Ask Mr. Wizard

Dry Hop Timing


Wesley Smith — via Live Chat asks,

When you dry hop, do you typically blow most of the yeast from the fermenting beer before your dry hop doses Or Dry hop On the yeast? Do you buy into biotransformation reactions occurring between hops and yeast?


I have dry hopped during fermentation with yeast, blown yeast towards the end of fermentation and dry hopped, have racked beer from one fermenter to another before dry hopping, and have dry hopped beer in the keg. And yes, I do believe that yeast enzymatically change certain hop compounds during fermentation. I like these easy questions!

Digging a bit deeper into biotransformation seems timely as hazy/New England IPAs continue to be a topic of keen interest in the craft beer world. I am really glad that I am not a gambler because I would have lost big time on the longevity of this style, but that’s another story for another day. Research into the ability of yeast to enzymatically change hop monoterpenes has been ongoing for at least 20 years. Brewing and hop chemists have clearly demonstrated that yeast are capable of liberating monoterpenes, primarily citronellol and nerol, from hop glycosides by enzymatic hydrolysis, and have also clearly demonstrated that the hop monoterpenes geraniol and linalool are enzymatically changed, aka biotransformed, during fermentation into other terpene compounds, such as citronellol, citronellyl acetate, geraniol, nerol, and α-terpineol. Similar research has been the focus of enologists (wine folk) since at least the early 1980s, and winemakers commonly use hydrolytic enzymes, such as beta-glycosidase, to liberate terpenes from grapes before fermentation. And like hop terpenes, grape terpenes are biotransformed by yeast during fermentation.

The topic of hop terpene biotransformation is a great example of how science follows practice. Dry hopping was generally uncommon before the growth of craft brewing in the early 1980s, and the very high hopping rates common today among craft brewers was almost unheard of as recently as 15 years ago. Now that more beers are dry hopped at varying rates and at different times in the process, more emphasis has been placed on the empirical results of these practices. Hop research will be very interesting to follow for the foreseeable future as scientists continue learning more about what is really happening as brewers continue to push the boundaries of hopping!

A practical challenge associated with adding piles and piles of hops to the fermenter is beer loss. These losses are largely due to beer absorption by hops and by the relatively low density sediment in tank bottoms that is easily disturbed and moved by beer during racking. New technologies, such as Sierra Nevada’s Torpedo and Mueller’s maxxLup, nicknamed the Odeprot by Anchor Brewing’s Brewmaster Scott Ungermann and featured on a one-off beer called Odeprot IPA, have been developed to dry hop externally. Meanwhile, hop suppliers are continuing to develop new hop products to help deliver hoppiness to beer with reduced plant matter, brewers are improving brewing techniques to drive yield, and brewing scientists are looking at sensory saturation to determine when adding more hops ceases to add more perception. It’s a great time to be a hop lover!

Response by Ashton Lewis.