Investigation of beer oxidative stability conferred by thiol-containing proteins

Abstract

Beer is the world's most widely consumed alcoholic beverage. Beer is known to undergo chemical changes during storage leading to loss of sensory quality and consequently its rejection by the consumer. The chemical changes during the storage are associated with oxidative reactions mainly initiated by the presence of free radicals, in special the 1-hydroxyethyl radical, the major radical found in beer. On the other hand, several studies have appointed out sulfite as the most efficient natural antioxidant in beer, prompt to react with reactive oxygen species halting or delaying the oxidative changes. It has been observed that natural occurring thiol-containing proteins are also active in redox balance of beer. However, despite several studies have been conducted towards thiol-containing proteins in beer, most of them are related to foaming properties and little is known about the efficiency and the antioxidant mechanism behind the protective effect of these components in beer. Aiming to better known the antioxidant chemistry behind the redox balance promoted by sulfite and thiol-containing proteins in beer, the present research project purposes the investigation of the reactivity of thiol-containing compounds, in special beer proteins, towards 1-hydroxyethyl radical as probed by a competitive spin-trapping approach monitored by Electron Paramagnetic Resonance (EPR) or Mass Spectrometry. Additionally, a analytical protocol to proper quantify thiol-containing compounds will be developed by liquid chromatography - mass spectrometry (LC-MSn) and the thiol compounds concentration changes during accelerated ageing will be monitored in a model system and real beer samples in companion to radical evolution probed by spin-trapping EPR. The outcome of this research project is to improve the knowledge of the redox balance promoted by thiol- containing compounds and sulfite in beer enabling possible industrial driven changes in beer production. (AU)