Hot Break - What is it and how is it formed?

[Gremlyn]

Taken from How to Brew:

The foam is caused by proteins in the wort that coagulate due to the rolling action of the boil. The wort will continue to foam until the protein clumps get heavy enough to sink back into the pot. You will see particles floating around in the wort. It may look like Egg Drop Soup.

I believe it is not disputable that the 'hot break' is the point at which constant form formation ceases. What I'm unclear about is how that/which that occurs. According to Palmer, in the above snippet from his book, the proteins coagulate together and fall out of solution in big clumps during the boil. I'm a little leery of this as in order to coagulate in the first place, the proteins must denature. As we all should know, protein denaturing occurs when they are heated up, so why, if the proteins are heated up and breaking their internal bonds and unfolding, would they then stick together with other proteins that have done exactly the same thing? The bonds between those proteins would be the same bonds that allow the protein to fold into it's desired shape in the first place, which has quite obviously been disrupted by heat from the boil. I can't imagine the proteins would be able to form enough bonds between them to form clumps big enough to sink to the very bottom of the kettle where is will be the hottest of all and remain there.

It would make more sense to me that the proteins, as the wort is heat to boiling temp, are beginning to denature and as they do so find other partially denatured proteins and stick together in long chains, which is what causes the foam to occur. Once they boil temp is reached, the proteins would no longer be bale hold on to each other and be (nearly) completely denatured and just rolling around in the wort unable to bind to anything, which causes the foam to go away. Then, once you're done boiling and begin to chill the proteins would start to refold, but since you're cooling rapidly, they end up sticking together and then they form big clumps and drop out to the bottom of the kettle.

The only way I can see Palmer's statement being true is if there is something else binding to the denature proteins in the wort that is strong enough to resist the heat of the boil...

 

[Jakemo]

I think that your second paragraph is a self-clarification of the misinterpretation of your first paragraph

I believe "sink back into the pot" refers solely to the vanishing of the foam, and the presence of particles floating around in the boil, not actually sinking all the way down to the bottom of the kettle *during* the boil.

When I think "egg drop soup" I think huge chunks of egg. I've not seen that in the few batches that I've brewed, and I suspect that I won't. Perhaps he should've clarified; "the smallest particles of egg protein that you may notice in egg drop soup" may've been a more accurate description.

It seems to me like the descriptions used by Palmer in this passage are vague enough as to potentially be misinterpreted.

Hope that helps you settle what sounds to me like you've already settled.

 

[beerkrump]

The process of denaturing a protein involves chemical or physical forces changing the secondary and/or tertiary structures. Heat vibrates the protein violently enough to cause these changes. Changes in the secondary structures are the result of breaking of hydrogen bonds to amides and will change the shape of the protein, unfolding it in random ways. This does two things, it allows new bonds to occur where the break happened and exposes tertiary structures, physically protected by the protein's original structure, to degradation.

Once boiling is reached, the proteins denature into individual proteins or very small clumps. Rising to the top of the pot, they form bubbles and foam. The tiny clumps will stick together as they collide. As the boil continues, the clumps become larger and fewer, bumping into each other less. These eventually precipitate. Kind of like snow flakes building up until they are big enough to fall.

Boiling doesn't prevent the denatured proteins from bonding with each other, it just breaks the original protein.

 

[Gremlyn]

Boiling doesn't prevent the denatured proteins from bonding with each other, it just breaks the original protein.

The heat is enough to break the bonds initially, so why wouldn't it be enough keep them broken or re-break newly formed bonds? From a little more reading, it may be that I have not had vigorous enough boils to see this kind of hot break form but I'm a little unsure on the scientific explanation for it. I feel like there has to be something else besides more protein in there if big clumps start to form.

 

[GodsStepBrother]

I also would be curious to see the exact science behind what happens during the hot break. I am chugging along through brewing science and practice hopefully they will go over that soon.

In my case, because of the vigorous boil I do. It is hard to make out almost anything during the hot break because of the boil and the convections of the wort disrupting everything. Right when it starts to boil I do notice the wort starting to get tiny little clumps of material that kind of resemble miso soup. Like this

This also happens when i cool the beer down and the cold break happens, but it is a lot more obvious because there is no more boiling or steam that block visibility. I also find myself spending half an hour looking at the carboy after I have pitched and just noticing the beer clump up and settle.

 

[beerkrump]

Protein is a long molecule consisting of a folded chain of amino acids. The folding is integral in the proteins function and there are bonds in every protein that help keep its shape and therefore in function. When a protein is denatured the chain of amino acids is unaffected. However, the shape of the protein and the chemistry of branches on the protein do change.

This new shape and chemistry allow the protein to bond to other proteins and compounds. These new bonds are not effected by the heat of the boil and prevent the protein from returning to its original shape during cooling. The flocculation and subsequent precipitation during the initial boil is the hot break. The cold break is essentially the same thing happening to proteins that bonding properties were influenced by the heat.

 

[Gremlyn]

These new bonds are not effected by the heat of the boil and prevent the protein from returning to its original shape during cooling.

While I agree with the latter part of this, you can't possibly state that new bonds formed by denatured proteins are across the board unbreakable by heat. Those bonds shouldn't really be any different than the bonds formed during protein folding. Most bonds formed are going to be hydrogen bonds on secondary and tertiary fold with van der waals forces coming into play in tertiary and quaternary structures. Covalent bond is much more scarce at the protein level, though is memory serves it is seen occasionally, and this is what would be required to form the bonds unbreakable by the heat of boiling.

 

[beerkrump]

A hard boiled egg doesn't return to a runny mess when it cools. Same process occuring there.

Yes, I am saying that bonds formed by denatured proteins during boiling are not affected by the heat of boiling. These are not the same bonds that were changed when the protein was denatured.

 

[Jakemo]

I like the "miso soup" analogy much better than the "egg drop soup" analogy. The former paints a much more accurate picture.

 

[beerkrump]

 

[pjj2ba]

A hard boiled egg doesn't return to a runny mess when it cools. Same process occuring there.

Yes, I am saying that bonds formed by denatured proteins during boiling are not affected by the heat of boiling. These are not the same bonds that were changed when the protein was denatured.

Good analogy. And more coooking will definitely not make it return to a liquid state.

Yes the bonds are more stable. Once in a more linear structure they can fit together much better and will have many more bonds formed.

My analogy is a snow flake. Early on, the ice crystal is very small, and can stay aloft for a long time (and cause excessive foaming). As time goes on the flake gets bigger and bigger, and eventually falls from the sky.

And like rolling a snow ball. Eventually you get to the point where it is to large to push any more

 

[Gremlyn]

OK, the egg analogy makes sense, hadn't really thought along those lines. The video was a little basic and didn't really touch on the more technical side of things, though the chick was kinda cute for a nerdy scientist-type I guess all the biology I've taken goes into how to denature proteins, but didn't go too in depth on the coagulation side of things... unless I skipped those days? I'll see if i can dig up some more info and read through. Thanks beerkrump.

 

[camus]

What??

I still have Dr. Kiki burnt into my eyes.

Pardon the interruption.

 

[Handsaw]

I tuned in late. Is it the heat, or is it the motion that causes the proteins to colagulate?
If it is the heat, could you cause a better hot break by using a pressure cooker?

 

[daksin]

I tuned in late. Is it the heat, or is it the motion that causes the proteins to colagulate?
If it is the heat, could you cause a better hot break by using a pressure cooker?

It's the heat, but at the molecular level, heat IS motion (kinetic energy). The faster you can heat your liquid to boiling, the more hot break you will get, but most people don't have any trouble heating up their wort fast enough to denature proteins. More would just be overkill, although it is nice not having to wait as long.

 

[Barfield]

Zombie thread alert!

I think this can be explained with thermodynamics.

It's really hard to get your head around why a hot break would form as temperature INCREASES. Hot break formation is really a two-step process: proteins must denature THEN denatured proteins must coagulate. Protein denaturation occurs at (what we perceive as) a high temperature, e.g., boil temperature. While this temperature is “high”, it’s still lower than the temperature at which coagulated proteins would “de-coagulate” (e.g. decompose). Therefore, the second, forward reaction (coagulation of the now-denatured proteins) occurs.

The Gibbs Free Energy (ΔG) equation (ΔG = ΔH - TΔS) tells us that a reaction (or series of reactions) is spontaneous if the change in free energy, over the course of the reaction(s), is negative. It must be that the free energy of these two reactions, when combined, is negative.

I would speculate that the denaturation process (step one) is spontaneous at “high” temperatures. The coagulation process (step two) is spontaneous at “low” temperatures, but these “high” and “low” temperatures are relatively different for the two processes. These two processes are ruled by different thermodynamics, but, because they're chained reactions, the second one (coagulation) can't occur until after the first one does. Both occur spontaneously in their own separate temperature regimes.

This is rank speculation by a former AP chemistry instructor! Please correct any obvious errors on my part!