The Professor found this rather odd and interesting method for estimating the bitterness of hops in an old edition of Zymurgy…
Written by Patrick D’Luzansky
The old standard method to estimate alpha-acid percentage is to make an educated guess and then modify the guess as you gain brewing experience with your hops. Because homegrown hops are fresher and have suffered less handling, they are more bitter than commercial hops. Estimating their alpha as 50 percent higher than the average alpha for the same commercial cultivar is a pretty good guess. Knowing the exact alpha of your hops is less critical if you use them only for flavor and aroma additions.
We can improve on this guess with a taste-testing technique I call “ratiometric titration.” The approach here is to compare a same-cultivar hop of known alpha content with our unknown alpha hop. We compare the ratio of quantities of sugar needed to overcome the bitterness and infer that this ratio will equal the ratio of alphas. Thus, if it takes five teaspoons of sugar to offset the bitterness of our homegrown hops and three teaspoons to null the commercial hops, then our hops are five-thirds as strong, and our alpha-acid content is five-thirds the commercial alpha. If the commercial alpha is 6 percent, then our alpha is 5/3 times 6, or 10 percent.
I make up two hop tea samples – one from our unknown alpha fresh hops, and the second from commercial whole leaf hops of the same cultivar with known alpha. Stir one-quarter ounce hops plus one teaspoon sugar into two cups of boiling water (the sugar is needed because the hop resins are nearly insoluble in plain water.) Next, reduce the heat and simmer with the lid on for 30 minutes. Now add enough boiled water to each sample to bring their volumes back to two cups. Let the teas settle and cool to room temperature. Next, decant and filter the teas through a coffee filter to remove sediment.
Now comes the tasting part. It’s best to do the tasting in the morning when your taste buds are freshest. Measure a quarter cup of each of the hops teas. Now taste a few drops of the unknown alpha tea and rinse off your tongue. The tea will taste bitter, of course. Next, add one-quarter teaspoon sugar and taste. It will taste a little less bitter. Continue titrating the tea with the sugar in quarter-teaspoon increments (and doing a tongue rinsing between each tasting) while tasting for the point when the predominantly bitter taste finally gives way to a sweet taste (with bitter overtones). This is when the bitter loses its bite. Record the amount of sugar it took to reach this turning point. Now repeat the titration with the known alpha tea. The ratio of the titrated sugar for the unknown hops to the sugar required for the known hops is our estimate of the ratio of the alphas of the respective hops.
If this method seems too imprecise for you, send a one-ounce sample of hops to Jim Murphey at Murphey Analytical Laboratories Inc., (509) 577-8969. He will do an alpha-acid and beta-acid spectrographic analysis for about $28 and a hop oil profile analysis for $80. He also will perform an IBU analysis of your beer for $25. (Send two bottles – one for testing and one for qualitative analysis while doing the write-up – to 7 W. Mead Ave., Yakima, WA 98902.)