The use of Oxygen 18 in appraising the impact of oxidation process during beer storage

To appraise the incidence of oxygen: in bottled beer, the stable nonradioac tive oxygen isotope 18O(2) was injected into the headspace just before agei ng and subsequently analysed by proton bombardment and isotopic mass spectr oscopy of all the most interesting beer fractions. Although oxygen did caus e considerable oxidation of sulphites, polyphenols, and isohumulones, it wa s not incorporated into the carbonyl fraction, indicating that the cardboar d flavour in beer is not due to lipid oxidation but to wort preparation. No nenal potential measurement was found to be a good indicator of beer flavou r staling. The impact of beer stabilisation treatments (addition of polyvin yl pyrolidone powder, potassium metabisulphite, ascorbic acid) was also inv estigated.