Ecco ho trovato l'articolo che mi ricordavo, scusate la lunghezza ma è interessante:
"Observations on Mash Hopping by Marc Sedam
Every brewer knows when to add hops in the wort. You need some for the long boil to bitter the beer, some between 10-20 minutes from the end of the boil for flavor, and a handful at the end of the boil to get the intoxicating aroma into the beer. The hopheads among us even dry hop beer for that extra something in many pale ales. Oh, and of course you can add hops to the mash.
The mash?
Hops in the mash have a history in brewing. I first came upon this concept while trying to make the ultimate Berliner Weiss. Eric Schneider's article on Berliner Weiss in Brewing Techniques a few years back mentioned that aged leaf hops were often placed in the mash to aid in filtration. My attempt at the recipe came out well, but the concept of adding some hops to the mash was intriguing. What would hops do in the mash? Could you use pellets?
My first mash-hopped brew was a simple lager made using 10 pounds of pilsner malt, two ounces of Hallertauer Hersbrucker in the mash, and an ounce of Bullion in the boil for bittering. The resulting beer was shocking. It had hop aroma and flavor that I'd never been able to get in a beer before. When the beer was warmed up a bit, one whiff put me closer to a hop field than any glass ever before.
I continued to experiment with the amounts of hops to use in the mash, trying to make recipes I knew so I could subjectively predict the bitterness contributed. Pilsners, brown ales, barleywines, and pale ales - all of these styles seemed to benefit from mash hopping. A few postings to the Homebrew Digest (
http://www.hbd.org) led me to Paddock Wood Brewing Supplies, a homebrew shop in Canada run by Stephen Cavan. Little did I know that Stephen had been dabbling in mash hopping as well and had some information up on his website. I began to share what I was doing with other homebrewing web groups and convinced a few people to give it a shot. Many were impressed with the result. Some were not. I encouraged people to write me with their experiences and asked for as much detail on the brewing process as they could remember. Several e-mails were swapped over the next few months and some "best methods" began to emerge.
How do you mash hop?
Not all beers are worth mash hopping. But those beers that are characterized by hop flavor or aroma certainly seem to benefit. My Classic American Pilsner really shines when mash hopped. Others have tried it in a decoction and, other than a slightly increased bittering contribution of the mash hops, enjoyed the results. I have a few simple rules for converting a normally hopped beer to a mash hopped brew:
Replace the amount of late addition flavor and aroma hops with 1.5x the amount of mash hops. For example, if your recipe calls for an ounce of Saaz as a flavor addition and another ounce for the aroma addition, you would add three ounces of Saaz to the mash. Hops are added directly to the mash at dough-in.
Use pellets. I have mash hopped with leaf and with pellets and the pellets give much better results. This could be because the hop oils are more exposed in the pellets through processing.
Add slightly more bittering hops. Current observations indicate that mash hopping provides almost no bitterness to the finished beer. Thus when you move hops from the boil to the mash, you must compensate for the bitterness that is lost. I do this by calculating the IBUs that would have been contributed to the original recipe by the flavor and aroma hops and then increasing the bittering hop addition accordingly.
Sparge, boil, chill, ferment, enjoy! That's it. After adding hops to the mash, the rest of the brewing cycle proceeds as normal. Surprisingly, the hops do not get in the way of lautering. I always start the lauter slowly, but have never had a stuck mash since starting mash hopping.
Why does it work?
The short answer is that I don't know. Traditional beers generate hop flavor and aroma through late hop additions because the volatile oils that provide these properties are driven off in the boil. Mash hopping is targeting the aromatic oils and not the bittering oils. Mash hopped beers have plenty of hop flavor and aroma, yet the wort is boiled for over an hour. My main theory is that the otherwise volatile hop oils are stabilized during extended periods at mashing pH (5.2-5.5). A reason to believe this theory is found in Jean DeClerck's classic Textbook of Brewing (1957). DeClerck states that hop aromatic oils form chemical bonds at higher pH values and lower temps than found in boiling wort. The bonds which are formed are not broken during the boil; hence the permanent aromatic profile. DeClerck even suggested steeping hops in warm water. So the mash provides an attractive temperature and pH profile to allow the hop aromatic oils to form permanent bonds and making them less volatile. Even the eventual boil of the wort isn't enough to drive off the aromas. Again, this is my theory that seems to have a toehold in previous scientific observation. But this is far from the definitive answer.
I have done ten mash-hopped beers and the other feedback I've received gives a sample size of over 50 batches. Most folks report achieving a smoother hop flavor and aroma. In addition, of course, everyone gets less debris in the kettle since the hops are added to the mash and not the boil. This helps to increase wort yield and I've eked out an extra quart of wort on each batch due solely to this effect.
I have received other feedback on mash hopping from personal e-mails and public postings on the HBD. Some people have not seen a great effect from trying the process. Most of these were attributed to using too few hops in the mash. But there are still others who don't have an explanation. Other factors such as water chemistry and mash pH may play a role, but these would require further exploration.
Summary
Mash hopping isn't for every beer and it may not be financially sound for commercial breweries. But home brewers should certainly try the process once to test it out for themselves. As most of what is presented here has come from experimentation by myself and others, I'd be happy to hear about your experiences. I always appreciate feedback from those who have tried it and someday hope to have a mash-hopped beer analyzed for content to empirically determine what's happening.
This article was published on Thursday 12 February, 2004."
