent rate constant 1.8 10 e 9.2 L mol s, respectively. dihydro-iso-acids studied similar to diastereoisomeric mixture, showing Constant 1.5 s. tetrahydro-iso-acids analogues did not suggesting allilic hydrogens reaction sites. In addition, ab initio DFT calculations demonstrated BDE values prenyl isohexenoyl side chains equivalents according higher transdiastereoisomer be accounted an entropic factor since goups same plane space. oxidation products were determined LC-ESI-MS its verified formation hydroxyl-allo-isoacids. data colected allows a mechanism proposed process loss acids beverage aging.The aging.