Decrease of 4-vinylguaiacol during beer aging and formation of apocynol and vanillin in beer.

In this study the decrease of 4-vinylguaiacol (4VG) during beer aging was investigated and the products that arise from it were identified. Two compounds, vanillin and apocynol, were identified in beer model solutions after forced aging and in naturally aged beers by GC-MS and HPLC-ECD analyses. Both account for up to 85% of the decrease of 4VG. Only in the presence of substantial amounts of oxygen in the bottle headspace was vanillin detected. Apocynol [4-(1-hydroxyethyl)-2-methoxyphenol] was found to be the main degradation product, and its formation was shown to be highly dependent on the beer pH. Because both apocynol and vanillin have a clear vanilla-like aroma, the decrease of 4-vinylguaiacol during beer aging might impart a shift from a clove-like aroma in fresh specialty beers (such as wheat beers and other top-fermented blond or dark ales) to a sweeter, more vanilla-like flavor impression of aged specialty beers.