[yso191]

What comes to my mind is the creation of melanoidins.  The harder the boil the more melanoidins, which means more flavor and color components.  I know this doesn't relate to how much the kettle is covered, but it does relate to 'boiling good and hard FWIW.

Melanoidins do not create flavor, but the reactions that create melanoidins also create flavor.

I am not disputing that. Are there any references so that I can read more on Melanoidins vs Maillard reactions?

The only book I have that does more than brush over the issue is 'Designing Great Beers,' by Ray Daniels.  One can find the reference on pages 51-52.

[tomsawyer]

Just perusing the wiki on Maillard reactions, I'd have to say there isn't much of this going on.  The reaction occurs between sugars (plentiful in wort) and amino acids from protein (less plentiful and mostly coagulated early on) and is enhanced by an alkaline environment (wort is acidic).  On the other hand, simple browning of sugars via pyrolysis, aka caramelization, seems likely to be the primary mechanism behind the darkening of wort during boiling.

On the other hand, kilning of malt certainly involves Maillard reactions.  So of course there are plenty of Amadori compounds and other tasty stuff coming into the wort.

For this reason, I don't see boiling as creating a lot of flavor/aroma other than caramelization.

By the way, when I was going to school at Mizzou ther were a couple of profs working on Maillard reaction stuff, Dr. Milton Feather and Dr. Tom Mawhinney.  That tidbit just came to me as I was typing this.

[denny]

Just perusing the wiki on Maillard reactions, I'd have to say there isn't much of this going on.  The reaction occurs between sugars (plentiful in wort) and amino acids from protein (less plentiful and mostly coagulated early on) and is enhanced by an alkaline environment (wort is acidic).  On the other hand, simple browning of sugars via pyrolysis, aka caramelization, seems likely to be the primary mechanism behind the darkening of wort during boiling.

On the other hand, kilning of malt certainly involves Maillard reactions.  So of course there are plenty of Amadori compounds and other tasty stuff coming into the wort.

For this reason, I don't see boiling as creating a lot of flavor/aroma other than caramelization.

By the way, when I was going to school at Mizzou ther were a couple of profs working on Maillard reaction stuff, Dr. Milton Feather and Dr. Tom Mawhinney.  That tidbit just came to me as I was typing this.

Lennie, caramelization doesn't happen until about 360F or so.  A kettle full of wort can't get much above 215F.  I can't see how you can get caramelization in the kettle.

[klickitat jim]

So much of the h2o has to be gone to get that high, right?

[tomsawyer]

I see what you're saying Denny, and I guess that goes with what I've seen in making caramelized sugar.  it stays clear right up till the water is gone, then it caramelizes fast.  Wort still doesn't seem to be the ideal environment for production of Amadori products, and I'm still skeptical that a long hard boil produces a lot of additional flavor components.  I just wonder how much it drives off.

I will ponder this tonight, with a BDS.

[denny]

So much of the h2o has to be gone to get that high, right?

Yep.  For instance, the reason you add water when you make caramel in a saucepan is to slow down the caramelization.  But the sugar won't caramelize until the water is gone.

ETA:  I see Lennie already mentioned this.

[denny]

I see what you're saying Denny, and I guess that goes with what I've seen in making caramelized sugar.  it stays clear right up till the water is gone, then it caramelizes fast.  Wort still doesn't seem to be the ideal environment for production of Amadori products, and I'm still skeptical that a long hard boil produces a lot of additional flavor components.  I just wonder how much it drives off.

I will ponder this tonight, with a BDS.

THAT'S the way to ponder!

[HoosierBrew]

I could ponder just about anything with a good BDSA !

[yso191]

According to Ray Daniels, "Carmelization occurs in the boil but to a limited extent in most cases..."

What I found very interesting is the list of "Flavors attributable to Maillard Browning reaction products," which include:

"Chocolate, Rye bread, Musty, Violets, Buttery, Burnt, Toasted, Fruity aromatic, Rose perfume, Rock candy, Caramel, Bready, Maple syrup, Burnt protein, and sweet"

He states that "...Maillard-reation products are the major source of color for beer..."  But it is clear that he is mainly, though not exclusively, talking about kilning of the grain.  He also says that formation of  browning products is rapid at temperatures above 100*c.

[leejoreilly]

Just perusing the wiki on Maillard reactions, I'd have to say there isn't much of this going on.  The reaction occurs between sugars (plentiful in wort) and amino acids from protein (less plentiful and mostly coagulated early on) and is enhanced by an alkaline environment (wort is acidic).  On the other hand, simple browning of sugars via pyrolysis, aka caramelization, seems likely to be the primary mechanism behind the darkening of wort during boiling.

On the other hand, kilning of malt certainly involves Maillard reactions.  So of course there are plenty of Amadori compounds and other tasty stuff coming into the wort.

For this reason, I don't see boiling as creating a lot of flavor/aroma other than caramelization.

By the way, when I was going to school at Mizzou ther were a couple of profs working on Maillard reaction stuff, Dr. Milton Feather and Dr. Tom Mawhinney.  That tidbit just came to me as I was typing this.

Lennie, caramelization doesn't happen until about 360F or so.  A kettle full of wort can't get much above 215F.  I can't see how you can get caramelization in the kettle.

But the metal bottom of the kettle can exceed the boiling temp even if the wort above it doesn't, though, right? So I wonder if some limited caramelization could happen "locally" on the hot bottom, rather than throughout the (cooler) wort?

[denny]

According to Ray Daniels, "Carmelization occurs in the boil but to a limited extent in most cases..."

What I found very interesting is the list of "Flavors attributable to Maillard Browning reaction products," which include:

"Chocolate, Rye bread, Musty, Violets, Buttery, Burnt, Toasted, Fruity aromatic, Rose perfume, Rock candy, Caramel, Bready, Maple syrup, Burnt protein, and sweet"

He states that "...Maillard-reation products are the major source of color for beer..."  But it is clear that he is mainly, though not exclusively, talking about kilning of the grain.  He also says that formation of  browning products is rapid at temperatures above 100*c.

No offense to Ray, but I'd have to hear the science behind his statement.  Many people have said the same thing and it makes me wonder of maybe it's one of those things that's repeated so often that it's taken as truth, whether it is or not.

[denny]

But the metal bottom of the kettle can exceed the boiling temp even if the wort above it doesn't, though, right? So I wonder if some limited caramelization could happen "locally" on the hot bottom, rather than throughout the (cooler) wort?

As long as there is liquid in contact with it, I don't think so.

[hopfenundmalz]

But the metal bottom of the kettle can exceed the boiling temp even if the wort above it doesn't, though, right? So I wonder if some limited caramelization could happen "locally" on the hot bottom, rather than throughout the (cooler) wort?

As long as there is liquid in contact with it, I don't think so.

A while back I read an analyis that had the boil off rate to determine the Delta T between the liquid and metal. It was not very hig, the metal temp was less than 220F at the interface, below caramelization temps.

[denny]

A while back I read an analyis that had the boil off rate to determine the Delta T between the liquid and metal. It was not very hig, the metal temp was less than 220F at the interface, below caramelization temps.

Thanks for the info, Jeff.  I can't imagine why it would be any different.

[morticaixavier]

A while back I read an analyis that had the boil off rate to determine the Delta T between the liquid and metal. It was not very hig, the metal temp was less than 220F at the interface, below caramelization temps.

Thanks for the info, Jeff.  I can't imagine why it would be any different.

I will add this one data point to the discussion, though I imagine there were mitigating circumstances:

I accidentally pinned a cotton hop bag to the bottom of my kettle with the IC for the last 15 minutes of the boil. When I discovered this, after draining the wort into fermenters, the hop bag was black and charred through (there was actually a hole burned through the hop bag). It had carbonized while under 10 gallons of boiling wort. I"m pretty sure spontaneous combustion of cotton requires temps in excess of 400*. So at least locally, sandwiched between a stainless pot bottom and a copper coil with a 200k BTU (or whatever a bayou classic is) propane burner, you can achieve temps well above 212.