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Tonight's extract brewing had us waiting 30 minutes to get down to a reasonable temp. What did we lose in the process?

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 I don't know that 30 minutes is a very long time... – PJ Mar 10 at 6:09
I agree with PJ. 30 minutes is a reasonably quick cool down. I usually get a good bit of cold break material from a half-hour cool down of an extract + specialty brew. – JackSmith Mar 10 at 13:56

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Relax, don't worry

Firstly, thirty minutes is not a long time. It's not particularly quick, but you're probably fine. Secondly, some pioneering Australian brewers developed a no-chill brewing method. Google it up.

Cold Break

Proteins coagulate during the cooling process. Because the coagulated particles of protein are heavier than the proteins themselves, they fall out of solution in the kettle or fermenter. Good cold break begets clearer beer. There may be small flavor impacts but probably not noticeable in beer.

DMS

Dimethyl sulfide (DMS) is an organic sulfur compound. In most beers it is present above its flavor threshold. It has a characteristic taste and aroma of cooked corn or creamed corn.

DMS precursors are found in malt and is formed by heating them above 160ºF. In the boil DMS is created, but easily driven off by the roiling boil. (This is one reason why you shouldn't boil with the cover on.) At flameout production continues until the temperature drops below 160º. The longer the wort is in this range, the more DMS you get in your fermenter.

In the fermenter, the evolution of CO2 scrubs DMS. Despite all its volatility small amounts (10-150 parts per billion) are perceptible in beer. It is better to reduce this off flavor and rapidly chilling your wort is an important step.

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Great point about DMS. I noticed on my last brew that took about 30 minutes to cool that I was down to 147F in just 5 minutes. The temperature graph versus time during cooling is asymptotic and all that... – JackSmith Mar 10 at 15:56
Thanks, this is very helpful. Why the big jump in quality from your counterflow chiller? Is that all cosmetic? – Rich Armstrong Mar 10 at 19:25
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 My brewing mentor came over last night. He inherited an immersion chiller, and much of his other equipment, from a guy who was giving up the hobby. He admitted that in his hundred or so batches, he'd only used his immersion chiller twice... and one of those was when I was visiting, to impress me! Often, he'll just let it sit on the stove and cool in the kettle overnight. And people like his beer! The mad fool. – Rich Armstrong Mar 11 at 13:07
All these years, he's been doing it wrong. ;-) – Dean Brundage Mar 11 at 16:46
It's been a long time since the switch to CFC. I just remember my beers "got better" after the switch. – Dean Brundage Mar 11 at 16:48
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Cooling your wort quickly causes cold break material to precipitate out of solution. It can then be left behind in the brew pot or easily strained when transferring your cooled wort to your fermenter. If you cool slowly, cold break does not occur and the proteins remain in solution. The end result is cosmetic - your beer may suffer from chill haze. That is, it will be crystal clear at room temperature, but the proteins will precipitate slightly when cooled to serving temperature, but not enough to fall to the bottom, causing your beer to appear cloudy when cooled.

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I should mention that cold break is less abundant with extract brews, because the break was already removed from the wort that was dehydrated to become the extract. Most of the break you get in your extract brews comes from your specialty grains. It's a bigger deal with all-grain brewing than with extract brewing. – JackSmith Mar 10 at 14:05

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