Fermentation Hopping & Biotransformations

This makes sense to me. I was dry hopping in the primary fermenter long before I heard the term "fermentation hopping." When Stan H's hops book came out, he talked briefly about biotransformations that might be happening if the yeast are active, and suddenly dry hopping in primary seemed a little cooler. I think his book shed light on some things pros were doing and discussing, stimulating widespread discussion. I really only heard the term "fermentation hopping" when NEIPAs started getting some buzz (ok, buzz is an understatement -- there are some epically long threads on the topic)

 

Wow. That goes back a decade or so from Stan H's book. The topic is somewhat older than the timeline I suggested.

 

There was a presentation at the EBC conference in Porto last year entitled "Genetic metabolism of hop terpenoids by yeast in beer" (related publication: https://www.ncbi.nlm.nih.gov/pubmed/23200656). They found that the ATF1 gene is central for the biotransformation of linalool and geraniol to their acetate esters. Atf1p is also the main enzyme responsible for the formation of the common esters found in beer: isoamyl acetate (banana), isobutyl acetate, 2-phenylethyl acetate and ethyl acetate. So yeast strains that produce loads of (acetate) esters (e.g. "Belgian" and Hefeweizen strains) are potentially good biotransformers of hop terpenoids. They also found that the OYE2 gene is central for the biotransformation of geraniol to citronellol (the role of OYE2 seems to be poorly understood, so it is more difficult to tell which strains/conditions result in high expression levels). This means that different yeast strains (depending on their genetic background and the activity of the corresponding enzymes) may produce beers with different hop aroma profiles

 

Last week I specifically asked the two head brewers that finished first and second in this year's Alpha King and both wait until fermentation is complete (and D rest) and then add dry hop additions. This year's winner used 2.25oz per gallon (if my math is correct)

No additions during fermentation.

 

The narrative up until maybe 3 years ago was that yeast will attach themselves to hop oils and actually strip hop profiles from your beer as they flocc out. That's true and because of that, many waited for fermentation to complete and yeast to flocc before dry hopping. Some now are doing multiple dry hops. So the first dry hop is during fermentation to get the biotransformation effects. Then they'll dry hop again post-fermentation to get the more traditional dry hop effect.

If you really want to go overboard, read that whole study from Wolfe. His studies also suggest that agitation during dry hopping can lead up to 40% more abstraction and in much less time.

 

I'd have to go back and dig. When I started reading up on it earlier this year, I think I went through 100 websites, reviews, comments, and write ups. I can try and find them again but I remember seeing it a couple times where they were talking about specific strains. Scott Janish might have written on this topic as well.

They also listed the brewery's (mainly East Coast at the time of the articles) were focusing on it and they were all using English strains. London Ale III and 007 were reference a lot which you also see out of the east coast.

 

Get this man a beer!

 

The effect of yeast enzymes on hop glycosides is very interesting and complex- since several investigations point to their high potential as precursors of highly flavor-active aroma compounds that may contribute to the hoppy aroma of beer.

I find that adding my first round of dry hops during later stages of active fermentation gives me a longer lasting hop aroma and flavor as well as adding to the overall complexity of the flavor and especially the aroma.

There's a lot of research out there to dig into on the subject.

 

Looking for a recommendation on the topic. My beer has attenuated 67%, from 1.060 to 1.020. I'm hoping it gest down to 1.010. Is it time to add fermentation hops?

 

I see no problem with adding a dose now. I have added hops in the mid 20s before. I would just also do another addition when you hit FG.

 

do it...