Tempering chocolate masses
Considering the graying of chocolate mass in the light of the basic concepts of polymorphism of cocoa butter, it should be noted that the cause of graying chocolate is the transformation of the metastable form of cocoa butter in the stable.
Fig. 36. Curves pour cocoa butter.
In order to avoid fat bloom, it is necessary to create conditions under which the initial crystallization centers are formed in the cocoa butter, mainly in the form of a stable β-phase, even before the chocolate mass is poured into the molds. In order to form crystallization centers and distribute them evenly in the chocolate mass, i.e.
maximize uniformity resorted to mass called stirring while being cooled.
Fig. 36 solidification curves presented cocoa butter in different crystallization conditions.
Illustrates the variation curve ABCD oils- cocoa temperature, cooled at room temperature without stirring.
Part of the curve AB corresponds to the period when cools cocoa butter, remaining all the time in the liquid state, it is becoming more low temperature and supercooled, almost chostigaya temperature conversion of gamma-phase.
The starting point in the crystallization process accompanied by heat. Part of the curve reflects the sun and the temperature rise. Since then, the crystals begin to appear following the metastable form, having a melting temperature 23-25 °.
Curve A \ B \ C \ D \ illustrates a variation of oil temperature when the cocoa-cooling and stirring.
Segment A \ B \ corresponds to the period when the cocoa butter is stored in a liquid state. The segment B \ C \
It corresponds to a period from nucleation release of latent heat of crystallization.
The main differences of cooling oil, cocoa process, reflected in the curve A \ B \ C \ Du previous lie in the elimination of hypothermia and a significant increase in the period of the formation of crystals.
Since the chocolate contains a significant amount of cocoa butter, the process of preparing chocolate for molding is to create the proper conditions for cooling the chocolate mass to form crystallization centers in it in the form of crystals of stable shape. Recall that the greater the number of
nucleation, the smaller size crystals; fine-grained structure of chocolate makes it gentle "melting" taste.
To increase the number of crystallization centers, according to foreign literature, it is recommended to introduce into the chocolate mass small amounts of finely chopped finished chocolate (0,001-5% of the weight of cocoa butter); While the initial freezing point of cocoa butter from 27,2 ° increases with the addition of 0,001% to 31,9 ° for the 5% additive.
In cocoa butter, and shaping the crystallization process of the chocolate mass has great influence viscosity. The low viscosity of the chocolate mass contributes to a more complete and uniform crystallization of cocoa butter and facilitates the distribution process chocolate into molds.
Consequently, a small amount of moisture in the chocolate mass, careful finishing, the introduction of lecithin and other additives that reduce the viscosity of chocolate, contribute to the elimination of fatty graying. In addition, surface-active substances significantly reduce the surface energy of the crystals, causing inhibition of polymorphic transformations.
The process of preparing the chocolate mass for molding is called tempering and is performed on tempering machines of various designs,
Fig. 37 schematic sectional screw tempering machine.
The machine consists of a hopper B, horizontal auger W, TS tube for feeding the cooled chocolate in the form of aggregates, and the pipe from the return for the chocolate mass and the hopper. Warm chocolate mass, the temperature of which is equal to 45-55 °, is pumped into the hopper in a water-jacketed AA, by which circulates coolant iodine. The top of mesh reinforced funnel for filtering the feed hopper in the chocolate mass. The vertical axis of the funnel mounted roller bearing the BB
Ris.37.Schematic section of auger tempering machine.
HS blades which stir the mass to be treated, and promote it to the screw. Last situated inside the horizontal pipe DDD, EEE provided with a water jacket. The screw is a hollow cylinder, on the outer
The surface of which are coils. The height of the turns, which determines the distance between the inner surface of the pipe and the outer cylindrical surface of the screw, does not exceed 5 mm. Thus, the captured mass moves in a layer of about 5 mm.
Due to the small layer thickness of the same temperature in the mass is established quickly, in spite of its low thermal conductivity (0,2 kcal / m degrees per hour).
In contact with the inner surface of the pipe, which equals the temperature of the circulating water in the water jackets EEE, a thin layer of chocolate mass is cooled, moving through a pipe D.
At the exit of the pipe D chocolate mass, pushed by the screw W is sent to the machine via a pipe shokoladoformuyuschey TS with a water jacket of MM. If for any reason the machine can not shokoladoformuyuschaya take chocolate mass closed valve and open valve K G; then the chocolate mass is directed through pipes from and returns to the hopper B. pipe from the well is equipped with a water jacket SS.
Before starting the machine in motion, and before his arrest at the end of the work, all you need to warm up for the purpose of cleaning the chocolate mass balances. To warm up the machine in all of his hot water flows.
Detained in the pipes and other parts of the chocolate remains of the device moving under the influence of hot water warming device in the molten state and descend through located in the terminal part of the valve device.
To cool the chocolate mass moved by the auger, three isolated cooling zones are provided. In each of the water jackets of any zone, cooling water is supplied, the temperature of which is adjusted automatically. To this end, between the first and second cooling zones (between the flanges Ф1 and Ф2) and between the second and third cooling zones (between the flanges Ф3 and Ф4) are inserted HH rings equipped with contact thermometers PP showing the temperature of the chocolate mass at the time of its exit from The first zone and, respectively, from the second cooling zone. In the shirts of the first and second zones, cooling water comes from a special mixer. In the latter, water coming out of the water jackets is collected, and fresh tap water is also added here; If necessary, the water in the mixer can be heated by steam. Cold water is supplied to the water jackets of the first two cooling zones, the temperature of which is most often within 12-16 °.
The temperature of the chocolate mass at the outlet of the first cooling zone should be 33-34 °, and at the exit of the second cooling zone 31-32 °. In those cases where the chocolate mass temperature at the outlet of the first and second cooling zones for any reason, rise above the set level, contact thermometer includes a mechanism, a guide to the water jacket additional quantity of cold water to cool the chocolate mass.
Such regulation makes it possible to maintain the temperature of the chocolate mass at a constant level at the outlet of the first and second cooling zones. Thus, the chocolate mass entering the third cooling zone has a constant temperature close to 30 e '. Therefore, water is directed into the water jacket of the third cooling zone, the temperature of which is preliminarily and accurately controlled in a separate vessel and maintained within the range of 31-32 °. *
This temperature is above the transformation temperature you most sokoplankon metastable polymorphic cocoa oils-phase, and therefore excludes the presence of the metastable phase in the chocolate mass. In this way a large extent eliminated the conditions favorable for polymorphic transformations or bloom in the solid molded chocolate.
Any noticeable changes this temperature until the cast chocolate into molds unacceptable.
Therefore, the water jacket pipe TS also directed the water, the temperature of the pre-and precisely controlled and maintained at 31-32 °.
Fig. 38. Driving the four-tempering machine with acoustic vibrator.
The best effect is achieved in tempering machines, which with the help of sound vibrations produced
homogenization of the chocolate mass. In these machines provides four cooling zones.
Driving the four-tempering machine with acoustic vibrator shown in Fig. 38.
The chocolate mass is fed into a tank with an agitator 2 3 and 4 shirt. From the tank the chocolate mass through a pipe with
Іlslonkoy 5 6 enters the screw. The motor rotates the agitator 1 and 32 from the yoke through the drive transmits the motion to the auger.
Moving up the peg and then the pipes and the 7 8 9 to the nozzle, the mass passes mgtyre tempering zone. First
zone has a shirt 12. Here along the pipe through the 17 and 18 gate valve incoming cold water. of the valve tube bifurcates and its upper branches through the valve sent water 20 13 shirt in the second tempering zone.
Used water is removed for connection with stopcock 19. Opening the valve in one or the other challenge, adjust the height of the column of water in the jacket. The higher the water column, the better the cooled chocolate mass.
21 heater is used to heat water circulating in the jacket 4 2 tank. Part of the used water is returned to the heater on 22 pipe, and the other part through the pipe with the valve 23 14 shirt comes in third 7 zone. Water from the shirt to the heater back on 21 24 pipe.
The fourth zone of tempering 8 is equipped with a shirt 15. In this shirt and in the 16 shirt 9 nozzle circulates water of constant temperature. The water preheated by the electric heater 25 to 30 ° is fed through the pipe 27 into the shirt 15 and further into the shirt 16, from which it flows along the pipe 28 to the heater. The 26 thermometer records the temperature of the water and, at the same time, regulates the supply of current to the heater. The 29 thermometer indicates the temperature of the chocolate before leaving the third tempering zone and regulates the water supply through the 17 valve. In the first cooling zone, the temperature of the chocolate mass is reduced to 34-33 °, after leaving the second zone - to 32-31 °, and then in the third and fourth zones, the temperature of the mass decreases to 31-30 °. This tempering determines the intensity of the formation of crystallization centers, and the use of the 11 vibrator promotes the process of homogenization of the chocolate mass. The vibrator is an electromagnetic converter of electrical energy into the energy of sound vibrations. The cooled chocolate mass, passing through the 10 9 nozzle grid, is filtered and sent to the molding. If filtering devices are not provided in the design of the tempering machine, they must be included in the total flow of processing the chocolate mass by installing filters between the tempering and forming machines.
To filter the chocolate masses, glazes and other viscous fluids successfully used a mechanical filter is a continuous design and Smolyanitsky Fuerst.
In fig. 39 shows a diagram of the operation of a filter operating under pressure from a rotary pump pumping liquid. The filter consists of a welded body 1, a rotating mesh cylinder 3 and a knife 5. The liquid to be filtered enters the body 1 through the inlet pipe 6. Having passed through the mesh cylinder 3, the filtered liquid is drained through the pipe 2. The sediment released on the cylinder surface is continuously removed with the knife 5 and goes into a sludge pocket, from where, as it accumulates, it is discharged outside.
Fig. 39. Driving filter action for viscous liquids: 1-body; 2-cover with the outlet; 3-mesh
cylinder; 4-cover on the drive side; 5-knife; 6- inlet.