On 10/03/2021 22:48, Rod Speed wrote:


"newshound" wrote in message
o.uk...
On 07/03/2021 17:39, Rod Speed wrote:


"Jethro_uk" wrote in message
...
On Sun, 07 Mar 2021 07:11:39 +0000, Chris Hogg wrote:

On Sat, 6 Mar 2021 21:59:29 +0000, newshound
wrote:

On 04/03/2021 19:06, Rod Speed wrote:


No bugs like an ethanol water mix.

I was going to say that too, then I realised that I don't actually
know
what oxidises it to acetic acid. I assume that is mediated by some
biological activity.

AIUI wine is oxidised to acetic acid by bacteria, but above a certain
strength (e.g. sherry or stronger), the bacteria are either killed or
inactivated, I don't know which, so the beverages can be stored
without
special precautions to exclude air.

One of the homebrew forums I used had a subsection for making vinegar.

Seems to be a bit harder than you'd imagine. Which supports my personal
experience of never once accidentally making it when making beer and
wine.

Yeah, I havent either. Tho a mate of mine has made a couple of
bad batches of beer where it got infected and was undrinkable.

It certainly happens regularly to "real ale" stored in pubs.

How is it stored in pubs where that happens ?

Real ale is "alive", it still contains live yeast although most of that
is in a layer at the bottom of the barrel in a pub because finings are
added just before it is shipped from the brewery. This makes the yeast
settle over a few hours after delivery so that the served beer is clear.
But the yeast is still working slowly, so carbon dioxide is continuously
generated. This serves as a "cover gas" to keep air (oxygen) away from
the beer. As you will be familiar down under, "keg" beer which has been
pasteurised to kill any remaining yeast is kept with carbon dioxide
supplied from a regulated cylinder into the barrel. This usually
provides the propulsive force to deliver it at the tap. British beer was
traditionally stored in cellars below ground level, although for
practical reasons these days most establishments store it at floor
level. (A very few keep it at bar level and use gravity feed). The
traditional beer pump is a simple lift pump. While this draws air into
the barrel as the beer is removed, that passes through a slightly porous
"spile" which serves as a coarse filter, and relies on the density of
CO2 to keep oxygen away from the beer surface. But, as the barrel
empties more and more air gets drawn in; also the older beer produces
less CO2 so the protection is imperfect. Acid-forming bacteria can also
make their way back from the pump. Good pubs flush or clean the pipes
daily, and disinfect them frequently to avoid this.

In the very old days, beer lines were made from lead. Publicans would
always draw off the beer that had been in the lines overnight before
serving any, but the mean ones would sometimes drink it themselves. This
was a regular source of acute lead poisoning in publicans.

In pubs that keep several different "real ales" some barrels are used
more slowly than others. It's also possible that small amounts of "bad"
bacteria get into the beer at the barrelling stage either air-bourne,
during the filling, or because the barrels are imperfectly sterilised
(usually by steam cleaning).

Well you did ask.

I might detect signs of beer "turning" a few times a year (this does not
make it undrinkable). I only reject a pint once every few years (but I
am fussy about my pubs).