Effect of High-Temperature and High-Pressure Treatment of Aqueous Hop Solutions on the Extraction of Various Components from Hops

The aroma, flavor, and bitterness characteristics of hops in beer vary greatly depending on the timing of hop addition during the brewing process. In general, whirlpool and dry hopping are used to give the beer a rich aroma. However, these techniques are very inefficient uses of hops. In this study, we investigated a brewing process in which hops are boiled in a sealed high-temperature, high-pressure (HTHP) aqueous solution and then added to a whirlpool to achieve both rich hop aroma and flavor. Hop addition concentration, temperature above 100 °C, time, pH, and dissolved oxygen were investigated to understand the effects of different conditions on the extraction of different hop components. The results showed that HTHP treatment was effective in the isomerization of humulone, utilization of aroma compounds and polyphenols, release of aglycones and free thiols, and formation of fatty acid esters after fermentation, giving the beer a rich aroma and pleasant bitterness.