No Chill IPA - Staggered IBU

[Lord Raja Goomba I]

Finally got around to brewing my house AIPA, which is SWMBO favourite.

Trouble is, as I've mentioned on other topics, I don't reckon the 'hoppiness' qualitative factor is quite there, but the bitterness seems to be higher (perceived, I know) than is typical for this recipe (which is very much unchanged for several years). In Tassie, I had this same recipe feel less bitter and more hoppy punchy type flavour.

My very non-measured opinion is that the temp difference between here and Tassie means that no-chill stays above isomerisation temps longer in Qld due to the slower temp decline (or less gap between the wort temp and outside temp). This seems to be further reinforced by the fact that I could leave a no-chill cube overnight in Tassie and it would be at pitching temp in a shorter period of time (say "it was ready when I got out of bed", rather than midday or 1pm here).

So I decided to do a semi-scientific, semi-dark ages experiment. Given that 'hoppiness' in no-chilled IPA tends to be a very qualitative thing and we have educated guesses as to what the extra time gives us over chilled beers, this is probably in keeping with the slightly non-scientific manner of measuring no-chill variables at any rate.

It's basically a case of whacking the hops into the cube after a period of time has elapsed, to reduced the bitterness and increase the qualitative hop factors of IPA (aroma, flavour), so that the (generally anecdotally assigned) +20 minutes that no-chill adds to a hopping regime, can be adjusted down to +15 minutes or even possibly +ten.

So, assuming that the wort goes in at boiling (100 degrees C), and isomerisation is generally considered, from my reading to be around 79 degrees, I wanted to aim at 95 degree pitch.

Now, I know that cooling does not happen in a straight line, but in the absence of any research I've found that gives a calculation to get a 'line in the sand' moment, this is the best I can do.

So given that 95 degrees is 5 degrees of 21 degrees from 100 degrees to 79 (isomerisation ceases from literature reading), I back calculated the IBU to be a no-chill 70 IBU, which, using the formulate (isomerisation range - drop in temp) / isomerisation range * IBU, I calculate this to be 53 IBU. Ideal.

All other variables (hop variety, base malt, recipe, yeast) are the same. I want to see if I get more qualitative 'aroma' and 'flavour' that we normally associate with 'hoppiness'.

If this works (or the result is in the ballpark of where I think it might be), I can then hone a method (much like the housewives of 1660) that allows me to produce a fairly replicable and predictable result with hopping IPA using no chill but staggering the hop additions.

I'm also timing how long it takes to drop 5 degrees and I'll see if this needs to be tweaked depending on outside temp/season.

This is no brulosophy. It may give me a false positive, though I have a very harsh critic. It's only the stuff I can measure reasonably predictably not the 'whole picture'. But it will hopefully give me an idea of where to go.

 

[Lyrebird_Cycles]

I have the calculation required for the "line in the sand" incorporated into my bitterness calculator. All you need is the temperature when the hops go in and the time taken to a suitable end point such as 50 degrees. It assumes that heat loss follows a log curve between these two points as dE/dt = k * deltaT

BTW isomerisation doesn't magically stop at a particular temperature, it has a typical first order Arrhenius kinetic curve.

 

[Lord Raja Goomba I]

I figured that there might be a calc and that it wouldn't be a straight line thing.

This gives me a starting point in a numbers game.

I'll incorporate that into the next attempt as I fine tune it.

Thanks heaps

 

[Phoney]

I have the calculation required for the "line in the sand" incorporated into my bitterness calculator. All you need is the temperature when the hops go in and the time taken to a suitable end point such as 50 degrees. It assumes that heat loss follows a log curve between these two points as dE/dt = k * deltaT

Whaoh whaoh whaoh! Slow down egg head, what's dE, k and the rest of it?

 

[Lyrebird_Cycles]

"dE/dt" is the rate of flux of energy (in this case heat) with time*. "k" is a rate constant. "DeltaT" is the temperature difference between the two fluids (in this case one fluid is air). I have glossed over the surface factors and just assumed they are constant so they get rolled into k.

In engineering calulations it's normal to use Q for heat transfer rate but I thought that would be even more obscure.

 

[Lyrebird_Cycles]

I'll incorporate that into the next attempt as I fine tune it.

The reason for the usual end point number given somewhere around 80 oC is that it's the point at which the isomerisation rate falls to 1% of its value at 100 oC.

It is usual practice when considering reaction rates in biochemistry to assume that, all things being equal, once the rate falls to 1% of its peak value leaving the rest out won't cause significant errors.

In the case of no chill, the "all things being equal" doesn't apply because you are comparing boil times in minutes with cooling times in hours: if the wort spent 24 hours at the temperature where the isomerisation rate was 1% of boiling, that would contribute the equivalent of almost 15 minutes of boil time.

 

[manticle]

Sure but how would wort remain at that temp for anything close to 24 hours?

 

[Lyrebird_Cycles]

It's just an example of a situation where applying the idea of a cutoff temperature introduces a quantifiable error.

 

[manticle]

Fair enough.

 

[Coodgee]

I have the calculation required for the "line in the sand" incorporated into my bitterness calculator. All you need is the temperature when the hops go in and the time taken to a suitable end point such as 50 degrees. It assumes that heat loss follows a log curve between these two points as dE/dt = k * deltaT

BTW isomerisation doesn't magically stop at a particular temperature, it has a typical first order Arrhenius kinetic curve.

Not sure if trying to be helpful or seeking to show how smart you are.

 

[Lord Raja Goomba I]

The reason for the usual end point number given somewhere around 80 oC is that it's the point at which the isomerisation rate falls to 1% of its value at 100 oC.

It is usual practice when considering reaction rates in biochemistry to assume that, all things being equal, once the rate falls to 1% of its peak value leaving the rest out won't cause significant errors.

In the case of no chill, the "all things being equal" doesn't apply because you are comparing boil times in minutes with cooling times in hours: if the wort spent 24 hours at the temperature where the isomerisation rate was 1% of boiling, that would contribute the equivalent of almost 15 minutes of boil time.

That makes so much more sense viz no chill.

 

[malt junkie]

LRG .... just tell the missus " with all these kids and summers getting hotter, we need a pool babe, ..... " she'll go for it for sure!

 

[manticle]

Not sure if trying to be helpful or seeking to show how smart you are.

LC developed a bitterness calculator which he shared free with the forum some time ago so my guess is the former.

This forum is at its best when it has a balance of various level members, including those with high level maths and science pertinent to brewing.

I'd rather arrhenius than LCD.

 

[wereprawn]

Not sure if trying to be helpful or seeking to show how smart you are.

Meh, having a chemistry wiz on the forum is a good thing. I often have not the slightest idea of what LC is talking about, but when I do I find his posts informative.

 

[Reedy]

Very interested to see the results of your exbeeriment LRG

 

[stewy]

Before I started throwing my cubes into the pool I would wait approx 30 mins after boil (crow urn, uninsulated), have all of my late hop additions in the cube & transfer the wort at that stage. Wort temp was generally around 85C at that point. It resulted in nice hop punch without excess bitterness. Another option for you is to transfer straight away, leave 20 mins in cube then put into a full bath (or pool if you have)... this works exceptionally well for me.

 

[Reedy]

Before I started throwing my cubes into the pool I would wait approx 30 mins after boil (crow urn, uninsulated), have all of my late hop additions in the cube & transfer the wort at that stage. Wort temp was generally around 85C at that point. It resulted in nice hop punch without excess bitterness. Another option for you is to transfer straight away, leave 20 mins in cube then put into a full bath (or pool if you have)... this works exceptionally well for me.

What do you consider late hop additions? Anything 20mins or less? I ask as I am still trying to 'perfect' my no chill technique for IPA's, and cube hopping is something I want to try.

 

[stewy]

Yep, 20 or less. Although I do IPA's with first addition at 20mins, a load at flameout, another load cube hopped. Come out much better. Huge aroma, nice smooth bitterness.
After boil finishes I let it sit 10mins, drain to cube & leave in cube for 20. I then chuck in pool. Works a treat. You could chuck in bath full of cold water. Don't need it to get to pitching temps, just knock as much off as quickly as possible to lock in the hop flavour/aroma

 

[stewy]

.

 

[Rocker1986]

I would have thought it was pretty standard practice with no chill brewing to let the wort sit in the kettle for 15 minutes or more before transferring it to the cube to allow the hot break to settle out in the bottom of the kettle first. If it's transferred basically immediately after flameout, most of that shit would still be floating around in the wort and end up in the cube, wouldn't it? :unsure:

I let mine sit 20 minutes before transferring now. I did test the temperature of the wort in the urn at transfer time once, which I think was after a 15 min stand, and unfortunately no idea what time of year it was now, but it was sitting at 92C by that stage. I imagine it would have lost a little more during the transfer into the cooler cube as well. Next brew day I'll have to test it after its 20 minute stand and also when the cube is ready to be sealed up. Would be interesting to see what the temps are.