it is not advisable to hasten the cooling of large quantities by
producing too low a temperature in small chambers. The cakes of
chocolate mass by that means come out of the moulds as hard as glass,
but it is questionable whether the consumer using the chocolate many
months afterwards, will make the same observation. Great care would
have to be taken with such rapidly cooled chocolate, to pass it
gradually through chambers of a medium temperature and thus prepare it
for exposure in the packing rooms and warehouses. Even when employing
artificial means for cooling, the reduction of the cellar temperature
and cooling upon pillars is to be preferred to the more direct
cooling upon a system of pipes, which after all is nothing else than
a cooling upon ice, as may be in some instances the only alternative.
Consequently, a well constructed cellar for cooling, furnished with a
system of cooling pipes on the roof is perhaps the most advantageous
arrangement, especially for large factories.
In carrying out artificial refrigeration various kinds of machines are
used for reducing temperature, in which the desired effect is produced
either directly by the condensation and evaporation of suitable
materials, such as liquid carbonic acid, ammonia, sulphurous acid, or
indirectly by making saline solutions (calcium chloride), cooled below
the freezing point, circulate through a system of pipes fitted on the
roof or walls of the space to be cooled. As the cold liquid is pumped
through the pipes, it takes up heat from the air in contact with them,
correspondingly reducing the temperature of the cooling chamber. The
cooling installations of the firm of C. G. Haubold, junior, Chemnitz,
are among the best and have long been extensively used in the chocolate
industry. Their cooling apparatus is a compressing machine, in
which coolness is obtained by the evaporation and recondensation of
such liquid gases as carbonic acid or ammonia. Like all compressing
machines, it is comprised of three main parts.
I. The evaporator or refrigerator, consisting of a wrought iron
system of pipes. The latter are placed in the spaces of the plant
to be cooled, with a so-called direct evaporation arrangement, and
are either arranged on the walls and ceiling, or built in a special
chamber as dry or moist air coolers, according to the quality of the
chocolate to be cooled, or the use for which it is destined. Whilst
in the former case cooling is effected directly in the rooms, in the
latter the air of the cooling room is conducted to the air coolers by
means of ventilator, in order to be cooled and dried there, and then
again introduced in the chamber.
II. The compressor, a gas suction and pressure pump, working both
simply and complex, which draws the refrigerating medium out of the
evaporator, compresses it, and forces it along to the condenser.
III. This condenser consists of a coil of wrought iron or copper
pipes, which are enclosed in a barrel and are often described as
the immersion condenser. There is another type, in which the pipes
are united to one or more pipe-walls, introduced in a vessel which
collects and drains off the condensations. In both cases the coil of
pipes is played upon by a continual stream of water, in order that the
gases which they contain may be condensed. The immersion condenser is
generally employed when there is a plentiful supply of cheap water
at hand, and the other in contrary cases. This latter condenser is
provided with a separate liquid “after-cooler”, constructed on analogy
with the before mentioned immersion condenser. The counter current
principle holds good in both types, and admits of a better using up of
the cooling water. The liquid gas then passes on to the evaporator,
where it is responsible for further refrigeration.
[Illustration: Fig. 59a.]
The refrigerator also occurs in the form of a brine cooler. In this
construction the evaporating pipes are likewise enclosed in a barrel,
containing a high percentage of salt brine. In consequence of the
refrigerating apparatus occurring on the interior of the pipes, the
brine contained therein is cooled down to a very low temperature,
pumped along to the cooling chambers, and after delivering its alloted
refrigeration unit re-conducted to the cooling apparatus, where it is
once more subjected to the same series of processes.
A well-known arrangement for such artificial refrigeration is that
constructed by Wegelin & Hübner at Halle o. S., in which carbonic acid
is employed, and it has been found well adapted for use in chocolate
factories. The accompanying illustrations figures 59 a and 59 b
represent an arrangement of that kind in which the cooling is effected
on cooling trays judiciously arranged.
[Illustration: Fig. 59b.]
The refrigerating machine is constructed on the carbonic acid gas
compression system; it consists of 1. the compressing pump =a=, 2. the
condenser =b=, and 3. the system of pipes =c= and =d=, that constitute
the refrigerator. The coil of pipes in the refrigerator is connected
at one extremity with the compressing pump and at the other extremity
with the condenser. Liquid carbonic acid passes from the condenser
into the coil of pipes and is there evaporated. The heat necessary
for that change is withdrawn, either directly or indirectly, from the
cooling chamber and from the chocolate placed in it, until the desired
reduction of temperature is brought about.
[Illustration: Fig. 60.]
The compressing pump =a= is a peculiarly constructed suction and
pressure pump, it draws out of the refrigerating pipes the vaporised
carbonic acid by which they have been cooled and then subjects it to a
pressure which helps to effect its reconversion into the liquid state.
The condenser =b= consists of a coil of pipes over which a current of
cold water is kept flowing and the compressed carbonic acid vapour,
passing from the compressor into these pipes, is there cooled and
condensed by the surrounding water, so as to be transferred back to
the refrigerator through a valve fitted to it for that purpose. The
outer vessel of the condenser is constructed of cast-iron, in one piece
with the compressor frame. These cooling arrangements are constructed
either with or without mechanical ventilators. In figures 63 a and 63
b the compressing pump and condenser are represented as placed on the
ground floor, while the refrigerator is situated in the cellar space
lying beside them and at a lower level, in such a manner that both the
systems of cooling pipes are not situated upon the roof of the cellar,
but run along it at regular distances parallel to the side walls of the
cellar. The compressor and condenser form one apparatus and the former
is driven by a steam engine.
In the cooling cellar, the refrigerator is generally fixed to the walls
in such a way that the warm chocolate, taken into the cellar, can be at
once placed upon the stages formed by the system of cooling pipes, and
so there is some advantage in having the system of cooling pipes fitted
along the roof of the cellar.
The machine which is diagrammed in fig. 60 possesses an hourly
output of some 70000 calories, measured in salt water at -5 ° C. The
compressor is driven directly by an electric motor, and a stirring
apparatus is put in motion by the crankshaft of the compressor, the two
being connected by an intermediate gearing.
Wegelin and Hübner put out cooling plants with salt water cooling,
smaller and medium sized plants are on the contrary provided with
so-called direct evaporation.
The diagram in fig. 61 shows an air-cooler as built of late by Esher,
Wyss & Co. for chocolate cooling plants.
These air coolers are especially used for direct evaporation of
carbonic acid gas. They consist of three groups of ribbed wrought-iron
pipes, the whole constituting a system supported in a frame work of
U-shaped and angular iron. The separate tubes are welded and bent
together. The ribbed bodies are in themselves square shaped, and apart
from the tube opening have a nozzle introduced in their centre, which
pressed firmly against the press pipe effects a favourable transmission
of heat in the case of large surface areas of the support, the more so
as the tubes are square shaped.
Among the numerous advantages of this machine can be numbered the
abolition of the refrigerator and brine pump, prompt and instantaneous
refrigeration when the machine is started, and ease of control, as a
flange connection occurs immediately in front of the machine.
[Illustration: Fig. 61.]
A wrought iron trough is fitted up underneath the air-cooler to catch
the water drops. Above, and to the left, the three systems of the
air-cooler are connected by means of a catch.
In the foreground of the illustration is given a miniature of the
ribbed tube system, which very clearly illustrates the arrangement of
the separate ribs.
A ventilator not apparent on the diagram conducts air to the tubes in
the cooling chamber, and these present a considerable cooling area,
in addition to which, the air-stream taking a parallel direction,
resistance to its passage is reduced to a minimum.
Another method of cooling[119], that is carried out in France
consists in placing the moulds, containing cakes of chocolate, upon a
travelling belt running horizontally through the whole length of the
cooling chamber. The requisite reduction of temperature is effected
by apparatus similar to that described above in Wegelin & Hübner’s
arrangement. The liquefied carbonic acid flows through a system of
pipes fitted to the roof of the cooling chamber, producing by its
vaporisation the necessary cooling and then it passes back to the
refrigerating machine. Circulation of the air in the cooling chamber is
provided for by a suitable ventilator under the pipes of the cooling
system, gutters being fixed to carry away any water condensing upon
their surface and prevent it from falling upon the chocolate. The
travelling belt passes along so slowly that the moulds, containing
chocolate, placed upon it at one end, take from ten to fifteen minutes
in passing to the other end where they are taken off and carried to the
packing rooms.
[Illustration: Fig. 62.]
Another cooling arrangement that works very well is constructed by T. &
W. Cole of the Park Road Iron Works, London E.; figure 62, represents
a plan of this arrangement, which has the great advantage of providing
for the exclusion of moisture from the cooling chamber. Refrigeration
is effected, by means of Cole’s Arctic-Patent Dry Cold Air machines, by
compressing atmospheric air and then allowing it to expand, after being
cooled by water and having moisture removed by suitable arrangements.
The machine is of very solid construction; it works at a pressure of
from 70 to 80 atmospheres and drives the dry cooled air through a
system fitted in the cooling chamber where the chocolate is spread
out, either on portable trucks or on a travelling belt, so that it
remains in the chamber long enough to become perfectly cold. The system
of cooling can be changed in various ways. The sudden removal of the
cold chocolate into another chamber where the air is moist, would be
attended with a deposition of water upon the goods. For that reason
the goods are first transferred, for a short time, to a warm chamber
(ante-room) where they acquire a temperature at which no deposition of
moisture can take place. The chief advantage of this arrangement is
that it furnishes dry cold air economically, both in summer and also
in a moist climate. Cole guarantees that this machine will effect a
refrigeration of 5 ° C.; according to the statement of Messrs. Negretti
and Zambra the cooled air contains only 40 % of moisture. The cold
air from one of these machines can be led, by a well insulated run
of pipes, to any part of the factory and thus be made available for
cooling purposes in different places.
The cooling plants hitherto described may be classified as “Space
Coolers”, because in each case a special compartment of the cooling
chamber must be utilised. The increased prices of estate constitute no
mean objection to such a system.
A critical valuation of these plants brings out a few undisguisable
deficiencies. A large proportion of the cold is lost in the chamber
itself, before it has been of any avail; and then again the rooms are
generally insufficiently, sometimes even not at all, insulated from
adjacent and warmer chambers, which once more involves raising of
the low temperature essential in the process.[120] Detrimental also
is the presence of the personnel, the illuminations, and many minor
influences. It is evident that the larger the output required the
larger must the cooling chamber be, involving corresponding economical
waste.
With the recognition of these evils arose the problem of their
abolition. The aim was to employ small chambers and avoid loss of cold
air. It is now solved by a system already used in many and various
industries, namely, cooling in closets. Larger or smaller closets
may be employed, as required, and in consequence of their thorough
insulation may even be introduced into the warmest rooms. Their
principle is maximum efficiency with minimum occupation of space, and
avoidance of loss of cold as far as possible. In consequence of this
latter aim, the refrigerators in this case can be constructed on a
smaller scale than those destined for an equal output of material,
which are fixed up in cooling chambers; or they may be larger, which
is yet more important, for the efficiency of the machine under
consideration can be considerably increased by connecting it with one
of the closets.
There are two sorts of cooling chambers, those which transport the
moulds automatically, and those which contain layers where the moulds
are placed one over another. Both types are cooled by the circulation
of air, so effected, that cooled air currents are sucked up by a fan
out of a tubular system fitted underneath a horizontal partition,
and then forced along to the chambers above, where they are evenly
distributed over the rows of sheet-iron, laden with moulds, or where
they play upon the travelling belt which transports the moulds out of
the cooling chambers. The air passes once more into the tube chamber
on the opposite side, where it delivers up the warmth it has in the
meantime acquired, to enter finally the same system of circulation as
before. The general temperature of the closets is a mean between 8 °
C. and 10 ° C., and the cooling lasts from 20-40 minutes, according to
the strength and size of the tablets. As the temperature never goes
lower than 8 ° C., it is impossible for the tablets to become moist
when exposed to the warmer outer atmosphere. Fig. 63a shows a Cooling
Chamber built by J. M. Lehmann, which is adapted for a daily output of
some 1000 kilos, and divided into compartments one above the other.
The sections of this chamber, which in the illustration plainly shows
the small amount of space required for its erection, are divided by
vertical cross-partitions into four compartments, each of which is
provided with a shelf or stand to take a charge of 10 cooling trays,
and accessible by three spring-doors, thus giving as small apertures
as possible and reducing the loss of cold when charging to a minimum.
In addition to this, each compartment is fitted with a contrivance for
regulating and, if necessary, completely cutting of the draught. The
position of the system of pipes is shown by the two pipe-ends to which
it is connected. On the opposite side, or front of the chamber, is the
fan-drive, either a small electric motor, or shafting. The perforated
cooling trays are visible through the open doors. The sides of the
chamber consist of two layers of wood with thick slabs of cork between
them. All chambers of this system, including those with automatic
conveyance of the moulds, can be taken to pieces for transport, the
single pieces afterwards only requiring to be fastened together again
when erecting the chamber.—The chamber illustrated serves for cooling
moulded chocolate. For pralinés and the like similar chambers are
supplied, which are, however, smaller and lighter in construction.
Fig. 63b represents a cooling chamber with forced air circulation
and automatic conveyance of the moulds, built by the same firm. This
chamber, which, owing to the travelling belt conveying the moulds, is
of considerable length, is nowhere connected with the outside air; the
whole manipulation of the moulds is carried on through small adjustable
openings at the points where the travelling band enters and leaves
the chamber. The band consists of chains in links on to which wooden
laths are screwed and its speed can be regulated to suit the size of
the tables to be dealt with. The width of the belt and chamber can at
any time be varied to suit the place of erection and correspond with
the length.
[Illustration: Fig. 63 a.]
[Illustration: Fig. 63 b.]
[Illustration: Fig. 63 c.]
As is to be seen from the illustration, this cooling chamber requires
the minimum of attendance and thus complies with the principles lately
adopted in all large factories, in which the tendency is to substitute
as much as possible mechanical appliances for manual work. It will
be seen from the preceding chapters that this tendency is especially
marked in the moulding department, where automatic tempering,
moulding and mould-filling plants and shaking tables have already
been introduced. In order to utilise fully such automatic plants the
last link in the chain only was wanting, namely, a suitable means of
transferring the moulds from the shaking tables to the cooling chamber
and through the latter to the demoulding and packing room. The purpose
of the cooling chamber above described is to fill up this gap, and its
proper place is thus ranged in among the automatic machinery described.
Thus it is that many modern factories have united the above machines to
form a single working plant, as shown by Groundplan Fig. 63c.
V. Special Preparations.
a) ~Chocolate Lozenges and Pastilles.~
These chiefly consist of cacao mass, sugar and spices. Formerly they
were made by placing the semi-liquid chocolate material on a stone
slab, furnished with a rim of uniform height which served to regulate
the thickness of the goods manufactured, and then rolling out the mass
as required. The lozenges were punched from the rolled-out layer by
means of a cutter. After allowing the mass to cool, these lozenges were
detached from the remaining portions, which were then rolled again and
the same process repeated.
Pastilles, on the surface of which impressions of varying import, such
as figures, names, firms etc. are required, may also be manufactured by
placing the soft chocolate mass upon tin-plates in which depressions
occur corresponding to the device desired. A roller is employed to make
the material fit into the depressions, and superfluous chocolate is
removed with a knife.
These impressions come out especially fine, when the pastille moulds
are subjected to a shaking on the tables with which we are already
acquainted.
[Illustration: Fig. 64.]
[Illustration: Fig. 65.]
Yet these processes are becoming obsolete, and the chocolate slabs
or plates are at the present time superseded by the two forms of
apparatus constructed by A. Reiche, which we accordingly describe below.
[Illustration: Fig. 66.]
In the first of these simply constructed machines, fig. 64, the
material oozes through perforations in a square sieve-like arrangement,
at length issuing on the sheet-iron plate fitted underneath. The
process is aided by repeated shaking, and when sufficient chocolate has
penetrated to the plate, the box is raised on its hinge and chocolate
mass left ready for further treatment. By gentle additional shaking,
the still irregular heaps are rounded off to perfection; they are now
cooled down and finally detached. The coating of the lozenges with
coloured sugar grains is effected by passing them, together with the
plate to which they still adhere, through a box containing sugar dust.
This machine is scarcely used now; in its place come the two
constructions of A. Reiche, as already stated, the one being intended
for solid material, and the other for semi-liquid chocolate mass.
[Illustration: Fig. 67.]
By means of his pastille machine Nr. 14091, which we give in Figs. 65
and 66, chocolate lozenges of the most diverse size can be prepared
very rapidly and to advantage. The chocolate material, which in this
case is solid, is pressed through perforations in a metal plate and
otherwise treated as in previous cases.
In working with this machine, it must be previously and sufficiently
warmed, then partially filled with chocolate material of a proper
consistency (not more than 75 % of the total capacity may be utilised).
It is highly important in the preparation of lozenges that the material
should neither be too hard nor too plastic, but strike a just medium.
[Illustration: Fig. 68.]
Before pressing down the plunger, worked by a screw, a metal plate
is laid upon the chocolate to prevent contact with the plunger. By
slight pressure, the chocolate mass is forced through the perforations,
according to the required size of the lozenges, but the plunger must
not be screwed down further. This will admit of the plate on which the
lozenges rest being drawn out and another inserted.
[Illustration: Fig. 69.]
To this machine belong the usual perforated plates _f_, Fig. 66 of
which there are three of different sizes for each machine, as shown by
figures _a_ _b_ _c_, also the plates _d_ used for making the perforated
confections which find their way to the Christmas Tree. These plates
are impressed with larger or smaller designs, and so make two different
sizes of goods possible. A third plate is supplied for the manufacture
of whole pieces (various varieties of chocolate croquette).
The machine works smoothly and noiselessly and delivers excellent
products. If instead of the usual plain lozenges, such with the name of
a firm or other device are desired, the corresponding impressions must
be stamped out on the plate in which the chocolate is received after
being forced through the perforations. See fig. 66, g, h, i.
Fig. 67 illustrates the pastille machine Nr. 14 178 for thin
chocolate mass, constructed by A. Reiche (German Patent 227 200).
It resembles the foregoing apparatus in principle and appearance,
being only distinguished by a different aim, namely the treatment
of thin material. Used in conjunction with the peculiar moulds also
manufactured by the same firm (marked “Durabula”), even the deepest
impressions can be effected with an enormous saving of time and
material and in a most practical manner, as will be seen on comparing
figs. 69 _a_ to _d_.
In order to get the full value out of this machine, some little
practice is necessary on the part of the workman in charge. But
possessed of an average amount of skill, he can soon turn out with this
apparatus ten times as much as can be made with the ordinary type of
lozenge machine.
For a favourable accommodation of the different pastille plates,
the hurdle diagrammed in fig. 68 (by A. Reiche) is quite excellent.
It is manufactured out of one complete sheet of steel, is free
from any suspicion of soldering, and entirely galvanised. It thus
offers a strong guarantee as regards wear and tear. It may also be
advantageously employed as a transporting device.
b) ~Coated chocolates, pralinés etc.~
These delicacies are now held in high esteem, and of late the
consumption of pralinés and cheaper forms with imitative contents has
increased very considerably.