This week I take a fresh look at mash hopping and why it might promote long term beer stability.
What is Mash Hopping?
The idea of adding hops directly to the mash tun in beer brewing actually has a long history. Many brewers experimented with mash hopping in the 1980’s and 1990’s as an alternative or supplement to boil hops, with the idea that it might promote a smoother finish on the beer. Unfortunately, given our limited knowledge of mash chemistry back then, what was likely happening is that the mash hop addition was lowering the pH slightly giving many of the benefits of a modern pH adjustment, now usually done with acid, but at a higher cost as hops are expensive.
Mash hopping also does add some bitterness, but the utilization at a typical mash temperature of 154F (68C) is equivalent to a whirlpool addition at the same time and temperature, but without the advantage of preserving hop oils, which will be boiled off later. This somewhere in the 8-9% level as compared to boiling the hops. So it is roughly equivalent to a 1/10th size boil addition of the same time period. Given that we could use a boil addition 1/10th the size to achieve the same bitterness, mash hopping is not a good way to get bitterness into your beer.
I’ve been a long time critic of mash hopping as it is an inefficient use of hops for bittering, and also none of the aromatic hop oils survive the boiling process so it adds basically no aromatics.
Mash Hopping For Beer Stability
In a recent podcast episode with Scott Janish, he makes the case that a mash hop addition will actually lower the levels of metals like iron remaining in the finished beer and therefore reduce problems with long term stability in the beer. Scott says that the alpha and beta acids in the hops react with iron and other metals during the mash and can reduce iron content in the finished beer by as much as 30%. This was with a fairly robust addition of hops equal to about 20 IBUs he says.
Iron and other metals are highly reactive, particularly with oxygen, and play a major role in spoiling your beer after it is packaged, so reducing metal content is important for long term beer stability. Metals will typically oxidize easily so any residual oxygen in the beer will create the classic stale cardboard finish of oxidized beer. Scott also claims it reduces aldehydes which can also generate off flavors. I encourage you to listen to the full episode here for more information.
Mash Hopping to Enhance Thiols
The other interesting development the last few years has been the use of mash hops to free thiols in certain styles like Hazy/New England IPAs. I’ve done a number of podcasts highlighting the role that thiols from hops play in creating fruity tropical flavors in an IPA including this one with Stan Hieronymus, and this one with Chris Graham and Vito Delluchi. However we’ve not covered the use of mash hopping as a technique.
This article from Yakima Valley Hops covers the technique in some detail. Thiols come in two forms, free and bound, but only the free thiols make a significant contribution to the flavor and aroma of the finished beers. The basic idea is that hopping during the mash converts some of the crystaline bound thiols in the hops into a form that can then be biotransformed by yeast during fermentation into free thiols. While thiols make up a tiny portion of the hop cone, they are perceptable in the parts per trillion scale and therefore have a big impact on the finished beer.
Yakima recommends choosing hops that are high in thiol content, such as Citra, Cascade, Galaxy, Eclipse as well as most of the Australian and New Zealand varieties. They also recommend using a thiol boosting yeast for best effect such as Omega’s Cosmic Punch Ale (OLY-402) for maximum impact. These newer, thiol boosting yeasts are better at completing the biotransformation of bound thiols to create free thiols. Yakima has some additional tips like bagging your pelllet hops in the mash, and I encourage you to read their full article for more details.
So does mash hopping make sense for your next beer? If you are planning a beer for longer term storage or perhaps developing a commercial beer that may sit on the shelf for some time, then mash hopping to reduce metals in your beer might make sense. Similarly if you are developing a big tropical hazy IPA then combining mash hops with a thiol boosting yeast might also be a good choice.
I hope you enjoyed this week’s article on mash hopping. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing.
