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Fragment of art Lit



By Dr MUCCULLOCH, Woolwich.

In a Letter to Mr NEILL,
Secretary of the Caledonian Horticultural Society.

HINTS, &c.

IN compliance with the wishes of some of the
members of the Caledonian Horticultural Society,
I have attempted to sketch the general principles
and practices used in the manufacture of wine,
with a view of assisting the efforts of those whom
the Society, by its annual premiums, has encoura-
ged to cultivate the art of making this liquor from
fruits of domestic growth.

In laying down these rules, and in describing
these usages, 1 have been chiefly careful in select-
ing, and solicitous in inforcing, those which could
most readily be brought to bear on our domestic
manufacture ; being desirous rather to point out
such analogies as were applicable to the practices
which the Society has so laudably patronized,
than to enter either into the chemical history of
this most interesting process, or to give a detailed


account of the art, as it is practised in those more
favoured climates, where the grape is the sole
fruit in use for this purpose. The magnitude of
the subject, would have otherwise led me into
discussions, of a length incompatible with the lim-
its of the Society's publications. In condensing
and abridging the materials originally collected
for this purpose, I have perhaps reason to fear
that I have omitted matters essential to the per-
fect understanding of this subject. Yet I hope
that I have not neglected any thing which will
prove a material want, in reducing to practice the
views which I have held out, and that some light,
however feeble, will be afforded to those, who
have hitherto been guided by rules of a dogmati-
cal and positive nature.

It is evident that, in the complicated process of
fermentation, some rules should be laid down as
the foundation of our proceedings, and the test to
which we must have recourse in examining the
accuracy of our manipulations. I cannot too
strongly enforce the necessity of familiarizing our-
selves with general principles, which alone can
assist us through the obscure paths, which this, as
well as every art connected with chemistry, is
obliged to pursue. And it is the address display-
ed by the artist in converting these general prin-
ciples to his changing processes, that will give him
a certain pre-eminence over those who are govern-
ed by invariable rules, In fact, however these


rules may appear fixed, they cannot be generally
applied, because, under the mutable circumstances
in which the application is made, they must fre-
quently be rendered futile, and sometimes even

The constituent parts of the fruits used in the
experiments now under consideration, are malic
acid, either in a state of purity, or one of combina-
tion with potash, (a circumstance not yet perfectly
ascertained) ; vegetable mucilage, or extractive
matter ; supertartrite of potash ; sugar \ water the
sweet principle ; the colouring principle ; tannin ;
super-oxalateof potash; and the principle of flavour.
The proportions of these, vary much in different
fruits, and it sometimes happens that one or more of
them is entirely absent. In the white currant for in-
stance, the colouring substance is often deficient,
whilst it abunds in the elder-berry and red grape.
So the super-oxalate of potash is rarely found ; and,
on the contrary, those salts to which the tartarous, or
malic acid appertain, are more frequent. So like-
wise, the sugar is much less abundant than the
sweet principle, which is indeed the general cause
of the sweetness of the greater number of our
fruits. The vegetable mucilage is, if any, the only
principle whose presence is invariable ; and this
principle^ is one of the most essential in the fabrica-
tion of a vinous liquor, as we shall see hereafter.
The main diversities of character, in the products
of the various fruits, is owing to the varying pro-


r>ortions of the several ingredients which they con*
tain. It is true, that difference of management
may produce different effects ; but no contrivance
can give to the gooseberry the constituent elements
of the grape, nor can any mode of procedure ex-
tract the flavour of champaigne from the juice of
gooseberries, although many, who have not been
much accustomed to the flavour of the foreign wine^
have been deceived by that made from our humble

Among the principles enumerated, tartar, water,
sugar, the sweet principle, and the vegetable ex-
tract or mucilage, are the most essential in the
conversion of fruits into wine. Colour and flavour
may be considered as adventitious ; and the prin-
ciples which yield them, are in nowise essential to
the process of wine-making. The effect produced
by the super-oxalate of potash is unknown, as it ha&
not been the subject of experiment,

Tartar, however, seems essential to the for-
mation of a genuine vinous liquor ; and aft
addition of it where it is naturally wanting,
is found, not orily to ameliorate the produce,
but even to increase the quantity of alcoliol,
which a given proportion of sugar and ' the
vegetable extract is capable of producing. Fer-
mentation is more easily induced xvhere this salt
is present ; and the experiments of some of the
Tfench Chemists, seem to shew that it is decom-
posed during this process, Their opinion, that it



is converted into the malic acid is questionable,
The presence of tartar is the circumstance which
most strongly distinguishes the grape from all the
fruits which have been applied to the making of
wine. In this fruit, it exists in the greatest quan-
tity before ripening, and a portion of it disappears
during this process. From this peculiarity of the
grape, the practice has been introduced of mixing
tartar with those washes, which makers of sweets
intend for the basis of their wines ; and from it I
have also derived the practice of mixing tartar
with those native fruits which are deficient in this
substance ; a practice which has been attended
with the best results. The details of this practice

will be treated of hereafter in their proper place.


The effect of the malic acid, another of the'
enumerated ingredients in fruits, is very different
from that of tartar, inasmuch as it has been found
injurious to the fabrication 1 of wine. It is remark-
ed, that all wines which abound in malic acid
are of a bad quality, although in many cases it has
not been determined, whether this acid was an ori-
ginal ingredient in the fruit, or whether it was not
generated during the process of fermentation."

In either case, since its existence in wine is found
to be injurious, it is important to attend to this fact,
as our native fruits seem all to be characterized by
an excess of malic acid. This is perhaps one of
the most fundamental and least corrigible defects in
our domestic wines. To render the nature of this


defect more obvious, it must be remarked, that thd
essential distinction between cider and wine, con-
sists in the quantity of malic acid which enters in-
to the composition of the former. From this cause
our native wines are more apt to partake of the
nature of cider than wine, although these are often
rather disguised than changed by the predominance
of undecomposed sugar, of brandy, and other fo-
reign matters which enter into their composition.
It is a question, worthy of consideration, whether
some chemical means might not be adopted for de-
stroying a portion of this acid, eithet before or
after the process of fermentation. In the manu-
facture of sherry wine, lime is added to the grapes
before this process is commenced. However
empirical this practice may be among the manu-
facturers, it probably acts by neutralizing this acid^
as well as a portion of the tartarous acid, and to
this is probably owing the peculiarly dry quality
of that wine. A hint may probably be borrowed
from this practice towards the amelioration of our
domestic wines ; and I may here venture to point it
out as a practice worthy of imitation, worthy at
least of a careful trial. It is only from the results
of such, and similar experiments, that we can hope
ever to place our domestic manufacture on a sound
and rational basis.

Of all the substances which are called into ac-
tion, during the process of wine- making, Sugar
must be considered the most essential, being that



on which the strength of the wine depends. ThoSe
fruits which contain the greatest proportion of su-
gar, furnish the strongest wine ; the alcohol ge-
nerated in the act of fermentation, being always
found to bear a proportion to the pre-existing su-
gar. The principal defect in our domestic fruits
is the small proportion of sugar which they con-
tain ; but it is at the same time that which we are
most easily able to remedy ; and it is on this basis in-
deed that the whole system of our domestic wine
manufacture is founded. But even in this part of the
process, difficulties occur, and lead to the imperfect
fermentation of these wines, and the consequent
sweetness by which they are too often character-
ized. The saccharine matter has indeed been con-
sidered as existing in two distinct states in veget-
ables, that of pure sugar and that of the sweet
principle ; but it is perhaps more correct to con-
sider sugar as an artificial substance formed by
chemistry from the sweet principle, the only state
in whrch sugar truly exists in vegetables. The
sweet principle is characterized by its want of ten-
dency to crystallize, and by the facility with
which, on the addition of water,- it runs into fer-
mentation. Sugar, on the contrary, is crystalliz-
able, and has no tendency to ferment, except in as
far as it contains a portion of the sweet principle,
or of that peculiar substance by which this prin-
ciple is distinguished from sugar. If a solution
of pure sugar in water be allowed to repose, k


crystallizes without fermenting ; nor does even the
residuary syrup, or mother water as it may be called,
undergo this process. But if it has been imperfect-
ly refined, the remaining syrup, will, after the de-
position of the crystals, contain so large a propor-
tion of the sweet principle, that it will readily run
into fermentation ; an accident well known to con-
fectioners. The juice of the sugar-cane readily
allows of the separation of the sugar from the
sweet principle, and has hence become the almost
exclusive subject of this manufacture. The resi-
duary matter, known by the name of Molasses, is
the sweet principle of the French Chemists, and
is a peculiar compound of sugar, with vegetable
extractive matter, similar to that which exists in
the generality of sweet fruits. In considering this
substance, therefore, it will be most consistent with
the accuracy of chemical language, to speak of it
as a peculiar compound of sugar and vegetable mat-
ter, and not to consider it, with Deyeux, Proust,
and Seguin, as a simple substance. Hence we
should not say with these chemists, that in some
fruits, and in some varieties of the grape, sugar
predominates, and in others, the sweet principle ;
but that the sugar of the fruit is in some cases
combined with more, and in others with less of the
vegetable extract. These varying proportions of
the two substances under consideration, are the
cause of the various effects, which are observed in
he results of fermentation in different fruits, if



the sugar predominates, the wine will be sweet,
unless expedients are used to complete the fermen-
tation of the sugar, and convert the whole into
wine. If the sweet principle is most abundant,
pr, to speak more correctly, if there is much vege-
table extract combined with the sugar, the fer-
mentation will be complete, and the wine dry, un-
less artificial means, hereafter to be described, are
used to prevent this effect. The distinction which
I have here drawn, though appearing to partake
of unnecessary refinement, will be found to lead to
practical utility,

Among the enumerated ingredients of fruits, the
vegetable extract naturally falls next under con-
sideration. Although this substance has not been
analyzed, we know that it differs from mere vege-
table mucilage, by containing azote, or a sub-
stance which on decomposition produces it, since
azotic gas has been detected in the produce of fer-
mentation, both in arj uncombined state, and in
one of its, most frequent combinations, forming
ammonia. These substances are known to ex-
ist in yeast, which is a modification of the veget-
able extract, In many vegetables, and conspicu-
ously in the gluten of wheat, it exists in great
proportion. It is for this reason that wheat as
well as rye, act powerfully as ferments. It is al-
o found in many flowers, in that of the elder for
, in the leaves of the vine, in


grape, in the gooseberry, and in many other
fruits as well as leaves. It is observed to abound
in those vegetable juices which gelatinise on boil-
ing. This substance, then, is the true natural
Jeaven of fruits, or that by which the sugar which
they contain, is rendered capable of undergoing
fermentation : And in the artificial process of vini-
fication, which is the subject of this paper, it is
to this substance that we must look for the con-
version into wine of that sugar which may en-
ter into the compound. But I shall have occasion
to enlarge on this subject, when I consider the
process of fermentation.

Water > enumerated among the principles of
fruits, simple as it may appear, is a substance re-
quiring consideration. If the proportion of water
be too small in the liquor subjected to fermenta-
tion, that process is difficultly either established
or maintained. This is a matter of constant occur-
rence in those countries, 'where the juice of the
grape is boiled to a certain consistence, or where
the fruit before pressing, is allowed to undergo a
partial desiccation. From these practices, result
sweet and half-fermented wines, those of Cyprus
and other places, as well as that class of wines
known in Italy by the name of Vino cotto. The
vina cocta of the antients, appear to have been of
a similar quality from the same cause. The wines
0f Tokay and San Lucar, are known to derive ad


ditional richness and strength, from a moderate
use of this practice. This process can be of no
use in the manufacture of our domestic wines,
nor does the nature of our fruits admit of it. An
excessive addition of sugar may produce a similar
effect ; but I know not that any of the receipts in
use, approximate t that excess. That sweetness
which is the prevalent fault of our wines, arises
from other causes, which I shall consider here-

The fruits of this country possess so little of the
three remaining substances, which were enumer-
ated as constituents, that it is unnecessary to dwell
much on them.

Scarcely any colour is contained in our fruits, if
we except the black cherry and the elder-berry,
and as colour may be considered in the light of
an ornament, and is easily procured by colouring
ingredients, its want is not to be regretted ; the
essential parts of wine-making in nowise depend
on it.

The tanning principle, which is the cause of
astringency, is contained in the husks and stems
of some grapes, and communicates at the pleasure
of the operator, that roughness known in Port
wines. The sloe and damson possess it, but as it
can readily be communicated by kino or catechu,
and is not a very desirable quality, it is sufficient
to have noticed it, considering, as we may, the imt-


tation of foreign wines by circuitous means, as a
fruitless attempt.

The last principle, that of flavour, is so uncer-
tain and fugacious, that it is difficult to establish
any general rules respecting it. In many grapes,
as those of Frontignan, the flavour of the fruit is
absolutely identified 'with the wine which they
yield ; but in all such cases the wine is sweet and
half fermented. The finer flavours of the supe-
rior wines, those of claret, hermitage and burgun-
dy, bear no resemblance to that of the fruit, but
are the result of the vinous process. In the
manufacture of many wines, recourse is had to
flavouring ingredients, such as orris-root, grape-
flowers, almonds, mignonette, a process which is
imitated in this country in the making of elder
and cowslip wines. If the flavour of fruits could
be transmitted with certainty to the wines, we
might expect similar results from the strawberry
and raspberry ; but the effect of fermentation is
generally such as to volatilize or destroy this de-
licate principle. Hereafter I shall point out a
probable method of attaining this object.

If a knowledge of the circumstances which at-
tend and modify the intricate process of fermenfa-
tion, be necessary in the making of wine from the
grape, it is still more requisite to investigate the
various accidents and causes which may affect it,
^hen the substances exposed to its action, are,


those used in our domestic manufacture, artificially
compounded. It is thus only that we can hope
to establish such general rules, as may be appli-
cable to those ever-varying cases, where particular
rules of practice would be unattainable. A gener-
al notion has already been given of the substances,
to whose mixture the process of fermentation is
owing, and the essential ones will be found to con-
sist of sugar, vegetable extract, tartarous and malic
acid, and water. These are indispensable, and to
their varieties in proportion, some of the most re-
markable differences in the results of fermentation
will be found owing. Among these, sugar is the
most essential, since the alcohol of wine is more
particularly derived from the decomposition of
this substance. The strength of the wine is pro-
portioned to the quantity of sugar fermented, and
the most saccharine juices, therefore, afford the
strongest wine, or in the artificial process, if so it
may be termed, that compound to which the great-
est proportion of sugar has been added, will be
capable of giving the strongest, if duly managed.
But we have already seen, that sugar and water
alone do not ferment, if the sugar be pure, and
that this process only takes place in clayed sugars,
or in those which contain a portion of that vegeta-
ble extract which characterizes the sweet princi-
ple. In the juices of fruits, the sugar and extract
exist in a state of combination, to which, as I be-
fore remarked, the term of Sweet Principle ha,$


been applied. If the juice of the grape, for ex-
ample, be exposed to heat and rest, a coagulable
substance is separated. The juice then ceases to
ferment with the same facility, but may again be
induced to undergo that change, by a re- addition
of a matter similar to that which was separated
from it. This matter is found in all vegetables,
in some, as in wheat, conspicuously ; and it appears
to constitute the greater proportion of yeast, as
well as of the lees of wine and beer, or other fer-
mented fluids. Here, then, we have the theory of
this process, as it is applied to artificial com-
pounds. It consists of mixing with a solution of
pure sugar in water, a certain proportion of this
unknown substance, which, to distinguish it from
common yeast, I shall hereafter call by the name
of leaven. It is on the proportion, quality and
management of the leaven, that the most import-
ant consequences in vinification depend. I must
therefore describe at more length, the various
modes under which it appears.

The natural leaven of fruit, is coagulable, and par-
tially separable by heat, but it is not entirely render-
ed inert. From this cause, as well as from the partial
dissipation of the water and concentration of the
sugar, boiled juices produce a sweet wine, the pro-
cess of fermentation being rendered incomplete
by a partial separation of the leaven. When the
process of fermentation is suffered to proceed in
of the natural compounds formed in tho


grape or other fruits, a portion of the leaven is
separated from the wine, and is exhibited in two
forms of yeast and lee t part rising to the surface
in froth, and the remainder subsiding to the bot-
tom of the vessel. It is essential to attend to this
distinction, and to understand the true nature of
these substances, as some of the most important
practices in wine-making depend on it. I must
add, that it still remains uncertain, whether any
portion, of the leaven enters into combination with
the vinous produce, or whether it acts solely by
exciting the requisite changes in the sugar, and is
then finally and entirely separated. The yeast
and lee form the artificial leaven, which, in some
important particulars, differs from the natural.
It is soluble in hot water, whereas the natural is
not. But it is insoluble in cold, and it is thus se-
parated by the act of fermentation. I may add,
that, notwithstanding the numerous experiments
to which yeast has been subjected, its composition,
like that of many other vegetable matters, remains
obscure. It is important, however, to recollect,
that it contains ammonia, or at least the princi-
ples of this substance, as Proust has shown.
Those who have been engaged in the manufacture
of domestic wines, must know, that one of the
most frequent defects of these wines, is an am-
moniacal taste ; and there is little reason to doubt,
that it arises from some mismanagement in the
process of fermentation, or an improper introduce


tion of artificial leaven. Although I cannot point
out a precise remedy for this evil, these remarks
may perhaps turn the attention of wine-makers to
search for one. ,

It will from these considerations be evident,
that if certain proportions of sugar and of leaven,
whether natural or artificial be taken, and the pro-
cess of fermentation be suffered to proceed to its
natural termination, the result will be a fluid per-
fectly vinous, containing neither sugar nor acid,
and analogous either to beer or to wine, according
to other circumstances hereafter to be considered.
If the proportion of leaven be deficient, the pro-
duce will contain unchanged sugar ; and the same
effect will take place, if the fermentation be pre-
maturely stopped by artificial means. If, on the
contrary, the leaven is in excess, or the fermenta-
tion has been designedly protracted by artificial
means, a new product will be formed, and the
whole, or a portion of the alcohol, will disappear,
and acetic acid will be found in its place. Sweet
wine, therefore, is an imperfect wine, or one in
which the leaven has borne so small a proportion
to the sugar, as to have been incapable of convert-
ing the whole into a vinous liquor. This is the
case with our domestic wines, when a large
quantity of sugar is added to so small a proportion
of fruit, that the compound does not contain na-
tural leaven enough to convert the whole into
wine. This evil may be corrected by the use of


the artificial leaven yeast, but the quantity added

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