Choosing bittering hops

In my experience, variety does matter whether you are substituting hops in a recipe primarily for bittering or for aroma. The compounds in hops that contribute bitterness to beer are the alpha acids, with humulone, adhumulone and cohumulone being the most significant in terms of amount. Hop chemists use several methods to separate the various compounds in hops and brewing scientists have tried to figure out the effect these compounds have on finished beer flavor. One conclusion scientists made over decades of this type of research is that beers made from hop varieties high in cohumulone have a harsh and unpleasant bitterness. As it turns out, the so-called noble hop varieties are low in cohumulone and this “noble” rank may have been originally assigned to those hop varieties that produce a mellow bitterness.

When you substitute one bittering hop variety for another I think it is important to understand what you are brewing and what that hop variety means to the recipe. If, for example, you are brewing a recipe for a beer that you have never brewed and the recipe calls for a hop variety that is not available at your local shop, substituting just about any variety will not end up in disaster. After all, you have never brewed this beer, have no preconceived expectations and will not know how your change affected the outcome of the brew. If you choose a variety that you like and have used before, then the substitution is not a big deal.

On the other hand, if you have been brewing McConnell’s award-winning Irish Ale for the last 20 years using a specific hop variety, and suddenly that hop variety is not available, things get a bit more complicated. In this case a brewer is certainly not going to grab whatever source of alpha acids is lying about in the hop room. Instead they are more likely to select a replacement variety that has a similar alpha acid profile as the original variety.

I also like a substitute that has a similar alpha acid content because the plant matter in the hop does contribute flavor. Let’s assume a hop variety has been used with a very low alpha acid content and the beer being brewed has a target bitterness level of 25 IBU. If we substitute a variety for the original that has five times more alpha that means that the weight of bittering hops will decrease by a factor of five. If the high hopping rate in the original formulation contributed a grass-like character to the beer then this high-alpha substitute is likely to alter the flavor profile.

Some readers are probably mocking my example . . . “well Mr. Wizhead, this new brew is obviously a marked improvement and the judges at the brew competition are not going to blah, blah, blah” . . . but in the commercial world of brewing consistency is extremely important. So this question has a very different answer depending on the brewer. In the commercial world, when a beer has a glaring defect it is important for it to be consistent because it is part of that beer’s identity. It’s the equivalent of “fixing” the gap in Lauren Hutton’s charming smile.

Aroma variety substitutions become more difficult because humans are more able to detect small variations in aroma than we are at detecting small variations in compounds that we perceive with taste buds and the trigeminal nerve. We are able to differentiate thousands of aromas while only a small handful of tastes. This is why it is difficult to taste food when you have a cold and is also why little kids hold their noses when being forced to eat something new with an objectionable taste. It’s really the sense of small that is being disturbed, not the taste buds or trigeminal nerve.

This is an obtuse way of saying that if you change from one aroma variety to another the differences probably will be detectable, assuming that enough aroma hops are used to make a reasonable contribution to the overall bouquet of the beer and that you have a sniffer that is in good working order. Again, if you are not selling your beer things get easier. I like changing things up because it broadens my personal knowledge of things and if you substitute Perle for Northern Brewer, or vice versa, not only will you have first-hand experience of how this affects aroma, you may also stumble upon something that you really like. You cannot learn this from a table. This is why commercial brewers use pilot breweries to test new ingredients, process changes, etc.

A substitution guide is usually subjective and is based on a combination of conclusions drawn by evaluating data on a hop’s composition and personal experience. I would substitute Perle for Northern Brewer and Northern Brewer for Perle if the hop is used as a bittering hop. In fact, I recently had to find a substitute for Perle used for bittering and Northern Brewer was what we chose. No significant difference in the bitterness character of any of beers was noticed. If the substitution was for an aroma addition I would not have chosen the same variety since Northern Brewer has a coarser aroma to my nose in comparison to Perle. But since the aroma compounds evaporate during boil this difference is not noted in the finished beer.

Brewing is a blend of art and science. While this phrase is uttered by many a brewer, diligently copied down by journalists and has been printed so many times that it has truly become cliché, it is also very appropriate when discussing hop selection.

Response by Ashton Lewis.