This term pops up from time to time and it often cited as a reason to go to all grain. But maybe its because I don't really know what it tastes like.
Do you believe in extract twang?
How do you get rid of it, aside from all-grain brewing? Can you get rid of it?
It's reasonable to assume that something happens in the process of evaporating down to syrup or DME, and that that something differs from a wort made fresh by mashing. From what I've read, it's a combination of sweetness from under-attenuation, and off flavors from the production/storage of syrup. I've not really identified a particular flavor that I associate with it. Perhaps when there were fewer and less fresh options on the market, it was a more common occurrence.
For a pretty scientific hobby, brewers tend to be rather superstitious. Superstitions arise whenever there's unpredictable results from a complicated process over which you cannot have full control (e.g., life). Unfortunately, for most defects and off-flavors, the only explanation or advice, even from experienced brewers, is "Do it again and be more rigorous in your sanitation and temperature control."
Extract twang would seem to be in a different class of defects. It's associated with the major ingredient in your beer, and apparently cannot be got rid of, but only masked. If it's a problem with all extracts, it should show up to some degree or another with every extract batch made from the same lot. If you're brewing with the level of consistency that allows you to taste a consistent off-flavor with every extract batch, you're doing pretty well. If you detect this consistent off-flavor across multiple styles, you might consider the extract as a culprit and include a partial-mash step in your brewing to mitigate it.
If you are stuck in the extract world, but you don't want your beer to taste like extract, there is one thing you can do: put your extract in later in the boil. This may or may not be the "twang" that you're talking about, but it can hide the fact that it's an extract beer from some discriminating folks.
There's no real reason to boil the heck out of your extract, since it's already had the heck boiled out of it to dry it up. So put maybe 1/3 or so in a full volume boil. Do your normal recipe, and throw your last 2/3 in 10 or 15 minutes from the end of the boil (I always go completely off-heat to add extract). Guys that usually can detect "that extract taste" have a harder time detecting that flavor with beer made this way.
I saw a new answer on here- what the hell- I'll post.
In my experience- what you're describing is typically a byproduct of old (oxidized) liquid malt extract. It gets a really cloying flavor due to oxidation, and typically won't ferment out to 1.010 clean. It becomes sweet, cloying, and has that twang.
Since the posting of this question and now (what, 12 years!?) things have really changed. Better quality control in LME have made huge advances, but this is still a problem today.
I've worked in a homebrew shop long enough and can tell when brewers have brewed with old liquid malt extract- it's even very obvious based on color depending on what they steeped.
I still recommend extract brewers to folks use only DME as it's a bit more stable and ferments down to 1.010 more consistently.
I don't know what it tastes like, either, because I don't have a developed enough beer palate I think. I jump around from style to style too much and never really brew the same beer twice. I don't brew enough batches to want to spend time perfecting a single recipe. Anyways, I've read that you can avoid extract twang by using fresher extract and by using lighter extract. I think the color is more important. I've often heard to only use light DME and get all your color & flavor from steeping specialty grains. The reason to use DME as opposed to LME is that DME is going to taste fresher and the reason to use light is becuase the darker stuff provides more twang. I can't explain why, though. I'm just regurgitating what I've heard.
I probably should know better than to respond to an 12 year old thread, but here goes: it is my impression that the amount and type of organic acids produced in the fermentation of malt extract is different, and probably greater, than in the fermentation of an all-grain based wort.
I speculate that this might be related to malt minerals. Grains have a certain inherent buffering capacity which malt extract may lack.
It would be interesting to do a back-to-back comparison and test the wort pH during and after fermentation, but for that one would need both the malt exact and the malt it is made from, which requires the co-operation of the extract manufacturer.
My guess is that there is definitely an association with the type of extract used. I bought about 20kg of extra pale no brand spray malt for brewing with speciality grain. Every batch had a slight astringent note and more ester than I expected. I tried everything (better temp control, different yeast.....). The off taste only went away when I returned to reliable spray malt.
