mium wines. Heat can potentially transform
some taste elements. Bottle sterilization is the
best method for sterilizing sparkling wine.
Bottling-line sterilization can be accom-
plished (albeit expensively) with steam or hot
water. Where hot water is employed to sani-
tize lines, Zoecklein et al. (1995) recommends
a minimum temperature of 82ºC for at least
20 minutes. The temperature should be mon-
itored at the farthest point from the steam
source (i.e., fill spouts, end of the line, etc.)
Ultraviolet light is effective against microbes,
but it has low penetrative capabilities, and a
thin film provides a barrier between radiation
and the microbes. Ozone can be used to san-
itize in cold-water re-circulation.
Sterile Filtration
Sterilization by filtration is attained
through use of sterile filter pads or, better,
with membranes. Diatomaceous earth filtra-
tion reduces yeasts but will not eliminate
bacteria. This step is followed by membrane
filtration.
Reinfection
Any efforts in sterile filtration are ruined
by postfiltration infections if the entire bot-
tling line is not sterile. The filter, as well as
the bottling line, should be sterilized before
admitting the wine. The most effective
method of sterilization is to use a steam gen-
erator hooked to the filter, which is hooked
to the bottling line. A slow flow of low-pres-
sure steam is run for 30 minutes through the
entire system. The steaming is followed by
cold water to cool off the machinery before
allowing the wine to enter. Steam may not
be available or may injure some equipment,
such as plastic filter plates. Sterilization may
then be achieved by running a solution of
300g/hl citric acid and 10 g/hl SO 2 (or 20
g/hl metabisulfite) at 60ºC. Some parts of
the bottling line, such as the corker, are
more difficult to sterilize. The corker jaws or
diaphragm should be sterilized with alcohol.
Membrane filters may be sterilized with
water at 90ºC.Corks
Modern cork suppliers provide sterile
corks. In case of doubt, corks should be
dipped before use in a 10 g/hl of SO 2 solu-
tion.Bottles
Bottles can be re-contaminated from dust
and cardboard. A rinsing and sterilization
station must be provided for a solution of
SO 2 at 500 ppm. Sterile water (obtained after
cooling the sterile filter) is used to wash off
excess SO 2 solution from the bottle. A dis-
penser for SO 2 can be set in line off of the
main water supply using a medicator or
other similar device. Iodophors are used fre-
quently for bottling sanitation, followed by a
cold-water rinse.Barrels
Spent empty barrels are difficult to main-
tain. Approximately 12 liters of wine soaks
into the wood surfaces of a new barrel the
first time is filled. When barrels are stored
empty, the wine soaked into the wood acidi-
fies, turns to vinegar, and becomes contami-
nated with acidophilic bacteria. Although
soda ash can be used for cleaning contami-
nated barrels, sterilization is practically
impossible. Thus, contaminated barrels with
a vinegar smell should be discarded.
Empty barrels may be safely stored for
several weeks of they are gassed with sulfur
dioxide and kept tightly sealed. Barrels
gassed with sulfur dioxide should be washed
with clean water before they are filled.
Another limitation of using spent barrels is
that the wood in an empty barrel becomes
dry and the staves shrink. As the wood
shrinks, the hoops become loose and barrels
lose their shape and leak.