The SCIENCE of off-flavors... - Home Brew Forums
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Old 12-08-2011, 06:10 PM   #1
year2beer
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SUBJECT: Extract TWANG SCIENCE

MISSION: Provide some science to back up the extract "twang" theories...which typically appear more opinion than fact.


1. Why would old (past it's shelf life) DME/LME lead to the "twang"?

2. What by-product would yeast produce, that could lead to that "twang" flavor? What enviroment would help develop those by products (light, sound, temp, etc.?

3. Why does a full boil have an effect on long term extract beer flavor? How does less boiled H2O=greater chances for "twang"?

4. How does the temperature of the liquid at extract addition time have any effect on overall flavor once fermented?


I hope this helps with the science of extract brewing...something I think is greatly overlooked.


GOAL: Find the #1 Culprit based on real science (that can hopefully be controlled)... chemists, engineers, biologists, and scientific minds please chime in!!!

Thanks again!

J



 
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Old 12-08-2011, 06:46 PM   #2
Yooper
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I don't think you need much science to know the answers to those questions.

1. "Old" anything doesn't taste as good as fresh, that's why even canned goods from the grocery store have "best by" dates on them. Old canned extract darkens and ages, while the bulk LME (which is stored and poured under inert gas) will be exposed to oxygen when it's placed in the container you buy. It's fine when fresh, but with age will oxidize and darken and start to stale. You can taste the difference if you open a can of old extract vs a jug of freshly poured bulk extract.

2. Yeast off-flavors occur just as often in all-grain brewing. That has nothing to do with the extract. Poor technique (underpitching, fermenting at too high of a temperature, etc) related to yeast health cause yeast off-flavors.

3. Less maillard reactions, and less scorching will occur in a bigger boil as there would be less sugar per gallon.

4. It wouldn't. The temperature of the extract when added to wort has nothing to do with the final flavor, unless it was on the flame, sunk to the bottom and burned.

Nothing very "scientific" about any of that, in my opinion.


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Old 12-08-2011, 08:12 PM   #3
year2beer
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I appreciate the feedback, but I posted in the brew science forum because I tend to look deeper into concepts.

I guess I didn't make it clear enough...

I am truly interested in understanding the interaction of chemistry, biology, time and other scientific variables that can be manipulated to develop flavors in beer.

I've read a ton on this forum about theorized opinions, based on general knowledge. I'm looking to geek out a bit... and develop a keen association between science and experience...

For the geeks like me out there, I look forward to your perspective...even if this seems elementary to base it off of extract brewing.

 
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Old 12-08-2011, 08:27 PM   #4
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Quote:
Originally Posted by Yooper View Post
I don't think you need much science to know the answers to those questions.
Hence brewing dogma persists...

I applaud your efforts year2beer.
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Old 12-08-2011, 08:33 PM   #5
wildwest450
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This thread is wasting valuable internet space.


_

 
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Old 12-08-2011, 08:38 PM   #6
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Quote:
Originally Posted by insubordinateK View Post
Hence brewing dogma persists...

I applaud your efforts year2beer.
Well, call it "brewing dogma", but someone assuming that there is "different" science for an extract brew vs an all-grain brew is why I answered the way I did.

There is definitely a whole science to brewing- but not anything that needs to be dedicated to extract. Canned extract darkens and stales, and boiling it in a condensed volume encourages maillard reactions. That's just the way it is.

But aside from using extract to make wort and using grain to make wort in an extract batch, extract and all-grain brewing are the same. Once the wort is made (either through purchasing fresh LME/DME or mashing) there are NO functional differences. That was my point. Or at least, intended to be my point.
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Old 12-08-2011, 08:39 PM   #7
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Quote:
Originally Posted by wildwest450 View Post
This thread is wasting valuable internet space.


_
Agreed. But I think Yooper did a pretty good job of answering the questions.

OP, the issue is that you are essentially dealing with the science of food and cooking. In terms of flavor changes, the predominate reactions are oxidizing reactions and browning/Maillard reactions. But these reactions excompass innumerable substrates and resultant innumerable reaction products. It is my understanding that the reactions are largely extremely difficult to predict or at least to separately characterize because of the shear number of different types of reactions.

If you want more on the science of brewing, look in Briggs. Its about the most scientific source you will find about brewing. But based on your reaction to Yooper's post, you may not even be satisfied with that.

 
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Old 12-08-2011, 09:49 PM   #8
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Quote:
Originally Posted by ayoungrad View Post
In terms of flavor changes, the predominate reactions are oxidizing reactions and browning/Maillard reactions. But these reactions excompass innumerable substrates and resultant innumerable reaction products. It is my understanding that the reactions are largely extremely difficult to predict or at least to separately characterize because of the shear number of different types of reactions.
From what I gather, I think there is a lot of truth to this. Probably not possible to nail it down to "one culprit". I did dig up a nice review on the role of polyphenols (as antioxidants) in beer flavor stability with plenty of references if you have access to a university library:

http://www.scientificsocieties.org/j...1-0107-106.pdf

However this is regarding finished beers, but I think it can be applied to stored malts as this is the source of polyphenols (along with hops). Also malt extracts contained extracted compounds that will be more accessible to oxidation reactions which is why, I think, extracts will have a shorter shelf-life than whole grain.

Also the presence of metals will play role in the formation or reactive oxygen species which will definitely affect flavor. Yet polyphenols can bind to transition metals and indirectly act as antioxidants.

From reading through the article, the presence of polyphenols not only protect other compounds from being oxidized, they can add astringency (tannins) to flavor as well as beer haze so it is a catch-22.

We need some food chemists' input.
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Old 12-10-2011, 08:52 AM   #9
year2beer
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I read the study, and completely agree with those conclusions. Its actually led me down the road of understanding the molecular structure of extracts vs. Barley.

At this point I believe the off flavor culprit does not sit with the age of the extract, and rather the vehicle it is transported in.

It makes me wonder why extract isn't vacuum sealed in silicone or polymer packages? It would extend shelf life and minimize unsatisfied customers.... which equals repeat customers!

As a business owner, it leaves me slightly flabbergasted... thoughts?

 
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Old 12-10-2011, 02:43 PM   #10
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My thought is that if vacuum sealing in polymer package improved shelf life then they would probably do it that way which suggests that your hypothesis is may be wrong i.e. that it is mainly age that is responsible. Staling reactions take place slowly which is why sherry, barleywine etc. improve with age. Beyond that a sealed can (with polymer lining to prevent the previously mentioned metal catalyzed staling reactions) should be as effective at excluding oxygen. The oxygen (or other high ORP substances) in the syrup are doubtless there before it goes into the package. Perhaps chelating transition metals would be an effective means of lengthening shelf life. Storage at cold temperature would probably help too.



 
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