Studies on the Sunlight Flavour of Beer

In order to establish the mechanism of occurrence of sunlight flavour of beer in continuation of the preceding paper, humulone, lupulone, and their analogues and degradation compounds, i.e., cohumulone, adhumulone, 5-acetyl-3-methylfilicinic acid including analogues, tetrahydrohumulone, hexahydrolupulone, humulinic acid and lupuloxinic acid, were tested for the occurrence of sunlight flavour of beer.

As a result, among the above-mentioned compounds, humulone, lupulone, cohumulone, adhumulone, tetrahydrohumulone and hexahydrolupulone were found to cause the sunlight flavour, but the other compounds did not cause typical sunlight flavour. This fact shows that some specific structural components seem requisite for the occurrence of sunlight flavour of beer.

It was also revealed that isomerization caused by boiling accelerates the occurrence of the sunlight flavour of beer. Finally, the result of the experiment conducted by the gas chromatographic procedure showed that any new component is not detected by the exposure of beer to sunlight but, two components somewhat increased.