“No chill” brewing

My first thought is that this method is certainly not new. Rapid
chilling is a very recent development in the history of brewing. Prior
to the advent of the plate heat exchanger, brewers had to wait for wort
to cool prior to pitching. Most breweries eventually settled on
coolships, which are large shallow pans resembling Olympic-sized kiddy
pools, to cool wort prior to fermentation. Although cooling required
only eight hours or so, wort contamination was a real issue with the
coolship design. Then, in 1856, Jean Louis Baudelot invented a novel
wort chiller and the brewing world was changed forever when his
invention made rapid chilling a reality. The Baudelot chiller was copied
and later modified into enclosed designs. Baudelot’s basic design is
still widely used in all sorts of different heating and cooling
applications.

There are two real problems with slow wort chilling. One is the risk of
microbiological contamination. The other problem associated with slow
wort cooling is DMS formation after wort boiling. The precursor for DMS,
S-methyl-methionine, decomposes when heated and becomes DMS (DMS smells
like cooked corn and most brewers consider it a defect in almost all
beer types). Although much of this compound is transformed to DMS and
removed with steam vapor during wort boiling, some does remain. This
means that the wort DMS concentration increases after boiling and prior
to cooling, and is especially noticeable if wort is in a sealed
container that prevents the volatile DMS to escape.

The good news is that homebrewers do not have a very large volume of
wort to chill and it is certainly possible to cool a carboy of wort in a
reasonable time frame if the carboy is plunged into a cold water bath
that is kept cold during cooling. Agitating the carboy will also
dramatically increase the heat transfer rate during cooling. My personal
preference is to cool wort using a wort chiller either in the kettle
with an immersion chiller or en route to the fermenter with a plate or
shell-in-tube chiller. I suppose if I were brewing on a desert island
and only had the no-chill method I would make do, but neither one of us
is stranded on an island.

Response by Ashton Lewis.