Use of Polyphenol-Rich Hop Products to Reduce Sunstruck Flavor in Beer

Abstract

Sunstruck flavor is a widely known off-flavor in beer described as having meaty, sulfury, and skunky-foxy notes. It occurs when beer is exposed to sunlight during storage owing to photodecomposition of isohumulone in the presence of riboflavin. Polyphenols, tryptophan, ascorbic acid, and tryptophol are known to be off-flavor inhibitors. Hops are an important source of polyphenols and humulone. The aim of this study was to specify a suitable hop product and the process parameters to reduce the sunstruck flavor perception in beer. A selection of six hop products was analyzed for their content of total and single polyphenols as well as their bittering acid content. Moreover, brewing trials were carried out with single hop product batches. Because of the high total and single polyphenol content and low sunstruck flavor perception in beer, the tannin extract was selected for further trials. First, the time for hop addition and any added concentration during boiling were optimized to maximize the polyphenol transfer rate to the wort. Then, depending on these results, beers with different tannin extract concentrations and iso-extract were produced. After exposure to light, the tasting results concluded that the higher the tannin extract level the lower the sunstruck perception. Furthermore, the effect on beer standard attributes resulting from the addition of the tannin extract was also evaluated.

• Sunstruck flavor
• Polyphenols
• Hop products
• Tannin extract