Cooling the boiled wort

[Cadbury]

G'day men,
When cooling the wort after the boil, what sort of time frame should I be looking at? Normally I can get the temp down to 24 degrees in about 30 min. But I have had a few brews go off lately and I think I am picking up a bug during this stage. The reason is because i leave the lid off a give it a stir to speed up the cooling process. I read somewhere that you need to get the temp down as fast as possible. Can anyone help with some hands on information?
Cadbury

[Tipsy]

24 degrees in 30 mins sounds pretty good to me.

This time of year I'm getting to around 30 degrees in 30 mins, then I give up and put it in the brew freezer.

I also stir the wort while it's chilling as it makes a huge difference.

I don't know about your bug though

[Kevnlis]

As long as you get below 60C or so ASAP you are fine. Leave the lid on, Put the lid on at the end of the boil to sanitise it and then remove from heat and cool as per usual. I highly recommend counterflow as it will get you below this temp very quickly!

[Trough Lolly]

Sorry to disagree, but the wort is producing DMS (from SMM, which in turn is generated by amino acids during the malting process) and it's being driven off in the vapour generated by the boil - which is why you should uncover your kettle during a boil. Excess DMS in beer is often tasted as a cooked vegetable / corn flavour and is quite apparent in lagers.

DMS will continue to form after flameout, until the boiled wort drops well below 70C. So, if you cover the kettle after flameout, you risk trapping the DMS in the steam vapour and having it run back into the wort. Cool it quick, sure, but don't cover the wort until you're sure that the wort has stopped throwing off steam unless you like DMS in your beer...

Cheers,
TL

[Kevnlis]

DMS is exactly the reason you want to cool the wort to 60C ASAP. However if you put an unsanitised lid on, trapping contaiminated air, then let it sit for hours to cool, you risk infecting the wort. I think I would rather the few minutes of DMS formation...

Of course if your not using a counterflow chiller, you are probably going to get DMS either way. Even if the lid is off, the wort will most likely spend a great deal of time at a temperature at which the gases are trapped and DMS is still being produced.

I think in both cases it is probably best to wait til the gases stop escaping before replacing the sanitised lid.

[Trough Lolly]

Sorry, I worked on the assumption that you'd do something more than whack the lid on and watch forlornly as the temperature crept down without any assistance....

Air is not "contaminated" as such. I totally agree that we enter the danger zone as soon as we turn off the kettle flame, but to be honest, you'd have to be pretty unlucky to fatally infect a wort at 80C...

In the instance you've cited, Kev, yes the lid is probably best left on, as you're just inviting infection during a prolonged chill, but I've promptly chilled open stock pots of wort in the kitchen sink, using cold tap water, and never had an infection.

I use the TL "ghetto" counter flow chiller method:

• Stir the wort in one direction
  Stir the cold water in the sink the opposite direction
  Replace the sink water when hot regularly until you reach the desired temp

Cheers,
TL

[Neil]

This isn't an issue for me anymore as I don't do extract or partial extract brews anymore but I thought you weren't supposed to do anything with the wort that might introduce oxygen into it until it got down to c. 24C? My method was to take my brewpot full (or half full whatever) of piping hot wort and sit it in the laundry tub which was packed with ice. I would rotate the pot in the ice to try and get some heat transfer thing happening (like TL's method perhaps) until I got it down to the right temp. This could take an hour or so but usually less, and the wort was covered by the lid so nothing could get in. I guess I'd lift the lid from time to time to check on things and so the vapour would dissipate. I don't know. I don't remember having any DMS tastes in my beer. I'd then carefully tip the wort into my sterilised fermenter, making sure it got plenty of air on the into the fermenter, then pitched the yeast and topped up with sterilised rainwater. Prior to this I used to get those cardboardy characters in my beer - afterwards, not a problem. I do recommend having the magic spray bottle of idophor, etc. to spray about when lifting lids, etc. Didn't have any problems with infections either.

My 2 bobs worth (for what it's worth!)

Neil

[Trough Lolly]

A gentle stir is all that's needed to get a whirlpool going in the pot - you're right that it's not a good idea to thrash and bubble piping hot wort. There are a number of reactions taking place in wort above 60-70C and adding oxygen at that time is one good way to introduce cardboard flavours in the final product. Leave whatever you used to stir the wort during the boil, in the wort at flameout - it will be relatively sterile and safe to leave in the cooling wort so you can periodically stir - replace sink water often as it rapidly heats and you'll get a quicker cool if you replace the sink of water - remember, in an average sink and using a 12L or so stock pot, you only need to 1/3rd fill the sink as the stock pot will displace its own volume and you'll end up with a full sink.

A tip if I may - beware of cheap plastic plugs in the sink - they happily stick to very hot metals such as the bottom of stock pots!!

Unless you're working in a very dusty place or you can clearly detect smells in the air, you can cool the wort with the lid off - just use your judgement; I would agree that it's better to leave the lid on and risk DMS staying in the wort compared to infecting the wort with insects or anything else that's airborne, if you had to make a choice.

Cheers,
TL

[Neil]

Fair points TL. I must admit I got a bit anal about the wort being exposed to the open air for even a fraction of a second after having a bad run of infections (many years and umpteen brews ago, I must add). As you say, commonsense gets you a long way ('cept it's increasingly rare)

Neil