Eureka, its time for another experiment. But not about yeast this time… Sorry! The following experiment is all about hops and their role during dry hopping and bitterness. All started with a batch of Pale Ale where I tried the first wort hopping technique and added some hops for dry hopping (100 g of 14% AA Simcoe to 22 L (5.8 gal)). And the tasting revealed an overpowering bitterness. And some really grassy notes as well. This made me wonder how the bitterness could increase to such a high level in the first place. And there are two possible explanations in my opinion: The first wort hopping technique or the dry hopping. And this experiment was to find out, if the dry hopping can increase the bitterness in some way. Some say that the bitterness only increases when the hops are boiled and the alpha acids isomerize. Others say that the bitterness can increase as well if the hops are not boiled. Lets find out how is right.
What I did was the following: I took a Vodka and diluted it down to have 400 mL of a 5% alcohol solution. I did so to have the same amount of alcohol like you would have it in an average beer. Using pure Vodka could lead to false conclusions since the higher alcohol content could extract different/less/more compounds from the hops. I then added 100 mL of the diluted Vodka to a bottle each and added some Simcoe hops to have the following hops to volume ratio: 4 g L-1, 8 g L-1, 16 g L-1 and 32 g L-1. Common rates for dry hopping are in the range of 3.9- to 7.8 g L-1 (according to Calagione Sam mentioned in “Extreme brewing”).
03/02/12: Added 14% alpha acid Simcoe hops to the four bottles according to the mass to volume ratios mentioned above. I stored the bottles at room temperature at a dark place for nearly three weeks before a tasting.
03/22/12: The tasting begun. I first start with the color differences of the liquids. It could be easily observed that a higher amount of hops lead to a darker, more orange pronounced color (Fig 1). Unfortunately, there is a light difference between the two bottles shown in Fig 1 (brighter on the left side). Nevertheless, there was a difference.
Fig 1: Hop infused Vodka, 4 g hops per liter (left), 8 g per liter (right)
Then the tasting. I have to mention first, this was by far the worst tasting ever! I advice you not to replicate these results. It was just horrible. But step by step:
4 g L-1: At the lower end of the dry hopping rates. Alcohol was easy detectable, very faint hop aroma. Maybe some hints of oranges. And the taste was just bitter. Not overpowering, but bitter.
8 g L-1: At the higher end of dry hopping rates. More intense hop aroma than the previous one. Very grassy. And the taste was just horrible. Just like eating a hop pellet. And it was definitely more bitter than the previous one as well.
16 g L-1: Extreme hoping rate 1. Orange notes in the aroma. Floral notes as well. This one is my favorite of the four concerning the aroma. And the bitterness was comparable with the one before.
32 g L-1: Extreme hoping rate 2. Floral notes, very aromatic hop aroma. The aroma is too intense for my taste. And again, the bitterness is very similar to the one before.
To conclude, the intensity of the aroma increases with the amount of the hops you add for dry hopping. I guess this is no surprise. What I am a bit more surprised is the fact, that the bitterness increases with the amount of hops as well. But only to a level of 8 g per liter of liquid. Further addition of hops does not increase the bitterness. Or at least not in a way that I could taste it. I have to mention here that I am talking about perceived bitterness not IBUs. I have no idea about the IBUs of the four samples.
Lets assume the IBUs of the different beers are the same if we consider that the IBUs originate from isomerized hops. Lets further assume that no isomerization happened during the experiment. How could we explain the increase in bitterness now? One possibility could be the extraction of compounds from the hops by the alcohol present. This would imply that further compound(s) in the hops can increase the bittering sensation. And basically lead to the conclusion that a higher amount of dry hops can increase the bitterness. Not the IBUs but the perceived bitterness.
I assumed that hops for dry hopping could maybe just add a bit of bitterness. But here we are talking about huge impacts. The liquids with the highest amounts of hops tasted like liquid hop pellets… I am still not really convinced here. Maybe this is just something happening only in the used Vodka-based liquids. It is therefore advisable to replicate these results using a fermented barley-based liquid. However, I conclude that a higher amount of hops in a Vodka-based liquid leads to an increasing perceived bitterness (can’t tell if the IBUs increased).
Please let me know if anyone out there has an idea what happened here or if you obtained different/same results as well. Cheers and stay tuned for further post.