On the Behavior of the Important Hop Odorant 4-Mercapto-4-methylpentan-2-one (4MMP) during Dry Hopping and during Storage of Dry Hopped Beer

The transfer of the potent, black currant-like smelling hop odorant 4-mercapto-4-methylpentan-2-one (4MMP) from Eureka hops into a Pilsener style beer was monitored during static dry hopping. Quantitation of 4MMP, also known as 4MSP (4-methyl-4-sulfanylpentan-2-one), was accomplished by using a previously developed approach based on a stable isotope dilution assay, selective isolation of thiols by mercurated agarose gel, and analysis by GC×GC-TOFMS. Major transfer of 4MMP happened during days 1 and 2 of dry hopping, whereas only little further increase was observed between days 2 and 8. The concentration data were well in line with the sensory evaluation of the dry hopped beers and suggested a hop contact time of 2 days during dry hopping for a both efficient and economic transfer of 4MMP from hops into beer. The same quantitation approach was also applied to assess the stability of 4MMP during storage of the dry hopped beers. Storage resulted in severe losses of 4MMP after 3 months and a further decrease in 4MMP between months 3 and 6 of storage. Losses during storage were significantly higher at 20 °C than at 5 °C.