Why cool the wort quickly?

[Paradigm]

Is it just to have the shortest possible temperature interval where bacteria can survive between boiling and sealing the bucket? Or is it something more complex?

I think it's just to get through the "danger zone" as fast as possible, but there could be something involving certain temperature ranges we want to skip over to avoid certain breakdowns?

 

[jonmohno]

A good cold break, is part reason.

 

[zachattack]

From John Palmer

At the end of the boil, it is important to cool the wort quickly. While it is still hot, (above 140°F) bacteria and wild yeasts are inhibited. But it is very susceptible to oxidation damage as it cools. There are also the previously mentioned sulfur compounds that evolve from the wort while it is hot. If the wort is cooled slowly, dimethyl sulfide will continue to be produced in the wort without being boiled off; causing off-flavors in the finished beer. The objective is to rapidly cool the wort to below 80°F before oxidation or contamination can occur.

Rapid cooling also forms the Cold Break. This is composed of another group of proteins that need to be thermally shocked into precipitating out of the wort. Slow cooling will not affect them. Cold break, or rather the lack of it, is the cause of Chill Haze. When a beer is chilled for drinking, these proteins partially precipitate forming a haze. As the beer warms up, the proteins re-dissolve. Only by rapid chilling from near-boiling to room temperature will the Cold Break proteins permanently precipitate and not cause Chill Haze. Chill haze is usually regarded as a cosmetic problem. You cannot taste it. However, chill haze indicates that there is an appreciable level of cold-break-type protein in the beer, which has been linked to long-term stability problems. Hazy beer tends to become stale sooner than non-hazy beer.

 

[Epimetheus]

Those are excellent reasons to cool wort quickly, backed up by observations and experience.

In contrast, Australian brewers have used no-chill and state it is successful. The motivation is water conservation, it does not require water for cooling. People using this method are happy with the resulting beer. I do not know if it is higher in DMS or if it is more cloudy. I've read Aussies love their brews, so perhaps beer standing around going stale is not an issue {grin}.

In no-chill, the hot wort is transferred directly to a flexible water container. Most of the air is excluded by squishing the container. It cools at ambient temperatures and the container shrinks overnight, excluding air. The next day it is ready for the yeast.

There are few wrong processes, except for being unsanitary. There are many procedures, like quick cooling, that improve your odds of creating good, repeatable product.

 

[Lost1anguage]

Also lets not forget that around 180 degrees is when isomerization of the alpha acid in hops occurs. Aside from sanitation and off flavors, you will essentially "over boil" your hops if you allow the temperature to slowly drop below that level.

 

[aStoutObserver]

Not to get too far off subject. I have no chilled all of my all grain batches (4, so not a great many) and I have had no issues with clarity.

Sent from my SAMSUNG-SGH-I727 using Home Brew mobile app

 

[Paradigm]

Also lets not forget that around 180 degrees is when isomerization of the alpha acid in hops occurs. Aside from sanitation and off flavors, you will essentially "over boil" your hops if you allow the temperature to slowly drop below that level.

Ah yes, I almost forgot the isomerization of the alpha acid in hops. *Readies google*