Author Topic: Chemistry of beer flavors  (Read 897 times)

Offline Jimmy K

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Chemistry of beer flavors
« on: March 12, 2014, 06:38:58 AM »
Interesting Popular Science article on Maillard and caramelization reactions in beer.
 
http://www.popsci.com/science/article/2012-12/beersci-how-beer-gets-its-color
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Offline dkfick

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Re: Chemistry of beer flavors
« Reply #1 on: March 12, 2014, 07:47:16 AM »
Hmm... Will have to give it a read later.  Interesting topic for sure.
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Re: Chemistry of beer flavors
« Reply #2 on: March 12, 2014, 08:12:42 AM »
He implies that caramelization happens in beer.  As far as I've been able to find, it does not.  He does say that it requires "elevated temperature" but doesn't say that you can't achieve that temp in a kettle of wort.
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Offline Jimmy K

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Re: Chemistry of beer flavors
« Reply #3 on: March 12, 2014, 08:16:37 AM »
Maybe you inferred the implication? ;)
 
I didn't get that, but I guess he doesn't explicitely say it doesn't either. He does talk about caramelization reactions during malting. Doesn't really address reactions during malting/boiling.
« Last Edit: March 12, 2014, 08:22:49 AM by mtnrockhopper »
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Offline bonjour

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Re: Chemistry of beer flavors
« Reply #4 on: March 12, 2014, 09:38:43 AM »
using the simplified research of Wiki
Quote
http://en.wikipedia.org/wiki/Nucleate_boiling
DNB is also known as Transition boiling, unstable film boiling, and partial film boiling. For water boiling as shown on the graph, transition boiling occurs when the temperature difference between the surface and the boiling water is approximately 30 °C (54 °F) to 120 °C (220 °F) above the TS. This corresponds to the high peak and the low peak on the boiling curve. The low point between transition boiling and film boiling is the Leidenfrost point.
DNB is the rolling boil we use, so temps from 212+54 = 266F to 212+220 = 432F

Quote
http://en.wikipedia.org/wiki/Caramelization
The process is temperature-dependent. Specific sugars each have their own point at which the reactions begin to proceed readily.
Caramelization temperatures[1] Sugar    Temperature
Fructose    110°C, 230°F
Galactose    160°C, 320°F
Glucose    160°C, 320°F
Sucrose    160°C, 320°F
Maltose    180°C, 356°F


The caramelization reactions are also sensitive to the chemical environment. By controlling the level of acidity (pH), the reaction rate (or the temperature at which the reaction occurs readily) can be altered. The rate of caramelization is generally lowest at near-neutral acidity (pH around 7), and accelerated under both acidic (especially pH below 3) and basic (especially pH above 9) conditions.[2]
The conclusion I draw is that carmelization is possible in a boil kettle with a 266F to 432F temp on the kettle surface where the Temps are the highest.

without question Maillard reactions also occur.
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Offline Jimmy K

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Re: Chemistry of beer flavors
« Reply #5 on: March 12, 2014, 09:58:50 AM »
I'd been wondering about this. The temperature of boiling liquid water cannot exceed 210F, but the temperature of steam can.
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Offline bonjour

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Re: Chemistry of beer flavors
« Reply #6 on: March 12, 2014, 10:06:39 AM »
I doubt the temp of the steam, but the temp of the metal kettle where the steam forms and bits (small bits) of sugar are left behind, then redissolved once the surface is wetted again.

And backing Denny, no one has proven that this actually occurs in beer.
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Offline kramerog

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Re: Chemistry of beer flavors
« Reply #7 on: March 12, 2014, 10:12:09 AM »
using the simplified research of Wiki
Quote
http://en.wikipedia.org/wiki/Nucleate_boiling
DNB is also known as Transition boiling, unstable film boiling, and partial film boiling. For water boiling as shown on the graph, transition boiling occurs when the temperature difference between the surface and the boiling water is approximately 30 °C (54 °F) to 120 °C (220 °F) above the TS. This corresponds to the high peak and the low peak on the boiling curve. The low point between transition boiling and film boiling is the Leidenfrost point.
DNB is the rolling boil we use, so temps from 212+54 = 266F to 212+220 = 432F

Quote
http://en.wikipedia.org/wiki/Caramelization
The process is temperature-dependent. Specific sugars each have their own point at which the reactions begin to proceed readily.
Caramelization temperatures[1] Sugar    Temperature
Fructose    110°C, 230°F
Galactose    160°C, 320°F
Glucose    160°C, 320°F
Sucrose    160°C, 320°F
Maltose    180°C, 356°F


The caramelization reactions are also sensitive to the chemical environment. By controlling the level of acidity (pH), the reaction rate (or the temperature at which the reaction occurs readily) can be altered. The rate of caramelization is generally lowest at near-neutral acidity (pH around 7), and accelerated under both acidic (especially pH below 3) and basic (especially pH above 9) conditions.[2]
The conclusion I draw is that carmelization is possible in a boil kettle with a 266F to 432F temp on the kettle surface where the Temps are the highest.

without question Maillard reactions also occur.

The steam is that hot but what about the sugars?  My intuition is that the sugars remain dissolved in the wort because I don't see caramel on the inside bottom of the pot.  I do often see coagulated protein, which is not soluble, on the bottom of the pot.
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Offline bonjour

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Re: Chemistry of beer flavors
« Reply #8 on: March 12, 2014, 10:43:03 AM »
the question is how much sugar stays dissolved in the steam.  Not much.  sugars are highly soluble so they would re-dissolve almost instantly.  The sugars in the wort, that stay in the wort, will not caramelize.  At any point in time that would be most of them.

Engineers go thru a lot of trouble to prevent dissolved solids from depositing in boilers (these are agents to prevent corrosion) because they hurt the vessel.  DNB greatly reduces heat transfer so they try to stay below that point.  We don't. When the water evaporates (forms steam) where do the solids go, some will go back to the wort, but some will temporarily deposit on the kettle surface.  They have to.

Again, no one has proven that this occurs in beer.

FWIW. If you use this argument on the BJCP written exam, you will likely be raked over the proverbial coals
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Offline tschmidlin

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Re: Chemistry of beer flavors
« Reply #9 on: March 12, 2014, 11:53:35 AM »
FWIW. If you use this argument on the BJCP written exam, you will likely be raked over the proverbial coals
I'd be tempted to give bonus points for it. :)

The problem with trying to prove that it occurs in the boil kettle is that it is hard to measure.  The products of caramelization and maillard reactions are somewhere between similar and identical, and not all of the compounds have been identified.  It would be great if there was some product that was only formed by caramelization, then we could just check for that forming in the kettle.  I don't know that such a product exists though.
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Offline erockrph

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Re: Chemistry of beer flavors
« Reply #10 on: March 12, 2014, 12:06:16 PM »
FWIW. If you use this argument on the BJCP written exam, you will likely be raked over the proverbial coals
I'd be tempted to give bonus points for it. :)

The problem with trying to prove that it occurs in the boil kettle is that it is hard to measure.  The products of caramelization and maillard reactions are somewhere between similar and identical, and not all of the compounds have been identified.  It would be great if there was some product that was only formed by caramelization, then we could just check for that forming in the kettle.  I don't know that such a product exists though.

Or you could simulate it by boiling a malt sugar solution of comparable gravity to wort in the absence of amino acids. If true caramelization was possible then you should detect some caramelization products. Otherwise, it would be reasonable to conclude that these are caused through the Maillard reactions in boiled wort.
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Offline tschmidlin

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Re: Chemistry of beer flavors
« Reply #11 on: March 12, 2014, 12:40:12 PM »
Or you could simulate it by boiling a malt sugar solution of comparable gravity to wort in the absence of amino acids. If true caramelization was possible then you should detect some caramelization products. Otherwise, it would be reasonable to conclude that these are caused through the Maillard reactions in boiled wort.

That might work.  Although you'd have to adjust the pH to mimic wort because that will have an effect.

Quote
http://en.wikipedia.org/wiki/Caramelization
By controlling the level of acidity (pH), the reaction rate (or the temperature at which the reaction occurs readily) can be altered. The rate of caramelization is generally lowest at near-neutral acidity (pH around 7), and accelerated under both acidic (especially pH below 3) and basic (especially pH above 9) conditions.[2]

I'm happy to do the experiment and look for a color change, but I don't have a pH meter.  That's also probably not the best way to detect the reactions.  It will likely taste different, but can we say that it is from caramelization?
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Offline wsoublo

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Re: Chemistry of beer flavors
« Reply #12 on: March 12, 2014, 01:07:51 PM »
I'm happy to do the experiment and look for a color change, but I don't have a pH meter.  That's also probably not the best way to detect the reactions.  It will likely taste different, but can we say that it is from caramelization?

One way to test for caramelization would be to mix a glucose/distilled water solution and acidify to the 5.2 - 5.5 range, boil the mixture for an hour, and then run a GCMS sample of the solution to see if any of the caramelization byproducts were formed. 

My hypothesis would be you'd only find a higher concentration of glucose than you started with.  If you selected fructose as your sugar, then you might find some carmelization byproducts forming if you acidified the solution enough.
« Last Edit: March 12, 2014, 01:13:19 PM by wsoublo »

Offline anthony

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Re: Chemistry of beer flavors
« Reply #13 on: March 12, 2014, 02:12:50 PM »
I think if you roll this all back and look at his comments regarding caramelization in context he is clearly talking about caramelization during the malting process which definitely happens, not in the boil kettle.

Offline bonjour

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Re: Chemistry of beer flavors
« Reply #14 on: March 12, 2014, 03:41:52 PM »
it seemed like a good segway
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