This is a question frequently brought up on homebrew forums and after doing some further research online there‘s a lot of debate about the most effective temperature for end of boil hops. The theory behind doing this at 80°C is that delicate hop essences are less likely to be driven off and there will be a higher proportion in the wort, meaning greater hop aroma and flavour. JK has personally never done it this way as he prefers to utilise the alpha acids contained within the hops to provide a smoother bitterness while at the same time providing aroma and flavour to the beer. He’s always stuck with this as it means that he gets a pleasant bitterness, use less bittering hops and suffer less wort loss.
However JK loves to experiment and decided he needed a definitive answer to this so he brewed two batches of a New Zealand Pilsner;
OG: 1.050
95.2% Pilsner Malt
4.8% Acidulated Malt
10g Herkules at 60 minutes
160g Motueka
Theoretical IBU: 43.7
After the boil JK hopped the batch that was still at 100°C with 80g of Motueka for 30 mins and after chilling the second batch to 80°C he hopped that with 80g of Motueka for 30 mins.
This was fermented for 14 days at 12°C, bottled and then lagered for four weeks at 1°C
To determine what effect end of boil hopping at two different temperatures has on the overall hop character of the beer JK conducted a blind triangle tasting focusing on:
  • Flavour
  • Aroma
  • Overall Preference
100% of the tasters correctly identified the ‘different’ sample with regards to flavour, aroma and bitterness.
With regards to impact:
FLAVOUR: 100% of the tasters choose the 100°C sample stating it had superior hop flavour.
AROMA: 100% of the tasters choose the 100°C sample to be aromatically superior.
PREFERENCE: Overall preference was split but comments collected showed that those who preferred the 80*C sample liked the mellow bitterness and weren’t fans of high IBU beers i.e. they preferred it as it had less hop character – wierdos! 
JK tested the bitterness of both samples by running them through the Spectrophotometer at work; results were as follows:
IBU 100°C Hopping: 45.5
IBU 80°C Hopping: 30.8