As those of you who read this blog will know I have been talking about a technique called hop bursting recently. I first tried it back in Nov 2009 whilst brewing my Dog Fish Head 90min without really knowing how the technique worked. I came across it again last week when I brewed Northern Brewers 115th Dream Imperial IPA, which shipped with over 1 lb of hops. How can you add 1 lb of hops to a 5 gallon brew and it not taste disgusting? I was curious and wanted to find out more, especially given how clean the bottom of boil kettle was where the hops had settled while cooling.
First up lets quickly review the big hop post I did a few back. First thing to remember are the Alpha Acids, these cause bittering and are not very water soluble so require an hour of boiling to fully extract. Then there are the Beta Acids, these are water soluble and actually evaporate if left too long in the water. Beta acids provide the hop aroma and flavour. The more the beta acids evaporate the less the aroma which is why we have flavour additions with 10-15mins of a boil to go and aroma at 0 mins.
Hop bursting is a technique used to impart massive amounts of hop flavour and aroma by adding large amounts of hops at the end of the boil, typically beginning at the last 20 mins. Some bitterness will be extracted (use the formula in the hop post and replace the 60 with 15 and play around with the hop quantity and see how much more you would need) so in order to get the same level as a 60 min boil we need a lot more hops. Here is a simple example. In the hop post we calculated the IBU’s for a recipe with a 60 min and a 15 min addition, it was approx 29 for a 2.5 gl batch using 1.2 oz of hops. What if we want to create a 29 IBU recipe with a big hop aroma and flavour using hop bursting with no bittering hops at the beginning of the boil.
Here is the same formula used in the hop post but this time using 4 additions a 15 min, 10, min, 5 min and 1 (assuming we are a using a generic 4.5% alpha hop in pellet form, same batch size and OG).
First calculate the utilization for each addition
15 min: ( 1.65 * 0.000125^( 1.060 – 1 ) ) * ( ( 1 – 2.72^( -0.04 * 15 ) ) / 4.14 ) = 11.54%
10 min: ( 1.65 * 0.000125^( 1.060 – 1 ) ) * ( ( 1 – 2.72^( -0.04 * 10 ) ) / 4.14 ) = 8.43%
5 min: ( 1.65 * 0.000125^( 1.060 – 1 ) ) * ( ( 1 – 2.72^( -0.04 * 5 ) ) / 4.14 ) = 4.64%
1 min: ( 1.65 * 0.000125^( 1.060 – 1 ) ) * ( ( 1 – 2.72^( -0.04 * 1 ) ) / 4.14 ) = 1%
Next calculate the IBU for each addition given its utilization and add them all together to make the final total.
15 min: 11.54 * ( 0.5 * ( 4.5 / 100 ) * 7490 ) / 2.5 = 7.78
10 min: 8.43 * ( 1 * ( 4.5 / 100 ) * 7490 ) / 2.5 = 11.37
5 min: 4.64 * ( 1 * ( 4.5 / 100 ) * 7490 ) / 2.5 = 6.25
1 min: 1 * ( 3 * ( 4.5 / 100 ) * 7490 ) / 2.5 = 4.06
Total IBU = 29.46
So we have an ale with the same IBU made with the same hops as the traditional bittering method except the hop load is 5 1/2 oz as compared with 1.2 oz giving us an really BIG hop flavour and aroma. Another advantage for homebrewers like myself that do not own filtration equipment is strong hoppy IPA’s can be made without the need for a dry hop addition and all the additional complexities that come along with the process.
So go ahead and try the NB recipe, its a 1 lb of hops for a 5 gallon brew, have no idea how it will turn out but I love the quote on the web site which I will end this post with:
If you serve this beer to a Michelob Ultra drinker, he or she will cry. If life were a 1950s horror flick, this I2PA would climb out of the fermenter and turn on its master. Your dentist does not want you to brew or drink this beer. Sorry in advance about your tooth enamel