[net.cooks] Chemicals in Wine?

cjy (03/22/83)

I haven't submitted anything for a while, but I noticed this stream
of verbage about chemicals in wine, veggies, and the like.  I also
noticed some confusion about how sulfur dioxide is used in the food
and wine industries.  While not a food chemist, I have a great many
friends that are and have gone through many of the Michigan
wineries.  I have also made lots and lots of wine, so I know of
which I speak.

First of all, sulfur dioxide is used primarily to kill wild airborne
yeast cells.  These cells adhere themselves to many things, your
nose, fruit skins, your skin - anything at all!  If given sufficient
quantities of sugar and water these yeast and also airborne bacteria
( I forgot! )  begin to divide and produce many by-products.  Yeast
will produce either ethanol or acetic acid, depending upon the
strain and the amount of available oxygen.  Airborne bacteria will
produce lots of things, most of which are undesirable from either a
health, taste, or an appearance standpoint.

Yeast and bacteria can be killed in two primary ways, either heat or
chemicals.  With some substances ( like wine ) heat is impractical.
Commercial wineries will filter finished wine until there are very
few yeast cells left in the wine.  Sodium ( or Potassium  for
salt-free diets ) metabisulfite is then added to the wine to
prevent the yeast culture from starting up again.  The concentration
of this chemical is quite low and I really doubt if you can ever
taste it.

If you really want to smell sulfur, and ammonia be at a winery when
they are starting a batch of wine.  First of all, they will kill off
all wild yeast and bacteria using sulfur dioxide.  After the fruit
pulp bleaches a little, they dilute it and add a controlled strain
of yeast that will produce ethanol.  They then add ammonia to make
the yeast grow like crazy.  Additional ammonia may be used to cool
down the vats once the fermentation is started ( They use it in
cooling coils, not in the must. )  So some wineries STINK when a new
batch is started.

Not all wineries use the above process, but instead will kill off
the wild yeast and bacteria using heat ( pasteurization (sp?)).  In
so doing, however, they create a wine that is hard to clear due to
the excessive amount of pectin in the must.  If ammonia is not used
to encourage yeast growth, there is a chance of the wine spoiling
and also it takes longer to ferment.  Both of these factors
eventually result in higher prices to the consumer.

If you are outraged at the chemicals used in wine, go make some
"natural stuff".  Your chances of making something considered
palatable by anyone but yourself will be very small without the use
of chemicals.  ( If you leave enough live yeast in it, you get a
poor wine, but a great laxative. )



				Chuck Young at ihuxi!cjy

benson (03/23/83)

If wineries use ammoia to accelerate the yeast growth, could a similar trick
be applied to yeast doughs ?

Peter Benson
decvax!ittvax!dcdwest!benson