BREWING
Cascade hop pellets (clearly a seminal brewing masterpiece), the iso- α -acids level dropped to 18mg/L, humulinones concentration increased to 48mg/L and even the level of sparingly soluble α -acids rose to 36mg/L. One would imagine the level of polyphenols also somewhere near doubled. Aroma Hop essential oils are the source of dry hop aroma. It is estimated that hop essential oil is made up of just under 500 compounds. Only a few of these are thought to be important to beer a- vour. Table 1 separates these into three different avour groups. Hop oils in the hop cone are in a constant state of ux, changing as the hop matures and the hop material ages after harvest. The chemical prole of aroma compounds in the hop analysis and total oil level in the hop you are using isn’t always mirrored in the beer you have dry hopped. Once dissolved in beer some of the hop oil derived aromas can be changed by bio transformation by yeast (varies with strain) and hydrol- ysis due to the acidic nature of beer. Some components will enhance the perception of other aroma compounds and others will suppress them (1 + 1
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Graph 1: Effect on NIBEM foam stability after three days dry hopping (Data: Hopsteiner)
equals 2, but also equals 3, 1 and 0). As I said above, complicated! And – as it stands - justication for using sensory evaluation over GC to meas- ure the effectiveness of dry hopping on a commercial level. There is more information on dry hop chemistry in the bibliography at the end of this article. The point where it is of practical use to the brewer lies in the future. Other considerations Dry hopping tends to raise beer pH which will impact on palate, stability and
shelf life. As a rough guide, 400g/hL of dry hop addition increases pH by 0.1. Dry hops also carry with them amylolytic enzymes which have the potential to hydrolyse dextrins in the beer. Levels of up to 0.76 enzyme units per gram have been reported in some varieties. This phenomenon has been known since the late 1800s but has recently been given the name ‘hop creep’. Unless you are dry hopping at the extreme rates identied above, the level of both the enzymes and substrate should be too low to have any signicant impact
Like most practices in brewing, dry hopping can deliver wonderful results when done well but catastrophic ones when performed without respect for and understanding of the process and consumer. (Photo: Shutterstock).
40 ● BREWER AND DISTILLER INTERNATIONAL I october 2019
i bd.org.uk
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