SULPHURING—ARRESTING FERMENTATION.
Casks are sulphured for the purpose of destroying the activity of the
ferments contained in the lees which may remain in them, and thereby to
prevent their moulding or souring, and must and wine are sulphured to
prevent or to check fermentation, and white wine also to keep it from
turning yellow.
=Sulphurous Oxide, or Sulphur Dioxide=, is produced by burning sulphur.
It is a colorless gas, of a suffocating odor, and is composed of equal
weights of sulphur and oxygen, or, one part of the former and two of
the latter, SO₂, and with water becomes sulphurous acid. It arrests
fermentation in two ways: first, it absorbs oxygen with avidity, and
thereby removes what may be in the must or wine, or in the cask, thus
taking away one of the conditions necessary to the life and activity
of the ferment. (See _Fermentation_.) In the second place, by the
absorption of oxygen, sulphuric acid is formed from the sulphurous
acid, in a highly concentrated state, which is destructive of the life
of the ferment.
[Illustration: _Fig. 13._ Sulphurer.]
[Illustration: _Fig. 14._ Maumené’s Sulphurer.]
=The Sulphurer, or Sulphur Burner=, the instrument used for the
purpose indicated, consists of a wire with a hook at one end, and the
other attached to the centre of a long, conical bung (fig. 13). It
is convenient to have the upper end pass entirely through the bung,
allowing the latter to move up and down on the wire, so that the hook
can be raised or lowered, according to the position to be occupied
in the cask. This is used by attaching the sulphur match to the hook
and lowering it into the cask, after lighting it. The objection to
this form of instrument is, that the coal or cinder left on the hook,
after burning the match, may fall into the cask and give the wine an
unpleasant flavor. To avoid this, Mr. Maumené invented a sulphurer,
provided with a deep perforated porcelain cup, into which the match is
placed and in which it burns, and which retains the carbonized linen
(fig. 14). A piece of wire cloth bent into a cup of a similar form and
attached to the lower end of the wire answers the purpose very well.
=Sulphur Matches or Bands= may be purchased, or they may be easily
manufactured. To make them, melt roll brimstone (stick brimstone), or
what is better, flowers of sulphur, over a slow fire (sulphur melts at
115° C. or 239° F.); tear linen or cotton cloth into strips an inch
and a half wide and 10 or 12 inches long, and dip them into the melted
sulphur, and lay them aside to cool. Then dip again, and repeat the
process, dipping and cooling, till the coating of sulphur is of the
required thickness, and they should be thickly coated, or it may be
necessary to burn too much linen to get sufficient gas. If the sulphur
is overheated, the match will be dark-colored.
Sweet scented powders are often added to the sulphur, whose essential
oils are disengaged when the sulphur is burned, and the cask is
perfumed by their vapors. The substances usually employed are ginger,
cinnamon, the flowers of the stock gilly, iris, lavender, thyme,
violet, etc., and the matches prepared with the addition of them is
generally preferred.
Mr. Maumené says that the smallest amount of this volatile oil gives a
perfume to the wine, which is generally advantageous, but Boireau is
of opinion, however, that these substances check the combustion of the
sulphur, and in a measure neutralize its action, and he prefers the
sulphur pure.
=To Sulphur a Cask=, take a piece of the sulphur match and light it and
lower it into the middle of the cask by means of the sulphur burner,
and lightly put in the bung of the instrument. By applying the ear to
the staves, it can be ascertained if the match is burning. If the air
is foul in the cask, and the match will not burn, the noxious gas must
be expelled as described under the head of _Casks_. When the fire is
extinguished the burner is withdrawn, care being taken, if the hook is
used, not to drop any of the carbonized linen into the cask. If that
should happen, the cask must be washed again. As the burning sulphur
fills the cask with gas, which exerts considerable pressure, care
should be taken that the bung is not blown out into the face of the
operator.
Sometimes a strip of the sulphured cloth is lighted at one end and
lowered into the cask, the other end being secured by putting in the
bung. This is objectionable, because it leaves the debris of the match
sticking to the bung and the stave, which may give a disagreeable
flavor to the wine. As already mentioned under the head of _Casks_,
never burn a match in a cask containing alcohol.
=To Sulphur Wine=, if the cask is only partly full, operate the same
as in sulphuring an empty cask, only care must be taken not to lower
the match into the wine. Here the sulphur burner with a movable bung
comes in play. If the cask is full, the gas may be drawn in by burning
a match close to a hole bored in the head of the cask somewhat higher
than the faucet, drawing from the latter at the same time. It is
evident that while the wine runs from the lower hole, the gas will
be drawn in at the vent. Where it is necessary to leave a cask with
a vacancy in it for some time, flowers and souring may be prevented
by burning in it a piece of sulphur match and bunging it up, and the
process should be repeated every two weeks, and besides as often as the
bung is removed for any purpose. It is better always to keep the cask
full, for in time the sulphurous gas will communicate a disagreeable
taste to the wine, which it takes a long time to remove.
=Sulphuring should be Avoided in Certain Cases.=—Ropy wines should not
be sulphured, for the presence of oxygen is necessary in order to help
their fermentation; nor should those wines be sulphured which it is
desirable to keep in a state of effervescence. Sulphur should be very
sparingly used in connection with red wines, as it causes them to lose
a portion of their color by rendering insoluble the coloring matter,
and precipitating it; and for the same reason it is used for bleaching
white wines, and it prevents the latter from turning yellow. Liqueur
wines which are slow of fermentation should not be sulphured, for they
need all the natural aids to fermentation.
=Fermentation is Arrested=, sometimes, in the manufacture of white
wines, by drawing them off into well sulphured casks, using two or
three squares of the match, if the fermentation is not very tumultuous;
but if it is very active, it may be treated as mentioned below for
musts. And in most cases the proper practice is, where wine needs
sulphuring, to draw it off into the sulphured cask, and in this way the
oxygen contained in the wine is more thoroughly exposed to the action
of the gas.
=Unfermented Must.=—By sulphuring the must, fermentation is prevented,
and thereby is produced what the French call _mute wine_; and it is the
must of white grapes as it comes from the press that is more generally
subjected to the process. It is first allowed to settle as described in
the chapter on white wine, but it must be drawn from the vat as soon
as signs of fermentation appear, and bubbles of carbonic acid rise to
the surface. And to have the must clear, it must be closely watched,
for as soon as fermentation sets in, it becomes turbid. The must should
be freed from all fragments of stems, skins, seeds, etc., and should
therefore be strained as it runs from the press.
=It is Prepared in Two Different Ways.=—First, the cask must be
scalded, rinsed, and drained in the usual way, and then as much sulphur
must be burned in it as can be consumed, or until the match goes out
for want of oxygen. Then the cask must be rapidly made half full of
the must, and closely bunged. It should then be rolled and thoroughly
shaken until the gas has been well absorbed by the juice. The must is
then drawn off without allowing it to come in contact with the air
(See _Racking_), and into another cask which has been sulphured in the
same manner, and is treated as before. While the second cask is being
agitated, sulphur is again burned in the one just emptied, until it
goes out, and then the must is transferred back in the same manner,
and is again shaken. It is subjected to this operation four times,
and the cask is finally filled with must treated in the same way, and
tightly bunged. The more successful will the operation be, the more the
liquid is kept from contact with the air, and therefore this method
is preferable to the next. The second method is as follows: burn in
an empty cask matches representing a couple of ounces of sulphur; pour
in about five gallons of must, bung it up and thoroughly shake; take
out the bung and put in another lighted match; if it will not burn for
want of oxygen, the air must be renewed by blowing in the cask with a
bellows. Then burn the match in the cask, and afterwards pour in five
gallons more of must, bung and shake as before. Continue the process
till the cask lacks about five gallons of being full. Then five gallons
must be sulphured in another cask, and the cask filled up with this and
tightly bunged. Of course, the sulphur burner must be shortened as the
cask fills up.
Must treated in this manner may be kept for a long time if well
clarified, and the cask is well sulphured at each racking, or a portion
sulphured when it commences to ferment.
If it is only necessary to keep the must a short time, a portion only,
say one-third, need be sulphured. In that case there will be less odor
of sulphur, and it will soon pass away.
=Clarification and Care of Unfermented Must.=—It should be kept in
good, strong casks, well hooped and well bunged, in closed cellars
of a constant temperature. The casks should be filled every few days
with sulphured must; and they should be frequently racked to free them
from ferments. They should not be exposed to the air when racking, and
should be racked into well sulphured casks. Boireau says that the must
may be completely clarified _before sulphuring_, by introducing about
one ounce of tannin per 100 gallons of must, and pouring into the casks
before completely filling about a quart of water in which has been
dissolved about four tablets of gelatine, and which has become cold.
=A Sulphur Flavor= is sometimes communicated to must treated as above,
and is also sometimes acquired by wines which are put into casks which
have been sulphured for some time, without first washing them, and also
by allowing the debris of the sulphur match to fall into the cask;
this flavor is apt to pass away with time if not very pronounced, or
in that case may be removed by racking into a clean cask. But if the
wine has a very decided sulphur flavor, it must be disinfected by wood
charcoal. Several large pieces[3] of coal well cleaned and well dried
are introduced into the cask and soaked in the wine, from which they
can be withdrawn by strings attached before putting them in the cask.
Forty-eight hours are generally sufficient to remove the flavor; but
if necessary, the process may be repeated, by changing the charcoal.
In operating on white wines, a large amount of charcoal may be used
without inconvenience, but in the case of red wine, there seems to be
some danger of depriving it of a portion of its color. Mr. Maumené
says, however, that the charcoal is liable to deprive the wine of the
carbonic acid dissolved in it, it being an absorbent of that gas, and
thereby rendering the wine more subject to the action of oxygen.
[3] Machard says about 125 grammes to a tonneau, or 4 or 5 ounces to
250 gallons of wine.
=Other Substances have been recommended to Prevent Fermentation
in a Must=, but notwithstanding the disagreeable flavor which is
communicated by an excessive use of sulphur, no other agent has been
found which is as satisfactory, on the whole.
=By Burning Alcohol in the Cask=, the oxygen may be removed, but the
ferments are not destroyed. Care must be taken to avoid an explosion.
Therefore, the spirit must not be poured into the cask and lighted, but
must be placed in a small vessel and lowered in through the bung, as in
the case of sulphuring.
=The Concentrated Aqueous Solution of Sulphurous Acid= has been
recommended, but Maumené says that not only is its preservation very
difficult, but its management is more difficult than the sulphur match,
and the chances of its being mixed with dangerous substances are
considerable; and therefore no one should think of using it.
=The Bisulphite of Lime= has been used to prevent fermentation in
wine and cider, but it does not always give satisfactory results,
and the salt is difficult to keep, and the use for wine, at least,
has generally been abandoned. In the experiments of Proust, given by
Maumené, the smallest quantity used was 15 grammes to 100 kilogrammes
of must, or about one-half ounce to 23 gallons.
=Salicylic Acid= has been much recommended within the past few years,
but like everything else, it affects the flavor, if sufficient is used
to prevent fermentation. The quantity necessary depends upon the amount
of alcohol, ferments, etc., contained in the wine. Prof. Neubauer,
quoted by H. Endemann in _American Chemist_, says that wine which is
yet fermenting should not receive any salicylic acid, since too large
quantities of the substance are required for effective use, but that
it may be used in wine when made to prevent after-fermentation; that
it will prevent disease, but will not cure wine when diseased. Though
infallible rules as to quantity cannot be given, experiments should be
made with from .02 to .06 gramme per litre, or say from 1.165 to 3.5
grains per gallon. A solution of 2 grammes (30.864 grains) of salicylic
acid to 100 c.c. (3.38 fluid ounces) of alcohol of 80° is employed; 1
c.c. = 0.02 grammes; 3 c.c. = 0.06 grammes; 61.44 minims or a little
more than one fluidram = 1.165 grains, and 3.7 fluidrams = 3.5 grains.
Salicylic acid being but sparingly soluble in water, it is preferable
to dissolve in strong alcohol, and these are convenient proportions.
It is said that 100 grammes (3½ Ap. ounces) will stop the fermentation
of 1000 litres (about 264 gals.) of must, when nearly completed;
800 grammes are necessary when in active fermentation; and 400 will
preserve the wine when made.
But now the intelligence comes that salicylic acid has an injurious
effect upon the teeth and bones, it having an affinity for calcareous
salts (_Boston Journal of Chemistry_, Vol. XI, 143), and the French
Minister of Agriculture and Commerce, on the report of the Committee
of Public Hygiene, recommends that the sale of articles of food
adulterated with it be prohibited as injurious to the public health.
(_Ib._ Vol. XV., 45.)