Were going to spend the next 45 minutes talking about hops. - PDF document

We’re going to spend the next 45 minutes talking about hops. Specifically, we’re going to be talking about some exciting research that’s going on in the world of hops, and how you can incorporate that research into your homebrewing. This is an ambitious seminar: we are trying to cover a lot of ground, spanning 4 different areas of hop research, and we aim to keep it accessible for beginning and intermediate homebrewers while still making sure you advanced folks walk away learning something new. So with that said, strap on your seatbelts, and let’s get after it. 1

Who are we? Chris: My name is Chris Hotz and I began homebrewing in 2004. In 2012 I began taking my brewing more seriously by joining QUAFF homebrew club in San Diego and entering my beers into competitions. In 2013 was accepted into the first class of UC San Diego brewing certificate program and was privileged to learn from the likes of Chris White, Yuseff Cherney and Mitch Steele. In 2014 I began working as a Quality Analyst at Ballast Point Brewing before becoming an R&D brewer two year later in 2016 where I currently remain. While I can not claim as many homebrew awards as this man (Doug Brown), I have earned two NHC medals. Doug: And I haven’t won any medals at NHC, but I’m working on it, and hoping that changes tomorrow. I am the current Vice President of the QUAFF homebrew club in San Diego. I started homebrewing in the year 2000, and played around with the hobby on and off for several years with extract brewing before taking the all-grain plunge around 2012. In late 2013 I started to get more serious about beer: I joined a homebrew club, QUAFF, and in January of 2014 I enrolled in the Brewing Program at UC San Diego., which I completed in June of 2015. That experience was a real turning point for me, not only because it was in that program that I met Chris, but also because I got my first exposure to the world of brewing research… 2

Doug: Much of that research today comes from the Master Brewers Association of the Americas. The MBAA is a global -- no longer limited to just “the Americas” -- community committed to expanding and sharing our collective understanding of brewing & fermentation. Founded in 1887, by German Americans who brought their brewing culture with them when they immigrated to the New World, today the MBAA is a 501(c)(3) non-profit organization with over 4,000 members from over 50 countries worldwide. Every year the MBAA holds its Master Brewers Conference, during which brewers, scientists, and other industry members present their findings and studies . I was fortunate to be able to attend the 2017 Master Brewers Conference, which was in Atlanta, and which takes us into our first topic for this seminar… 3

Auxiliary Bitter Compounds. Specifically, what are Auxiliary Bitter Compounds in hops, and how do they affect the quality of bitterness in beer? This is research coming out of Germany, and was presented at the Master Brewers Conference by Andreas Gahr, the Brewmaster of the Research Brewery at Hopfenveredlung St. Johann. I was really intrigued by his presentation, and Brewmaster Gahr graciously agreed to let me share his findings with y’all here today. 4

This wouldn’t be much of a scientific presentation without a bunch of three -letter acronyms being used incessantly. To make sure we’re on the same page, here are the main abbreviations I’ll be using. First, IAA, for Isomerized Alpha Acids. Most of us know isomerized alpha acids as being responsible for bitterness in beer. Hops contain alpha acids. When we buy hops, the packaging usually indicates the amount of alpha acids that are in the hops, as a percentage by weight. Those alpha acids aren’t very bitter, nor are they very soluble in water or beer. But when those alpha acids are heated, they undergo a chemical conversion – called isomerization – that turns them into isomerized alpha acids. Those isomerized alpha acids – or IAA – are very bitter, and they are relatively soluble in beer. This is one of the primary reasons we boil our wort, in order to isomerize the alpha acids in the hops to create Iso-Alpha Acid and add bitterness to the beer. 5

Next up are the Auxiliary Bitter Compounds, or ABC. These are the focus of this study, and we’ll get into some examples of them and their significance in a bit. For now, the important thing to know is that ABC refers to compounds contributing to the bitterness of beer other than the isomerized alpha acids, or IAA. 6

Our third acronym here is one we’re all probably familiar with: the IBU, for International Bittering Unit. And although this is a term that’s used all the time in the world of brewing, it’s a problematic word from a scientific perspective because it can refer to different things, and isn’t always used consistently. In theory, as it is often described, the IBU is defined such that 1 IBU is equal to 1 ppm, or 1 mg per Liter, of isomerized alpha acid. This is the definition of IBU that’s given in many brewing texts, and it’s something that can be measured in a lab using high - performance liquid chromatography, or HPLC, which is a piece of sophisticated and relatively new laboratory technology that is capable of isolating isomerized alpha acids and measuring their concentration in a solution. But an HPLC is expensive, and only very small percentage of breweries utilize them. So most people measure bitterness in a lab using a piece of equipment called a spectrophotometer, which is much less expensive and uses older technology. A spectrophotometer works by targeting a sample with a specific wavelength of light and measuring how much light is absorbed. It turns out that isomerized alpha acids strongly absorb light with a wavelength of 275 nm. So by using a spectrophotometer set at 275 nm, you can get an idea how much Iso-Alpha Acid is in a beer, and thus measure IBU that way. 7

However, Iso- Alpha Acids aren’t the only thing that absorb 275 nm light, nor are they the only thing in beer that contributes to bitterness. As it turns out, there are a host of other things in beer that also absorb 275 nm light, and some of them contribute to bitterness, too. There’s a non -exhaustive list on the slide in front of you, including: • Alpha acids, meaning un -isomerized alpha acids: these are not very bitter, and they absorb 275 nm light weakly, but they are sometimes found in beer and they do contribute somewhat to bitterness. • Humulinones: Chris will be talking to you about humulinones more in a bit, but for now, understand that they are also bitter, and they are also picked up by a spectrophotometer at 275 nm. • Also beta acids, some beta acid-derived compounds like hulupones, certain polyphenols, etc. Put all this together and hopefully some of the confusion around IBU is evident. If we think of IBU as referring only to Iso- Alpha Acid concentration, we’re missing the impact of all these other compounds that can contribute to bitterness. On the flip side, if we think of IBU as simply a measure of everything picked up by a spectrophotometer at 275 nm, we’re going to get a result that is only approximate, based heavily on how well these various compounds absorb 275 nm wavelength light, and one that for many beers that deviates from what we might expect based on any of the bitterness formulas we’re familiar with like Tinseth, Rager, Garetez, etc. 8

So there’s really no perfect way to quantify or measure bitterness. To make the best of this imperfect situation, going forward in this talk I’m going to use IBU to refer to bitterness as it would be measured by a spectrophotometer, capturing both Iso-Alpha Acids and Auxiliary Bitter Compounds. In other words, let’s think of IBU as being equal to the sum of IAA plus ABC. Using the term IBU in this way, the ratio of a beer’s IBU to Iso-Alpha Acid concentration becomes a useful proxy for identifying how much of a beer’s bitterness is derived from Auxiliary Bitter Compounds. Since IBU includes all of a beer’s IAA plus its ABC, a beer that derives all of its bitterness from Iso-Alpha Acid will have an IBU to IAA ratio of exactly 1. As the percentage of a beer’s bitterness coming from Auxiliary Bitter Compounds increases, the ratio of IBU to IAA will also increase, since adding more Auxiliary Bitter Compounds to a beer increases IBU (the numerator) while leaving the IAA (the denominator) constant. And now that I’ve set all this up, the question is: so what? Why do we care how much of a beer’s bitterness is derived from Auxiliary Bitter Compounds…? 9