Hypothesis of synergy between Sorachi Ace-derived geranic acid and various flavour compounds contributing to characteristic beer aroma.

The hop variety Sorachi Ace was bred and first licenced in Japan by Sapporo Breweies Ltd. in 1984. Recently, this hop has been used as a 'flavour hop' to give beer a unique characteristic aroma, for example, woody, pine-like, citrus, dill-like and lemon grass-like. In previous study, we identified geranic acid as one of the unique compounds comprising Sorachi Ace. As a result of model sensory evaluations, we reported that geranic acid itself had little flavour, but that this compound could enhance the flavour intensities of other hop-derived flavour compounds in spite of its very low flavour intensity. In this study, the mechanism of Sorachi Ace varietal aroma was further investigated using sensory omission test. The selected 16 compounds were separated to five groups, 'carboxylic acids', 'alcohols', 'aldehydes', 'esters', and 'hydrocarbons'. As a result of the omission test, it was concluded that all groups could affect to the varietal aroma of Sorachi Ace, despite the concentrations of several compounds were at very low levels. In addition, an effect of blend-hopping with Sorachi Ace and other flavour hop varieties was investigated. It was surprisingly found that blend-hopping between Sorachi Ace and certain hop varieties (Kazbek, Hallertau Blanc, and Cascade) could negatively affect to the flavour impression of test-beers. On the other hand, blend-hopping between Sorachi Ace and Citra or Mosaic could positively affect to the flavour impression of test-beers. Because of high concentrations of 4-Methyl-4-sulfanylpentan-2-one (4MSP) derived from these hops, it is assumed that 4MSP containing hops could be effective choice for blending with Sorachi Ace. [ABSTRACT FROM AUTHOR]