My All Centennial IPA is based on a recipe for All Amarillo IPA on homebrewtalk, which was touted as a well balanced IPA – not too hoppy, but good citrus and bitterness.

All Centennial IPA still isn’t ready so I can’t really tell yet what the final taste will be like, but from the hydrometer sample, my personal preference would be for a little more flavour and a little less bitterness.  That combined with barely even noticing the cascade I added to All Cock(-up) IPA (though I think that was probably just Morgan’s Finishing Hop pellets being not very good), I wanted to learn more about timings to add hops to affect aroma, flavour, and bitterness.

This graph from seemed to put into pictures what I had been reading – but I’m wondering whether there’s a flaw in it.

Hop Utilisation

Hop Utilisation

The graph seems to say this:

  • Adding a hop about 7 minutes before the end of the boil will give maximum aroma. The aroma will start to disappear if the hop is left boiling for longer than 7 minutes but the hop will start to influence flavour.
  • Optimal time for flavour is boiling for around 20 minutes. After 20 minutes, flavour will start to disappear and bitterness will increase.
  • After about 40 minutes the hop is bittering only, with maximum bittering effect around 60 minutes.

Using this graph I can see what effect adding a hop at a particular time will give me. For example, if I add a hop at 30 minutes, it will have no influence on aroma but some influence on both flavour and bitterness.

So what’s the flaw? Flame-out. According to this graph, adding at 0 minutes – which many recipes do – has no effect on aroma, flavour, or bitterness.

I’ve always felt uneasy about adding at 0 minutes. My understanding was this: Add the hops when switching off the gas, leave for about a minute, transfer to the cooling sink and take out the hop bag, then cool the wort down. Maximum time the hops would be in for is 1-2 minutes.

So, is my interpretation of flame-out wrong? Or should I be following the graph and adding at 7 minutes rather than flame-out?

Even with this uncertainty, the graph is still useful because it gives me a rough idea of the times that affect bitterness, flavour, and aroma. That will be useful when planning my own recipes.

Update: General opinion is that the Aroma section of this graph is wrong. Basically any boiling of the hops will take away the aroma. For peak aroma, add the hops at flameout or 1 or 2 minutes before flameout. Also, since it takes different people different lengths of time to cool the wort it’s difficult to be generically accurate about any times related to aroma and flavour.