Hard rolling boil & bitterness

[rockeye84]

Since upgrading to my new system been getting a harsh bitterness in my brews.

My processes & ingredients are all the same.

Main dif is all my pots are now alloy and my kettle runs 2x 3300w elements as opposed to 1x 2400w element to boil a 70l volume.

My old kettle had a pretty soft boil as opposed to this new one, that if ferocious at full noise.

Basically my question is will harder boil lead to more perceived bitterness?

 

[antiphile]

Now that is a bloody good question. Normally (using an external source of heat like a gas burner or electric element outside the pot) I'd suggest no. This is because irrespective of how vigorous the boil is, because the liquid is going through a phase change, the temperature will/should remain at the boiling point.

However, with the heating element inside the liquid, I'm not sure that the interface between the element and the liquid will become superheated or not. So the upshot of that is, I have absolutely no idea. Any chemists or physicists out there?

 

[klangers]

Now that is a bloody good question. Normally (using an external source of heat like a gas burner or electric element outside the pot) I'd suggest no. This is because irrespective of how vigorous the boil is, because the liquid is going through a phase change, the temperature will/should remain at the boiling point.

However, with the heating element inside the liquid, I'm not sure that the interface between the element and the liquid will become superheated or not. So the upshot of that is, I have absolutely no idea. Any chemists or physicists out there?

Not a physicist but an engineer who is good at physics.

Technically, only the water which is sufficiently close to the element is at boiling temperature and hence turns to steam. What is happening is that as the water evaporates and expands into steam, it rises due to the density difference and this causes huge convection currents. These convection currents are largely responsible for the heat transfer throughout the fluid being boiled. Greater heat transfer rate = more thermal power that can be absorbed into the fluid. Hence why a simmer cooks slower than a raging boil.

I would say that it's entirely plausible that a more violent boil could be isomerise alpha acids faster than a gentle boil.

 

[mr_wibble]

I always figured that harsh bitterness is a function of the initial bitternes Vs age of the beer.

Have you been leaving to mellow for the same time ?

Perhaps the harder boil is isomerising more hop acids leading to a higher bitterness, and thus needing longer storage.

 

[paulyman]

Have you adjusted your new boil off in your recipe?

If not then you have altered the BU:GU ratio for each recipe which may impact on perceived bitterness.

* Read on my phone and missed the huge change in wattage, that would surely cause more obvious process issues before this possibility if boil off was ignored. Safe to ignore my post I'd say.

 

[timmi9191]

Scorching of the wort at the element interface?

 

[Weizguy]

Coating coming off new elements during the boil?

As mentioned above, has the boil-off % increased?

 

[rockeye84]

Cheers for the input lads, I'll keep working on it.

I top up thru the boil to keep gravity an desired volume spot on. Elements are stainless steel.

 

[Lazarusnz]

I remember an episode of Brew Strong wher Jamil and John talk about too hard a boil/excessive boil off leading to off flavours in the beer but can't remember why. They said no more than 15% per hour as a guide. With my BIAB setup I boil off a bit more than that and my beers come out fine

 

[goid]

Cheers for the input lads, I'll keep working on it.

I top up thru the boil to keep gravity an desired volume spot on. Elements are stainless steel.

Hi rockeye,

Have you always topped up through the boil? Has the amount increased in the new system?

I am not at all knowledgeable about the subject but on a quick read if you have been adding more water during the boil this may be increasing your boiling wort PH. This will increase your hop utilization and also maybe increasing tannins and other components (from the hops) which are astringent. Higher PH in your boil can lead to harsher bitterness.

Goid

 

[rockeye84]

Yeh always have topped up a little, last batch in with he 6600w kettle I had to add about 6l of water over a 60min boil, batch size was 65l, so just under 10% top up.

The pid sits on 100 duty cycle when boiling and the temp struggles to get upto 100c, sits on 99c most of the time, using a 3wire rtd and its calibrated, you think my temp sensor is too far away from the elements?

 

[rockeye84]

 

[klangers]

Probably not; remember 100c for boiling is at sea level with pure water. We are boiling wort, which is far from pure water, and usually at a different pressure. I wouldn't worry about the temperature; don't try and seek 100c because you might never get there. Moving your temp probe will have a similar effect to dialling back the set point to 98-99.

 

[rockeye84]

Cheers 4 the info Klangers, saves me drilling additional holes I don't really need. Will give that a crack next brew.

 

[billygoat]

Rockeye84,
Why do you need to keep topping up the boil?
If you know what your boil off rate is, put that into your brewing program and sparge until you get your pre boil volume.
If you've got the boil off rate right, you should have pretty close to your required post boil volume at the end of the boil.
If your kettle is too small for your batch I can understand topping up, but if it's big enough I'm interested in the reason for topping up.

 

[danestead]

Have you adjusted your new boil off in your recipe?
If not then you have altered the BU:GU ratio for each recipe which may impact on perceived bitterness.
* Read on my phone and missed the huge change in wattage, that would surely cause more obvious process issues before this possibility if boil off was ignored. Safe to ignore my post I'd say.

BU:GU would be about the same right because the ibus would increase by the same percentage of the gravity increase (isomerisation in different density wort issues aside. Edit - had a mind blank - utilisation is the word)

 

[Coodgee]

you could write a blues song about this.

Well I'm a hard boilin' man,
give my wort six thousand watts,
Well I'm a hard boilin' man,
give my wort six thousand watts,
Want my beer to be real bitter,
and my woman sweet and hot.

 

[technobabble66]

I remember an episode of Brew Strong wher Jamil and John talk about too hard a boil/excessive boil off leading to off flavours in the beer but can't remember why. They said no more than 15% per hour as a guide...

This ^^^
I've read the same from pro's a few years ago when i was getting into brewing and reading everything.
No idea where from, but it was part of extensive reading i did on how vigorous your boil ideally should be, and seemed to be the conclusion they and others settled on a few years ago, and was in some more credible sources.
The contention basically stemmed from the mantra years ago being the more vigorous the better, and some people eventually questioned whether that was really the case on the various forums. That brought about lengthy discussions and debate, that gradually resolved into the idea of a nice rolling boil, but not too vigorous. Jamil & John were part of the groups that did some of the comparisons. Their's plus other people's similar opinions sealed the argument.
I appreciate it's ******/lazy not being able to quote a particular source(s) so others can objectively gauge the debate, but i'm at work, and i'm pretty sure of the gist of what was concluded. :lol:

 

[timmi9191]

I return to my original thought at post #6 of scorching at the wort/element interface. Those elements look quite small, so im thinking that they have a high watt per surface area (high density) and may be burning the wort. Is there any residue left on the element after the boil?

just a thought...

 

[Coodgee]

my first AG brew was with a rambo burner and high pressure regulator. Without knowing any better I boiled for an hour full bore and went through about 7kg of gas and had about 10 litres of wort in the fermenter. can't remember how it tasted.