Tuesday, 5 August 2014

A Quick Question: Dry Hops and Diastatic Enzymes

I've been following up on some of the research on Ron Pattinson's blog Shut Up About Berkeley Perkins, trying to get a better understanding of the processes used in brewing older British beers, and in particular of the role played by secondary fermentation.

One thing I've been wondering about, with respect to IPAs, was whether or not they were aged on dry hops.  From what I can piece together from Mitch Steele's book, dry hops were added as the beer was racked into casks, after which it was aged for many months before shipping.  That would mean that the beer spent a considerable time on these hops.

I thought that was pretty interesting in its own right, but today I stumbled upon something related that was even more intriguing.  Following up a reference from Ron's blog, I found the following in Principles & Practice of Brewing (Walter J. Sykes & Arthur R. Ling, 1907):
"During secondary fermentation the more resistant maltodextrins are gradually and slowly degraded by the hydrolytic actions of the special yeasts concerned, assisted by that of the diastase of the dry hops when these are added at the time of racking, and perhaps also to some extent by the carbonic acid existing under pressure." (p.539)
If I understand this correctly, it says that hops added at racking contributed diastatic enzymes that eventually facilitated the breakdown of dextrins in the aging beer; and that the resulting sugars were fermented by brettanomyces and perhaps any remaining saccharomyces as well.  What I'm wondering is whether anyone can confirm that long aging on dry hops could have this effect?

Update: Based on the experiment described here (p.107-8), the answer seem to be yes.  Now I'm wondering whether aging on dry hops contributed anything to secondary fermentation that wouldn't have been achieved by the action of brettanomyces alone.  It might have kept LAB at bay, for instance; but I'm thinking in particular of the fermentation and its by-products.

Update II:  Further confirmation here.

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